U.S. patent application number 15/083921 was filed with the patent office on 2017-06-29 for diode control device.
This patent application is currently assigned to STMicroelectronics (Alps) SAS. The applicant listed for this patent is STMicroelectronics (Alps) SAS. Invention is credited to Patrik Arno.
Application Number | 20170187165 15/083921 |
Document ID | / |
Family ID | 55300711 |
Filed Date | 2017-06-29 |
United States Patent
Application |
20170187165 |
Kind Code |
A1 |
Arno; Patrik |
June 29, 2017 |
DIODE CONTROL DEVICE
Abstract
A diode control device include a first terminal for receiving a
first power supply voltage and a second terminal for receiving a
second power supply voltage. A circuit of the diode control device
applies a regulated voltage on the anode of the diode in response
to a control voltage. The control voltage is equal to a preset
voltage when a reference voltage is less than or equal to zero.
Conversely, when the reference voltage is greater than zero, the
control voltage is equal to the sum of the present voltage and a
difference between cathode voltage of the diode and the reference
voltage.
Inventors: |
Arno; Patrik; (Sassenage,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STMicroelectronics (Alps) SAS |
Grenoble |
|
FR |
|
|
Assignee: |
STMicroelectronics (Alps)
SAS
Grenoble
FR
|
Family ID: |
55300711 |
Appl. No.: |
15/083921 |
Filed: |
March 29, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01S 5/06223 20130101;
H05B 45/38 20200101; H01S 5/06808 20130101; H05B 45/37 20200101;
H01S 5/042 20130101; H01S 5/06812 20130101; H01S 5/0261 20130101;
H05B 45/375 20200101; H05B 45/3725 20200101 |
International
Class: |
H01S 5/062 20060101
H01S005/062; H05B 33/08 20060101 H05B033/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 2015 |
FR |
1563353 |
Claims
1. A device for controlling a diode, comprising: a first terminal
configured to receive a first power supply voltage; a second
terminal configured to receive a second power supply voltage; a
circuit configured to apply a voltage onto a third terminal
configured to be connected to an anode of the diode, said third
terminal being connected to a first input terminal of said circuit;
a second input terminal of said circuit; and a resistor coupled
between said second terminal and a fourth terminal configured to be
coupled to the cathode of said diode, said fourth terminal being
coupled to a third input terminal of the circuit; wherein the
circuit comprises: a converter circuit configured to generate said
voltage applied to the third terminal as a function the signal at
the first input terminal and a control signal; a comparator
configured to compare the signal at the second input terminal to
the signal at the third input terminal to generate an error signal;
and an adder configured to selectively add the error signal to a
preset voltage to generate said control signal for application to
the converter circuit.
2. (canceled)
3. (canceled)
4. The device of claim 1, wherein: if a first voltage of the signal
at the second input of the comparator has a value smaller than or
equal to zero, the circuit applies onto the anode of the diode a
second voltage having a value equal to the preset voltage; and if
said first voltage of the signal at the second input of the
comparator has a positive value, the circuit applies onto the anode
of the diode a voltage having a value equal to the sum of the error
signal and said preset voltage.
5. The device of claim 4, wherein the preset voltage has a positive
value smaller than a conduction threshold of the diode.
6. The device of claim 1, wherein the diode is a laser diode.
7. The device of claim 6, wherein the diode is a light-emitting
diode.
8-9. (canceled)
10. A circuit for controlling a diode having an anode terminal and
a cathode terminal, comprising: a DC-DC converter circuit
configured to generate an anode voltage for direct application to
the anode terminal in response to a control voltage, said anode
voltage being regulated by the DC-DC converter circuit to a voltage
as a function of the control voltage; a comparison circuit
configured to determine a difference between a cathode voltage at
the cathode terminal and a first reference voltage and generate an
error voltage; and an adder configured to add a second reference
voltage to the error voltage to generate the control voltage.
11. The circuit of claim 10, wherein said comparison circuit is
further configured, if the first reference voltage is less than or
equal to a threshold voltage, to generate the error voltage equal
to zero so that the control voltage is equal to the second
reference voltage.
