CN114153259A - 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 PDF

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CN114153259A
CN114153259A CN202111428501.6A CN202111428501A CN114153259A CN 114153259 A CN114153259 A CN 114153259A CN 202111428501 A CN202111428501 A CN 202111428501A CN 114153259 A CN114153259 A CN 114153259A
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CN114153259B (en
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陈捷
徐建华
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Suzhou Hongxin Integrated Circuit Co ltd
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Suzhou Hongxin Integrated Circuit Co ltd
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
    • G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices

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Abstract

The invention discloses a multichannel constant-current source voltage regulating circuit.A control unit is additionally arranged on the basis of a plurality of LED lamp strings and a traditional drive circuit, and consists of a multichannel current adapter, a reference source, a self-regulating loop reference voltage and a filter capacitor CAVRError amplifier, compensation network RCOMP‑CCOMPThe pulse generator is connected with the comparator, the pulse signal generator is connected with the sawtooth wave generator, and the sawtooth wave generator is connected with the peak current sampling and ramp wave compensator; by reducing the effective charging and discharging time Tc in unit time, the filter capacitor C is reducedAVRVoltage AVR of (1). By applying the voltage regulating circuit and the control method thereof, the largest LED lamp string voltage drop branch can be automatically identified, and the LED driving voltage is dynamically regulated by generating the reference voltage through the self-regulating loop, so that the smallest saturation voltage drop of the constant current circuit is realized; and the self-regulation loop realizes accurate dynamic regulation of reference voltage through current charging and discharging, does not need extra filter capacitor, can realize single-chip integration, and reduces system cost and complexity.

Description

Multichannel constant-current source voltage regulating circuit and control method thereof
Technical Field
The invention relates to a circuit design controlled by a switching power supply, in particular to a multichannel constant-current source voltage regulating circuit and a control method thereof, belonging to the field of integrated circuit design.
Background
With the rapid development of smart phones, tablet computers, new energy vehicles and the like, LCD panels serving as main channels of human-computer interaction have been increased explosively in recent years. Earlier, the display industry had been faced with a "lack of cores and screens". Nowadays, the yield of the liquid crystal panel is increased day by day, and the problem of screen panel shortage is solved with the rise of display enterprises such as oriental, TCL huaxing, weixinuo, huike and Tianma. The improvement of the manufacturing capability of the downstream panel brings important opportunities for upstream ring segments such as display driving chips, however, the driving chips are still mainly imported products at present. Data show that in 2020 of Jingdong, only the drive chip of the liquid crystal panel is purchased by more than 60 billion elements, and the proportion of the domestic chip in the drive chip is less than 5%.
At present, a multi-chip scheme is mainly used for display driving, peripheral application is complex, the demand of a market on a single-chip integrated display driving chip is urgent along with the requirements of miniaturization and high reliability, and chip design companies at home and abroad carry out product development around the demand.
The multichannel constant current is a commonly used technical scheme for realizing dimming and color mixing, for example, 4-channel constant current, 6-channel constant current and the like, because individual voltage drops of LED lamp beads have deviation, after a plurality of LED lamp beads are cascaded into a string, the voltage drop deviation of LED lamp strings is amplified, and in order to realize multichannel constant current consistency, a multichannel constant current circuit is usually adopted to work in a saturation region to eliminate the voltage drop deviation of each LED lamp string, which means that the saturation voltage drops of the multichannel constant current circuits are different. Although the setting of high saturation voltage drop is beneficial to the consistency of 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 the reliability risk exists. Therefore, under the condition of meeting the requirement of constant current consistency, the branch circuit with the largest voltage drop of the LED lamp string usually works at the lowest saturation voltage drop, and the chip is required to automatically identify the branch circuit with the largest voltage drop of the LED lamp string so as to dynamically adjust the LED driving voltage. However, the LED string voltage drop is not a fixed value, and it varies with the switching between multiple channels and the dimming ratio, and a large capacitor is usually added in the art to filter out the high frequency signal. In reality, the filter capacitor cannot be integrated in a common chip because the capacitance value of the filter capacitor is required to be too large. In the circuit design of the multichannel constant current source voltage regulation, 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 high-capacitance-value capacitor, reducing the system cost and simplifying the system application.
