U.S. patent application number 16/266194 was filed with the patent office on 2019-06-06 for sensing resistor short determiner, switch control circuit including the same and power supply including the switch control circu.
This patent application is currently assigned to SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. The applicant listed for this patent is SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. Invention is credited to Hyun-Chul EUM, In-Ki PARK, Yong-Sang SHIN.
Application Number | 20190170803 16/266194 |
Document ID | / |
Family ID | 53368127 |
Filed Date | 2019-06-06 |
United States Patent
Application |
20190170803 |
Kind Code |
A1 |
PARK; In-Ki ; et
al. |
June 6, 2019 |
SENSING RESISTOR SHORT DETERMINER, SWITCH CONTROL CIRCUIT INCLUDING
THE SAME AND POWER SUPPLY INCLUDING THE SWITCH CONTROL CIRCUIT
Abstract
According to the exemplary embodiments, a short-circuit of a
sense resistor is detected according to a result of comparison
between a sense voltage and a reference voltage at a time based on
at least one of a period set based on an input sense voltage and a
turn-on time of a power switch. A blanking period is set based on
the input sense voltage in a current mode, and a short-circuited
resistor detection period is set based on the input sense
voltage.
Inventors: |
PARK; In-Ki; (Seoul, KR)
; EUM; Hyun-Chul; (Gwangmyeong-si, KR) ; SHIN;
Yong-Sang; (Bucheon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC |
Phoenix |
AZ |
US |
|
|
Assignee: |
SEMICONDUCTOR COMPONENTS
INDUSTRIES, LLC
Phoenix
AZ
|
Family ID: |
53368127 |
Appl. No.: |
16/266194 |
Filed: |
February 4, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14567693 |
Dec 11, 2014 |
10241143 |
|
|
16266194 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02M 1/32 20130101; H03K
17/0822 20130101; G01R 31/40 20130101; H02M 2001/0009 20130101;
G01R 1/203 20130101; G01R 31/50 20200101; G01R 31/52 20200101; H02M
3/33507 20130101; H03K 2217/0027 20130101 |
International
Class: |
G01R 31/02 20060101
G01R031/02; H03K 17/082 20060101 H03K017/082; G01R 31/40 20060101
G01R031/40; H02M 3/335 20060101 H02M003/335 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2013 |
KR |
1020130154981 |
Claims
1-24. (canceled)
25. A short-circuit detection circuit, comprising: an input voltage
detector circuit configured to detect an input voltage coupled to a
power switch and to generate an input sense voltage according to
the input voltage; a sense voltage comparator circuit configured to
compare a sense voltage and a reference voltage to generate a
comparison signal, the sense voltage being generated by a current
that flows from the input voltage through the power switch and a
sense resistor when the power switch is turned; and a blanking
period setting circuit configured to assert a blanking signal when
the power switch is on, wherein the blanking period setting circuit
determines a duration of the blanking signal according to the input
sense voltage, wherein the short-circuit detection circuit is
configured to: not detect a short-circuit of the sense resistor
when the blanking signal is asserted, and detect the short-circuit
of the sense resistor according to the comparison signal when the
blanking signal is not asserted and the power switch is on.
26. The short-circuit detection circuit of claim 25, wherein the
assertion of the blanking signal is synchronized to a turn-on time
of the power switch.
27. The short-circuit detection circuit of claim 26, wherein the
duration of the blanking signal is decreased in response to an
increase in the input sense voltage and is increased in response to
a decrease in the input sense voltage.
28. The short-circuit detection circuit of claim 25, wherein the
short-circuit detection circuit is configured to not detect a
short-circuit of the sense resistor when the power switch is
off.
29. The short-circuit detection circuit of claim 25, further
comprising: a signal generator circuit that asserts a short-circuit
detection signal in response to a rising edge of a shut-down
signal, wherein the short-circuit detection circuit is configured
to assert the shut-down signal in response to detecting the
short-circuit of the sense resistor.
30. The short-circuit detection circuit of claim 25, wherein the
input voltage is coupled to the power switch through a first coil
of a transformer, and wherein the input sense voltage is generated
using a current generated by a second coil of the transformer.
31. The short-circuit detection circuit of claim 25, wherein the
input sense voltage is generated using a voltage produced by a
voltage divider coupled to the input voltage.
32. The short-circuit detection circuit of claim 25, wherein the
short-circuit detection circuit is configured to: not detect the
short-circuit of the sense resistor during an interval after the
power switch is turned on and before a determination to turn off
the power switch; and detect the short-circuit of the sense
resistor according to the comparison signal when the blanking
signal is not asserted during the interval after the determination
to turn off the power switch and before the power switch is turned
off.
33. The short-circuit detection circuit of claim 32, further
comprising: a peak detector signal to determine a peak voltage of
the input sense voltage; and a peak reference generator circuit to
determine a peak reference voltage according to the determined peak
voltage, the peak reference voltage being less than the peak
voltage, wherein the blanking period setting circuit asserts the
blanking signal when the power switch is on and the input sense
voltage is greater than the determined peak reference voltage, and
de-asserts the blanking signal when the power switch is off or the
input sense voltage is less than the determined peak reference
voltage.
34. A short-circuit detection circuit, comprising: a blanking
period setting circuit configured to receive an input sense voltage
and produce a blanking signal having an asserted duration
determined using the input sense voltage; a first comparator
circuit configured to compare a sense voltage to a reference
voltage and assert a comparison signal when the sense voltage is
less than the reference voltage; and an AND gate configured to
receive the blanking signal, the comparison signal, and a gate
control signal and to assert a shut-down signal when the blanking
signal is asserted, the comparison signal is asserted, and the gate
control signal is asserted, wherein the gate control signal being
asserted indicates a power switch is turned on.
35. The short-circuit detection circuit of claim 34, wherein the
asserted duration of the blanking signal is synchronized to the
assertion of the gate control signal.
36. The short-circuit detection circuit of claim 35, wherein the
blanking period setting circuit is configured to increase the
asserted duration when the input sense voltage decreases and to
decreases the asserted duration when the input sense voltage
increases.
