U.S. patent application number 13/776811 was filed with the patent office on 2013-06-27 for charge pump feedback control device and method using the same.
This patent application is currently assigned to REALTEK SEMICONDUCTOR CORP.. The applicant listed for this patent is Realtek Semiconductor Corp.. Invention is credited to Cheng-Pang Chan.
Application Number | 20130162229 13/776811 |
Document ID | / |
Family ID | 47055587 |
Filed Date | 2013-06-27 |
United States Patent
Application |
20130162229 |
Kind Code |
A1 |
Chan; Cheng-Pang |
June 27, 2013 |
CHARGE PUMP FEEDBACK CONTROL DEVICE AND METHOD USING THE SAME
Abstract
Charge pump feedback control device and method are provided. The
device is coupled to the charge pump unit which receives an input
voltage so as to generate an output voltage and has switches and at
least one capacitor, the device includes: a compensation unit, a
modulation unit, and a phase control unit. The compensation unit
receives the output voltage, compensates the output voltage for
stability, and generates an error signal. The modulation unit
receives the error signal, modulates the error signal, and
correspondingly generates a modulation signal. The phase control
unit receives the modulation signal so as to generate phase signal,
and controls the plurality of switches of the charge pump unit
according to the plurality of phase signal so as to generate the
output voltage through the input voltage charging/discharging at
least one capacitor of the charge pump unit.
Inventors: |
Chan; Cheng-Pang; (HsinChu,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Realtek Semiconductor Corp.; |
Hsinchu |
|
TW |
|
|
Assignee: |
REALTEK SEMICONDUCTOR CORP.
Hsinchu
TW
|
Family ID: |
47055587 |
Appl. No.: |
13/776811 |
Filed: |
February 26, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13457052 |
Apr 26, 2012 |
|
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13776811 |
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Current U.S.
Class: |
323/268 |
Current CPC
Class: |
H02M 3/07 20130101; H02M
1/14 20130101; H02M 2003/077 20130101 |
Class at
Publication: |
323/268 |
International
Class: |
G05F 1/625 20060101
G05F001/625 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2011 |
TW |
100114623 |
Claims
1. A charge pump feedback control device, coupled to a charge pump
unit which receives an input voltage so as to generate an output
voltage and has a plurality of switches and at least one capacitor,
the device comprising: a comparator, coupled to the charge pump
unit, wherein an output end of the comparator is coupled to at
least one capacitor and generates a comparative signal after
comparing the output voltage and a reference voltage; and a
modulation unit, coupled to the comparator, receiving the error
signal, modulating the error signal, and correspondingly generating
a modulation signal of pulse skipping modulation; and a phase
control unit, coupled to the modulation unit, receiving the
modulation signal so as to generate a plurality of phase signal,
controlling the plurality of switches of the charge pump unit
according to the plurality of phase signal so as to generate the
output voltage through the input voltage charging/discharging the
at least one capacitor of the charge pump unit.
2. The charge pump feedback control device according to claim 1,
further comprising: a voltage divider, coupled between the charge
pump unit and the comparator, receiving the output voltage
generated from the charge pump unit, and dividing the output
voltage for the comparator.
3. The charge pump feedback control device according to claim 1,
wherein the modulation unit is a voltage controlled oscillator
(VCO), coupled to the compensation unit for receiving the error
signal, and generates the modulation signal using pulse frequency
modulation according to the error signal.
4. The charge pump feedback control device according to claim 3,
wherein the compensation unit comprises: an oscillator, used for
generating an oscillation frequency; and a switch, coupled to the
comparator and the oscillator, wherein the oscillation signal being
pass when the comparative signal is at a high voltage level, and
the oscillation signal being cut off when the comparative signal is
at low voltage level so as to generate the modulation signal of
pulse skipping modulation.
5. A method for feedback control of charge pump, comprising:
controlling an input voltage to charge/discharge at least one
capacitor for generating an output voltage according to a plurality
of phase signal; comparing a voltage level of the output voltage to
generate an comparative signal; generating a modulation signal by
skipping the output voltage according to the comparative signal;
and generating the plurality of phase signal according to the
modulation signal.
6. The method for feedback control of charge pump according to
claim 5, further comprising: dividing the output voltage.
7. The method for feedback control of charge pump according to
claim 6, wherein the modulation signal is a pulse skipping
modulation signal.
8. The method for feedback control of charge pump according to
claim 7, wherein the pulse skipping modulation is performed by a
switch controlled by a voltage level of the comparative signal, the
modulation signal being pass when the comparative signal is at a
high voltage level, and the modulation signal being cut off when
the comparative signal is at low voltage level.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a Divisional of co-pending patent
application Ser. No. 13/457,052, filed Apr. 26, 2012, which claims
the benefit of Taiwan application Serial No. 100114623, filed Apr.
