CN114153259B - Multichannel constant current source voltage regulating circuit and control method thereof - Google Patents
Multichannel constant current source voltage regulating circuit and control method thereof Download PDFInfo
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Abstract
The invention discloses a multichannel constant current source voltage regulating circuit, which is characterized in that a control unit is additionally arranged on the basis of a multichannel LED lamp string and a traditional driving circuit, and the control unit consists of a multichannel current adapter, a reference source, a self-regulating loop reference voltage and a filterWave capacitor C AVR Error amplifier and compensation network R COMP ‑C COMP The device comprises a comparator, a pulse signal generator, a sawtooth wave generator, a peak current sampling and ramp wave compensator and a trigger; by reducing the effective charge-discharge time Tc in unit time, the filter capacitor C is reduced AVR Is set to the voltage AVR of (a). By applying the voltage regulating circuit and the control method thereof, the voltage drop branch of the largest LED lamp string can be automatically identified, the LED driving voltage is dynamically regulated by generating the reference voltage through the self-regulating loop, and the minimum saturation voltage drop of the constant current circuit is realized; and the self-regulating loop realizes accurate dynamic regulation of reference voltage through current charge and discharge, does not need additional filter capacitance, can realize single chip integration, and reduces system cost and complexity.
Description
Technical Field
The invention relates to a circuit design for controlling a switching power supply, in particular to a multichannel constant current source voltage regulating circuit and a control method thereof, and belongs to the field of integrated circuit design.
Background
With rapid development of smart phones, tablet personal computers, new energy automobiles and the like, LCD panels as main channels for man-machine interaction have been growing in recent years. Previously, the display industry has faced the situation of "lack of core and screen". Today, the yield of liquid crystal panels is increasing, and the problem of shortage of screen panels is rapidly solved along with the rise of display enterprises such as Beijing east, TCL Huaxing, venue, hui Ke, tianma and the like. The downstream panel manufacturing capability is improved to display the upstream ring section such as the driving chip, but the driving chip still mainly takes imported products at present. The data show that only the driving chip of the liquid crystal panel is purchased for more than 60 hundred million yuan in the Beijing Oriental 2020, and the ratio of the domestic chips is less than 5%.
At present, the display drive mainly adopts a multi-chip scheme, the peripheral application is complex, along with the miniaturization and high reliability requirements, the market demands on the display drive chip integrated on a single chip are urgent, and chip design companies at home and abroad are all developing products around the demands.
The multi-channel constant current is a commonly adopted technical scheme for realizing dimming and color mixing, such as 4-channel constant current, 6-channel constant current and the like, and because of the deviation of individual voltage drops of the LED lamp beads, the voltage drop deviation of the LED lamp strings is amplified after the LED lamp beads are cascaded into strings. Although the arrangement of high saturation voltage drop is beneficial to the consistency of the multi-channel constant current, the dissipation power of the multi-channel constant current circuit can be increased, the temperature rise of a chip is increased, and reliability risks exist. Therefore, under the condition of meeting the constant current consistency requirement, the branch with the largest voltage drop of the LED lamp string is usually operated at the lowest saturation voltage drop, and the chip is required to automatically identify the branch with the largest voltage drop of the LED lamp string so as to dynamically adjust the LED driving voltage. However, the voltage drop of the LED string is not a fixed value, and it varies with the switching between multiple channels and the dimming ratio, and a large capacitor is usually applied in the art to filter out the high-frequency signal. In reality, the filter capacitor is often too large in capacitance, so that the filter capacitor cannot be integrated in a common chip. In the circuit design of the voltage regulation of the multi-channel constant current source, the dependence on large capacitance needs to be reduced.
Disclosure of Invention
The invention aims to provide a multichannel constant current source voltage regulation control method and a multichannel constant current source voltage regulation control circuit, which are used for solving the problem that a single chip cannot integrate a capacitor with a high capacitance value, reducing the system cost and simplifying the system application.
