Constant-current load driving circuit, constant-current load circuit and constant-current load driving method

Abstract

The invention provides a constant-current load driving circuit, a constant-current load circuit and a constant-current load driving method. The constant-current load driving circuit comprises a constant-current control circuit, a detection control circuit, a charging and discharging control circuit and a power-on and power-off protection circuit. And the constant-current control circuit is connected with the constant-current load and is used for adjusting the current passing through the constant-current load. The detection control circuit is connected with the constant-current load and used for detecting the current of the constant-current load and outputting compensation voltage based on the current of the constant-current load. The charging and discharging control circuit is connected with the energy storage capacitor and the detection control circuit and used for controlling charging and discharging of the energy storage capacitor according to the compensation voltage. And the power-on and power-off protection circuit is connected with the bus and the detection control circuit, and is connected with the constant-current control circuit and the charging and discharging control circuit. During power-off, when the bus voltage is smaller than a first voltage threshold value and the voltage of the energy storage capacitor is larger than a second voltage threshold value, the loop of the constant current load, the bus and the grounding end is controlled to be disconnected, and the loop of the energy storage capacitor, the bus and the grounding end is controlled to be disconnected.

Description

Constant current load drive circuit, constant current load circuit and constant current load driving method Technical Field

[0001] This application relates to the field of circuit design, and in particular to a constant current load driving circuit, a constant current load circuit, and a method for driving a constant current load. Background Technology

[0002] In circuits that supply constant current loads with rectified AC power, compensation is typically applied to the constant current load to achieve flicker-free output current. The constant current load drive circuit needs to detect the output current of the constant current load circuit, perform real-time compensation, and control the compensation amount by adjusting the compensation voltage. When power is off, as the bus voltage V-in decreases, the compensation voltage V-comp will first rise and then fall. If power is suddenly applied before the compensation voltage V-comp has fully decreased, the circuit power transistor will be on, and the bus voltage V-in will suddenly increase, causing a sudden increase in the current I-CH through the power transistor and energy storage capacitor, as shown in Figure 1, which malfunctions the chip. Summary of the Invention

[0003] This application provides a constant current load drive circuit, a constant current load circuit, and a control method thereof to improve safety.

[0004] In a first aspect, this application provides a constant current load driving circuit for driving a constant current load, wherein the constant current load is connected between a bus and a ground terminal, and is connected to an energy storage capacitor, wherein the energy storage capacitor is connected between the bus and the ground terminal, and the constant current load driving circuit includes:

[0005] A constant current control circuit, connected to the constant current load and the constant current control circuit, is used to adjust the magnitude of the current passing through the constant current load after being adjusted by the constant current control circuit;

[0006] A detection control circuit, connected to the constant current load, is used to detect the current of the constant current load and output a compensation voltage based on the current of the constant current load.

[0007] A charge / discharge control circuit, connected to the energy storage capacitor and the detection control circuit, is used to control the charging and discharging of the energy storage capacitor according to the compensation voltage; and

[0008] A power-on / off protection circuit is connected to the busbar and the detection and control circuit, and is also connected to the constant current control circuit and the charge / discharge control circuit. When the constant current load drive circuit is powered off, if the busbar voltage is less than a first voltage threshold and the voltage of the energy storage capacitor is greater than a second voltage threshold, the circuit is controlled by the constant current control circuit to disconnect the circuit between the constant current load, the busbar, and the grounding terminal, and the circuit is controlled by the charge / discharge control circuit to disconnect the circuit between the energy storage capacitor, the busbar, and the grounding terminal.

[0009] The constant current control circuit adjusts the current of the constant current load to regulate its operation under different constant current conditions. The detection control circuit detects the current of the constant current load and outputs a compensation voltage based on this current. The charge / discharge control circuit controls the charging and discharging of the energy storage capacitor according to the compensation voltage. When the bus voltage is lower than the turn-on voltage of the constant current load, the detection control circuit increases the compensation voltage for the energy storage capacitor, and the charge / discharge control circuit controls the energy storage capacitor to discharge the constant current load. When the bus voltage is higher than the turn-on voltage of the constant current load, the detection control circuit decreases the compensation voltage for the energy storage capacitor, and the charge / discharge control circuit controls the energy storage capacitor to charge the constant current load.

[0010] When the constant current load drive circuit is powered down, the bus voltage continuously decreases, while the compensation voltage output by the detection and control circuit continuously increases. When the bus voltage is less than the first voltage threshold and the compensation voltage is greater than the second voltage threshold, the constant current control circuit disconnects the loop between the constant current load, the bus, and the ground terminal, and the charge / discharge control circuit disconnects the loop between the energy storage capacitor, the bus, and the ground terminal. This causes the compensation voltage to drop rapidly, and the constant current control circuit and the charge / discharge control circuit stop working, reducing the power consumption of the constant current load drive circuit. When the circuit is powered on again, the loops between the constant current load, the bus, and the ground terminal are disconnected, and the loops between the energy storage capacitor, the bus, and the ground terminal are also disconnected. The higher voltage and current on the bus will not affect the constant current control circuit and the charge / discharge control circuit, thus contributing to the safety of the constant current load drive circuit during power-on.

[0011] Optionally, the constant current control circuit includes a first power switch, which is connected in series with the constant current load between the bus and the ground terminal;

[0012] The power-on / off protection circuit includes a first switching circuit. The protection control circuit is connected to the bus, the detection control circuit, and the first switching circuit. The first switching circuit is connected to the constant current control circuit and to the gate of the first power switch and the ground terminal. When the constant current load drive circuit is powered off, if the bus voltage is less than the first voltage threshold and the compensation voltage is greater than the second voltage threshold, the protection control circuit controls the first switching circuit to turn on, thereby controlling the first power switch to turn off.

[0013] Optionally, the charging and discharging control circuit includes a second power switch, which is connected in series with the energy storage capacitor between the bus and the ground terminal;

[0014] The power-on / off protection circuit includes a second switching circuit. The protection control circuit is connected to the bus, the charge / discharge control circuit, and the second switching circuit. The second switching circuit is connected to the charge / discharge control circuit and to the gate of the second power switch and the ground terminal. When the constant current load drive circuit is powered off, if the bus voltage is less than the first voltage threshold and the compensation voltage is greater than the second voltage threshold, the protection control circuit controls the second switching circuit to turn on, thereby controlling the second power switch to turn off.