27, 2011, the subject matter of which is incorporated herein by
reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The disclosure relates to a charge pump, and more
particularly, to a charge pump feedback control device and
method.
[0004] 2. Related Art
[0005] Recently, portable electronics products have flourished in a
variety of fields, and power management issues have arisen as a
consequence. Due to the limited electric power of the portable
electronics products, the power management IC has become a key
component for managing power consumption effectively. A power
management IC transforms a voltage of the battery into the
different operation voltages of the sub-circuits of the portable
electronics product, such as transforming 3.3V to 1.2V, or 3.3V to
2.5V, etc. The design rules for the power management IC's voltage
transformation are high efficiency, high precision, low noise, and
small volume. Generally speaking, there are three kinds of voltage
transformer inside the power management IC: switching regulator,
linear regulator, and charge pump regulator, of which the charge
pump has advantages of smaller volume and lower design cost than
the switching regulator and linear regulator.
[0006] A charge pump regulator has a capacitor array core, which is
a circuit designed using several switches and capacitors. By
controlling the switches to be opened/closed to change the
connection relationship of the capacitors, the capacitors are
charged or discharged by the connection and the power is
transferred as different voltages. Generally, charge pumps are
separated into open loop and close loop control schemas.
[0007] Usually, a conventional charge pump adopts the open loop
schema. Please refer to FIG. 1A, in which the conventional charge
pump includes: charge pump unit 50 and controller 60. Please also
refer to FIG. 1B, in which the charge pump unit 50 includes a first
switch S1, a second switch S2, a third switch S3, a fourth switch
S4, a capacitor C1, where the controller 60 generates several phase
control signal for the charge pump unit 50, please refer to FIG.
1C. The controller 60 generates a first phase for the charge pump
unit 50 to close the switches S1 and S2, then the input voltage Vi
charges capacitors C0 and C1, please refer to FIG. 1D. Please refer
to FIG. 1E, in which controller 60 generates a second phase for the
charge pump unit 50 to close switches S3 and S4, then the capacitor
C1 discharges the resistor RL and capacitor C0. The ratio of the
output voltage Vo and the input voltage V1 is derived thus:
Q 1 - = ( Vi - Vo ) * C 1 F .1 Q 1 + = Vo * C 1 F .2 Q 1 - - Q 1 +
= I * T I = Vo RL , and T = 1 fs , for F .3 ( Vi - Vo - Vo ) * C 1
= Vo RL * 1 fs , F .3 ##EQU00001##
then, F.4 is acquired as below:
V o V i = C 1 2 C 1 + 1 R L f s F .4 ##EQU00002##
[0008] From the derivation of F.4, the relationship of the output
voltage Vo and the input voltage Vi of the charge pump unit 50 are
related with a switching frequency fs and a load RL. When RL is
fixed, a gain of the output voltage Vo and the input voltage Vi is
related with the switching frequency fs and the capacitance of the
capacitor C1 according to F.4. Due to the open loop schema of the
conventional charge pump regulator, when the switching frequency fs
is fixed, the gain of the output voltage Vo divide input voltage Vi
changes following the impedance of the resistor RL changes. That
is, Vo=gain*Vi; when the output voltage Vo changes following the
gain changes, the ripple voltage variation becomes too large. For
this reason, the charge pump under open loop schema is only
suitable for a fixed load, the output voltage Vo changes following
the load changes.
[0009] Therefore, two problems typically happen when using the
conventional charge pump under an open loop schema in which the
switching frequency fs is fixed.
[0010] Firstly, when the switching frequency fs is fixed, if the
impedance of the load RL became small, the load current becomes
large and the output voltage Vo becomes small when derived by F.4.
If the situation continues without control, the output voltage
becomes too small to disable the connected circuit.
[0011] Secondly, when the switching frequency fs is fixed, if the
impedance of the load RL became large, the load current becomes
small and the output voltage Vo becomes large when derived by F.4.
If the situation continues without control, the output voltage
becomes too large to damage the connected components of the
circuit.
[0012] Furthermore, the close loop schema charge pump design is
developed to resolve the problems of open loop schema. The close
loop schema charge pump has a comparative circuit to be used as a
feedback control for the switching of the charge pump. Furthermore,
the close loop schema charge pump adopts a feedback circuit to
compare a reference voltage to generate at least one clock signal
according to an input voltage. The clock signal controls switching
of the charge pump to charge/discharge at least one capacitor for
boosting or bucking the output voltage. The output voltage is then
stable, and includes less ripple signal.