37. The short-circuit detection circuit of claim 34, further
comprising: a signal generator circuit that asserts a short-circuit
detection signal in response to a rising edge of a shut-down
signal.
38. The short-circuit detection circuit of claim 34, wherein the
blanking period setting circuit comprises: a peak detector signal
to determine a peak voltage of the input sense voltage; and a peak
reference generator circuit to determine a peak reference voltage
according to the determined peak voltage, the peak reference
voltage being less than the peak voltage, a second comparator
circuit configured to compare the input sense voltage to the peak
reference voltage and assert the blanking signal when the input
sense voltage is greater than the peak reference voltage.
39. The short-circuit detection circuit of claim 34, further
comprising: an input voltage detector circuit to produce the input
sense voltage according to an input voltage coupled to the power
switch.
40. A method for detecting a short circuit, the method comprising:
determining, using an input voltage detector circuit, an input
sense voltage corresponding to an input voltage coupled to a power
switch; generating, using a blanking period setting circuit, a
blanking signal having an asserted duration determined using the
input sense voltage; determining, using a sense voltage comparator
circuit, whether a sense voltage is less than a reference voltage;
determining whether the power switch is turned on; and asserting a
shut-down signal in response to the sense voltage being less than
the reference voltage when the blanking signal is not asserted and
the power switch is turned on, wherein the sense voltage is
generated using a sense resistor coupled in series with the power
switch.
41. The method of claim 40, wherein the assertion of the blanking
signal is synchronized to the power switch being turned on.
42. The method of claim 41, wherein the asserted duration of the
blanking signal is decreased in response to an increase in the
input sense voltage and is increased in response to a decrease in
the input sense voltage.
43. The method of claim 40, further comprising: asserting a
short-circuit detection signal in response to a rising edge of a
shut-down signal.
44. The method of claim 40, further comprising: determining a peak
voltage of the input sense voltage; determining a peak reference
voltage using the determined peak voltage, the peak reference
voltage being less than the peak voltage; asserting the blanking
signal when the input sense voltage is greater than the determined
peak reference voltage; and de-asserting the blanking signal when
the input sense voltage is less than the determined peak reference
voltage.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2013-0154981 filed in the Korean
Intellectual Property Office on Dec. 12, 2013, the entire contents
of which are incorporated herein by reference.
BACKGROUND
(a) Field
[0002] Exemplary embodiments relate to a sense resistor
short-circuit determiner, a switch control circuit including the
same, and a power supply including the switch control circuit.
(b) Description of the Related Art
[0003] A switch current flowing to a power switch that controls
operation of a power supply can be sensed using a sense resistor.
The switch current flows to the sense resistor and thus a sense
voltage is generated. A PWM controller controls switching operation
of the power switch using the sense voltage.
[0004] However, when the sense resistor is short-circuited, no
sense voltage is generated and thus an on-time of the power switch
may be controlled to be the maximum. Then, the power supply may be
abnormally operated.
[0005] The above information disclosed in this Background section
is only for enhancement of understanding of the background of the
invention and therefore it may contain information that does not
form the prior art that is already known in this country to a
person of ordinary skill in the art.
SUMMARY
[0006] Exemplary embodiments of the present invention have been
made in an effort to sense a short-circuit of a sense resistor.
[0007] A sense resistor short-circuit determiner according to an
exemplary embodiment includes: an input voltage detector detecting
an input voltage and generating an input sense voltage; and a sense
voltage comparator generating a comparison signal according to a
result of comparison between a sense voltage and a reference
voltage, the sense voltage being generated by a current that flows
from a power switch to a sense resistor. A short-circuit of the
sense resistor is detected according to the comparison signal at a
time based on at least one of a period set based on the input sense
voltage and a turn-on time of the power switch.
[0008] The sense resistor short-circuit determiner further includes
a blanking period setting unit that sets a blanking period based on
the input sense voltage and generating a blanking signal indicating
the blanking period. The blanking period setting unit sets the
blanking period based on a time for the sense voltage to reach the
reference voltage when the sense resistor is in a normal state in a
detected input voltage condition.
[0009] The blanking period setting unit sets the blanking period
based on an inverse of variation of the input sense voltage.
[0010] A short-circuit of the sense resistor is detected according
to the blanking signal and the comparison signal during a turn-on
period of the power switch.
[0011] The sense resistor short-circuit determiner further includes
a logic gate the detects a short-circuit of the sense resistor by
performing a logic operation on the comparison signal, the blanking
signal, and a gate control signal that controls switching operation
of the power switch.
[0012] A short-circuited resistor detection period is set according
to a result of comparison between the input sense voltage and a
predetermined peak reference voltage that is based on a peak
voltage of the input sense voltage.
[0013] The sense resistor short-circuit determiner further includes
an input comparator generating an input high signal that indicates
the short-circuited resistor detection period when the input sense
voltage is higher than the peak reference voltage.
[0014] In the short-circuited resistor detection period, a
short-circuit of the resistor is detected according to the
comparison signal at a power switch turn-off determination time
during a turn-on period of the power switch.
[0015] The sense resistor short-circuit determiner further includes
a logic gate detecting a short-circuit of the sense resistor by
performing a logic operation on the input high signal, the
comparison signal, and an on-time signal generated by being
synchronized at the power switch turn-off determination time.
[0016] The sense resistor short-circuit determiner further
includes: a peak detector detecting a peak voltage of the input
sense voltage; and a multiplier generating the peak reference
voltage by multiplying a predetermined gain by the peak
voltage.
[0017] The sense resistor is determined to be short-circuited when
the reference voltage is higher than the sense voltage at a
termination time of a blanking period set based on the input sense
voltage during a turn-on period of the power switch.
[0018] A short-circuit resistor detection period is set according
to a result of comparison between the input sense voltage and a
predetermined peak reference voltage based on a peak voltage of the
input sense voltage, and the sense resistor is determined to be
short-circuited when the reference voltage is higher than the sense
voltage during a turn-on period of the power switch during the
short-circuited resistor detection period.