The technical solution for achieving the above object of the present invention is as follows: the utility model provides a multichannel constant current source voltage regulating circuit, includes inductance L1, power tube M, sampling resistor RCS, rectifier diode D1, output capacitor COUT, output divider resistance RFB1, RFB2, LED string of lamps LED1~ LEDn, its characterized in that: the voltage regulating circuit is provided with a control unit, and the control unit comprises a multichannel current adapter, a reference source, a self-regulating loop reference voltage and a filter capacitor C AVR Error amplifier and compensation network R COMP -C COMP The multi-channel current adapter is used for switching the current of each LED lamp string and inputting the current into the self-regulating loop reference voltage together with the reference source, and the output of the self-regulating loop reference voltage is opposite to the filter capacitor C AVR The charge and discharge are connected to the positive input end of the error amplifier, the negative input end of the error amplifier is connected to the output voltage dividing signal VFB, and the output VC of the error amplifier is connected to the compensation network R COMP -C COMP And the negative end of the comparator is connected with the sum of the peak current sampling signal VCS and the ramp compensation quantity, wherein the ramp compensation quantity is matched with the output signal proportion of the sawtooth wave generator and is synchronous with the pulse signal generator; the set end of the trigger is connected with the pulse signal generator, the reset end is connected with the output of the comparator, and the state is connected with the G pole of the power tube M.
Further, a reference voltage V is arranged in the multichannel current adapter ILED And n groups of constant current control circuits corresponding to the number of the LED lamp strings, wherein each group of constant current control circuits comprises an operational amplifier OP i Power tube M i Resistance R i Wherein each operational amplifier OP i The output end of the power tube is connected with the power tube M of the group i G pole of (1), each operational amplifier OP i Is connected with the reference voltage V in parallel at the positive electrode input end ILED Positive electrode of each operational amplifier OP i Is connected with the negative electrode input end of the group of power tubes M i And pass through the S pole of the group of resistors R i Parallel connection reference voltage V ILED Is a negative electrode of the power tube M i The D pole of (2) is the constant current I corresponding to the LED lamp string LEDi I is any integer from 1 to n.
Further, the self-adjusting loop reference voltage includes a minimum voltage selection circuit, a transconductance operational amplifier, a narrow pulse width circuit, an inverter, a voltage follower and two switches, wherein the minimum voltage selection circuit is used as an input of the self-adjusting loop reference voltage to connect the current of each LED lamp string, a signal Vmin output by the minimum voltage selection circuit is connected with a negative terminal of the transconductance operational amplifier, a positive terminal of the transconductance operational amplifier is connected with a reference voltage signal VR, an output of the narrow pulse width circuit is connected with the two switches, one switch is controlled to be turned on and the other switch is controlled to be turned off by the inverter, a branch corresponding to one switch is located, and an output of the transconductance operational amplifier is directly filtered by a capacitor C AVR Charging and discharging, corresponding to the branch where the other switch is located, the output of the transconductance operational amplifier is connected with a filter capacitor C through a voltage follower AVR 。
Furthermore, the minimum voltage selection circuit comprises a bias current source Ibias, a current mirror load MN0-MN1, a sampling and holding circuit corresponding to n paths of LED lamp string currents and n+1 PMOS tubes, wherein the bias current source Ibias is connected with the S poles of all the PMOS tubes, the sampling and holding circuit is connected with the G poles of the first n PMOS tubes in a shunt way, the D poles of the first n PMOS tubes are connected with the current mirror load MN0-MN1, and the G poles and the D poles of the rest of the PMOS tubes are commonly connected with the current mirror load MN0-MN1, and the minimum voltage Vmin is output.
The technical solution for achieving the other purpose of the invention is as follows: a multichannel constant current source voltage regulation control method is characterized in that: the common end voltage V1-Vn of each LED lamp string is connected into the self-regulating loop reference voltage through the multichannel current adapter, the minimum value is taken, the differential operation is carried out with the reference source VR, and the output transconductance current is used for the filter capacitor C AVR Charging and discharging are performed to obtain a dynamically changed voltage avr= [ max (V LED1 ,…,V LEDn )+VR]* RFB 2/(RFB1+RFB2), along with filter capacitor C AVR Balance between charge and discharge, voltage AVR is within error range Δavr=i AVR *T C /C AVR Tend to stabilize internally, wherein I AVR To charge and discharge current, T C Is effective charge-discharge time in unit time, C AVR Is the capacitance of the filter capacitor.
Further, by reducing the effective charge-discharge time Tc per unit time, the filter capacitance C is reduced AVR Is set to the voltage AVR of (a).