[0013] Another conventional charge pump under close loop schema is
using a voltage controlled oscillator (VCO) or current controlled
oscillator (CCO) to achieve close loop control. Through detecting
the variation of the load voltage or current of the output end
according to a detection and control circuit, and generating at
least one clock signal by VCO or CCO to control switching of the
charge pump to charge/discharge at least one capacitor for boosting
or bucking the output voltage, the output voltage is stable and
includes less ripple signal.
[0014] However, the conventional close loop schema charge pump also
has several problems.
[0015] Firstly, if the conventional charge pump uses the close loop
schema and the load changes, the charge pump is not able to adjust
the output voltage instantly with precision.
[0016] Secondly, if the conventional charge pump uses the close
loop schema and adopts a comparator for comparing the output
voltage and a reference voltage to generate a feedback control
signal, the feedback control signal is used to generate at least
one clock signal for switching the charge pump. Such a comparator
type schema results in an unstable system.
SUMMARY
[0017] A charge pump feedback control device is, coupled to a
charge pump unit which receives an input voltage so as to generate
an output voltage and has switches and at least one capacitor, the
device includes: a compensation unit, a modulation unit, and a
phase control unit. The compensation unit is coupled to the charge
pump unit, receiving the output voltage, compensating the output
voltage for stability, and generating an error signal. The
modulation unit is coupled to the compensation unit, receives the
error signal, modulates the error signal, and correspondingly
generates a modulation signal. The phase control unit is coupled to
the modulation unit, receives the modulation signal so as to
generate phase signal, and controls the plurality of switches of
the charge pump unit according to the plurality of phase signal so
as to generate the output voltage through the input voltage
charging/discharging at least one capacitor of the charge pump
unit.
[0018] A charge pump feedback control method, includes: controlling
an input voltage to charge/discharge at least one capacitor for
generating an output voltage according to phase signal;
compensating the output voltage to generate an error signal;
modulating the error signal to generate a modulation signal; and
generating the plurality of phase signals according to the
modulation signal.
[0019] A charge pump feedback control device, coupled to a charge
pump unit which receives an input voltage so as to generate an
output voltage and has switches and at least one capacitor, the
device includes: a comparator, a modulation unit, and a phase
control unit. The comparator is coupled to the charge pump unit,
wherein an output end of the comparator is coupled to the at least
one capacitor and generates a comparative signal after comparing
the output voltage and a reference voltage. The modulation unit is
coupled to the comparator, receives the error signal, modulates the
error signal, and correspondingly generates a modulation signal of
pulse skipping modulation. The phase control unit is coupled to the
modulation unit, receives the modulation signal so as to generate
phase signal, and controls the plurality of switches of the charge
pump unit according to the plurality of phase signal so as to
generate the output voltage through the input voltage
charging/discharging the at least one capacitor of the charge pump
unit.
[0020] A charge pump feedback control method, includes: controlling
an input voltage to charge/discharge at least one capacitor for
generating an output voltage according to phase signal; comparing a
voltage level of the output voltage to generate an comparative
signal; generating a modulation signal through skipping the output
voltage according to the comparative signal; and generating the
plurality of phase signal according to the modulation signal.
[0021] In order to make these and other objectives, features and
advantages of the disclosure comprehensible, preferred embodiments
accompanied with figures are described in detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The disclosure will become more fully understood from the
detailed description given herein below for illustration only, and
thus not limitative of the present invention, wherein:
[0023] FIG. 1A is a functional block diagram of a conventional
charge pump regulator;
[0024] FIG. 1B is a circuit diagram of a conventional charge pump
regulator;
[0025] FIG. 1C is a timing diagram of a controller of the
conventional charge pump regulator;
[0026] FIG. 1D is a charging circuit diagram of a conventional
charge pump regulator;
[0027] FIG. 1E is a discharging circuit diagram of a conventional
charge pump regulator;
[0028] FIG. 2A is a exemplified functional block diagram of the
embodiment of the disclosed charge pump feedback control
device;
[0029] FIG. 2B is the other exemplified functional block diagram of
the embodiment of the disclosed charge pump feedback control
device;
[0030] FIG. 3A is the first detailed functional block diagram of
the embodiment of the disclosed charge pump feedback control device
according to FIG. 2B;
[0031] FIG. 3B is a voltage-frequency diagram of the VCO of the
first example of the embodiment of the disclosed charge pump
feedback control device according to FIG. 3A;
[0032] FIG. 3C is a first frequency timing diagram of a phase
control unit of the first example of the embodiment of the
disclosed charge pump feedback control device according to FIG.
3A;
[0033] FIG. 3D is a second frequency timing diagram of a phase
control unit of the first example of the embodiment of the
disclosed charge pump feedback control device according to FIG.