[0019] A switch control circuit according to an exemplary
embodiment controls a switching operation of a power switch that is
electrically coupled to an input voltage. The switch control
circuit includes: a PWM controller controlling the switching
operation of the power switch using a sense voltage generated by a
current of the power switch flowing to a resistor; and a sense
resistor short-circuit determiner generating an input sense voltage
by detecting the input voltage, and detecting a short-circuit of
the sense resistor according to a result of a comparison between
the sense voltage and a reference voltage at a time based on at
least one of a period set based on the input sense voltage and a
turn-on period of the power switch.
[0020] A power supply according to an exemplary embodiment
includes: a power switch electrically coupled to an input voltage;
a sense resistor coupled to the power switch to sense a current
flowing through the power switch; and a sense resistor
short-circuit determiner generating an input sense voltage by
detecting the input voltage, and detecting a short-circuit of the
sense resistor according to a result of comparison between a sense
voltage of the sense resistor and a reference voltage at a time
based on at least one of a period set based on the input sense
voltage and a turn-on period of the power switch.
[0021] The sense resistor short-circuit determiner determines the
sense resistor to be short-circuited when the reference voltage is
higher than the sense voltage at a termination time of a blanking
period which is set based on the input sense voltage during the
turn-on time of the power switch.
[0022] The sense resistor short-circuit determiner sets a
short-circuited resistor detection period according to a result of
comparison between the input sense voltage and a predetermined peak
reference voltage based on a peak voltage of the input sense
voltage, and determines the sense resistor to be short-circuited
when the reference voltage is higher than the sense voltage during
a turn-on period of the power switch in the short-circuited
resistor detection period.
[0023] The power supply further includes an auxiliary wire
electromagnetically coupled with a primary wire coupled to the
input voltage, wherein an auxiliary voltage, which is a voltage
between lateral ends of the auxiliary wire, is a negative voltage
that depends on the input voltage during a turn-on period of the
power.
[0024] The sense resistor short-circuit determiner may generate the
input sense voltage using a voltage sense current supplied to the
auxiliary wire to clamp a voltage of a node coupled to the
auxiliary wire to a predetermined voltage during the turn-on period
of the power switch.
[0025] The reference voltage is based on the input sense
voltage.
[0026] According to the exemplary embodiments of the present
invention, a sense resistor short-circuit determiner that can sense
a short-circuit of a sense resistor, a switch control circuit
including the same, and a power supply including the switch control
circuit can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 shows a power supply to which a sense resistor
short-circuit determiner is applied.
[0028] FIG. 2 shows the sense resistor short-circuit determiner
according to the exemplary embodiment of the present invention.
[0029] FIG. 3 shows a sense resistor short-circuit determiner
according to another exemplary embodiment of the present
invention.
[0030] FIG. 4 is a waveform diagram of a sense voltage, a
comparison signal, a gate control signal, a blanking signal, a
shut-down signal, and a short-circuit detection signal according to
the exemplary embodiment of the present invention.
[0031] FIG. 5 is a waveform diagram of a sense voltage, a
comparison signal, a gate control signal, a blanking signal, a
shut-down signal, and a short-circuit detection signal according to
the exemplary embodiment of the present invention when the input
voltage is lower than the input voltage of FIG. 4.
[0032] FIG. 6 shows a sense resistor short-circuit determiner
according to another exemplary embodiment of the present
invention.
[0033] FIG. 7 is a waveform diagram illustrating an input sense
voltage, a sense voltage, an input high signal, and a peak
reference voltage according to another exemplary embodiment of the
present invention in a normal state.
[0034] FIG. 8 is a waveform illustrating an input sense voltage, a
sense voltage, an input high signal, a peak reference voltage, and
a short-circuit protection signal according to another exemplary
embodiment of the present invention in a case in which a
short-circuit of a sense resistor occurs outside of the
short-circuited resistor detection period.
[0035] FIG. 9 is a waveform diagram illustrating an input sense
voltage, a sense voltage, an input high signal, a peak reference
voltage, and a short-circuit protection signal according to another
exemplary embodiment of the present invention in a case in which a
short-circuit of a sense resistor occurs during a short-circuit
resistor detection period.
[0036] FIG. 10 is a waveform diagram illustrating a sense voltage,
a comparison signal, an on-period signal, an input high signal, a
shut-down signal, and a short-circuit protection signal according
to another exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0037] In the following detailed description, only certain
exemplary embodiments of the present invention have been shown and
described, simply by way of illustration. As those skilled in the
art would realize, the described embodiments may be modified in
various different ways, all without departing from the spirit or
scope of the present invention. Accordingly, the drawings and
description are to be regarded as illustrative in nature and not
restrictive. Like reference numerals designate like elements
throughout the specification.
[0038] Throughout this specification and the claims that follow,
when it is described that an element is "coupled" to another
element, the element may be "directly coupled" to the other element
or "electrically coupled" to the other element through a third
element. In addition, unless explicitly described to the contrary,
the word "comprise" and variations such as "comprises" or
"comprising" will be understood to imply the inclusion of stated
elements but not the exclusion of any other elements.
[0039] A sense resistor short-circuit determiner according to the
exemplary embodiment detects a short-circuit of a sense resistor by
controlling a blanking period according to an input voltage. An
input voltage rectified from an AC input is changed, and a rising
slope of a switch current is changed according to the input
voltage. When the sense resistor is in a normal state, a sense
voltage is determined according to the switch current and therefore
the rising slope of the sense voltage is changed according to the
input voltage.
[0040] Time for sensing whether or not the sense resistor is in the
normal state is changed according to the input voltage. For
example, time consumed for sensing whether or not a sense voltage
is generated is shortened as the rising slope of the sense voltage
is increased. On the contrary, time consumed for sensing whether or
not a sense voltage is generated is increased as the rising slope
of the sense voltage is decreased.
[0041] The sense resistor short-circuit determiner according to the
exemplary embodiment senses the input voltage to control a blanking
period according to the input voltage, and determines the sense
resistor to be short-circuited if the sense voltage is lower than a
reference voltage after the blanking period has passed.