[0015] Optionally, the constant current control circuit includes a first power switch, which is connected in series with the constant current load between the bus and the ground terminal;

[0016] The detection control circuit includes a detection module and a compensation control module. The detection module is connected between the first power switch and the compensation control module. The detection module is used to compare the drain voltage of the first power switch with a first reference voltage and a second reference voltage, and output a detection signal. The compensation control module is used to output the compensation voltage according to the detection signal.

[0017] Optionally, the detection module includes a first amplifier and a second amplifier. One input terminal of the first amplifier is connected to the drain of the first power switch, and the other input terminal of the first amplifier is used to receive the first reference voltage. One input terminal of the second amplifier is connected to the drain of the first power switch, and the other input terminal of the second amplifier is used to receive the second reference voltage.

[0018] The output terminals of the first amplifier and the second amplifier are connected to the input terminal of the oscillator to control the oscillation frequency output by the oscillator.

[0019] Either the output terminal of the first amplifier or the output terminal of the second amplifier is connected to the counter and used to control the carry and borrow operations of the counter.

[0020] Optionally, the detection module includes a third amplifier, one input terminal of which is connected to the gate of the first power switch, the other input terminal of which is used to receive a third reference voltage, and the output terminal of which is connected to the input terminal of the oscillator to control the oscillation frequency output by the oscillator.

[0021] Optionally, the power-on / off protection circuit includes a delayed start module, which is connected to the output terminal of the detection and control circuit;

[0022] The protection control circuit is used to control the constant current control circuit to make the loop of the constant current load, the bus and the ground terminal conduct when the constant current load drive circuit is powered on. The delayed start module is used to output a start signal when the compensation voltage is greater than the third voltage threshold. The protection control circuit is used to control the charge and discharge control circuit to make the loop of the energy storage capacitor, the bus and the ground terminal conduct in response to the start signal.

[0023] In a second aspect, a constant current load circuit includes a bus, a constant current load, and a ground terminal. The constant current load is connected between the bus and the ground terminal and is connected to an energy storage capacitor. The energy storage capacitor is connected between the bus and the ground terminal. The circuit also includes a constant current load driving circuit as described in the first aspect, which is used to drive the constant current load.

[0024] When power is off, the bus voltage continuously decreases, and the compensation voltage output by the detection and control circuit of the constant current load drive circuit continuously increases. When the bus voltage is less than the first voltage threshold and the compensation voltage is greater than the second voltage threshold, the constant current control circuit disconnects the loop between the constant current load, the bus, and the grounding terminal, and the charge / discharge control circuit disconnects the loop between the energy storage capacitor, the bus, and the grounding terminal. This causes the compensation voltage to drop rapidly, and the constant current control circuit and the charge / discharge control circuit stop working, reducing the power consumption of the constant current load drive circuit. When the circuit is powered on again, the constant current control circuit disconnects the loop between the constant current load, the bus, and the grounding terminal, and the charge / discharge control circuit disconnects the loop between the energy storage capacitor, the bus, and the grounding terminal. The higher voltage and current generated by the bus will not affect the constant current control circuit and the charge / discharge control circuit, thus improving the safety of the constant current load drive circuit when the constant current load is powered on and off.

[0025] Thirdly, this application provides a method for driving a constant current load, wherein the constant current load is connected between a bus and a ground terminal, and is also connected to an energy storage capacitor, wherein the energy storage capacitor is connected between the bus and the ground terminal, and the driving method includes:

[0026] Detect the current of the constant current load;

[0027] A compensation voltage is generated based on the current of the constant current load;

[0028] The charging and discharging of the energy storage capacitor is controlled according to the compensation voltage;

[0029] When power is off, if the bus voltage is less than the first voltage threshold and the voltage of the energy storage capacitor is greater than the second voltage threshold, the constant current control circuit is controlled to disconnect the circuit between the constant current load, the bus, and the grounding terminal, and the charge / discharge control circuit is controlled to disconnect the circuit between the energy storage capacitor, the bus, and the grounding terminal.

[0030] When power is off, if the bus voltage is less than the first voltage threshold and the compensation voltage is greater than the second voltage threshold, the constant current control circuit disconnects the loop between the constant current load, the bus, and the grounding terminal, and the charge / discharge control circuit disconnects the loop between the energy storage capacitor, the bus, and the grounding terminal. This causes the compensation voltage to drop rapidly, and the constant current control circuit and the charge / discharge control circuit stop working, reducing the power consumption of the constant current load drive circuit. When power is on again, the constant current control circuit disconnects the loop between the constant current load, the bus, and the grounding terminal, and the charge / discharge control circuit disconnects the loop between the energy storage capacitor, the bus, and the grounding terminal. The higher voltage and current generated by the bus will not affect the constant current control circuit and the charge / discharge control circuit, thus improving the safety of the constant current load drive circuit during power-on.

[0031] Optionally, the driving method for constant current loads also includes:

[0032] When powered on, the circuits controlling the constant current load, the busbar, and the grounding terminal are connected;

[0033] When the compensation voltage is greater than the third voltage threshold, the circuit of the energy storage capacitor, the busbar and the grounding terminal is controlled to be turned on. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0035] Figure 1 shows the signal waveforms of the bus voltage, compensation voltage, and current through the energy storage capacitor and power transistor after the bus voltage is powered on and off in the related technology.

[0036] Figure 2 shows a schematic block diagram of an embodiment of the constant current load circuit of this application.

[0037] Figure 3 shows a circuit diagram of one embodiment of the constant current load circuit shown in Figure 2.

[0038] Figure 4 shows a circuit diagram of an embodiment of the compensated operational amplifier of the constant current load circuit shown in Figure 2.

[0039] Figure 5 shows a circuit diagram of an embodiment of the protection control circuit of the constant current load circuit shown in Figure 2.

[0040] Figure 6 is a schematic diagram of an embodiment of the constant current load driving method of this application.