12. The circuit of claim 11, wherein the second reference voltage
is less than a conduction threshold of the diode.
13. The circuit of claim 12, wherein said comparison circuit is
further configured, if the first reference voltage is greater than
the threshold voltage, to generate the error voltage equal to the
difference between the cathode voltage at the cathode terminal and
the first reference voltage.
14. The circuit of claim 10, further comprising a resistor
connected between the cathode terminal and a supply node.
15. The circuit of claim 10, wherein the diode is a laser
diode.
16. The circuit of claim 15, wherein the diode is a light-emitting
diode.
17. The circuit of claim 10, wherein the anode voltage is equal to
the control voltage multiplied by a gain value.
18. A circuit for controlling a diode, comprising: a voltage
generator circuit configured to output an anode voltage to said
diode, said voltage generator circuit including: a first loop
coupled to the diode, said first loop operating to control the
anode voltage to provide a positive voltage across said diode that
is smaller than or equal to a conduction threshold of the diode;
and a second loop coupled to the diode, said second loop operating
to control the anode voltage to provide a positive voltage across
said diode that is greater than the conduction threshold of the
diode; and a control input configured to receive a control voltage
having a first level for enabling the first loop and a second level
for enabling the second loop.
19. The device of claim 18, wherein the first control loop controls
the anode voltage according to a preset voltage.
20. The device of claim 18, further comprising a resistor connected
in series with the diode and configured to generate a sense voltage
in response to a current through the diode.
21. The device of claim 20 wherein: the first level of the control
voltage is less than or equal to the sense voltage; and the second
level of the control voltage is greater than the sense voltage.
22. The device of claim 20, wherein the second loop controls the
current through the diode according to a difference between the
control voltage and the sense voltage.
Description
PRIORITY CLAIM
[0001] This application claims the priority benefit of French
Application for Patent No. 1563353, filed on Dec. 24, 2015, the
contents of which are hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present disclosure generally relates to electronic
circuits and more particularly to devices for controlling the light
intensity of laser or light-emitting diodes.
BACKGROUND
[0003] Devices for controlling the light intensity of laser or
light-emitting diodes generally comprise a current source which
imposes the intensity of the current flowing through the diode
according to the required light intensity.
[0004] Certain systems further comprise a regulation of the voltage
applied across the diode to minimize the voltage drop across the
current source. However, there remains a significant energy loss
due to the current source which is in series with the diode.
[0005] It is thus needed to improve the energy performance of diode
control devices.
SUMMARY
[0006] Thus, an embodiment provides improving the electric power
consumption of devices for controlling the light intensity of laser
or light-emitting diodes.
[0007] More particularly, an embodiment provides a diode control
device comprising: a first terminal of application of a first power
supply voltage; a second terminal of application of a second power
supply voltage; a circuit of application of a voltage onto a third
terminal intended to be connected to an anode of the diode, said
third terminal being connected to a first input terminal of said
circuit; a second input terminal of said circuit; and a resistor
coupled between said second terminal and a fourth terminal intended
to be connected to a cathode of said diode, said fourth terminal
being coupled to a third input terminal of the circuit.
[0008] According to an embodiment, the voltage provided by said
circuit on the third terminal is a function of signals present on
the first, second, and third input terminals of said circuit.
[0009] According to an embodiment, said circuit comprises: a
circuit for generating said voltage on said third terminal,
comprising a first input terminal intended to receive a signal and
a second input terminal connected to said first input terminal of
said circuit; a comparator having a first input connected to said
third input terminal and having a second input connected to said
second input terminal; and an adder having a first input connected
to the output of said comparator and having a second input
connected to a terminal of application of a voltage, the output of
the adder being connected to said first input terminal of the
circuit for generating said voltage.