[0042] Hereinafter, the sense resistor short-circuit determiner
according to the exemplary embodiment will be described with
reference to the accompanying drawings.
[0043] FIG. 1 illustrates a power supply to which the sense
resistor short-circuit determiner is applied.
[0044] As shown in FIG. 1, a power supply 1 includes a
rectification circuit 10, a capacitor C1, a transformer 20, a
rectification diode D1, an output capacitor C2, a power switch SW,
a sense resistor RS, and a switch control circuit 30.
[0045] An AC input AC is rectified through the rectification
circuit 10, and the rectified AC input becomes an input voltage Vin
through the capacitor C1. The rectification circuit 10 may be a
full-bridge diode which is a full-wave rectification circuit. For
example, the input voltage Vin may be a full-wave rectified sine
wave.
[0046] The transformer 20 includes a primary wire CO1 connected to
the input voltage Vin and a secondary wire CO2 connected to an
output voltage Vout. The primary wire CO1 and the secondary wire
CO2 are coupled in an insulated manner with a predetermined turn
ratio (turns of primary wire CO1:turns of secondary wire CO2).
[0047] A first end of the primary wire CO1 is connected to the
input voltage Vin and a second end of the primary wire CO1 is
connected to a first electrode (i.e., a drain) of the power switch
SW. A current that flows during a turn-on period of the power
switch SW flows to the primary wire CO1 such that energy is
stored.
[0048] A first end of the secondary wire CO2 is connected to an
anode of the rectification diode D1 and a second end of the
secondary wire CO2 is connected to a secondary ground. During a
turn-off period of the power switch SW, energy stored in the
primary wire CO1 is transmitted to the secondary wire CO2.
[0049] The power switch SW is electrically connected to the input
voltage Vin, and controls output power of the power supply 1. A
gate of the power switch SW is connected to a gate voltage VG
supplied from the switch control circuit 30, and a second electrode
(i.e., a source) of the power switch SW is connected to a primary
ground through the sense resistor RS. The power switch SW is turned
on by a high-level gate voltage VG and turned off by a low-level
gate voltage VG.
[0050] The sense resistor RS is connected between the source and
the primary ground of the power switch SW, and a resistor voltage
VCS is generated in the sense resistor RS according to a current
flowing to the power switch SW.
[0051] The output capacitor C2 is connected between lateral output
ends of the power supply 1. A first electrode of the output
capacitor C2 is connected to a cathode of the rectification diode
D1 and a second electrode of the output capacitor C2 is connected
to the secondary ground.
[0052] A current flowing to the secondary wire CO2 passes through
the rectification diode D1. The current passed through the
rectification diode D1 may be applied to a load (not shown) or
charge the output capacitor C2.
[0053] The switch control circuit 30 includes a PWM controller 200
and a sense resistor short-circuit determiner 100.
[0054] The PWM controller 200 is synchronized by an oscillator
signal that determines a switching frequency and thus turns on the
power switch SW, and turns off the power switch SW when the sense
voltage VCS reaches a feedback voltage that corresponds to the
output voltage VOUT (hereinafter, a current mode). Alternatively,
the PWM controller 200 is synchronized by the oscillator signal and
thus turns on the power switch SW, and turns off the power switch
SW when a sawtooth wave signal having a predetermined period
reaches the feedback voltage (hereinafter, a voltage mode).
[0055] The sense resistor short-circuit determiner 100 generates an
input sense voltage VIS by sensing the input voltage Vin, and
determines whether or not the sense resistor RS is short-circuited
according to a result of comparison between the input sense voltage
VIS and a reference voltage VR at a time based on a period
(hereinafter referred to as a blanking period or a short-circuited
resistor detection period) set based on the input sense voltage VIS
and an on-period of the power switch SW. The reference voltage VR
may be set to a predetermined voltage or be set to be based on the
input voltage Vin. For example, the sense resistor short-circuit
determiner 100 determines the reference voltage VR based on the
input sense voltage VIS.
[0056] First, a blanking period is set based on the input sense
voltage VIS in the current mode, and the sense resistor
short-circuit determiner 100 sets the blanking period according to
the input sense voltage VIS and determines the sense resistor RS to
be short-circuited when the reference voltage VR is higher than the
sense voltage VCS at a time when the blanking period is passed
during the turn-on period of the power switch SW.
[0057] For example, in a normal state during which the sense
resistor RS is not short-circuited, the sense resistor
short-circuit determiner 100 may set a blanking period based on a
first period during which the sense voltage VCS reaches the
reference voltage VR in a detected input voltage condition. In
detail, the blanking period may be set to a period acquired by
adding a predetermined margin to the first period.
[0058] However, the exemplary embodiment of the present invention
is not limited thereto, and the blanking period may be set with
other methods.
[0059] For example, the sense resistor short-circuit determiner 100
may set the blanking period so as to have a predetermined ratio
with respect to the maximum allowable duty in the detected input
voltage condition. The predetermined ratio can be modified
according to a design condition.
[0060] FIG. 2 shows the sense resistor determiner according to the
exemplary embodiment of the present invention.
[0061] The sense resistor short-circuit determiner of FIG. 2 can be
applied to the current mode. The sense resistor short-circuit
determiner 100 according to the exemplary embodiment may use an
auxiliary wire CO3 for detection of the input voltage Vin. The
auxiliary wire is provided in the primary side of the power supply
1 of FIG. 1, and is electromagnetically coupled with the primary
wire CO1 with a predetermined turn ratio. Hereinafter, the turn
ratio of the primary wire CO1 and the auxiliary wire CO3 is set to
be 1:1 for convenience of description.
[0062] A voltage between both ends of the primary wire CO1 during
the turn-on period of the power switch SW is the input voltage Vin.
A polarity of a voltage (hereinafter referred to as an auxiliary
voltage VAUX) between both ends of the auxiliary wire CO3 is
opposite to a polarity of the voltage between both ends of the
primary wire CO1, and therefore the auxiliary voltage VAUX of the
auxiliary voltage VO3 is -Vin during the turn-on period of the
power switch SW.