The voltage regulating circuit and the control method thereof have the substantial characteristics and the improvement that: the scheme can automatically identify the voltage drop branch of the maximum LED lamp string, and dynamically adjust the LED driving voltage by generating reference voltage through a self-adjusting loop, so as to realize the minimum saturation voltage drop of the constant current circuit; and the self-regulating loop realizes accurate dynamic regulation of reference voltage through current charge and discharge, does not need additional filter capacitance, can realize single chip integration, and reduces system cost and complexity.
Drawings
Fig. 1 is a system control schematic diagram of an embodiment of the present invention.
Fig. 2 is a schematic diagram of a multi-channel constant current control in an embodiment of the invention.
FIG. 3 is a schematic diagram of a self-regulating loop reference voltage in accordance with an embodiment of the present invention.
FIG. 4 is a schematic diagram of a self-regulating loop reference voltage waveform according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a multi-channel signal minimum voltage selection circuit according to an embodiment of the invention.
Description of the embodiments
The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings, so that the technical scheme of the present invention is easier to understand and grasp, and the protection scope of the present invention is defined more clearly.
Aiming at a plurality of defects of the existing multi-channel constant current circuit design, the invention innovatively provides a multi-channel constant current source voltage regulating circuit and a control method thereof, which depend on the design experience of an integrated circuit, and realize single-chip integration.
From the technical overview, the main body part of the traditional voltage regulating circuit comprises an inductor L1, a power tube M, a sampling resistor RCS, a rectifying diode D1, an output capacitor COUT, output voltage dividing resistors RFB1 and RFB2 and LED lamp strings LED1-LEDn. As can be seen from the system control schematic diagram shown in fig. 1, the positive electrode of the input power source VIN is connected with the inductor L1 and the rectifying diode D1 in sequence and then connected with each LED lamp string in parallel; the electrode D of the power tube M is connected between the inductor L1 and the positive electrode of the rectifying diode D1, and the electrode S of the power tube M is grounded through the sampling resistor RCS and the negative electrode of the input power supply VIN; one end of the output capacitor COUT is connected with the cathode of the rectifier diode D1, and the other end of the output capacitor COUT is grounded; the output voltage dividing resistor is connected in series, and two ends of the output voltage dividing resistor are connected with the output capacitor COUT in parallel. Based on the main body part of the voltage regulating circuit, the invention adds a control unit as the core of the voltage regulating circuit, and consists of a multi-channel current adapter 111, a reference source 112, a self-regulating loop reference voltage 113 and a filter capacitor C AVR Error amplifier 114, compensation network R COMP -C COMP The multi-channel current converter is respectively connected with currents of the LED strings LED1-LEDn, the common terminals V1-Vn and the output voltage VR of the reference source 112 are input to the self-regulating loop reference voltage 113, the self-regulating loop reference voltage 113 respectively samples and holds the V1-Vn signals, the minimum value of the signals is calculated, and the differential operation is carried out with the reference source 112. Outputting the transconductance current to filter in the reference voltage chipCapacitor C AVR Charge and discharge, the filter capacitor C AVR The voltage AVR is a dynamically varying value. The output of the self-regulating loop reference voltage 113 is connected to the positive input of the error amplifier 114, the negative input of the error amplifier is connected to the output voltage dividing signal VFB (i.e. the voltage between the output voltage dividing resistors RFB1 and RFB 2), and the output VC of the error amplifier is connected to the compensation network R COMP -C COMP And a negative terminal of the comparator 115, the positive terminal of the comparator being connected to the sum of the peak current sampling signal VCS and the ramp compensation amount, wherein the ramp compensation amount is proportional to the output signal of the sawtooth generator 117 and is synchronized with the pulse signal generator 116; the set terminal S (digital circuit port symbol, distinguished from the power tube S pole designation) of the flip-flop 119 is connected to the pulse signal generator, the reset terminal R is connected to the output of the comparator, and the state terminal Q is connected to the G pole of the power tube M.