[0041] Figure 7 shows a signal waveform diagram of an embodiment of the constant current load circuit of this application.

[0042] Explanation of reference numerals in the attached figures:

[0043] Constant current load drive circuit 100; constant current control circuit 110; constant current control module 111; detection control circuit 120; detection module 121; compensation control module 122; oscillator 1221; counter 1222; digital-to-analog converter 1223; charge / discharge control circuit 130; power-on / off protection circuit 140; first switch circuit 141; second switch circuit 142; delayed start module 143; protection control circuit 144; logic gate module 145; comparison and judgment module 146; trigger 147.

[0044] First voltage threshold V-set1; Third voltage threshold V-set3; First power switch Q1; Second power switch Q2; First reference voltage V-ref1; Second reference voltage V-ref2; Third reference voltage V-ref3; Compensation voltage V-comp; First amplifier CMP1; Second amplifier CMP2; Third amplifier CMP3; First voltage divider resistor R1; Second voltage divider resistor R2; Third voltage divider resistor R3; Fourth voltage divider resistor R4; Fifth resistor R5; Bus voltage V-in; Trigger signal Load; Overflow signal A0;

[0045] 200 constant current load circuit; 210 AC power supply; 220 energy storage capacitor; 230 constant current load; 240 busbar; 250 rectifier module. Detailed Implementation

[0046] The technical solutions in the embodiments (or "implementations") of this application will be clearly and completely described herein with reference to the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0047] The terms "first" and "second" used in the embodiments of this application are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0048] Referring to Figure 2, this application provides a constant current load circuit 200, including a bus 240, a constant current load 230, a ground terminal GND, and a constant current load drive circuit 100. The constant current load circuit 200 also includes a rectifier module 250, which rectifies the current output from the AC power supply 210. The bus 240 is connected to the output terminal of the rectifier module 250. The bus voltage V-in is the voltage after rectification of the AC power supply 210. The constant current load 230 is connected between the bus 240 and the ground terminal GND, and is also connected to an energy storage capacitor 220, which is also connected between the bus 240 and the ground terminal GND. The bus 240 can supply power to the constant current load 230 and charge the energy storage capacitor 220. In some cases, the energy storage capacitor 220 can discharge to supply power to the constant current load 230. The constant current load drive circuit 100 is connected to the constant current load 230 and is used to drive the constant current load 230. The constant current load 230 can be an LED or other load.

[0049] The constant current load drive circuit 100 includes: a constant current control circuit 110, a detection control circuit 120, a charge / discharge control circuit 130, and a power-on / off protection circuit 140. The constant current control circuit 110 is connected to the constant current load 230 and is used to adjust the current flowing through the constant current load 230. The detection control circuit 120 is connected to both the constant current load 230 and the constant current control circuit 110, and is used to detect the current flowing through the constant current load 230 after adjustment by the constant current control circuit 110, and output a compensation voltage V-comp based on the current of the constant current load 230. The charge / discharge control circuit 130 is connected to the energy storage capacitor 220 and the detection control circuit 120, and is used to control the charging and discharging of the energy storage capacitor 220 according to the compensation voltage V-comp. The power-on / off protection circuit 140 is connected to the bus 240 and the detection and control circuit 120, and is also connected to the constant current control circuit 110 and the charge / discharge control circuit 130. When the constant current load drive circuit 100 is powered off, if the bus voltage V-in is less than the first voltage threshold V-set1 and the compensation voltage V-comp is greater than the second voltage threshold V-set2, the constant current control circuit 110 is controlled to disconnect the circuit between the constant current load 230, the bus 240 and the ground terminal GND, and the charge / discharge control circuit 130 is controlled to disconnect the circuit between the energy storage capacitor 220, the bus 240 and the ground terminal GND.

[0050] When power is off, the bus voltage V-in continuously decreases, while the compensation voltage V-comp output by the detection and control circuit 120 continuously increases. When the bus voltage V-in is less than the first voltage threshold V-set1 and the compensation voltage V-comp is greater than the second voltage threshold V-set2, the constant current control circuit 110 disconnects the circuit between the constant current load 230, the bus 240, and the ground terminal GND, and the charge and discharge control circuit 130 disconnects the circuit between the energy storage capacitor 220, the bus 240, and the ground terminal GND. This causes the compensation voltage V-comp to decrease rapidly, and the constant current control circuit 110 and the charge and discharge control circuit 130 stop working, reducing the power consumption of the constant current load drive circuit 100. When the circuit is powered on again, the compensation voltage V-comp has dropped to a low level when powered off, and the circuit between the constant current load 230, bus 240 and grounding terminal GND is disconnected. The circuit between the energy storage capacitor 220, bus 240 and grounding terminal GND is also disconnected. Therefore, the higher voltage and current on bus 240 will not affect the constant current control circuit 110 and the charge / discharge control circuit 130, which is beneficial to the safety of the constant current load drive circuit 100 when powered on.

[0051] Specifically, referring to Figure 3, the constant current control circuit 110 includes a first power switch Q1. The first power switch Q1 and the constant current load 230 are connected in series between the bus 240 and the ground terminal GND. In this embodiment, the constant current control circuit 110 includes a constant current control module 111, which is connected to the gate of the first power switch Q1. The drain of the first power switch Q1 is connected to the constant current load 230, and the source of the first power switch Q1 is connected to the ground terminal GND. The constant current control module 111 adjusts the current through the constant current load 230 by controlling the first power switch Q1 to achieve constant current control.

[0052] The detection control circuit 120 is connected to the first power switch Q1. It detects the current of the constant current load 230 by detecting the voltage of the first power switch Q1. Based on the voltage of the first power switch Q1, it outputs a compensation voltage V-comp to the charge and discharge control circuit 130 so that the charge and discharge control circuit 130 controls the charging and discharging of the energy storage capacitor 220.