[0010] According to an embodiment: if a first voltage applied to
the second input of the comparator has a value smaller than or
equal to zero, the voltage generation circuit applies onto the
anode of the diode a second voltage having a value equal to the
voltage applied to said second input terminal of the adder; and if
said first voltage has a positive value, the voltage generation
circuit applies onto the anode of the diode a voltage having a
value equal to the sum of the values of the output voltage of said
comparator and of said second voltage.
[0011] According to an embodiment, the voltage applied onto the
second input terminal of the comparator has a positive value
smaller than the conduction threshold of the diode.
[0012] An embodiment provides a system comprising: a diode control
device; and a diode.
[0013] According to an embodiment, the diode is a laser diode.
[0014] According to an embodiment, the diode is a light-emitting
diode.
[0015] An embodiment provides a diode control method comprising the
steps of: a) applying a first voltage onto an anode of said diode
according to the value of a control voltage; and b) applying onto a
cathode of said diode a second voltage having as a value the
product of the value of the current flowing through the diode and
of the value of a resistor coupled between said cathode of the
diode and the ground.
[0016] According to an embodiment, the setting of the value of said
first voltage comprises the steps of: c) initializing a third
voltage to a positive value smaller than or equal to a conduction
threshold of said diode; d) estimating the value of said control
voltage; e) setting the value of a fourth voltage to the zero value
if the value of said control voltage is smaller than or equal to
zero; f) setting the value of said fourth voltage to a positive
value if the value of the control voltage is positive; g) setting
the value of a fifth voltage to the sum of the values of the fourth
and third voltages; and h) setting the value of the first voltage
to a multiple of the value of said fifth voltage.
[0017] In an embodiment, a circuit for controlling a diode having
an anode terminal and a cathode terminal comprises: a DC-DC
converter circuit configured to generate an anode voltage for
direct application to the anode terminal in response to a control
voltage, said anode voltage being regulated by the DC-DC converter
circuit to substantially equal the control voltage; a comparison
circuit configured to determine a difference between a cathode
voltage at the cathode terminal and a first reference voltage and
generate an error voltage; and an adder configured to add a second
reference voltage to the error voltage to generate the control
voltage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The foregoing and other features and advantages will be
discussed in detail in the following non-limiting description of
specific embodiments in connection with the accompanying drawings,
wherein:
[0019] FIG. 1 shows a device for controlling the light intensity of
a laser diode or of a light-emitting diode;
[0020] FIG. 2 shows a device for controlling the light intensity of
a laser diode or of a light-emitting diode; FIG. 3 shows a device
for controlling the light intensity of a laser diode or of a
light-emitting diode;
[0021] FIG. 4 is a circuit of the control device of FIG. 3; and
[0022] FIG. 5 illustrates a method of controlling the light
intensity of a laser diode or of a light-emitting diode.
DETAILED DESCRIPTION
[0023] The same elements have been designated with the same
reference numerals in the different drawings. For clarity, only
those elements which are useful to the understanding of the
described embodiments have been shown and are detailed. In
particular, the functions of the boost DC/DC converters have not
been detailed, the described embodiments being compatible with
usual converters.
[0024] Unless otherwise specified, expressions "approximately",
"substantially", and "in the order of" mean to within 10%,
preferably to within 5%.
[0025] FIG. 1 shows a device for controlling the light intensity of
a diode. The device comprises a buck-boost DC/DC converter 101, a
diode 102, an NMOS transistor 103, and a resistor 104, connected in
series between a first terminal 106 of application of a power
supply voltage VCC and a ground connection terminal 108. The gate
of transistor 103 is coupled to the output of a differential
amplifier 105 operating as a comparator, having its inverting input
coupled to the source of transistor 103 and to the terminal of
resistor 104 which is not grounded. The non-inverting input of
comparator 105 is connected to a terminal 107 of application of a
control voltage VCOM'.
[0026] Transistor 103 operates as a voltage-controlled current
source by application of the output voltage of comparator 105 on
its gate. The current which flows through the transistor is
converted into a voltage at the level of its source due to resistor
104. This voltage is then compared with control voltage VCOM'. The
output voltage of comparator 105 is adjusted according to the
result of the comparison.