From the analysis of the working principle and the process, the voltage of V1-Vn is zero at the initial stage of system power-on, the output voltage VR of a Yu Jizhun source 112 is smaller, and the loop reference voltage 113 is self-regulated to the filter capacitor C AVR Charging, wherein the AVR voltage is gradually raised from zero; the feedback signal VFB follows the AVR change and the control output voltage VOUT is also stepped up, which is a soft start process of the system. When the voltage VOUT is larger than the voltage drop of the LED lamp string, the voltages V1-Vn rise from zero, and when the minimum value of the voltages V1-Vn is larger than the reference source 112, the self-adjusting loop reference voltage unit 113 starts to conduct the voltage adjustment on the filter capacitor C AVR Discharging to obtain filter capacitor C AVR Upper dynamically varying voltage avr= [ max (V LED1 ,…,V LEDn )+VR]* RFB 2/(rfb1+rfb2), as filter capacitor C AVR After charge-discharge balance, filter capacitor C AVR The voltage AVR over is stable within a certain error range:
ΔAVR=I AVR *T C /C AVR in the range of error depends on the charge-discharge current I AVR Charge-discharge time and filter capacitor C AVR The capacitance of (2) is larger than the capacitance of (3). Wherein the charge and discharge time is more accurate, namely, the effective charge and discharge time T in unit time C It will be appreciated that, in the multi-channel constant current source voltage regulating circuit system, the filter capacitor C AVR After charge-discharge balance, the smaller the voltage variation of the AVR in unit time is, the more stable the system loop is. Thus, the present invention is directed to by lowering I AVR *T C Coefficients to achieve ten picofarad level C AVR The voltage variation of the AVR under the filter capacitor is hundred microvolts, and the filter capacitor integration is realized.
Fig. 2 is a schematic diagram of multi-channel constant current control according to an embodiment of the present invention, corresponding to the multi-channel current adapter 111 in fig. 1. The LED lamp string voltage control circuit is provided with a reference voltage 210 and n groups of constant current control circuits corresponding to the number of LED lamp strings, wherein the reference voltage 210 outputs V ILED Each group of constant current control circuits comprises an operational amplifier OP i Power tube M i Resistance R i Wherein each operational amplifier OP i The output end of the power tube is connected with the power tube M of the group i G pole of (1), each operational amplifier OP i Is connected with the reference voltage V in parallel at the positive electrode input end ILED Positive electrode of each operational amplifier OP i Is connected with the negative electrode input end of the group of power tubes M i And pass through the S pole of the group of resistors R i Parallel connection reference voltage V ILED Is a negative electrode of the power tube M i The D pole of (2) is the constant current I corresponding to the LED lamp string LEDi I is any integer from 1 to n. As can be seen from the drawing, the constant current control circuit 200 is provided corresponding to the first string LED1, the constant current control circuit 210 is provided corresponding to the nth string LED n, and the remainder thereof is omitted from the drawing. Taking the constant current control circuit 200 as an example, the constant current controlled by the constant current control circuit is I LED1 =V ILED R1; in order to improve the consistency between the constant current circuits, the power tube M1 works in a saturation region, so that the power loss of the constant current circuit is P=I LED1 *V1。
As shown in fig. 3, a self-regulating loop reference voltage schematic diagram of an embodiment of the present invention corresponds to self-regulating loop reference voltage 113 of fig. 1. The LED lamp string comprises a minimum voltage selection circuit 300, a transconductance operational amplifier 301, a narrow pulse width circuit 302, an inverter 303, a voltage follower 304 and two switches 311 and 312, wherein the minimum voltage selection circuit is used as an input of a self-adjusting loop reference voltage to be connected with the current of each LED lamp string, a signal Vmin output by the minimum voltage selection circuit is connected with the negative end of the transconductance operational amplifier, the positive end of the transconductance operational amplifier is connected with a reference voltage signal VR, the output of the narrow pulse width circuit is connected with the two switches, and the two switches are openedThe switch selectively controls one to be turned on and the other to be turned off through an inverter, corresponds to a branch where one switch is positioned, and outputs the transconductance operational amplifier to directly filter the capacitor C AVR Charging and discharging, corresponding to the branch where the other switch is located, the output of the transconductance operational amplifier is connected with a filter capacitor C through a voltage follower AVR 。
In the sense of transconductance operational amplifier 301, when the signal Vmin signal is less than VR, current I AVR Flows out from the transconductance operational amplifier 301; when the signal Vmin signal is greater than VR, current I AVR Then reverse flows into transconductance op-amp 301; when the signal Vmin signal is equal to VR, current I AVR Zero. When the signal SW of the narrow pulse width circuit 302 is at high level, the switches 312 are turned on and 311 are turned off, and the current I AVR To filter capacitor C AVR Charging and discharging; when the signal SW is low, the switch 312 is turned off and 311 is turned on, and the output voltage of the transconductance operational amplifier 301 is controlled to be the filter capacitor C by the voltage follower 304 AVR Thereby avoiding the filter capacitor C when the signal SW is switched between high and low AVR Is a voltage jump of (a).