[0053] The charge / discharge control circuit 130 includes a second power switch Q2. The second power switch Q2 and the energy storage capacitor 220 are connected in series between the bus 240 and the ground terminal GND. The drain of the second power switch Q2 is connected to the energy storage capacitor 220, and the source of the second power switch Q2 is connected to the ground terminal GND. The charge / discharge control circuit 130 also includes a compensation operational amplifier CMP4. One input of the compensation operational amplifier CMP4 is connected to the detection control circuit 120 to receive the compensation voltage V-comp; the other input of the compensation operational amplifier CMP4 is used to receive the divided voltage V-div after dividing the bus voltage V-in. Referring to Figure 4, a third voltage dividing resistor R3 and a fourth voltage dividing resistor R4 are connected in series between the bus 240 and the source of the second power switch Q2. The other input of the compensation operational amplifier CMP4 is connected between the third voltage dividing resistor R3 and the fourth voltage dividing resistor R4 through a fifth resistor R5. The output of the compensation operational amplifier CMP4 is connected to the gate of the second power switch Q2. The compensation operational amplifier CMP4 is used to compare the compensation voltage V-comp and the voltage divider voltage V-div, control the conduction and disconnection of the second power switch Q2, and thus control the charging and discharging of the energy storage capacitor 220.

[0054] The power-on / off protection circuit 140 includes a protection control circuit 144 and a first switching circuit 141. The protection control circuit 144 is connected to the bus 240, the detection control circuit 120, and the first switching circuit 141. The protection control circuit 144 acquires the bus voltage V-in and the compensation voltage V-comp output by the detection control circuit 120, and controls the first switching circuit 141 to turn on and off based on the bus voltage V-in and the compensation voltage V-comp. The first switching circuit 141 is connected to the constant current control circuit 110 and is connected to the gate of the first power switch Q1 and the ground terminal GND. When the constant current load drive circuit 100 is powered off, the protection control circuit 144 controls the first switching circuit 141 to turn on when the bus voltage V-in is less than the first voltage threshold V-set1 and the compensation voltage V-comp is greater than the second voltage threshold V-set2. At this time, the gate of the first power switch Q1 is connected to the ground terminal GND, and the first power switch Q1 is turned off.

[0055] The power-on / off protection circuit 140 controls the constant current control circuit 110 through the first switching circuit 141, thereby disconnecting the loop between the constant current load 230, the bus 240, and the ground terminal GND. When the first switching circuit 141 is turned on, it grounds the gate of the first power switch Q1, causing Q1 to turn off, thus controlling the constant current control circuit 110 and disconnecting the loop between the constant current load 230, the bus 240, and the ground terminal GND. The first switching circuit 141 includes a controllable switch connecting the gate of the first power switch Q1 and the ground terminal GND. During normal operation of the constant current load 230, the first switching circuit 141 is in the off state. When the constant current load drive circuit 100 is powered off, the first switching circuit 141 is in the off state when the bus voltage V-in is not less than the first voltage threshold V-set1 and the compensation voltage V-comp is not greater than the second voltage threshold V-set2.

[0056] The protection control circuit 144 is used to control the first switching circuit 141 to turn on when the bus voltage V-in is less than the first voltage threshold V-set1 and the compensation voltage V-comp is greater than the second voltage threshold V-set2, so as to turn off the first power switch Q1 when the constant current load drive circuit 100 is powered off. This causes the compensation voltage V-comp to drop rapidly, and the constant current control circuit 110 and the charge / discharge control circuit 130 stop working, reducing the power consumption of the constant current load drive circuit 100. When powered on again, since the compensation voltage V-comp has dropped to a low level when powered off, and the circuit between the constant current load 230, the bus 240 and the ground terminal GND is disconnected, and the circuit between the energy storage capacitor 220, the bus 240 and the ground terminal GND is also disconnected, the higher voltage and current on the bus 240 will not affect the charge / discharge control circuit 130, thus improving the safety of the constant current load drive circuit 100 when powered on. The first switching circuit 141 can quickly shut off the circuit when the power is off, and can prevent the constant current control circuit 110 from being accidentally triggered and turning on the circuit of constant current load 230, bus 240 and ground terminal GND, thus greatly improving safety.

[0057] In some embodiments, the power-on / off protection circuit 140 includes a second switching circuit 142. A protection control circuit 144 controls the second switching circuit 142 to turn on and off based on the bus voltage V-in and the compensation voltage V-comp. The second switching circuit 142 is connected to the charge / discharge control circuit 130 and is connected to the gate of the second power switch Q2 and the ground terminal GND. When the constant current load drive circuit 100 is powered off, the protection control circuit 144 controls the second switching circuit 142 to turn on when the bus voltage V-in is less than a first voltage threshold V-set1 and the compensation voltage V-comp is greater than a second voltage threshold V-set2, thereby controlling the second power switch Q2 to turn off.

[0058] The protection control circuit 144 is used to control the second switching circuit 142 to turn on when the bus voltage V-in is less than the first voltage threshold V-set1 and the compensation voltage V-comp is greater than the second voltage threshold V-set2, so that the second power switch Q2 is turned off when the constant current load drive circuit 100 is powered off. This causes the compensation voltage V-comp to drop rapidly, and the constant current control circuit 110 and the charge / discharge control circuit 130 stop working, reducing the power consumption of the constant current load drive circuit 100. When powered on again, because the compensation voltage V-comp has dropped to a low level when powered off, and the circuit between the constant current load 230, the bus 240 and the ground terminal GND is disconnected, and the circuit between the energy storage capacitor 220, the bus 240 and the ground terminal GND is also disconnected, the higher voltage and current on the bus 240 will not affect the charge / discharge control circuit 130, thus improving the safety of the constant current load drive circuit 100 when powered on. The second switching circuit 142 can quickly shut off the circuit when the power is off, and can prevent the constant current control circuit 110 from being accidentally triggered and turning on the circuit of constant current load 230, bus 240 and ground terminal GND, thus greatly improving safety.

[0059] Referring to Figure 5, the power-on / off protection circuit 140 also includes a delayed start module 143. The delayed start module 143 is connected to the output terminal of the detection control circuit 120. When the compensation voltage V-comp is lower than the third voltage threshold V-set3, the delayed start module 143 outputs a low level; when the compensation voltage V-comp is greater than the third voltage threshold V-set3, the delayed start module 143 outputs a high level.

