Constant current load driving circuit and constant current load circuit

Abstract

The utility model provides a constant-current load driving circuit and a constant-current load circuit. 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

Technical Field

[0001] The present application relates to the field of circuit design, and in particular to a constant current load drive circuit and a constant current load circuit. Background Art

[0002] In circuits that power constant-current loads from a rectified AC power source, compensation is often implemented to achieve flicker-free output current. Constant-current load driver circuits must detect the output current of the constant-current load circuit and apply compensation in real time, controlling the compensation voltage. However, sudden changes in current and voltage during power-on and power-off can easily cause chip failure. Utility Model Content

[0003] The present application provides a constant current load driving circuit and a constant current load circuit with improved safety.

[0004] In a first aspect, the present application provides a constant current load driving circuit,

[0005] Used to drive a constant current load, 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, and the constant current load driving circuit includes:

[0006] A constant current control circuit, connected to the constant current load, for adjusting the current passing through the constant current load;

[0007] a detection control circuit connected to the constant current load and the constant current control circuit, configured to detect the current of the constant current load adjusted by the constant current control circuit, and output a compensation voltage based on the current of the constant current load;

[0008] a charge and discharge control circuit, connected to the energy storage capacitor and the detection control circuit, and configured to control the charge and discharge of the energy storage capacitor according to the compensation voltage; and

[0009] The power-on and power-off protection circuit includes a first detection end, a second detection end, and a control end. The first detection end is connected to the bus for receiving the bus voltage. The second detection end is connected to the detection control circuit for receiving the compensation voltage. The control end is respectively connected to the constant current control circuit and the charge and discharge control circuit. The power-on and power-off protection circuit is used to control the constant current control circuit and the charge and discharge control circuit through the control end according to the bus voltage and the compensation voltage.

[0010] The constant current load driving circuit includes a power-on and power-off protection circuit, which is connected to the bus and the detection control circuit, and is connected to the constant current control circuit and the charge and discharge control circuit. It can protect the circuit when the constant current load driving circuit is powered on and off, thereby improving safety.

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

[0012] The power-on and power-off protection circuit includes a protection control circuit and a first switching circuit. The protection control circuit includes a first detection end, a second detection end, and a control end. The control end is connected to the first switching circuit. The first switching circuit is connected to the gate of the first power switch tube and the ground end, and is used to control the on and off of the first power switch tube. The control end is used to control the first switching circuit.

[0013] Optionally, the charge and discharge control circuit includes a second power switch tube, and the second power switch tube and the energy storage capacitor are connected in series between the bus and the ground terminal;

[0014] The power-on and power-off protection circuit includes a second switching circuit, the control end is connected to the second switching circuit, the second switching circuit is connected to the gate of the second power switch tube and the ground end, and is used to control the on and off of the second power switch tube. The control end is used to control the second switching circuit.

[0015] Optionally, the first power switch tube and the constant current load are connected in series 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 tube and the compensation control module. The detection module is used to generate a detection signal based on the magnitude relationship between the drain voltage of the first power switch tube and the first reference voltage, as well as the magnitude relationship between the drain voltage of the first power switch tube and the second reference voltage. The compensation control module is used to output the compensation voltage based on the detection signal.

[0017] Optionally, the compensation control module includes an oscillator and a counter, the oscillator is connected to the detection module, the oscillator is used to obtain the detection signal, and generate oscillation signals of different frequencies according to different detection signals; the counter includes a counting input terminal and a carry and borrow input terminal, the counting input terminal is connected to the oscillator, and the carry and borrow input terminal is connected to 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;

[0018] The counter includes an overflow signal output terminal, which is connected to the upper and lower power protection circuit. The overflow signal output terminal is used to output the overflow signal of the counter. The upper and lower power protection circuit is used to control the constant current control circuit and the charge and discharge control circuit according to the overflow signal.

[0019] Optionally, the compensation control module also includes a digital-to-analog converter, the output end of the counter is connected to the digital-to-analog converter, the output end of the digital-to-analog converter is connected to the charge and discharge control circuit, and the digital-to-analog converter is used to convert the counting result of the counter into an analog signal as the compensation voltage.

[0020] Optionally, the detection module includes a first amplifier and a second amplifier, wherein one input end of the first amplifier is connected to the drain of the first power switch tube, and the other input end of the first amplifier is used to receive the first reference voltage; one input end of the second amplifier is connected to the drain of the first power switch tube, and the other input end of the second amplifier is used to receive the second reference voltage;

[0021] The output end of the first amplifier and the output end of the second amplifier are connected to the input end of the oscillator, so as to control the oscillation frequency output by the oscillator;

[0022] Any one of the output end of the first amplifier and the output end of the second amplifier is connected to the counter and is used to control the carry and borrow operations of the counter.