3A;
[0034] FIG. 4A is the second detailed functional block diagram of
the embodiment of the disclosed charge pump feedback control device
according to FIG. 2B;
[0035] FIG. 4B is a first phase control timing diagram of the
second example of the embodiment of the disclosed charge pump
feedback control device according to FIG. 4A;
[0036] FIG. 4C is a second phase control timing diagram of the
second example of the embodiment of the disclosed charge pump
feedback control device according to FIG. 4A;
[0037] FIG. 4D is a third phase control timing diagram of the
second example of the embodiment of the disclosed charge pump
feedback control device according to FIG. 4A;
[0038] FIG. 5A is the third detailed functional block diagram of
the embodiment of the disclosed charge pump feedback control device
according to FIG. 2B;
[0039] FIG. 5B is a boosting timing diagram of the third example of
the embodiment of the disclosed charge pump feedback control device
according to FIG. 5A;
[0040] FIG. 5C is a bucking timing diagram of the third example of
the embodiment of the disclosed charge pump feedback control device
according to FIG. 5A;
[0041] FIG. 5D is a boosting gain/phase control timing diagram of
the third example of the embodiment of the disclosed charge pump
feedback control device according to FIG. 5A;
[0042] FIG. 5E is a bucking gain/phase control timing diagram of
the third example of the embodiment of the disclosed charge pump
feedback control device according to FIG. 5A;
[0043] FIG. 5F is a common phase control timing diagram of the
third example of the embodiment of the disclosed charge pump
feedback control device according to FIG. 5A;
[0044] FIG. 6A is the exemplified flow chart of the embodiment of
the disclosed method for feedback control of charge pump; and
[0045] FIG. 6B is the other exemplified flow chart of the
embodiment of the disclosed method for feedback control of charge
pump.
DETAILED DESCRIPTION
[0046] The disclosure is to setup a device and method for feedback
control of a charge pump unit in a charge pump regulator. By
adapting an output voltage of the charge pump unit through feedback
control, the charge pump regulator has better output voltage and a
wider dynamic range of load capacity (Ex. 1 mA.about.100 mA). The
disclosure compensates the charge pump regulator through a
compensation unit, so that the output voltage of the charge pump
regulator is stabilized with lower noise. The device also generates
a modulation signal through signal modulations such as pulse
frequency modulation (PFM) or pulse skipping modulation (PSM), and
outputs multiple phase signals to control different charge pump
architectures according to the modulation signal.
[0047] Please refer to FIG. 2A, in which the charge pump feedback
control device 100 includes: a charge pump unit 50, a voltage
divider 110, a compensation unit 120, a modulation unit 130, and a
phase control unit 140. The compensation unit 120 is coupled to the
charge pump unit 50, and receiving the output voltage, compensating
the output voltage for stability, and generating an error signal.
The modulation unit 130 is coupled to the compensation unit 120,
receiving the error signal, modulating the error signal, and
correspondingly generating a modulation signal. The phase control
unit 140 is coupled to the modulation unit 130, receiving the
modulation signal so as to generate multiple phase signal,
controlling the plurality of switches of the charge pump unit 50
according to the plurality of phase signal in order to generate the
output voltage through the input voltage charging/discharging the
at least one capacitor of the charge pump unit.
[0048] Please refer to FIG. 2B, in which a voltage divider 110 is
coupled between the charge pump unit 50 and the compensation unit
120. The voltage divider 100 receives the output voltage generated
from the charge pump unit 50, and dividing the output voltage for
the compensation unit 120 through a first resistor and a second
resistor.
[0049] The charge pump unit 50 is composited by a first switch S1,
a second switch S2, a third switch S3, a fourth switch S4, and
capacitor C1, Please refer to FIG. 1B. The phase control unit 140
controls the charge pump unit 50 by generating a multiple phase
control signal. That is, phase control unit 140 generates a first
phase to close the switches S1 and S2, the input voltage Vi then
charges capacitors C0 and C1, Please refer to FIG. 1C. Next, the
phase control unit 140 generates a second phase to close the
switches S3 and S4, and the capacitor C1 then discharges to the
load RL.
[0050] In the open loop system, the output voltage of the charge
pump unit is unstable due to the variation of the load and the
interference of high frequency noise. When the output voltage level
is not stable, it is easier for the connected circuit to be damaged
or to burn out. Due to the instability of the open loop schema, the
disclosure uses close loop control to stabilize the output
variation and exclude the effects of either noise interference or
load variation. Furthermore, the disclosed compensation unit adopts
a stabilizing method of a control system to compensate the charge
pump regulator into a stable state. Consequently, the output
voltage of the disclosed charge pump is able to generate the output
voltage with a rapid speed and low ripple output voltage level.