[0027] Further, to keep diode 102 conductive, converter 101 imposes
a voltage on its anode, so that the voltage across the diode is
greater than the conduction threshold of the diode. The function of
converter 101 is to maintain (regulate) the voltage independent of
possible fluctuations of the power supply voltage.
[0028] A disadvantage of this device is the electric power
consumption.
[0029] A first cause of electric power consumption is that the
target voltage applied by converter 101 onto the anode of diode 102
is decorrelated from the current regulation. This target voltage
regulated by converter 101 is defined according to the type of
diode used. However, it is necessary to provide a margin to make
sure that the voltage applied across diode 102 is sufficient to
keep it conductive independently from manufacturing tolerances and
from the operating conditions of the device, for example,
temperature variations. This margin results in an additional power
consumption at the level of DC/DC converter 101.
[0030] A second cause of electric power consumption is the presence
of the current source (transistor 103) in series with diode
102.
[0031] FIG. 2 shows a device for controlling the light intensity of
a diode.
[0032] As compared with the device of FIG. 1, the device of FIG. 2
comprises a current driver circuit 203 for controlling the current
in the diode which replaces the assembly formed of differential
amplifier 105, of transistor 103, and of resistor 104 of FIG. 1.
The current driver circuit 203 is on the one hand coupled between
the cathode of diode 102 and the terminal of application of ground
108, and on the other hand connected to buck-boost DC/DC converter
101. The current driver circuit 203 further comprises a terminal
207 of application of a control voltage VCOM'.
[0033] Circuit 203 imposes a current in diode 102 via an internal
current source 203' according to control voltage VCOM'. The
difference with the device of FIG. 1 is that a feedback loop which
exists between circuit 203 and converter 101 enables to ensure the
application of a minimum voltage across diode 102 to keep it
conductive independently from manufacturing tolerances and from the
operating conditions. Such a device thus enables to do away with
the necessary margin provided in the case of the device of FIG. 1.
This results in an improvement of the electric power consumption
due to converter 101. However, current source 203', present in
control circuit 203 in series with diode 102, remains a significant
source of energy loss.
[0034] According to the embodiments described hereafter, it is
provided to do away with the current source in series with the
diode.
[0035] FIG. 3 shows a device for controlling the light intensity of
a laser diode or of a light-emitting diode.
[0036] The device comprises a diode 102 and a resistor 104
connected in series between an output terminal 306 of a circuit 301
of application of a voltage VANODE on the anode of the diode, and a
ground connection terminal 108. Circuit 301 further comprises an
input terminal 310 coupled to the cathode of diode 102, an input
terminal 308 coupled to the anode of diode 102, an input terminal
307 having a control voltage VCOM applied thereto, and a terminal
106 for application of a power supply voltage VCC. Circuit 301
itself comprises a DC/DC converter which is not detailed
herein.
[0037] Circuit 301 imposes voltage VANODE on the anode of diode 102
to control the current flowing therethrough according to set point
VCOM. This voltage applied onto the anode of the diode is regulated
by two feedback loops.
[0038] Where set point VCOM has a value smaller than or equal to
zero, in a first loop which couples the anode of diode 102 to
terminal 308 of circuit 301, circuit 301 provides across the diode
a positive voltage VPRESET smaller than or equal to the conduction
threshold of the diode.
[0039] When set point VCOM has a positive value, in a second loop
which couples the cathode of diode 102 to terminal 310 of circuit
301, circuit 301 compares the voltage applied across resistor 104
with the control set point and accordingly adjusts the voltage
applied on the anode of the diode to a value greater than voltage
VPRESET. The value of the voltage applied across resistor 104 is
obtained by the product of value R of resistor 104 and of the value
of current I flowing through the diode, to within the error of the
current sampled by input terminal 310. The error may be zero
according to the nature of the input stage connected to terminal
310. This second loop thus controls the current flowing through
diode 102 according to a voltage VCOM.