As already mentioned, the filter capacitor C AVR The minimum variation of the voltage of (2) depends on the charge-discharge current I AVR Is effective in the unit time of charge and discharge time T C And a filter capacitor C AVR For chip integration, the capacitance is usually required to be smaller than the level of hundred picofarads; from the above, when the signal Vmin signal is equal to VR after the system is stable, the charge-discharge current I AVR Zero, thus theoretically filtering capacitance C AVR The minimum voltage variation of (2) is zero. In practice, however, for a feedback system, the signal Vmin is not equal to VR but is close to VR, thus charging and discharging current I AVR Is not zero. To reduce C AVR Minimum change of capacitance voltage, and effective charge-discharge time T in unit time should be reduced as much as possible under the condition of meeting system response speed C . The parameter indicates that only T is present in a unit time C For filter capacitor C in time AVR Charging and discharging are carried out, and the voltage on the battery is kept in other time; for example, the unit time is 10us, and the effective charge and discharge time T C 100nS.
When the system dynamically changes, the difference between the signals Vmin and VR is large, and the charge and discharge current I is high AVR Gm (VR-Vmin) is also larger, filter capacitor C AVR Where gm represents the transconductance of the transconductance op-amp 301, and the system response speed and system stability are compromised by the transconductance of the transconductance op-amp 301.
FIG. 4 is a schematic diagram of a self-regulating loop reference voltage waveform according to an embodiment of the present invention. As can be seen from the graph, ts represents a unit time, and Tc represents an effective charge-discharge time; line 401 represents charge-discharge current I AVR Larger corresponding filter capacitor C AVR The error range 411 of (a) is large; while line 402 represents charge-discharge current I AVR Smaller, corresponding to the filter capacitor C AVR The error range 412 of (2) is also smaller. And the ratio of the visible time Tc to Ts greatly influences the filter capacitance C AVR Is a range of errors.
Fig. 5 is a schematic diagram of a multi-channel signal minimum voltage selection circuit according to an embodiment of the invention. The LED lamp string comprises a bias current source 501 for outputting Ibias, a current mirror load MN0-MN1, sampling and holding circuits 511 and 512 corresponding to n paths of LED lamp string currents and n+1 PMOS tubes MP 0-MPn, wherein the bias current source Ibias is connected with the S poles of all the PMOS tubes, the sampling and holding circuits are connected with the G poles of the first n PMOS tubes in a shunt way, the D poles of the first n PMOS tubes MP 1-MPn are connected with the current mirror load MN0-MN1, and the G poles and the D poles of the rest PMOS tubes MP0 are commonly connected with the current mirror load MN0-MN1. From the aspect of function implementation, the minimum voltage Vmin is output through the G pole of the PMOS transistor MP 0.
In summary, the embodiments of the multi-channel constant current source voltage regulating circuit and the control method thereof of the invention are detailed, and the scheme has substantial characteristics and improvements: the scheme can automatically identify the voltage drop branch of the maximum LED lamp string, and dynamically adjust the LED driving voltage by generating reference voltage through a self-adjusting loop, so as to realize the minimum saturation voltage drop of the constant current circuit; and the self-regulating loop realizes accurate dynamic regulation of reference voltage through current charge and discharge, does not need additional filter capacitance, can realize single chip integration, and reduces system cost and complexity.
In addition to the above embodiments, other embodiments of the present invention are possible, and all technical solutions formed by equivalent substitution or equivalent transformation are within the scope of the present invention as claimed.