Generally, the stability method of a control system uses Bod plot
with phase margin (PM) or gain margin (GM), or a Nyquist plot.
[0051] The modulation unit 130 of the charge pump feedback control
device 100 further adopts a modulation signal to output at least
one phase signal. The modulation signal is pulse frequency
modulation (PFM) or pulse skipping modulation (PSM).
[0052] The phase control unit 140 is composed using multiple
combinational logics, and used for synthesizing the modulation
signal to the plurality of phase signal. Generally, the charge pump
unit 50 composition is several capacitors and switches, which is
designed according to boosting or bucking The charge pump unit 50
switches according to the phase signal to charge/discharge the
capacitors for boosting or bucking the output voltage.
[0053] Please refer to FIG. 3A, in which an exemplified diagram of
PFM for the disclosed charge pump feedback control device. The
compensation unit 120 includes: a third resistor R3 (equivalent
resistor), and differential amplifier 122. The differential
amplifier 122 couples the voltage divider 110 and the third
resistor R3. The positive input end of the amplifier 122 is coupled
to the reference voltage Vref, and receives the divided voltage at
the second resistor R2 to generate an error signal through
stability compensation. The modulation unit 130 is a voltage
controlled oscillator (VCO), which is coupled to the differential
amplifier 122 for receiving the error signal, and generates the
modulation signal using pulse frequency modulation (PFM) according
to a voltage level of the error signal.
[0054] When input voltage Vi is equal to 3.3V and output voltage Vo
is equal to 1.2V, the voltage divider 100 receives 1.2V from the
output voltage and divides 1.2V by the first resistor R1 and the
second resistor R2. The output voltage Verror1 of the differential
amplifier 122 is calculated by Formula 5.
Vref - Verror R 3 + Vref R 1 + Vref - Vo R 2 = 0 F .5
##EQU00003##
[0055] The F.5 derives
Verror = ( 1 R 1 + 1 R 1 + 1 R 3 ) * Vref * R 3 - R 3 R 2 * Vo .
##EQU00004##
[0056] When the load current increases, the impedance of the load
decreases correspondently, the output voltage Vo decreases, then
the error signal Verror increases derived by F.5. Conversely, when
the load current decreases, the impedance of the load increases
correspondently, the output voltage Vo increases, then the error
signal Verror decreases derived by F.5.
[0057] Please refer to FIG. 3A, in which the modulation unit 130 is
a voltage-controlled oscillator (VCO) 132. The voltage-controlled
oscillator 132 generates different frequencies according to the
different voltage level of the compensation signal from the
compensation unit 120.
[0058] Please refer to FIG. 3B, in which the X axis is voltage
level of the error signal Error, and the Y axis is the output
frequency of the voltage controlled oscillator 132. The voltage
level of the error signal V1 corresponds to the frequency f1 of the
modulation signal, Please refer to FIG. 3C, in which the voltage
level of the error signal V2 corresponds to the frequency f2 of the
modulation signal, Please refer to FIG. 3D, in which when the
voltage level of the error signal is lower, the correspondent
frequency f1 of the modulation signal is slower; conversely, when
the voltage level of the error signal is higher, the correspondent
frequency f1 of the modulation signal is faster.
[0059] In the following paragraphs, the disclosure explains two
examples of load variation under the PFM system.
EXAMPLE 1
[0060] When the load current increases, the impedance of the load
decreases correspondingly, and the output voltage Vo decreases. To
sustain a stable output voltage, a voltage level of the error
signal generated by sampling, dividing, and stability compensating
the output voltage increases, which derives the output frequency of
the voltage controlled oscillator 132 faster. For example, after
the phase control unit 140 receives the output frequency is f2, it
then uses the combinational logic to synthesize several phase
signals, each of which has a different phase. Please refer to FIG.
3D, in which the phase signal f2 generated by the voltage
controlled oscillator 13 is outputted to the phase control unit
140, a first phase signal phase 1 and a second phase signal phase 2
are generated for the charge pump unit 50. The first phase signal
phase 1 and the second phase signal phase 2 are different in phase,
and not synchronized. The first phase signal phase 1 controls the
capacitor C1 of the charge pump unit 50 charged, and the second
phase signal phase 2 controls the capacitor C1 discharging to the
capacitor C0 and the load RL. From F.4, when the impedance of the
load RL decreases, to sustain the gain ratio of the output voltage
and the input voltage of the charge pump unit 50, adjusting the
switching frequency fs of modulation signal to a higher level makes
the output voltage more stable, and reduces the ripple of the
output voltage at the same time.