[0023] Optionally, the detection module includes a third amplifier, one input end of the third amplifier is connected to the gate of the first power switch tube, the other input end of the third amplifier is used to receive a third reference voltage, and the output end of the third amplifier is connected to the input end of the oscillator for controlling the oscillation frequency output by the oscillator.

[0024] Optional,

[0025] The power-on and power-off protection circuit includes a delayed start module, which includes a delay input terminal and a delay output terminal. The delay input terminal is connected to the output terminal of the detection control circuit and is used to receive the compensation voltage. The protection control circuit includes a start input terminal, and the delay output terminal is connected to the start input terminal.

[0026] The protection control circuit is used to control the constant current control circuit to connect the loop of the constant current load, the bus and the ground terminal when the constant current load drive circuit is powered on; the delayed start module is used to output a start signal through the delayed output terminal when the compensation voltage is greater than the third voltage threshold when the constant current load drive circuit is powered on; the protection control circuit is used to control the charge and discharge control circuit to connect the loop of the energy storage capacitor, the bus and the ground terminal in response to the start signal.

[0027] In a second aspect, a constant current load circuit comprises a bus, a constant current load and a ground terminal, wherein the constant current load is connected between the bus and the 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 further comprises a constant current load driving circuit as described in the first aspect, wherein the constant current load driving circuit is used to drive the constant current load.

[0028] When the power is turned off, the bus voltage continues to drop, and the detection control circuit output compensation voltage of the constant current load drive circuit continues to rise. 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 is controlled to disconnect the loop between the constant current load, the bus and the ground terminal, and the charge and discharge control circuit is controlled to disconnect the loop between the energy storage capacitor, the bus and the ground terminal, so that the compensation voltage drops rapidly, the constant current control circuit and the charge and discharge control circuit stop working, and the power consumption of the constant current load drive circuit is reduced. When the circuit is powered on again, the constant current control circuit disconnects the loop between the constant current load, the bus and the ground terminal, and the charge and discharge control circuit disconnects the loop between the energy storage capacitor, the bus and the ground terminal. The higher voltage and current generated by the bus will not affect the constant current control circuit and the charge and discharge control circuit, thereby facilitating the safety of the constant current load drive circuit when the constant current load is powered on and off.

[0029] In a third aspect, the present 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 connected to an energy storage capacitor, and the energy storage capacitor is connected between the bus and the ground terminal, and the driving method includes:

[0030] detecting the current of the constant current load;

[0031] generating a compensation voltage based on the current of the constant current load;

[0032] controlling the charging and discharging of the energy storage capacitor according to the compensation voltage;

[0033] When the power is turned off, when 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 loop between the constant current load, the bus and the ground terminal, and the charge and discharge control circuit is controlled to disconnect the loop between the energy storage capacitor, the bus and the ground terminal.

[0034] During power-off, when 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 loop between the constant current load, the bus, and the ground terminal, and the charge-discharge control circuit is controlled to disconnect the loop between the energy storage capacitor, the bus, and the ground terminal, thereby causing the compensation voltage to drop rapidly, causing the constant current control circuit and the charge-discharge control circuit to stop working, thereby reducing the power consumption of the constant current load drive circuit. When power is turned on again, 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. The higher voltage and current generated by the bus will not affect the constant current control circuit and the charge-discharge control circuit, thereby facilitating the safety of the constant current load drive circuit during power-on.

[0035] Optionally, the constant current load driving method further includes:

[0036] When power is turned on, controlling the loops of the constant current load, the busbar and the ground terminal to be conductive;

[0037] When the compensation voltage is greater than a third voltage threshold, the loops of the energy storage capacitor, the busbar, and the ground terminal are controlled to be conductive. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0039] Figure 1 The figure shows the signal waveforms of the bus voltage, compensation voltage and current passing through the energy storage capacitor and the power tube when the bus voltage is powered on again after being powered off in the related art.

[0040] Figure 2 Shown is a principle block diagram of an embodiment of a constant current load circuit of the present application.

[0041] Figure 3 Shown Figure 2 A circuit diagram of an embodiment of a constant current load circuit is shown.

[0042] Figure 4 Shown Figure 2 FIG. 1 is a circuit diagram of an embodiment of a constant current load circuit for compensating an operational amplifier.

[0043] Figure 5 Shown Figure 2 FIG. 1 is a circuit diagram of an embodiment of a protection control circuit for a constant current load circuit.

[0044] Figure 6 FIG. 1 is a schematic diagram of an embodiment of a method for driving a constant current load of the present application.

[0045] Figure 7 Shown is a signal waveform diagram of an embodiment of the constant current load circuit of the present application.