[0060] When powered on, the protection control circuit 144 controls the constant current control circuit 110 to conduct the loop between the constant current load 230, the bus 240, and the ground terminal GND. The delayed start module 143 outputs a start signal when the compensation voltage V-comp is greater than the third voltage threshold V-set3; the protection control circuit 144, in response to the start signal, controls the charge and discharge control circuit 130 to conduct the loop between the energy storage capacitor 220, the bus 240, and the ground terminal GND.

[0061] After power-down, the energy storage capacitor 220 discharges, reducing the charge within it. Upon power-up, the energy storage capacitor 220 cannot discharge the constant current load 230 when the bus voltage V-in is lower than the turn-on voltage of the constant current load 230. Therefore, through the above settings, the compensation voltage V-comp is greater than the third voltage threshold V-set3, allowing the voltage of the energy storage capacitor 220 to power the constant current load 230. This ensures that the energy storage capacitor 220 can discharge the constant current load 230 when the bus voltage V-in is lower than its turn-on voltage, thereby controlling the current flowing through the constant current load 230 to remain constant and reducing the risk of flickering in the constant current load 230.

[0062] Specifically, referring to Figure 3, the detection control circuit 120 includes a detection module 121 and a compensation control module 122. The detection module 121 is connected between the first power switch Q1 and the compensation control module 122. The detection module 121 compares the drain voltage of the first power switch Q1 with the first reference voltage V-ref1 and the second reference voltage V-ref2, respectively, and outputs a detection signal. The compensation control module 122 outputs a compensation voltage V-comp based on the detection signal. Taking the first reference voltage V-ref1 being less than the second reference voltage V-ref2 as an example, when the constant current load 230 is in operation, when the drain voltage of the first power switch Q1 is less than the first reference voltage V-ref1, the compensation control module 122 increases the output compensation voltage V-comp based on the detection signal, increasing the charging current of the energy storage capacitor 220 and thus increasing the discharge voltage of the energy storage capacitor 220. When the drain voltage of the first power switch Q1 is greater than the first reference voltage V-ref1, the compensation control module 122 reduces the output compensation voltage V-comp according to the detection signal, thereby reducing the charging current of the energy storage capacitor 220 and thus reducing the discharge voltage of the energy storage capacitor 220.

[0063] Specifically, as shown in Figure 3, the compensation control module 122 includes an oscillator 1221 and a counter 1222. The oscillator 1221 is connected to the detection module 121 and is used to acquire detection signals and generate oscillation signals of different frequencies according to different detection signals. The input terminal of the counter 1222 is connected to the oscillator 1221 and the detection module 121. The counter 1222 is used to count according to the oscillation signals and perform carry and borrow operations according to the detection signals. The oscillator 1221 acquires detection signals and generates oscillation signals of different frequencies according to different detection signals. The counter 1222 performs carry or borrow processing based on the number of pulses of the oscillation signals generated by the oscillator 1221. The frequency of the different oscillation signals generated by the oscillator 1221 according to different detection signals can be set according to different constant current load drive circuits 100.

[0064] Specifically, as shown in Figure 3, the compensation control module 122 also includes a digital-to-analog converter 1223. The output of the counter 1222 is connected to the digital-to-analog converter 1223, and the output of the digital-to-analog converter 1223 is connected to the charge / discharge control circuit 130. The digital-to-analog converter 1223 is used to convert the counting result of the counter 1222 into an analog signal as the compensation voltage V-comp. The digital-to-analog converter 1223 can decode the counting result of the counter 1222 to generate a corresponding analog signal as the compensation voltage V-comp.

[0065] Specifically, taking the first reference voltage V-ref1 being less than the second reference voltage V-ref2 as an example, when the constant current load 230 is in operation, the drain voltage of the first power switch Q1 is a periodic signal. When the drain voltage of the first power switch Q1 is less than the first reference voltage V-ref1, the counter 1222 is controlled by the detection signal to perform a carry operation; when the drain voltage of the first power switch Q1 is greater than the first reference voltage V-ref1, the counter 1222 is controlled by the detection signal to perform a borrow operation. The oscillator 1221 is used to acquire the detection signal and generate oscillation signals of different frequencies according to different detection signals. The counter 1222 performs carry or borrow processing according to the number of pulses of the oscillation signal generated by the oscillator 1221. The frequency of the different oscillation signals generated by the oscillator 1221 according to different detection signals can be set according to different constant current load drive circuits 100. When the drain voltage of the first power switch Q1 is less than the first reference voltage V-ref1, the oscillator 1221 increases the output of an oscillation signal of a specific frequency according to the detection signal. This controls the counter 1222 to perform a carry operation based on the number of pulses in the oscillation signal. The digital-to-analog converter 1223 decodes the count result of the counter 1222, increases the output compensation voltage V-comp, increases the charging current of the energy storage capacitor 220, and thus increases the discharge voltage of the energy storage capacitor 220. When the drain voltage of the first power switch Q1 is greater than the first reference voltage V-ref1, the counter 1222 performs a borrow operation. The digital-to-analog converter 1223 decodes the count result of the counter 1222, decreases the output compensation voltage V-comp, decreases the charging current of the energy storage capacitor 220, and thus decreases the discharge voltage of the energy storage capacitor 220. Through this method, the current through the constant current load 230 is kept constant. The counting result of counter 1222 is decoded by digital-to-analog converter 1223, establishing a correspondence between the counting result of counter 1222 and the compensation voltage V-comp output by digital-to-analog converter 1223. By setting this correspondence, when the compensation voltage V-comp output by digital-to-analog converter 1223 is greater than the third voltage threshold V-set3, counter 1222 can output an overflow signal A0 = 1.

[0066] It should be noted that the counting logic of counter 1222 and the method by which digital-to-analog converter 1223 decodes the counting result of counter 1222 can be adjusted and are not limited to this embodiment.

[0067] The counter 1222 includes an overflow signal output terminal 12221, which is connected to the power-on / off protection circuit 140. The overflow signal output terminal 12221 is used to output the overflow signal A0 of the counter 1222.