[0063] During the turn-off period of the power switch SW, the
voltage between both ends of the primary wire CO1 is a negative
voltage that is proportional to the output voltage VOUT, and the
auxiliary voltage VAUX is a positive voltage that is proportional
to the output voltage VOUT.
[0064] The sense resistor short-circuit determiner 100 detects the
input voltage Vin using the voltage sense current IVS supplied to
the auxiliary wire CO3 during the turn-on period of the power
switch SW. The sense resistor short-circuit determiner 100
generates a blanking signal BLK that indicates a blanking period
according to an input sense voltage VIS corresponding to the
detected input voltage Vin, and determines whether or not the sense
voltage RS is short-circuited during the turn-on period of the
power switch SW based on the blanking signal BLK and a result of
comparison between the sense voltage VCS and the predetermined
reference voltage Vref. The sense resistor short-circuit determiner
100 determines the sense resistor RS to be short-circuited when the
sense voltage VCS cannot reach the reference voltage RS during the
turn-on period of the power switch SW.
[0065] The sense resistor short-circuit determiner 100 includes an
input voltage detector 110, a blanking period setting unit 120, a
sense voltage comparator 130, an AND gate 140, and a signal
generator 150. Two resistors R1 and R2 are connected in series
between a first end of the auxiliary wire CO3 and a primary ground,
and a second end of the auxiliary wire CO3 is connected to the
primary ground.
[0066] The input voltage detector 110 generates the voltage sense
current IVS according to the auxiliary voltage VAUX generated
during the turn-on period of the power switch SW, and generates the
input sense voltage VIS corresponding to the input voltage Vin
according to the magnitude of the voltage sense current IVS.
[0067] In detail, the input voltage detector 110 generates the
voltage sense current IVS for clamping a voltage of a node N1 to be
higher than a predetermined voltage. When the predetermined voltage
is a primary ground voltage, the voltage sense current IVS is
Vin/R1 during the turn-on period of the power switch SW. That is,
the voltage sense current IVS may be proportional to the input
voltage Vin during the turn-on period of the power switch SW.
During the turn-off period of the power switch SW, the auxiliary
voltage VAUX is higher than the primary ground voltage and thus the
voltage sense current IVS does not flow.
[0068] The input voltage detector 110 generates the input sense
voltage VIS by converting the voltage sense current IVS to a
voltage. For example, the input voltage detector 110 mirrors the
voltage sense current IVS, and flows the mirrored current to the
resistor so as to generate the input sense voltage VIS.
[0069] The blanking period setting unit 120 sets the blanking
period based on the input sense voltage VIS, and generates a
blanking signal BLK that indicates the blanking period. For
example, the blanking period setting unit 120 may generate a
disable-level blanking signal BLK during the blanking period.
[0070] The blanking period setting unit 120 may set the blanking
period based on the inverse direction of the variation of the input
sense voltage VIS. That is, the blanking period is shortened when
the input sense voltage VIS is increased and the blanking period is
increased when the input sense voltage VIS is decreased. The
blanking period setting unit 120 may generate a low-level blanking
signal BLK during the blanking period.
[0071] The sense voltage comparator 130 generates a comparison
signal CV according to a result of comparison between the reference
voltage VR and the sense voltage VCS. The sense voltage comparator
130 includes a non-inversion terminal (+) to which the reference
voltage VR is supplied and an inversion terminal (-) to which the
sense voltage VCS is supplied, and generates a high-level
comparison signal CV when an input of the non-inversion terminal
(+) is higher than an input of the inversion terminal (-) and
generates a low-level comparison signal CV in the opposite
case.
[0072] The AND gate 140 generates a shut-down signal SC by
performing an AND operation on the blanking signal BLK, the gate
control signal VC, and the comparison signal CV. The gate control
signal VC is one of signals that control a switching operation of
the power switch SW, and may be one of enable-level signals in the
turn-on period of the power switch SW. For example, the gate
voltage VG may be the gate control signal VC.
[0073] In the present exemplary embodiment, the AND gate is used to
generate the shut-down signal SD that indicates a short-circuit of
the sense resistor RS, but the exemplary embodiment of the present
invention is not limited thereto. An appropriate logic gate may be
used according to the blanking signal BLK, the gate control signal
VC, and the comparison signal CV.
[0074] The signal generator 150 is triggered by the shut-down
signal SD and generates a sense resistor short-circuit detection
signal SRSD. For example, the signal generator 150 may be
synchronized with a rising edge of the shut-down signal SD and may
thus generate an enable-level sense resistor short-circuit
protection signal SRSP. The PWM controller 200 may generate a gate
voltage VG that turns off the power switch SW for protection by the
enable-level sense resistor short-circuit protection signal
SRSP.
[0075] In the exemplary embodiment of FIG. 1, the auxiliary wire
CO3 is used to detect the input voltage Vin, but the exemplary
embodiment of the present invention is not limited thereto. The
sense resistor short-circuit determiner may be connected to the
input voltage Vin without using the auxiliary wire CO3.
[0076] FIG. 3 shows a sense resistor short-circuit determiner
according to another exemplary embodiment of the present
invention.
[0077] As shown in FIG. 3, a sense resistor short-circuit
determiner 300 is connected to a node N2 where two resistors R3 and
R4 connected in series between an input voltage Vin and a primary
ground are connected. A voltage of the node N2 is Vin*(R4/(R3+R4)),
and is thus proportional to the input voltage Vin.
[0078] The sense resistor short-circuit determiner 300 includes a
blanking period setting unit 310, a sense voltage comparator 130,
an AND gate 140, and a signal generator 150. The sense voltage
comparator 130, the AND gate 140, and the signal generator 150 are
the same as those in the previous exemplary embodiment, therefore
no further description will be provided.
[0079] The blanking period setting unit 310 receives a voltage
(hereinafter referred to as an input sense voltage) VN2 of the node
N2, sets a blanking period based on the input sense voltage VN2,
and generates a disable-level blanking signal BLK during a blanking
period. For example, the blanking period setting unit 310 may set a
blanking period based on the inverse of a variation of the input
sense voltage VN2 and may generate a low-level blanking signal BLK
during the blanking period.