The technical solution of the present invention for achieving the above object is: the utility model provides a multichannel constant current source voltage regulator circuit, includes inductance L1, power tube M, sampling resistor RCS, rectifier diode D1, output capacitance COUT, output divider resistance RFB1, RFB2, LED lamp cluster LED1~ LEDn, its characterized in that: the voltage regulating circuit is provided with a control unit which consists of a multi-channel current adapter, a reference source, a self-regulating loop reference voltage and a filter capacitor CAVRError amplifier, compensation network RCOMP-CCOMPThe multi-channel current adapter is used for switching the current of each LED lamp string and inputting the current into a self-regulating loop reference voltage together with a reference source, and the output of the self-regulating loop reference voltage is coupled with a filter capacitor CAVRCharging and discharging and connecting with the positive input end of the error amplifier, the negative input end of the error amplifier is connected with the output voltage division signal VFB, and the output VC of the error amplifier is connected with the compensation network RCOMP-CCOMPThe positive 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 in proportion adaptation to the output signal of the sawtooth 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 end is connected with the G pole of the power tube M.
Furthermore, a reference voltage V is arranged in the multi-channel current adapterILEDAnd n groups of constant current control circuits corresponding to the number of the LED lamp strings, wherein each group of constant current control circuit comprises an operational amplifier (OP)iPower tube MiResistance RiWherein each operational amplifier OPiThe output end of the power tube M is connected with the group of power tubesiG pole of (1), each operational amplifier OPiThe anode input end of the transformer is connected with a reference voltage V in parallelILEDPositive electrode of (2), each operational amplifier OPiThe negative input end of the power tube M is connected with the group of power tubesiAnd through the resistor R of the groupiThe parallel line is connected with a reference voltage VILEDNegative electrode of (2), power tube MiD pole is a constant current I corresponding to the LED lamp stringLEDiI is 1 to nAny integer of (a).
Furthermore, the reference voltage of the self-adjusting loop 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 reference voltage of the self-adjusting loop and 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 through the inverter and selectively controls one of the two switches to be on and off, and the output of the transconductance operational amplifier directly filters a capacitor C corresponding to a branch where one of the switches is locatedAVRCharging and discharging, wherein the output of the transconductance operational amplifier is connected with a filter capacitor C through a voltage follower corresponding to the branch where the other switch is locatedAVR。
Furthermore, the minimum voltage selection circuit comprises a bias current source Ibias, current mirror loads MN0-MN1, a sample hold circuit corresponding to n paths of LED lamp string currents and n +1 PMOS tubes, wherein the bias current source Ibias is connected with S poles of all the PMOS tubes, the sample hold circuit is connected with G poles of the first n PMOS tubes in a shunt mode, D poles of the first n PMOS tubes are connected with the current mirror loads MN0-MN1, and the G poles and the D poles of the rest PMOS tubes are connected with the current mirror loads MN0-MN1 in a common mode and output the minimum voltage Vmin.
The technical solution of the invention for achieving the other purpose is as follows: a multi-channel constant current source voltage regulation control method is realized based on the voltage regulation circuit of any one of claims 1 to 4, and is characterized in that: the common end voltage V1-Vn of each LED lamp string is connected into the reference voltage of the self-regulating loop through the multi-channel current adapter, the minimum value is taken and is subjected to differential operation with the reference source VR, and transconductance current is output to the filter capacitor CAVRCharging and discharging are carried out, and a dynamically changing voltage AVR = [ max (V)LED1,…,VLEDn)+VR]RFB2/(RFB1+ RFB2), along with filter capacitor CAVRCharge and discharge balance, voltage AVR within error range delta AVR = IAVR*TC/CAVRIn an internal tendency to be stable, wherein IAVRFor charging and discharging current, TCIs the effective charge-discharge time per unit time, CAVRIs the capacitance value of the filter capacitor.