[0046] Description of reference numerals:

[0047] Constant current load driving 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; counting input terminal 1224; carry and borrow input terminal 1225; charge and discharge control circuit 130; power-on and power-off protection circuit 140; first switch circuit 141; second switch circuit 142; delay start module 143; delay input terminal 1431; delay output terminal 1432; protection control circuit 144; first detection terminal 1441; second detection terminal 1442; control terminal 1443; start input terminal 1444; logic gate module 145; comparison and judgment module 146; trigger 147;

[0048] 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;

[0049] Constant current load circuit 200; AC power supply 210; energy storage capacitor 220; constant current load 230; bus 240; rectifier module 250. DETAILED DESCRIPTION

[0050] Here, the technical solutions in the embodiments (or "implementations") of the present application will be clearly and completely described in conjunction with the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0051] The terms "first" and "second" in the embodiments of the present application are only used for descriptive purposes and should not be understood as indicating or implying relative importance.

[0052] In the related art, when the constant current load circuit 200 is powered off, as the bus voltage V-in drops, the compensation voltage V-comp will first rise and then drop. At this time, if the compensation voltage V-comp is not completely dropped before the power is suddenly turned on, the circuit power tube is in the on state, and the bus voltage V-in suddenly increases, resulting in a sudden increase in the current I-CH passing through the circuit power tube and the energy storage capacitor, such as Figure 1 As shown, the chip function is disabled.

[0053] See also Figure 2 As shown, the present application provides a constant current load circuit 200, including a busbar 240, a constant current load 230, a ground terminal GND and a constant current load driving circuit 100. The constant current load circuit 200 also includes a rectifier module 250, which rectifies the current output by the AC power supply 210, and the busbar 240 is connected to the output terminal of the rectifier module 250. The busbar voltage V-in is the voltage after the AC power supply 210 is rectified. The constant current load 230 is connected between the busbar 240 and the ground terminal GND, and is connected to the energy storage capacitor 220, which is connected between the busbar 240 and the ground terminal GND. The busbar 240 can supply power to the constant current load 230 or charge the energy storage capacitor 220. In some cases, the energy storage capacitor 220 can discharge and supply power to the constant current load 230. The constant current load driving circuit 100 is connected to the constant current load 230 for driving the constant current load 230. The constant current load 230 may be an LED or other loads.

[0054] The constant current load drive circuit 100 includes a constant current control circuit 110, a detection control circuit 120, a charge and discharge control circuit 130, and a power-on and power-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 passing through the constant current load 230. The detection control circuit 120 is connected to the constant current load 230 and the constant current control circuit 110 and is used to detect the current of the constant current load 230 adjusted 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 and 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 based on the compensation voltage V-comp. The power-on and power-off protection circuit 140 includes a first detection terminal 1441, a second detection terminal 1442, and a control terminal 1443. The first detection terminal 1441 is connected to the bus 240 and is used to receive the bus voltage. The second detection terminal 1442 is connected to the detection control circuit 120 for receiving the compensation voltage. The control terminal 1443 is connected to the constant current control circuit 110 and the charge and discharge control circuit 130 respectively, and is used to control the constant current control circuit and the charge and discharge control circuit through the control terminal according to the bus voltage V-in and the compensation voltage V-comp. Specifically, when the constant current load drive circuit 100 is powered off, 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 is controlled to disconnect the loop of 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 loop of the energy storage capacitor 220, the bus 240 and the ground terminal GND.

[0055] During power-off, the bus voltage V-in continues to drop, while the compensation voltage V-comp output by the detection control circuit 120 continues to rise. 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 is controlled to disconnect the loop between the constant current load 230, the bus 240, and the ground terminal GND. The charge-discharge control circuit 130 is controlled to disconnect the loop between the energy storage capacitor 220, the bus 240, and the ground terminal GND, thereby causing the compensation voltage V-comp to drop rapidly. The constant current control circuit 110 and the charge-discharge control circuit 130 stop operating, thereby reducing the power consumption of the constant current load drive circuit 100. When the circuit is powered on again, because the compensation voltage V-comp has dropped to a low level when the power is turned off, and the loop between the constant current load 230, the bus 240 and the ground terminal GND is disconnected, and the loop between the energy storage capacitor 220, the bus 240 and the ground terminal GND is disconnected, the higher voltage and current on the bus 240 will not affect the constant current control circuit 110 and the charge and discharge control circuit 130, thereby facilitating the safety of the constant current load drive circuit 100 when it is powered on.

[0056] For details, see Figure 3 As shown, 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 passing through the constant current load 230 by controlling the first power switch Q1, thereby achieving constant current control.