Claims (6)
1. The utility model provides a multichannel constant current source voltage regulating circuit, includes inductance L1, power tube M, sampling resistor RCS, rectifier diode D1, output capacitor COUT, output divider resistance RFB1, RFB2, LED string of lamps LED1~ LEDn, its characterized in that: the voltage regulating circuit is provided with a control unit, and the control unit comprises a multichannel current adapter, a reference source, a self-regulating loop reference voltage and a filter capacitor C AVR Error amplifier and compensation network R COMP -C COMP The multi-channel current adapter is used for switching the current of each LED lamp string and inputting the current into the self-regulating loop reference voltage together with the reference source, and the output of the self-regulating loop reference voltage is opposite to the filter capacitor C AVR The charge and discharge are connected to the positive input end of the error amplifier, the negative input end of the error amplifier is connected to the output voltage dividing signal VFB, and the output VC of the error amplifier is connected to the compensation network R COMP -C COMP And the negative end of the comparator is connected with the sum of the peak current sampling signal VCS and the ramp compensation quantity, wherein the ramp compensation quantity is matched with the output signal proportion of the sawtooth wave generator and is synchronous with the pulse signal generator; the set end of the trigger is connected with the pulse signal generator, the reset end is connected with the output of the comparator, and the state is connected with the G pole of the power tube M.
2. The multi-channel constant current source voltage regulating circuit according to claim 1, wherein: the multichannel current adapter is internally provided with a reference voltage V ILED And n groups of constant current control circuits corresponding to the number of the LED lamp strings, wherein each group of constant current control circuits comprises an operational amplifier OP i Power tube M i Resistance R i Wherein each operational amplifier OP i The output end of the power tube is connected with the power tube M of the group i G pole of (1), each operational amplifier OP i Is connected with the reference voltage V in parallel at the positive electrode input end ILED Positive electrode of each operational amplifier OP i Is connected with the negative electrode input end ofThe group of power tubes M i And pass through the S pole of the group of resistors R i Parallel connection reference voltage V ILED Is a negative electrode of the power tube M i The D pole of (2) is the constant current I corresponding to the LED lamp string LEDi I is any integer from 1 to n.
3. The multi-channel constant current source voltage regulating circuit according to claim 1, wherein: the self-regulating loop reference voltage comprises a minimum voltage selection circuit, a transconductance operational amplifier, a narrow pulse width circuit, an inverter, a voltage follower and two switches, wherein the minimum voltage selection circuit is used as the input of the self-regulating loop reference voltage to be connected with the current of each LED lamp string, a signal Vmin output by the minimum voltage selection circuit is connected with the negative end of the transconductance operational amplifier, the positive end of the transconductance operational amplifier is connected with a reference voltage signal VR, the output of the narrow pulse width circuit is connected with the two switches, one switch is controlled to be turned on and the other switch is controlled to be turned off through the inverter, the output of the transconductance operational amplifier is directly connected with a filter capacitor C corresponding to a branch where one switch is located AVR Charging and discharging, corresponding to the branch where the other switch is located, the output of the transconductance operational amplifier is connected with a filter capacitor C through a voltage follower AVR 。
4. The multi-channel constant current source voltage regulating circuit according to claim 3, wherein: the minimum voltage selection circuit comprises a bias current source Ibias, a current mirror load MN0-MN1, a sampling and holding circuit corresponding to n paths of LED lamp string currents and n+1 PMOS tubes, wherein the bias current source Ibias is connected with the S poles of all the PMOS tubes, the sampling and holding circuit is connected with the G poles of the first n PMOS tubes in a shunt way, the D poles of the first n PMOS tubes are connected with the current mirror load MN0-MN1, and the G poles and the D poles of the rest PMOS tubes are commonly connected with the current mirror load MN0-MN1, and the minimum voltage Vmin is output.
5. A multi-channel constant current source voltage regulation control method, based on the implementation of the voltage regulation circuit of any one of claims 1 to 4, characterized in that: the common end voltage V1-Vn of each LED lamp string is connected into the self-regulating loop reference voltage through the multichannel current adapter, and the minimum value is taken and differential operation is carried out with the reference source VR to output transconductance currentTo filter capacitor C AVR Charging and discharging are performed to obtain a dynamically changed voltage avr= [ max (V LED1 ,…,V LEDn )+VR]* RFB 2/(RFB1+RFB2), along with filter capacitor C AVR Balance between charge and discharge, voltage AVR is within error range Δavr=i AVR *T C /C AVR Tend to stabilize internally, wherein I AVR To charge and discharge current, T C Is effective charge-discharge time in unit time, C AVR Is the capacitance of the filter capacitor.
6. The multi-channel constant current source voltage regulation control method according to claim 5, wherein: by reducing the effective charge-discharge time Tc in unit time, the filter capacitor C is reduced AVR Is set to the voltage AVR of (a).
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