Furthermore, the effective charging and discharging time Tc in unit time is reduced, so that the filter capacitor C is reducedAVRVoltage AVR of (1).
The voltage regulating circuit and the control method thereof have the following substantial characteristics and progresses: the scheme can automatically identify the largest LED lamp string voltage drop branch circuit, dynamically adjust the LED driving voltage by generating the reference voltage through the self-adjusting loop, and realize the smallest saturation voltage drop of the constant current circuit; and the self-regulation loop realizes accurate dynamic regulation of reference voltage through current charging and discharging, does not need extra filter capacitor, can realize single-chip integration, and reduces system cost and complexity.
Drawings
FIG. 1 is a system control schematic of an embodiment of the present invention.
Fig. 2 is a schematic diagram of a multi-channel constant current control according to an embodiment of the present invention.
FIG. 3 is a schematic diagram of a self-regulating loop reference voltage of an embodiment of the present invention.
FIG. 4 is a schematic diagram of a self-regulating loop reference voltage waveform of an embodiment of the present invention.
Fig. 5 is a schematic diagram of a multi-path signal minimum voltage selection circuit according to an embodiment of the present invention.
Detailed Description
The following detailed description of the embodiments of the present invention is provided in connection with the accompanying drawings for the purpose of understanding and controlling the technical solutions of the present invention, so as to define the protection scope of the present invention more clearly.
The invention provides a multi-channel constant current source voltage regulating circuit and a control method thereof, which are innovated by designers aiming at various defects of the design of the existing multi-channel constant current circuit and relying on the design experience of an integrated circuit, thereby realizing single-chip integration.
From the technical overview, the main body of the conventional voltage regulating circuit includes an inductor L1, a power tube M, a sampling resistor RCS, a rectifier diode D1, an output capacitor COUT, output voltage dividing resistors RFB1 and RFB2, and LED strings LED 1-LEDn. As can be seen from the system control schematic diagram shown in fig. 1, the positive electrode of the input power VIN is connected to the inductor L1 and the rectifying diode D1 in sequence and then connected to each otherAll the LED lamp strings are connected; the D pole of the power tube M is connected between the inductor L1 and the anode of the rectifier diode D1, and the S pole of the power tube M is grounded through the sampling resistor RCS and the cathode of the input power 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 in parallel with the output capacitor COUT. Based on the main part of the voltage regulating circuit, the invention adds a control unit as the core of the voltage regulating circuit, which comprises a multi-channel current adapter 111, a reference source 112, a self-regulating loop reference voltage 113 and a filter capacitor CAVRError amplifier 114, compensation network RCOMP-CCOMPThe multi-channel current adapter is respectively connected with the currents of the LED lamp strings LED1-LEDn, common ends V1-Vn and the output voltage VR of the reference source 112 are input into the self-regulating loop reference voltage 113, and the self-regulating loop reference voltage 113 respectively samples and holds the V1-Vn signals, calculates the minimum value of the signals and carries out difference operation with the reference source 112. Then outputs the transconductance current to the filter capacitor C in the reference voltage chipAVRCharging and discharging, the filter capacitor CAVRThe voltage AVR on is a dynamically changing value. The output of the self-regulating loop reference voltage 113 is connected to the positive input terminal of the error amplifier 114, the negative input terminal of the error amplifier is connected to the output voltage division signal VFB (i.e. the voltage between the output voltage division resistors RFB1 and RFB2), and the output VC of the error amplifier is connected to the compensation network RCOMP-CCOMPAnd the negative terminal of the comparator 115, the positive terminal 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 adapted to the output signal proportion of the sawtooth generator 117 and is synchronous with the pulse signal generator 116; the flip-flop 119 has a set terminal S (a digital circuit port symbol, different from the power transistor S polar name) connected to the pulse signal generator, a reset terminal R connected to the output of the comparator, and a state terminal Q connected to the G pole of the power transistor M.