[0080] Hereinafter, an operation according to the exemplary
embodiments will be described with reference to FIG. 4 and FIG.
5.
[0081] FIG. 4 is a waveform diagram illustrating a sense voltage, a
comparison signal, a gate control signal, a blanking signal, a
shut-down signal, and a short-circuit detection signal according to
the exemplary embodiment of the present invention.
[0082] FIG. 5 a waveform diagram illustrating a sense voltage, a
comparison signal, a gate control signal, a blanking signal, a
shut-down signal, and a short-circuit detection signal when the
input signal is lower than the input voltage of FIG. 4 according to
the exemplary embodiment of the present invention.
[0083] As shown in FIG. 4, at T0, the gate control signal VC
becomes a high level and thus the power switch SW is turned on and
the sense voltage VCS starts to increase. At T1, the blanking
signal BLK becomes a low level, and at T4, the blanking signal BLK
becomes high level. A period T1 to T4 is a blanking period BT1. The
blanking period BT1 may be determined according to an input voltage
Vin measured during the previous cycle of the power switch SW
immediately before T1. T1 is synchronized by T0. For example, T0
and T1 may be an equivalent time.
[0084] At T2, the increasing sense voltage VCS reaches the
reference voltage VR and thus the comparison signal CV becomes the
low level. At T3, the gate control signal VC becomes the low level
and the power switch SW is turned off, the sense voltage VCS is not
generated, and the comparison signal CV becomes the high level.
[0085] At T5, the gate control signal VC becomes the high level
again and thus the power switch SW is turned on, and the sense
voltage VCS starts to increase. At T6, the blanking signal BLK
becomes the low level, and at T7, the blanking signal BLK becomes
the high level. A period T6 to T7 is a blanking period BT2. The
blanking period BT2 may be determined according to the input
voltage Vin measured during the switching cycle T0 to T5 of the
power switch SW.
[0086] In the normal state and when the sense resistor RS is not
short-circuited, the above-stated operation is maintained.
[0087] It is assumed that a short-circuit of the sense resistor RS
occurs at T8.
[0088] Although the gate control signal VC becomes the high level
at T9 and thus the power switch SW is turned on, the sense voltage
VCS is not increased with a normal slope, unlike in the normal
state. Although there is a difference according to the degree of
short-circuit, FIG. 4 exemplarily illustrates that the sense
voltage VCS increased with a less steep slope for convenience of
description. However, the exemplary embodiment of the present
invention is not limited thereto.
[0089] At T10, the blanking signal BLK becomes the low level, and
at T11, the blanking signal BLK becomes the high level. A period
T10 to T11 is a blanking period BT3.
[0090] Since the sense voltage VCS is lower than the reference
voltage VR at T11 at which the blanking period BT3 is terminated,
the comparison signal CV becomes the high level and the sense
voltage VCS is lower than the feedback voltage, and therefore the
gate control signal VC is the high level.
[0091] From T11, the blanking period BT3 is terminated and the
blanking signal BLK becomes the high level. Therefore, all inputs
of the AND gate 140 become the high level from T11 and thus the
shut-down signal SD becomes the high level. Then, the short-circuit
detection signal SRSP is increased to the high level at T13. That
is, the protection operation due to detection of a short-circuit is
triggered, and thus the gate control signal VC becomes the low
level at T12 and thus the power switch SW is turned off and the
short-down signal SD becomes the low level.
[0092] FIG. 4 illustrates that the blanking signal BLK is
maintained with the high level while the protection operation is
maintained after T11, but the exemplary embodiment of the present
invention is not limited thereto.
[0093] When the input voltage Vin is decreased, the blanking period
is increased.
[0094] As shown in FIG. 5, at T20, the gate control signal VC
becomes the high level and thus the power switch SW is turned on,
and the sense voltage VCS starts to increase. At T21, the blanking
signal BLK becomes the low level, and at T24, the blanking signal
BLK becomes the high level. A period T21 to T24 is a blanking
period BT4. The blanking period BT4 may be determined according to
an input voltage Vin measured during the previous switching cycle
of the power switch SW immediately before T20. T21 is synchronized
by T20. For example, T20 and T21 may be an equivalent time.
[0095] At T22, the increasing sense voltage VCS reaches the
reference voltage VR and thus the comparison signal CV becomes the
low level. Since the input voltage level of FIG. 5 is lower than
the input voltage level of FIG. 4, a rising slope of the sense
voltage VCS is less steep than that of FIG. 4. At T23, the gate
control signal VC becomes the low level and thus the power switch
SW is turned off, and the sense voltage VCS is not generated and
the comparison signal CV becomes the high level.
[0096] The blanking period BT5 and the blanking period BT6 may be
determined according to an input voltage Vin measured during the
previous switching cycle of the power switch SW. In the normal
state when the sense resistor RS is not short-circuited, the
above-stated operation is maintained.
[0097] It is assumed that a short-circuit of the sense resistor RS
occurs at T25.
[0098] Although the gate control signal VC becomes the high level
and thus the power switch SW is turned on at T26, the sense voltage
VCS is not increased as in the normal state.
[0099] At T27, the blanking signal BLK becomes the low level again,
and at T28, the blanking signal BLK becomes the high level. Since
the sense voltage VCS is lower than the reference voltage VR when
the blanking period BT6 is terminated at T28, the comparison signal
CV is the high level and the sense voltage VCS is lower than the
feedback voltage, and thus the gate control signal VC is the high
level.
[0100] The blanking period BT6 is terminated from T28, and the
blanking signal BLK becomes the high level. Therefore, all inputs
of the AND gate 140 become the high level from T28 so that the
shut-down signal SD becomes the high level. Then, the short-circuit
detection signal SRSP is increased to the high level at T30. That
is, the protection operation due to detection of a short-circuit is
triggered, and thus the gate control signal VC becomes the low
level, the power switch SW is turned off, and the shut-down signal
SD becomes the low level at T29.