[0040] A device for controlling the light intensity of a laser or
light-emitting diode which uses no current source in series with
the diode has thus been formed, which enables to improve power
consumption.
[0041] FIG. 4 shows the circuit 301 of application of voltage
VANODE of FIG. 3.
[0042] Circuit 301 comprises a buck boost DC-DC converter circuit
421 for generating voltage VANODE at the anode of diode 102
comprising an input terminal 401 receiving a signal VCTRL and
another input terminal 308 configured to be connected to the anode
of the diode. Circuit 301 further comprises, between terminal 310
(connected with terminal 311) configured to be connected to the
cathode of diode 102 and input terminal 401 of circuit 421, a
comparator 422. An input terminal 405 of comparator 422 is
connected to terminal 310 for application of a voltage VSENSE from
the cathode of the diode. Another input terminal 404 of the
comparator is connected to terminal 307 for application of control
voltage VCOM. Circuit 301 further comprises an adder 423, having an
input terminal 403 connected to the output of comparator 422 (to
receive the voltage VERROR), and having another input terminal 402
connected to a terminal for application of a second control voltage
VPRESET. The output of adder 423 is connected to input terminal 401
of circuit 421. Further, as in the case of FIG. 3, the forming of
the DC/DC converter comprised in circuit 421 is not detailed, such
circuits being well known to those skilled in the art.
[0043] FIG. 5 shows steps of a method describing the operation of
the device of FIG. 4.
[0044] At step S1, voltage VPRESET applied to input terminal 402 of
adder 423 is initialized to a positive value smaller than or equal
to the conduction threshold (VTHRESHOLD) of diode 102. At step S2,
the voltage VCOM applied to terminal 307 (input terminal 404 of
comparator 422) is compared to a threshold. If the voltage value is
smaller than or equal to zero (output Y of block S2), the voltage
VERROR of comparator 422 takes the value zero at step S3. If not
(output N of block S2), the output voltage VERROR of comparator 422
takes as a value, at step S4, greater than zero and equal to the
product of the voltage gain value of comparator 422 by the value of
the difference between voltage VCOM and voltage VSENSE. In an
embodiment comprising a positive power supply terminal VCC and a
ground terminal, voltage VERROR will be positive. At step S5,
output voltage VCTRL of adder 423 takes as a value the sum of
voltages VPRESET and VERROR. At step S6, circuit 421 applies onto
the anode of the diode the voltage VANODE according to the value of
voltage VCTRL. This function is the product by gain Gv between
output terminal 306 of circuit 421 and input terminal VCTRL. Thus,
VANODE=Gv.times.VCTRL. Gain Gv is greater than or equal to 1
according to the needs of the application. This results, at step
S7, in the application of voltage VANODE on the anode of the diode
and, at step S8, in the application of voltage VSENSE on the
cathode of the diode having a value equal to the product of value R
of resistor 104 and of current I flowing through the diode. It is
then returned to step S2 for the processing of a new voltage value
VCOM.
[0045] A device and a method for controlling the light intensity of
a laser or light-emitting diode which uses no current source in
series with the diode have thus been formed, which enables to gain
power consumption. It should be noted that the method of FIG. 5
also applies to the operation of the device described in FIG.
3.
[0046] Specific embodiments have been described. Various
alterations, modifications, and improvements will occur to those
skilled in the art. In particular, the value of voltage VPRESET
will be for example determined according to the constraints of
activation or deactivation of the diode or to any other constraint
associated with the system. Further, those skilled in the art will
select the structure of the DC/DC converter according, for example,
to the type of diode, to the power supply type, or to any other
constraint associated with the needs of the targeted application.
The embodiments have been described by referring to a positive
power supply voltage and to ground. They easily transpose to other
choices of pairs of power supply voltages, including negative.
[0047] Such alterations, modifications, and improvements are
intended to be part of this disclosure, and are intended to be
within the spirit and the scope of the present invention.
Accordingly, the foregoing description is by way of example only
and is not intended to be limiting. The present invention is
limited only as defined in the following claims and the equivalents
thereto.
* * * * *