From the analysis of the working principle and the process, at the initial stage of system power-on, the voltage of V1-Vn is zero and is less than the output voltage VR of the reference source 112, and the filtering is performed by the reference voltage 113 of the self-regulating loopCapacitor CAVRCharging, wherein the AVR voltage is gradually raised from zero; the feedback signal VFB follows the AVR and controls the output voltage VOUT to gradually rise, which is a system soft start process. When the VOUT voltage is greater than the voltage drop of the LED string, the V1-Vn voltage rises from zero, and when the minimum value of the V1-Vn voltage is greater than the reference source 112, the self-regulation loop reference voltage unit 113 starts to couple the filter capacitor CAVRDischarging to obtain a filter capacitor CAVRUpper dynamically changing voltage AVR = [ max (V)LED1,…,VLEDn)+VR]RFB2/(RFB1+ RFB2) as filter capacitor CAVRAfter the charge and discharge balance, the filter capacitor CAVRThe voltage AVR above is stable within a certain error range:
ΔAVR=IAVR*TC/CAVRwithin the error range, the error range depends on the magnitude of the charging and discharging current IAVRCharging and discharging time and filter capacitor CAVRThe magnitude of the capacitance. Wherein the charging and discharging time is more accurate, the effective charging and discharging time T in unit timeCIt is understood that for the multichannel constant current source voltage regulating circuit system, the filter capacitor C is arranged on the filter capacitor CAVRAfter the charge and discharge balance is carried out, the smaller the voltage variation of the AVR in unit time is, the more stable the system loop is. Therefore, the present invention is directed to reducing IAVR*TCCoefficient to achieve C of ten picofarads levelAVRThe voltage variation of the AVR under the filter capacitor is hundreds of microvolts, and the integration of the filter capacitor is realized.
Fig. 2 is a schematic diagram of a multi-channel constant current control according to an embodiment of the present invention, which corresponds to the multi-channel current adapter 111 in fig. 1. It is provided with a reference voltage 210 and n groups of constant current control circuits corresponding to the number of the LED lamp strings, wherein the reference voltage 210 outputs VILEDEach group of constant current control circuit comprises an operational amplifier OPiPower tube MiResistance RiWherein each operational amplifier OPiThe output end of the power tube M is connected with the group of power tubesiG pole of (1), each operational amplifier OPiThe anode input end of the transformer is connected with a reference voltage V in parallelILEDPositive electrode of (2), each operational amplifier OPiThe negative input end of the power tube M is connected with the group of power tubesiAnd through the resistor R of the groupiThe parallel line is connected with a reference voltage VILEDIs negativeElectrode, power tube MiD pole is a constant current I corresponding to the LED lamp stringLEDiAnd i is any integer from 1 to n. As can be seen, the constant current control circuit 200 is provided corresponding to the first string LEDs 1, the constant current control circuit 210 is provided corresponding to the nth string LEDs LEDn, and the rest is omitted. Taking the constant current control circuit 200 as an example, the constant current controlled by the constant current control circuit is ILED1=VILED/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 = ILED1*V1。
Fig. 3 is a schematic diagram of a self-regulating loop reference voltage according to an embodiment of the invention, corresponding to the self-regulating loop reference voltage 113 of fig. 1. The LED string light current regulation circuit 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 the input of a reference voltage of a self-regulation loop and connected with the current of each LED string light, 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 through the inverter and controls one of the two switches to be on and the other to be off, and the output of the transconductance operational amplifier directly filters a capacitor C corresponding to a branch where one of the switches is locatedAVRCharging and discharging, wherein the output of the transconductance operational amplifier is connected with the filter capacitor C through the voltage follower corresponding to the branch where the other switch is positionedAVR。
In view of the transconductance operational amplifier 301, when the signal Vmin is smaller than VR, the current I isAVRFlows out of transconductance operational amplifier 301; when the signal Vmin is greater than VR, the current IAVRThen the current flows back into the transconductance operational amplifier 301; when the signal Vmin is equal to VR, the current IAVRIs zero. When the signal SW of the narrow pulse width circuit 302 is at a high level, the switches 312 are turned on and 311 are turned off, and the current I is flowingAVRTo filter capacitor CAVRCharging and discharging; when the signal SW is at a low level, the switch 312 is turned off, the switch 311 is turned on, and the voltage follower 304 controls the output voltage of the transconductance amplifier 301 to be at the filter capacitor CAVRSo as to avoid the filtering capacitor C when the signal SW signal is switched between high and lowAVRVoltage jump.