[0068] When power is off, the drain voltage of the first power switch Q1 continuously decreases. The oscillator 1221 continuously outputs an oscillation signal based on the detection signal. The counter 1222 performs a carry operation based on the number of pulses of the oscillation signal. When all the bits (A1, A2, A3...) output by the counter 1222 are 1 or 0, an overflow signal A0 = 1 is generated. After receiving the overflow signal A0 = 1, the power-on / off protection circuit 140 determines that the constant current load 230 is in a power-off state when the bus voltage V-in is less than the first voltage threshold V-set1. The power-on / off protection circuit 140 controls the constant current control circuit 110 to disconnect the loop between the constant current load 230, the bus 240, and the ground terminal GND. It also controls the charge / discharge control circuit 130 to disconnect the loop between the energy storage capacitor 220, the bus 240, and the ground terminal GND. This causes the compensation voltage V-comp to drop rapidly. The constant current control circuit 110 and the charge / discharge control circuit 130 stop working, and the counter 1222 is reset to zero.

[0069] Specifically, as shown in Figure 3, the gate of the first power switch Q1 is connected to the input terminal of the oscillator 1221. The oscillation frequency output by the oscillator 1221 is controlled by comparing the voltage at the gate of the first power switch Q1 with the third reference voltage V-ref3. The third reference voltage V-ref3 can be an internal fixed value or provided externally.

[0070] The above settings enable the detection and control circuit 120 to obtain the magnitude of the current operating current of the constant current load 230. When the constant current load 230 is controlled to operate under low current conditions, the risk of the detection and control circuit 120 misjudging that the circuit is powered down is reduced, thereby reducing the risk of false triggering of the constant current load drive circuit 100.

[0071] Specifically, referring to Figure 3, the detection module 121 includes a first amplifier CMP1 and a second amplifier CMP2. One input terminal of the first amplifier CMP1 is connected to the drain of the first power switch Q1, and the other input terminal of the first amplifier CMP1 is used to receive the first reference voltage V-ref1. In the illustrated embodiment, the inverting input terminal of the first amplifier CMP1 is connected to the drain of the first power switch Q1, and the non-inverting input terminal of the first amplifier CMP1 is used to receive the first reference voltage V-ref1. When the drain voltage of the first power switch Q1, after being divided by the first voltage divider resistor R1 and the second voltage divider resistor R2, is less than the first reference voltage V-ref1, the output terminal of the first amplifier CMP1 outputs a high level; when the drain voltage of the first power switch Q1, after being divided by the first voltage divider resistor R1 and the second voltage divider resistor R2, is greater than the first reference voltage V-ref1, the output terminal of the first amplifier CMP1 outputs a low level.

[0072] One input terminal of the second amplifier CMP2 is connected to the drain of the first power switch Q1, and the other input terminal of the second amplifier CMP2 is used to receive the second reference voltage V-ref2. In the illustrated embodiment, the non-inverting input terminal of the second amplifier CMP2 is connected to the drain of the first power switch Q1, and the inverting input terminal of the second amplifier CMP2 is used to receive the second reference voltage V-ref2. When the drain voltage of the first power switch Q1, after being divided by the first voltage divider resistor R1 and the second voltage divider resistor R2, is less than the second reference voltage V-ref2, the output terminal of the second amplifier CMP2 outputs a low level; when the drain voltage of the first power switch Q1, after being divided by the first voltage divider resistor R1 and the second voltage divider resistor R2, is greater than the second reference voltage V-ref2, the output terminal of the second amplifier CMP2 outputs a high level.

[0073] Specifically, a first voltage divider resistor R1 and a second voltage divider resistor R2 are connected between the drain of the first power switch Q1 and the ground terminal GND. The inverting input terminal of the first amplifier CMP1 and the non-inverting input terminal of the second amplifier CMP2 are connected between the first voltage divider resistor R1 and the second voltage divider resistor R2. The output terminals of the first amplifier CMP1 and the second amplifier CMP2 are connected to the input terminal of the oscillator 1221 to control the oscillation frequency output by the oscillator 1221. Either the output terminal of the first amplifier CMP1 or the output terminal of the second amplifier CMP2 is connected to the counter 1222 and used to control the carry and borrow operations of the counter 1222. In this embodiment, when the drain voltage of the first power switch Q1, after being divided by the first voltage divider resistor R1 and the second voltage divider resistor R2, is less than the first reference voltage V-ref1, the counter 1222 is controlled by a detection signal to perform a carry operation; when the drain voltage of the first power switch Q1, after being divided by the first voltage divider resistor R1 and the second voltage divider resistor R2, is greater than the first reference voltage V-ref1, the counter 1222 is controlled by a detection signal to perform a borrow operation. Alternatively, the carry and borrow operations of the counter 1222 can be controlled based on the comparison result between the drain voltage of the first power switch Q1 and the second reference voltage V-ref2, and are not limited to this embodiment.

[0074] Specifically, referring to Figure 3, the detection module 121 includes a third amplifier CMP3. One input terminal of the third amplifier CMP3 is connected to the gate of the first power switch Q1, and the other input terminal of the second amplifier CMP2 is used to receive the third reference voltage V-ref3. In the illustrated embodiment, the positive input terminal of the third amplifier CMP3 is connected to the gate of the first power switch Q1, and the negative input terminal of the third amplifier CMP3 is used to receive the third reference voltage V-ref3. When the voltage at the gate of the first power switch Q1 is greater than the third reference voltage V-ref3, the third amplifier CMP3 outputs a high level; when the voltage at the gate of the first power switch Q1 is less than the third reference voltage V-ref3, the third amplifier CMP3 outputs a low level. The output terminal of the third amplifier CMP3 is connected to the input terminal of the oscillator 1221. The oscillator 1221 controls the oscillation frequency output by the oscillator 1221 according to the output signal of the third amplifier CMP3, thereby controlling the counting result of the counter 1222, and converting it into a compensation voltage V-comp through the digital-to-analog converter 1223, thereby realizing the control of the current passing through the constant current load 230.