EXAMPLE 2
[0061] When the load current decreases, the impedance of the load
increases correspondingly, and the output voltage Vo increases. To
sustain a stable output voltage, a voltage level of the error
signal generated by sampling, dividing, and stability compensating
the output voltage decreases, which derives the output frequency of
the voltage controlled oscillator 132 slower. For example, after
the phase control unit 140 receives the output frequency is f2 then
uses the combinational logic to synthesize as several phase
signals, each of which has a different phase. Please refer to FIG.
3C, in which the phase signal f2 generated by the voltage
controlled oscillator 13 is outputted to the phase control unit
140, a first phase signal phase 1 and a second phase signal phase 2
are generated for the charge pump unit 50. The first phase signal
phase 1 and the second phase signal phase 2 are different in phase
and not synchronized. The first phase signal phase 1 controls the
capacitor C1 of the charge pump unit 50 charged, and the second
phase signal phase 2 controls the capacitor C1 discharging to the
capacitor C0 and the load RL. From F.4, when the impedance of the
load RL increases, to sustain the gain ratio of the output voltage
and the input voltage of the charge pump unit 50, adjusting the
switching frequency fs of modulation signal to a lower level makes
the output voltage more stable, and reduces the ripple of the
output voltage at the same time.
[0062] Please note that the error signal generated by the
compensation unit 120 is a voltage signal, and the modulation unit
130 is a voltage controlled oscillator (VCO). The modulation signal
corresponding to the VCO is a pulse frequency modulation (PFM)
signal. However, in the other embodiment, the error signal
generated by the compensation unit 120 is a current signal, and the
modulation unit 130 is a current controlled oscillator (CCO). The
CCO receives a current signal and generates a modulation signal
correspondently, which is also a PFM signal.
[0063] Please refer to FIG. 4A, which is a diagram different from
FIG. 3A in modulation schema; that is, the embodiment depicted in
FIG. 4A adopts a pulse skipping modulation (PSM) to control the
charge pump unit 50. The compensation unit 120 in FIG. 4A includes:
a comparator 124. The comparator 124 is coupled to the charge pump
unit 50. The modulation unit 130 includes: an oscillator 160 and a
switch 170. The oscillator 160 generates an oscillation frequency.
The switch 170 is coupled to the comparator 124 and the oscillator
160. The oscillation signal generated by the oscillator 160 passes
when the comparative signal is at a high voltage level, and cuts
off when the comparative signal is at low voltage level so as to
generate the modulation signal of PSM.
[0064] Please refer to FIG. 4B., in which when the voltage divider
110 receives the output voltage generated by the charge pump unit
50, a dividing voltage is generated by the voltage divider 110 and
outputted to be compared with a reference voltage by the comparator
124. Please refer to FIG. 4B, in which when the dividing voltage is
smaller than the reference voltage, the comparator 124 generates an
output signal comp as high voltage level. Conversely, the
comparator 124 generates the output signal comp as low voltage
level when the dividing voltage is higher than the reference
voltage. The switch bypasses the frequency generated by the
oscillator 160 when the output signal generated by the comparator
124 is at a high voltage level; the switching frequency fs of
modulation signal is therefore generated, which is a PSM signal. In
this case, the value of the square wave of the switching frequency
fs of modulation signal is 2 during the output signal comp is at a
high voltage level. The phase control unit 140 receives the
switching frequency fs of modulation signal to generate a first
phase signal phase1 and a second phase signal phase2. The first
phase signal phase1 controls the input voltage Vi charging the
capacitor C1 of the charge pump unit 50. Conversely, the second
phase signal phase2 control the capacitor C1 discharging to the
capacitor C0 and the load RL.
[0065] Two load variation examples are illustrated in the following
paragraphs for a PSM modulation system.
EXAMPLE 1
[0066] When the load current increases, the impedance of the load
decreases correspondingly, and the dividing voltage decreases
following the output voltage Vo decreases. Therefore, when the
dividing voltage is lower than the reference voltage, the output
signal comp of the comparator 124 is set as high voltage level. The
time interval of the high voltage level of the output signal comp
in FIG. 4C is longer than that in FIG. 4B, and the value of the
square wave of the switching frequency fs of modulation signal is 3
during the output signal comp is at a high voltage level, which is
more than that in FIG. 4B. The phase control unit 140 receives the
phase and frequency of the switching frequency fs of modulation
signal and synthesizes as at least one phase signal through a
combinational logic. Each of the at least one phase signal is
independent. Please refer to FIG. 4C, in which the phase control
unit 140 utilizes the phase signal of the switching frequency fs of
modulation signal to generate a first phase signal phase1 and a
second phase signal phase2. The charge/discharge speeds of the
charge pump unit 50 increases due to receiving a greater value of
square wave of the first phase signal phase1 and the second phase
signal phase2. From F.4, to sustain the gain ratio of the output
voltage and the input voltage of the charge pump unit 50, it is
clear that when the load RL changes, increasing the amount of the
square wave of the switching frequency fs of modulation signal is
necessary for the stability of the output voltage.