As mentioned above, the filter capacitor CAVRIs dependent on the charging and discharging current IAVRMagnitude of (d), effective charging and discharging time T per unit timeCAnd a filter capacitor CAVRThe capacity value of (a) is generally required to be less than the hundred picofarad level in order to realize chip integration; from the above, when the Vmin signal is equal to VR after the system is stable, the charging/discharging current I is measuredAVRIs zero, so that the filter capacitance C is theoreticallyAVRHas a minimum variation of zero. In practice, however, for a feedback system, the signal Vmin is not equal to VR, but close to VR, so the charge-discharge current IAVRIs not zero. To reduce CAVRThe minimum variation of the capacitor voltage is to reduce the effective charging and discharging time T in unit time as much as possible under the condition of meeting the response speed of the systemC. The parameter indicates that only T is in the unit timeCTime-to-filter capacitor CAVRCharging and discharging are carried out, and the voltage on the capacitor is kept in other time; for example, the unit time is 10us, and the effective charging and discharging time TCIs 100 nS.
When the system is dynamically changed, the difference between the Vmin signal and the VR signal is large, and the charging and discharging current I is largeAVR= gm (VR-Vmin) is also large, and the filter capacitance CAVRThe voltage variation amount of (2) is large, and response speed is facilitated, wherein gm represents the transconductance amount of the transconductance operational amplifier 301, and the system response speed and the system stability are compromised by the transconductance amount of the transconductance operational amplifier 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, Ts represents unit time, and Tc represents effective charge and discharge time; line 401 represents the charging and discharging current IAVRLarge, corresponding filter capacitance CAVRThe error range 411 of (a) is large; and line 402 represents the charging and discharging current IAVRSmaller, then corresponding to the filter capacitor CAVRThe error range 412 of (a) is also small. And the ratio of the visible time Tc to Ts greatly influences the filter capacitance CAVRThe error range of (2).
Fig. 5 is a schematic diagram of a multi-channel signal minimum voltage selection circuit according to an embodiment of the present invention. The LED lamp string current sampling circuit 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 S poles of all PMOS tubes, the sampling and holding circuits are connected with G poles of the first n PMOS tubes in a shunt mode, D poles of the first n PMOS tubes MP 1-MPn are connected with the current mirror load MN0-MN1, and the G pole and the D pole of the rest PMOS tube MP0 are connected with the current mirror load MN0-MN 1. In terms of functional implementation, the minimum voltage Vmin is output through the G pole of the PMOS transistor MP 0.
In summary, the detailed description of the embodiments of the multi-channel constant current source voltage regulating circuit and the control method thereof of the present invention can be seen, and the scheme has the substantial characteristics and the progressiveness: the scheme can automatically identify the largest LED lamp string voltage drop branch circuit, dynamically adjust the LED driving voltage by generating the reference voltage through the self-adjusting loop, and realize the smallest saturation voltage drop of the constant current circuit; and the self-regulation loop realizes accurate dynamic regulation of reference voltage through current charging and discharging, does not need extra filter capacitor, can realize single-chip integration, and reduces system cost and complexity.
In addition to the above embodiments, the present invention may have other embodiments, and any technical solutions formed by equivalent substitutions or equivalent transformations are within the scope of the present invention as claimed.