[0101] As described, the blanking period varies according to the
input voltage, and a short-circuit of the sense resistor can be
determined according to the sense voltage after the blanking period
is passed.
[0102] Hereinafter, an exemplary embodiment in which a
short-circuit of the sense resistor is determined in the voltage
mode will be described. In the voltage mode, the sense resistor
short-circuit determiner sets a short-circuited resistor detection
period based on the input sense voltage, and determines the sense
resistor RS to be short-circuited when the reference voltage VR is
higher than the sense voltage VS during the turn-on period of the
power switch SW.
[0103] FIG. 6 shows a sense resistor short-circuit determiner
according to another exemplary embodiment of the present
invention.
[0104] A sense resistor short-circuit determiner 400 detects an
input voltage Vin, detects a peak voltage VP of an input sense
voltage VIS corresponding to the detected input voltage Vin, and
sets a peak reference voltage VPR based on the peak voltage VP. The
sense resistor short-circuit determiner 400 sets a short-circuited
resistor detection period according to a result of comparison
between the input sense voltage VIS and the peak reference voltage
VPR, and determines a sense resistor RS to be short-circuited when
the sense voltage VCS cannot reach the reference voltage VR during
a turn-on period of the power switch SW in the short-circuited
resistor detection period.
[0105] The sense resistor short-circuit determiner 400 shown in
FIG. 6 detects the input voltage Vin using a voltage sense current
IVS supplied to an auxiliary wire CO3, but the present exemplary
embodiment is not limited thereto. As shown in FIG. 3, the sense
resistor short-circuit determiner 400 may be connected to the input
voltage Vin.
[0106] The sense resistor short-circuit determiner 400 includes an
input voltage detector 410, a peak detector 420, a multiplier 430,
an input comparator 440, a sense voltage comparator 450, an AND
gate 460, and a signal generator 470.
[0107] The input voltage detector 410 generates the voltage sense
current IVS according to an auxiliary voltage VAUX generated during
a turn-on period of the power switch SW, and generates the input
sense voltage VIS corresponding to the input voltage Vin according
to the magnitude of the voltage sense current IVS. Since the input
voltage detector 410 is the same as the input voltage detector 110
of FIG. 2, no further description will be provided.
[0108] The peak detector 420 receives the input sense voltage VIS,
and generates a peak voltage VP by detecting a peak of the input
sense voltage VIS.
[0109] The multiplier 430 generates a peak reference voltage VPR
that determines the short-circuited resistor detection period by
multiplying a predetermined gain to the peak voltage VP. The gain
in the present exemplary embodiment is set to not determine whether
or not the sense resistor RS is short-circuited when the input
voltage Vin is a low-level voltage. For example, the sense voltage
VCS may be lower than the reference voltage VR during the turn-on
period of the power switch SW not by a short-circuit of the sense
resistor RS, but by a level of the input voltage Vin. When the
input voltage Vin is higher than a predetermined voltage, the gain
of the multiplier 430 may be set to set the short-circuited
resistor detection period for detecting a short-circuit of the
sense resistor RS.
[0110] The input comparator 440 generates an input high signal VIH
that instructs the short-circuited resistor detection period
according to a result of comparison between the input sense voltage
VIS and the peak reference voltage VPR.
[0111] The sense voltage comparator 450 generates a comparison
signal CV according to a result of comparison between the reference
voltage VR and the sense voltage VCS. The sense voltage comparator
450 includes a non-inversion terminal (+) to which the reference
voltage VR is supplied and an inversion terminal (-) to which the
sense voltage VCS is supplied, and generates a high-level
comparison signal CV when an input of the non-inversion terminal
(+) is higher than an input of the inversion terminal (-) and
generates a low-level comparison signal CV in the opposite
case.
[0112] The AND gate 460 generates a shut-down signal SD by
performing an AND operation on the input high signal, an on-time
signal TON, and the comparison signal CV. The on-time signal TON is
a signal generated by being synchronized at a turn-off time of the
power switch SW. The on-time signal TON will be described later
with reference to FIG. 10.
[0113] The signal generator 470 is triggered by the shut-down
signal SD and generates the sense resistor short-circuit detection
signal SRSD. For example, the signal generator 470 may generate an
enable-level sense resistor short-circuit protection signal SRSP by
being synchronized with a rising edge of the shut-down signal SD.
The PWM controller 200 may generate a gate voltage VG that turns
off the power switch SW as a protection operation by the
enable-level sense resistor short-circuit protection signal
SRSP.
[0114] Hereinafter, operation of the sense resistor short-circuit
determiner 400 will be described with reference to FIG. 7 to FIG.
10.
[0115] FIG. 7 is a waveform diagram illustrating an input sense
voltage, a sense voltage, an input high signal, and a peak
reference voltage according to another exemplary embodiment of the
present invention in a normal state.
[0116] FIG. 7 illustrates that an input sense voltage VIS is a
full-wave rectified sine wave corresponding to an input voltage Vin
illustrated as a full-wave rectified sine wave. However, the
waveform of the input voltage Vin is not limited to the exemplary
embodiment shown in FIG. 7.
[0117] A sense voltage VCS is increased with a slope that depends
on the input voltage Vin during a turn-on period of the power
switch SW, and has a waveform that is decreased to a zero voltage
at a turn-off time of the power switch SW. For convenience of
description, the sense voltage VCS shown in FIG. 7 is illustrated
as a waveform that connects peaks of the sense voltage VCS
generated at every switching period.
[0118] As shown in FIG. 7, a peak reference voltage VPR is lower
than a peak voltage VP because a gate of the multiplier 430 is
multiplied to the peak voltage VP.
[0119] Periods during which the input sense voltage VIS is higher
than the peak reference voltage VPR, that is, P1, P2, and P3, are
set to short-circuited resistor detection periods, and the input
high signal VIH is the high level in P1, P1, and P3.
[0120] FIG. 8 is a waveform illustrating an input sense voltage, a
sense voltage, an input high signal, a peak reference voltage, and
a short-circuit protection signal according to another exemplary
embodiment of the present invention in a case in which a
short-circuit of a sense resistor occurs not during the
short-circuited resistor detection period.