EXAMPLE 2
[0067] When the load current decreases, the impedance of the load
increases correspondingly, and the dividing voltage increases
following the output voltage Vo increases. Therefore, when the
dividing voltage is greater than the reference voltage, the output
signal comp of the comparator 124 is set at a low voltage level.
The time interval of the high voltage level of the output signal
comp in FIG. 4D is shorter than that in FIG. 4B, and the value of
the square wave of the switching frequency fs of modulation signal
is 1 while the output signal comp is at a high voltage level, which
is less than the one in FIG. 4B. The phase control unit 140
receives the phase and frequency of the switching frequency fs of
modulation signal and synthesizes as at least one phase signal
through a combinational logic. Each of the at least one phase
signal is independent. Please refer to FIG. 4D, in which the phase
control unit 140 utilizes the phase signal of the switching
frequency fs of modulation signal to generate a first phase signal
phase1 and a second phase signal phase2. The charge/discharge
speeds of the charge pump unit 50 increases due to receiving a
lower value of square wave of the first phase signal phase1 and the
second phase signal phase2. From F.4, to sustain the gain ratio of
the output voltage and the input voltage of the charge pump unit
50, it is clear that when the load RL changes, reducing the value
of the square wave of the switching frequency fs of modulation
signal is necessary for the stability of the output voltage.
[0068] Please note that the compensation unit 120 compensates the
charge pump regulator to improve the relative stability of the
whole system. The system becomes stable rather than unstable, or
more stable than the original system. The compensation circuit is
used for PFM schema rather for the PSM schema, because the PSM
schema uses the comparator mechanism. The compensation unit 120 is
not limited by the examples in FIG. 3A and FIG. 4A; any other
architectures improving the close loop stability is also able to be
used for the disclosure.
[0069] Please refer to FIG. 5A, in which the phase control unit 140
receives the switching frequency fs of modulation signal and
adjusts the switch in FIG. 5A according to the output voltage to
boost or buck the output voltage for a constant voltage level.
[0070] Please refer to FIG. 5A, in which the charge pump unit 50
has 3 capacitors and 19 switches. By controlling the 19 switches,
the capacitors are charged or discharging to derive a gain ratio of
the output voltage and the input voltage. The gain ratios of the
schema are the multiple of 2, 1, 1/2, 3/2, 2/3, 4/3, 3/4.
[0071] Following are two examples descriptive of the embodiment in
FIG. 5A, which perform boosting/bucking of the output voltage to
3.3V.
EXAMPLE 1
Boosting.
[0072] When the input voltage is 1.65V, the charge pump unit 50
boosts the output voltage to 3.3V. The output voltage of the charge
pump unit 50 is set as 2 times of the input voltage. Please refer
to FIG. 5B, in which in the phase timing diagram, the phase control
unit 140 receives the switching frequency fs of modulation signal,
and outputs the phase signals Ps7, Ps10, Ps12, Ps15, and Ps16 to
control the switches S7, S10, S12, S15, and S16 of the charge pump
unit 50. This is called a gain phase control mode, in which the
input voltage Vi charges the capacitors C2 and C3. If the output
phase signals are Ps2, Ps3, Ps4, Ps5, Ps6, and Ps9, the switches
S2, S3, S4, S5, S6, and S9 of the charge pump unit 50 are closed.
This is called a common phase control mode, in which the capacitors
C1, C2, and C3 discharge to the capacitor C0.
[0073] Please refer to the following derivations.
[0074] Please refer to FIG. 5D, in which is a gain phase control
mode, the voltage level of the capacitor C2 is Vc2, the voltage
level of the capacitor C3 is Vc3, and Vc2=Vc3=Vi.
[0075] Please refer to FIG. 5F, in which is a common phase control
mode, Vo=Vc3+Vi, due to Vc3 is equal to Vi, Vo=2*Vi, Vo/Vi=gain=2.
Therefore, when the input voltage Vi is equal to 1.65V, the output
voltage Vo=2*1.65=3.3V.