[0075] Referring to Figure 5, specifically, the protection control circuit 144 includes a comparison and judgment module 146, a logic gate module 145, and a flip-flop 147. The comparison and judgment module 146 is connected to the bus 240 and is used to compare the bus voltage V-in with a first voltage threshold V-set1. When the bus voltage V-in is lower than the first voltage threshold V-set1, the comparison and judgment module 146 outputs a low level; when the bus voltage V-in is greater than the first voltage threshold V-set1, the comparison and judgment module 146 outputs a high level. The input terminals of the logic gate module 145 are respectively connected to the output terminal of the delayed start module 143 and the overflow signal output terminal. When the overflow signal output terminal outputs the overflow signal A0 = 1 from counter 1222, and the comparison and judgment module 146 outputs a high level, the trigger signal Load = 0, which controls the first power switch Q1 and the second power switch Q2 to turn off, is output through trigger 147. This controls the constant current control circuit 110 to disconnect the loop between the constant current load 230, the bus 240, and the ground terminal GND, and controls the charge and discharge control circuit 130 to disconnect the loop between the energy storage capacitor 220, the bus 240, and the ground terminal GND. This causes the compensation voltage V-comp to drop rapidly, and the constant current control circuit 110 and the charge and discharge control circuit 130 to stop working, reducing the power consumption of the constant current load drive circuit 100. When the overflow signal output terminal outputs the overflow signal of counter 1222, and the comparison and judgment module 146 outputs a low level, the trigger signal Load = 1, which controls the first power switch Q1 and the second power switch Q2 to turn on, is output through trigger 147. At this time, the compensation voltage V-comp is greater than the third reference voltage V-ref3, ensuring that the energy storage capacitor 220 can discharge the constant current load 230 when the bus voltage V-in is lower than the turn-on voltage of the constant current load 230, thereby controlling the current through the constant current load 230 to be constant and reducing the risk of flickering of the constant current load 230.

[0076] This embodiment provides a driving method for a constant current load 230, as shown in Figure 6, including steps S10, S20 and S30.

[0077] In step S10, the current I-CH of the constant current load 230 is detected.

[0078] In step S20, a compensation voltage V-Comp is generated based on the current of the constant current load 230.

[0079] In step S30, when power is off, if the bus voltage V-in is less than the first voltage threshold V-set1 and the compensation voltage V-comp is greater than the second voltage threshold V-set2, the constant current control circuit 110 is controlled to disconnect the circuit between the constant current load 230, the bus 240 and the ground terminal GND, and the charge and discharge control circuit 130 is controlled to disconnect the circuit between the energy storage capacitor 220, the bus 240 and the ground terminal GND.

[0080] When power is off, the bus voltage V-in continuously decreases, while the compensation voltage V-comp output by the detection and control circuit 120 continuously increases. When the bus voltage V-in is less than the first voltage threshold V-set1 and the compensation voltage V-comp is greater than the second voltage threshold V-set2, the constant current control circuit 110 disconnects the circuit between the constant current load 230, the bus 240, and the ground terminal GND, and the charge and discharge control circuit 130 disconnects the circuit between the energy storage capacitor 220, the bus 240, and the ground terminal GND. This causes the compensation voltage V-comp to decrease rapidly, and the constant current control circuit 110 and the charge and discharge control circuit 130 stop working, reducing the power consumption of the constant current load drive circuit 100. Upon power-up, the constant current control circuit 110 disconnects the circuit between the constant current load 230, bus 240, and ground terminal GND. The charge / discharge control circuit 130 disconnects the circuit between the energy storage capacitor 220, bus 240, and ground terminal GND. The higher voltage and current generated by bus 240 will not affect the constant current control circuit 110 and the charge / discharge control circuit 130. See Figure 7, where the bus voltage is V-in, the overflow signal is A0, the trigger signal is Load, and the compensation voltage is V-comp. As a result, the current of the constant current load 230 (LED in this embodiment) is I-LED, and the current through the energy storage capacitor 220 is I-CH. During times t0 to t1, the constant current load 230 is continuously powered on; during times t1 to t2, it is powered off; and after time t2, it is powered on again. This configuration improves the safety of the constant current load drive circuit 100 during power-up.

[0081] Referring to Figure 6, the driving method of the constant current load 230 also includes step S40.

[0082] In step S40, when power is applied, the circuit of the constant current load 230, bus 240 and grounding terminal GND is turned on. When the bus voltage V-in is greater than the third voltage threshold V-rep3, the circuit of the energy storage capacitor 220, bus 240 and grounding terminal GND is turned on.

[0083] After power-off, the energy storage capacitor 220 discharges, reducing the charge within it. Upon power-on again, the energy storage capacitor 220 cannot discharge the constant current load 230 when the bus voltage V-in is lower than the turn-on voltage of the constant current load 230. Therefore, through the above settings, the compensation voltage V-comp is greater than the third voltage threshold V-set3, ensuring that the energy storage capacitor 220 can discharge the constant current load 230 when the bus voltage V-in is lower than the turn-on voltage of the constant current load 230. This setting controls the current flowing through the constant current load 230 to remain constant, reducing the risk of flickering in the constant current load 230.

[0084] It should be noted that the technical solutions or features described in the above embodiments can be combined or supplemented with each other without conflict. The scope of protection of this application is not limited to the precise structures described in the above embodiments and shown in the accompanying drawings; all modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A constant current load drive circuit, characterized in that, For driving a constant current load, the constant current load is connected between a busbar and a ground terminal, and is also connected to an energy storage capacitor, which is connected between the busbar and the ground terminal. The constant current load driving circuit includes: a constant current control circuit connected to the constant current load, used to adjust the current passing through the constant current load; a detection control circuit connected to the constant current load and the constant current control circuit, used to detect the current of the constant current load after adjustment by the constant current control circuit, and output a compensation voltage based on the current of the constant current load; and a charge / discharge control circuit connected to the energy storage capacitor and the ground terminal. A detection and control circuit is connected to control the charging and discharging of the energy storage capacitor according to the compensation voltage; and a power-on / off protection circuit is connected to the bus and the detection and control circuit, and is also connected to the constant current control circuit and the charging and discharging control circuit. When the constant current load drive circuit is powered off, if the bus voltage is less than a first voltage threshold and the compensation voltage is greater than a second voltage threshold, the constant current control circuit is controlled to disconnect the circuit between the constant current load, the bus, and the grounding terminal, and the charging and discharging control circuit is controlled to disconnect the circuit between the energy storage capacitor, the bus, and the grounding terminal.