Claims (6)

1. The utility model provides a multichannel constant current source voltage regulator circuit, includes inductance L1, power tube M, sampling resistor RCS, rectifier diode D1, output capacitance COUT, output divider resistance RFB1, RFB2, LED lamp cluster LED1~ LEDn, its characterized in that: the voltage regulating circuit is provided with a control unit which consists of a multi-channel current adapter, a reference source, a self-regulating loop reference voltage and a filter capacitor CAVRError amplifier, compensation network RCOMP-CCOMPThe multi-channel current adapter is used for switching the current of each LED lamp string and inputting the current into a self-regulating loop reference voltage together with a reference source, and the output of the self-regulating loop reference voltage is coupled with a filter capacitor CAVRCharging and discharging, and connecting to positive input terminal of error amplifier and negative input terminal of error amplifierThe input end of the pole is connected with the output voltage division signal VFB, and the output VC of the error amplifier is connected with the compensation network RCOMP-CCOMPThe positive 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 in proportion adaptation to the output signal of the sawtooth 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 end is connected with the G pole of the power tube M.
2. The multi-channel constant current source voltage regulating circuit of claim 1, wherein: a reference voltage V is arranged in the multi-channel current adapterILEDAnd n groups of constant current control circuits corresponding to the number of the LED lamp strings, wherein each group of constant current control circuit comprises an operational amplifier (OP)iPower tube MiResistance RiWherein each operational amplifier OPiThe output end of the power tube M is connected with the group of power tubesiG pole of (1), each operational amplifier OPiThe anode input end of the transformer is connected with a reference voltage V in parallelILEDPositive electrode of (2), each operational amplifier OPiThe negative input end of the power tube M is connected with the group of power tubesiAnd through the resistor R of the groupiThe parallel line is connected with a reference voltage VILEDNegative electrode of (2), power tube MiD pole is a constant current I corresponding to the LED lamp stringLEDiAnd i is any integer from 1 to n.
3. The multi-channel constant current source voltage regulating circuit of claim 1, wherein: the self-regulation 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-regulation loop reference voltage and 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 through the inverter and is selected to control the on and off of one of the switches, and the output of the transconductance operational amplifier is directly connected with a filter capacitor C corresponding to a branch where one of the switches is locatedAVRCharging and discharging corresponding to the branch where another switch is locatedThe output of the transconductance operational amplifier is connected with a filter capacitor C through a voltage followerAVR。
4. The multi-channel constant current source voltage regulating circuit of claim 3, wherein: the minimum voltage selection circuit comprises a bias current source Ibias, a current mirror load MN0-MN1, a sample hold circuit corresponding to n paths of LED lamp string currents and n +1 PMOS tubes, wherein the bias current source Ibias is connected with S poles of all the PMOS tubes, the sample hold circuit is connected with G poles of the first n PMOS tubes in a shunt mode, 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 connected with the current mirror load MN0-MN1 in a common mode and output minimum voltage Vmin.
5. A multi-channel constant current source voltage regulation control method is realized based on the voltage regulation circuit of any one of claims 1 to 4, and is characterized in that: the common end voltage V1-Vn of each LED lamp string is connected into the reference voltage of the self-regulating loop through the multi-channel current adapter, the minimum value is taken and is subjected to differential operation with the reference source VR, and transconductance current is output to the filter capacitor CAVRCharging and discharging are carried out, and a dynamically changing voltage AVR = [ max (V)LED1,…,VLEDn)+VR]RFB2/(RFB1+ RFB2), along with filter capacitor CAVRCharge and discharge balance, voltage AVR within error range delta AVR = IAVR*TC/CAVRIn an internal tendency to be stable, wherein IAVRFor charging and discharging current, TCIs the effective charge-discharge time per unit time, CAVRIs the capacitance value of the filter capacitor.
6. The voltage regulation and control method of the multi-channel constant current source according to claim 5, characterized in that: by reducing the effective charging and discharging time Tc in unit time, the filter capacitor C is reducedAVRVoltage AVR of (1).
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CN117498658A (en) * 2023-12-29 2024-02-02 晶艺半导体有限公司 Ramp signal generating circuit and generating method

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