EXAMPLE 2
Bucking
[0076] When the input voltage is 4.4V, the charge pump unit 50
bucks the output voltage to 3.3V. The output voltage of the charge
pump unit 50 is set to 3/4 of the input voltage. Please refer to
FIG. 5C, in which in a phase timing diagram, the phase control unit
140 receives the switching frequency fs of modulation signal, and
outputs the phase signals Ps8, Ps11, Ps10, and Ps13 to control the
switches S8, S11, S10, and S13 of the charge pump unit 50. This is
called a gain phase control mode, in which the capacitors C1, C2
and C3 discharge to the output voltage Vo. If the output phase
signals are Ps2, Ps3, Ps4, Ps5, Ps6, and Ps9, the switches S2, S3,
S4, S5, S6, and S9 of the charge pump unit 50 are closed. This is
called a common phase control mode, in which the capacitors C1, C2,
and C3 discharge to the capacitor C0.
[0077] Please refer to the following derivations.
[0078] Please refer to FIG. 5D, in which in a gain phase control
mode, the voltage level of the capacitor C2 is Vc2, the voltage
level of the capacitor C3 is Vc3, and Vc1=Vc2=Vc3=1/3Vo.
[0079] Please refer to FIG. 5F, in which in a common phase control
mode, Vo=Vc1+Vi=-1/3Vo+Vi, due to Vo+1/3Vo=Vin, Vo=3/4*Vi,
Vo/Vi=gain=3/4. Therefore, when the input voltage Vi is equal to
4.4V, the output voltage Vo=3/4*4.4=3.3V.
[0080] Please note that the disclosure improves the load adaptive
rate and linear adaptive rate of the charge pump regulator.
Usually, the output voltage changes correspondently when the load
changes. Through the modulation signal generated by the feedback
control, the disclosure decreases the ripple voltage of the output
voltage and gains a better output current range (Ex. 1 mA.about.100
mA). Therefore, in the situation of voltage variation, .DELTA.Vo is
lower than ever, and the current variation .DELTA.Io is greater
than ever; the disclosure is therefore able to gain a better load
adaptive rate. Even if the input voltage changes over time, the
charge pump regulator adopting the disclosure is able to sustain a
stable output voltage.
[0081] Please refer to FIG. 6A, in which in the exemplified flow
chart of the method for feedback control of charge pump in the
disclosure, the steps are as follows:
[0082] In Step 501: Controlling an input voltage to
charge/discharge at least one capacitor for generating an output
voltage according to multiple phase signals.
[0083] In Step 502: Compensating the output voltage to generate an
error signal.
[0084] In Step 503: Modulating the error signal to generate a
modulation signal.
[0085] In Step 504: Generating the plurality of phase signal
according to the modulation signal.
[0086] The modulation signal is a pulse frequency modulation
signal, which utilizes a voltage controlled oscillator to modulate
the input voltage according to the error signal. The error signal
is an analog signal. The stability is gained by continuously
adjusting the oscillation frequencies.
[0087] Please refer to FIG. 6B, in which is another exemplified
flow chart of the method for feedback control of charge pump in the
disclosure, the steps of which are as follows:
[0088] In Step 511: Controlling an input voltage to
charge/discharge at least one capacitor to generate an output
voltage according to multiple phase signals.
[0089] In Step 512: Comparing a voltage level of the output voltage
to generate an comparative signal.
[0090] In Step 513: Generating a modulation signal through skipping
the output voltage according to the comparative signal.
[0091] In Step 514: Generating the plurality of phase signals
according to the modulation signal.
[0092] The modulation signal is a pulse skipping modulation signal,
which is performed by a switch controlled by a voltage level of the
comparative signal, the modulation signal being sent when the
comparative signal is at a high voltage level, and the modulation
signal being cut off when the comparative signal is at low voltage
level.
[0093] Please note that, in comparison with the conventional charge
pump regulator, the disclosure improves the load adaptive rate and
linear adaptive rate of the charge pump regulator. Furthermore, the
closed loop control design of the disclosure has a more stable
output voltage and lower ripple. Additionally, the disclosure uses
a compensation unit to improve the stability of the charge pump
feedback control device, resulting in a faster system response.
Practically, the disclosure improves the stability issue of the
conventional schema, and the ripple range of the output voltage.
The disclosure utilizes a modulation unit and modulation method to
generate multiple phase signals to control the plurality of
switches and at least one capacitor of the charge pump unit, the
capacitor then being charged or discharged to generate the output
voltage. The detail of boosting or bucking the charge pump and the
schema of the charge pump is easily understood by those skilled in
the art, and has therefore not been illustrated in the
disclosure.
[0094] While the present invention has been described by the way of
example and in terms of the preferred embodiments, it is to be
understood that the invention need not be limited to the disclosed
embodiments. On the contrary, it is intended to cover various
modifications and similar arrangements included within the spirit
and scope of the appended claims, the scope of which should be
accorded the broadest interpretation so as to encompass all such
modifications and similar structures.
* * * * *