2. The constant current load drive circuit as described in claim 1, characterized in that, The constant current control circuit includes a first power switch transistor, which is connected in series with the constant current load between the bus and the ground terminal. The power-on / off protection circuit includes a protection control circuit and a first switching circuit. The protection control circuit is connected to the bus, the detection control circuit, and the first switching circuit. The first switching circuit is connected to the gate of the first power switch transistor and the ground terminal. When the constant current load drive circuit is powered off, the protection control circuit controls the first switching circuit to turn on when the bus voltage is less than the first voltage threshold and the compensation voltage is greater than the second voltage threshold, so as to control the first power switch transistor to turn off.

3. The constant current load drive circuit as described in claim 2, characterized in that, The charge / discharge control circuit includes a second power switch, which is connected in series with the energy storage capacitor between the bus and the ground terminal. The power-on / off protection circuit includes a second switching circuit. The protection control circuit is connected to the bus, the charge / discharge control circuit, and the second switching circuit. The second switching circuit is connected to the gate of the second power switch and the ground terminal. The protection control circuit is used to control the second switching circuit to turn on when the bus voltage is less than the first voltage threshold and the compensation voltage is greater than the second voltage threshold during power-off, so as to control the second power switch to turn off.

4. The constant current load drive circuit as described in claim 2, characterized in that, The first power switch is connected in series with the constant current load between the bus and the ground terminal; the detection and control circuit includes a detection module and a compensation control module. The detection module is connected between the first power switch and the compensation control module. The detection module is used to generate a detection signal based on the relationship between the drain voltage of the first power switch and the first reference voltage, and the relationship between the drain voltage of the first power switch and the second reference voltage. The compensation control module is used to output the compensation voltage based on the detection signal.

5. The constant current load drive circuit as described in claim 4, characterized in that, The compensation control module includes an oscillator and a counter. The oscillator is connected to the detection module and is used to acquire the detection signal and generate oscillation signals of different frequencies according to different detection signals. The input terminal of the counter is connected to the oscillator and the detection module. The counter is used to count according to the oscillation signal and perform carry and borrow operations according to the detection signal. The counter includes an overflow signal output terminal, which is connected to the power-on / off protection circuit. The overflow signal output terminal is used to output the overflow signal of the counter. When the power-on / off protection circuit receives the overflow signal and the bus voltage is less than the first voltage threshold, it controls the constant current control circuit to disconnect the loop of the constant current load, the bus, and the ground terminal, controls the charge / discharge control circuit to disconnect the loop of the energy storage capacitor, the bus, and the ground terminal, and controls the counter to be set to zero.

6. The constant current load drive circuit as described in claim 5, characterized in that, The compensation control module further includes a digital-to-analog converter. The output terminal of the counter is connected to the digital-to-analog converter, and the output terminal of the digital-to-analog converter is connected to the charge-discharge control circuit. The digital-to-analog converter is used to convert the counting result of the counter into an analog signal as the compensation voltage.

7. The constant current load drive circuit as described in claim 5, characterized in that, The detection module includes a first amplifier and a second amplifier. One input terminal of the first amplifier is connected to the drain of the first power switch transistor, and the other input terminal of the first amplifier is used to receive the first reference voltage. One input terminal of the second amplifier is connected to the drain of the first power switch transistor, and the other input terminal of the second amplifier is used to receive the second reference voltage. The output terminals of the first amplifier and the second amplifier are connected to the input terminals of the oscillator to control the oscillation frequency output by the oscillator. Either the output terminal of the first amplifier or the output terminal of the second amplifier is connected to the counter and used to control the carry and borrow operations of the counter.

8. The constant current load drive circuit as described in claim 7, characterized in that, The detection module includes a third amplifier. One input terminal of the third amplifier is connected to the gate of the first power switch, and the other input terminal of the third amplifier is used to receive a third reference voltage. The output terminal of the third amplifier is connected to the input terminal of the oscillator and is used to control the oscillation frequency output by the oscillator.

9. The constant current load drive circuit as described in claim 2, characterized in that, The power-on / off protection circuit includes a delayed start module connected to the output of the detection and control circuit. When the constant current load drive circuit is powered on, the protection and control circuit controls the constant current control circuit to make the loop between the constant current load, the bus, and the ground terminal conduct. The delayed start module outputs a start signal when the compensation voltage is greater than a third voltage threshold when the constant current load drive circuit is powered on. In response to the start signal, the protection and control circuit controls the charge / discharge control circuit to make the loop between the energy storage capacitor, the bus, and the ground terminal conduct.

10. A constant current load circuit, characterized in that, The circuit includes a busbar, an energy storage capacitor, a constant current load, and a grounding terminal. The constant current load is connected between the busbar and the grounding terminal and is also connected to the energy storage capacitor. The energy storage capacitor is connected between the busbar and the grounding terminal. The constant current load circuit further includes a constant current load driving circuit as described in any one of claims 1-9, which is used to drive the constant current load.

11. A method for driving a constant current load, characterized in that, The constant current load is connected between the bus and the ground terminal, and is also connected to an energy storage capacitor. The energy storage capacitor is connected between the bus and the ground terminal. The driving method includes: detecting the current of the constant current load; generating a compensation voltage based on the current of the constant current load; controlling the charging and discharging of the energy storage capacitor according to the compensation voltage; and, when the bus voltage is less than a first voltage threshold and the compensation voltage is greater than a second voltage threshold, controlling the circuit of the constant current load, the bus, and the ground terminal to disconnect, and controlling the circuit of the energy storage capacitor, the bus, and the ground terminal to disconnect.

12. The driving method as described in claim 11, characterized in that, Also includes: When powered on, the circuit of the constant current load, the busbar and the grounding terminal is turned on; when the compensation voltage is greater than the third voltage threshold, the circuit of the energy storage capacitor, the busbar and the grounding terminal is turned on.

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