[0121] In FIG. 8, it is assumed that a short-circuit of a resistor
RS occurs at T31 after a short-circuited resistor detection period
P12 is terminated.
[0122] An input sense voltage VIS is generated in a normal state,
and the input sense voltage VIS is higher than a peak reference
voltage VPR during short-circuited resistor detection periods P11
and P12. Thus, the input high signal VHI is the high level during
the short-circuited resistor detection periods P11 and P12.
[0123] At T31, a sense voltage VCS is not generated due to a
short-circuit of the sense resistor RS. However, since the
short-circuited resistor detection period P12 is terminated and the
input high signal VIH is the low level, a shut-down signal SD,
which is an output of an AND gate 460, is the low level. Therefore,
a short-circuit protection signal SRSP is not triggered.
[0124] From T32, the input sense voltage VIS is higher than the
peak reference voltage VPR and the input high signal VIH is
increased to the high level. Then, all inputs of the AND gate 460
become the high level at a time that an on-time signal TON becomes
the high level (i.e., turn-off time of the power switch), and the
shut-down signal SD is increased to the high level. Thus, the
short-circuit protection signal SRSP is triggered to the high level
at T33, and the protection operation starts. The switching
operation of the power switch SW is stopped by the protection
operation. Then, from T33, no input sense voltage VIS is generated
and no input high voltage VIH is generated.
[0125] However, when the input voltage Vin is detected using the
method shown in FIG. 3, the input sense voltage VIS and the input
high signal VIH may be generated as shown as the dotted line in
FIG. 8.
[0126] FIG. 9 is a waveform diagram illustrating an input sense
voltage, a sense voltage, an input high signal, a peak reference
voltage, and a short-circuit protection signal according to another
exemplary embodiment of the present invention in a case in which a
short-circuit of a sense resistor occurs during a short-circuit
resistor detection period.
[0127] An input sense voltage VIS is generated in a normal state,
and the input sense voltage VIS is higher than a peak reference
voltage VPR during short-circuited resistor detection periods P21
and P22. Thus, an input high signal VIH is the high level during
the short-circuited resistor detection periods P21 and P22.
[0128] At T41, a sense voltage VCS is not generated due to the
short-circuit of the sense resistor RS. Then, after T41, all inputs
of an AND gate 460 become high level at a time that an on-time
signal TON becomes the high level (i.e., a turn-off time of the
power switch), and a shut-down signal SD is increased to the high
level. Then, at T42, a short-circuit protection signal SRSP is
triggered to the high level, and the protection operation starts.
The switching operation of the power switch SW stops by the
protection operation. Then, from T42, no input sense voltage VIS is
generated and no input high signal VIH is generated.
[0129] However, when the input voltage Vin is detected using the
method shown in FIG. 3, the input sense voltage VIS and the input
high signal VIH may be generated as shown as the dotted line in
FIG. 9.
[0130] Hereinafter, a generation process of a short-circuit
protection signal SRSP in the case of occurrence of a short-circuit
will be described with reference to FIG. 10.
[0131] FIG. 10 is a waveform diagram illustrating a sense voltage,
a comparison signal, an on-period signal, an input high signal, a
shut-down signal, and a short-circuit protection signal according
to another exemplary embodiment of the present invention. FIG. 10
partially illustrates a short-circuited resistor detection
period.
[0132] As shown in FIG. 10, at T50, a power switch SW is turned on
and a sense voltage VCS starts to increase. At T51, the increasing
sense voltage VCS reaches a reference voltage VR, and thus a
comparison signal CV becomes the low level. At T52, the power
switch SW is turned off, no sense voltage VCS is generated, and the
comparison signal CV becomes the high level.
[0133] When the turn-off of the power switch SW is determined at
T53, the on-time signal TON is increased to the high level, and
then the on-time signal TON is decreased to the high level at T54.
A predetermined delay may occur between the turn-off determination
time T53 and the turn-off time T52 of the power switch SW. For
example, a transmission delay .DELTA.d may occur between T53 at
which the power switch SW is determined to be turned off in a PWM
controller 200 and T52 at which the power switch SW is turned off
by a low-level gate voltage VG.
[0134] As described, a section during which all inputs of the AND
gate 460 become high level does not occur in a normal state.
[0135] Assume that the sense resistor RS is short-circuited at T55.
Although the power switch SW is turned off, a sense voltage VCS
does not reach a reference voltage VR during a turn-on period P30
as shown in FIG. 10.
[0136] Then, while a comparison signal CV is maintained at the high
level, an on-time signal TON is generated as a high-level pulse
during T56 and T57. At T56, all inputs of the AND gate 460 become
the high level and a shut-down signal SD is increased to the high
level, and when the on-time signal TON is decreased to the low
level at T57, the shut-down signal SD is also decreased to the low
level.
[0137] At T56, a short-circuit protection signal SRSP is increased
to the high level due to an increase of the shut-down signal SD,
and the protection operation is triggered.
[0138] As described, a short-circuit of the sense resistor can be
determined by the above-described exemplary embodiments.
[0139] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
DESCRIPTION OF SYMBOLS
[0140] power supply 1 [0141] rectification circuit 10 [0142]
capacitor C1 [0143] transformer 20 [0144] rectification diode D1
[0145] output capacitor C2 [0146] power switch SW [0147] sense
resistor RS [0148] switch control circuit 30 [0149] sense resistor
short-circuit determiner 100, 300, and 400 [0150] PWM controller
200 [0151] input voltage detector 110 and 410 [0152] blanking
period setting unit 120 and 310 [0153] sense voltage comparator 130
and 450 [0154] AND gate 140 and 460 [0155] signal generator 150 and
470 [0156] auxiliary wire CO3 [0157] peak detector 420 [0158]
multiplier 430 [0159] input comparator 440 [0160] resistor R1, R2,
R3, R4 [0161] primary wire CO1 [0162] secondary wire CO2
* * * * *