[0057] The detection control circuit 120 is connected to the first power switch tube Q1, and detects the current of the constant current load 230 by detecting the voltage of the first power switch tube Q1. The compensation voltage V-comp is output to the charge and discharge control circuit 130 according to the voltage of the first power switch tube Q1, so that the charge and discharge control circuit 130 controls the charging and discharging of the energy storage capacitor 220.

[0058] The charge and 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 and discharge control circuit 130 also includes a compensation operational amplifier CMP4. One input terminal of the compensation operational amplifier CMP4 is connected to the detection control circuit 120 for receiving the compensation voltage V-comp; the other input terminal of the compensation operational amplifier CMP4 is used to receive the divided voltage V-div after the bus voltage V-in is divided. Figure 4 As shown, a third voltage-divider resistor R3 and a fourth voltage-divider resistor R4 are connected in series between busbar 240 and the source of the second power switch Q2. The other input of compensation operational amplifier CMP4 is connected between the third voltage-divider resistor R3 and the fourth voltage-divider resistor R4 via a fifth resistor R5. The output of compensation operational amplifier CMP4 is connected to the gate of the second power switch Q2. Compensation operational amplifier CMP4 is used to compare the compensation voltage V-comp with the divided voltage V-div to control the conduction and disconnection of the second power switch Q2, thereby controlling the charging and discharging of energy storage capacitor 220.

[0059] The power-on / off protection circuit 140 includes a protection control circuit 144 and a first switch circuit 141. A first detection terminal 1441 of the protection control circuit 144 is connected to the bus 240 for receiving the bus voltage. A second detection terminal 1442 is connected to the detection control circuit 120 for receiving the compensation voltage. A control terminal 1443 is connected to the first switch circuit 141 for controlling the first switch circuit 141. The first switch 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 to control the on / off state of the first power switch Q1. Specifically, when the constant current load drive circuit 100 is powered off, the protection control circuit 144 controls the first switch circuit 141 to conduct 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. At this point, the gate of the first power switch Q1 is connected to the ground terminal GND, and the first power switch Q1 is turned off.

[0060] The power-on and power-off protection circuit 140 controls the constant current control circuit 110 via the first switch circuit 141, thereby disconnecting the loop between the constant current load 230, the busbar 240, and the ground terminal GND. When the first switch circuit 141 is turned on, the gate of the first power switch Q1 is grounded, turning off the first power switch Q1. This controls the constant current control circuit 110, disconnecting the loop between the constant current load 230, the busbar 240, and the ground terminal GND. The first switch circuit 141 includes a controllable switch that connects the gate of the first power switch Q1 to the ground terminal GND. During normal operation of the constant current load 230, the first switch circuit 141 is in the disconnected state. When the constant current load drive circuit 100 is powered off, the first switch circuit 141 is in the disconnected state when the busbar 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.

[0061] The protection control circuit 144 is configured to control the first switch circuit 141 to conduct, turning off the first power switch Q1, 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 when the constant-current load driving circuit 100 is powered off. This causes the compensation voltage V-comp to drop rapidly, halting the operation of the constant-current control circuit 110 and the charge-discharge control circuit 130, thereby reducing the power consumption of the constant-current load driving circuit 100. When the constant-current load driving circuit 100 is powered on again, because the compensation voltage V-comp has already dropped to a low level during power-off, and the circuits between the constant-current load 230, the bus 240, and the ground terminal GND are disconnected, and the circuits between the energy storage capacitor 220, the bus 240, and the ground terminal GND are disconnected, the higher voltage and current on the bus 240 will not affect the charge-discharge control circuit 130, thereby enhancing the safety of the constant-current load driving circuit 100 during power-on. By using the first switch circuit 141, the loop can be quickly shut down when the power is off, and the constant current control circuit 110 can be prevented from being triggered by mistake to turn on the loop of the constant current load 230, the bus 240 and the ground terminal GND, thereby greatly improving safety.

[0062] In some embodiments, the power-on and power-off protection circuit 140 includes a second switch circuit 142. A first detection terminal 1441 of the protection control circuit 144 is connected to the bus 240 for receiving the bus voltage. A second detection terminal 1442 is connected to the detection control circuit 120 for receiving the compensation voltage. A control terminal 1443 is connected to the first switch circuit 141 for controlling the first switch circuit 141. The second switch circuit 142 is connected to the charge and discharge control circuit 130. The second switch circuit 142 is connected to the gate of the second power switch Q2 and the ground terminal GND to control the on and off of the first power switch Q1. Specifically, the protection control circuit 144 is configured to control the second switch circuit 142 to conduct 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 when the constant current load drive circuit 100 is powered off, thereby controlling the second switch circuit 142 to turn on and turn off the second power switch Q2.

[0063] The protection control circuit 144 is configured to control the second switch circuit 142 to conduct 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 during power-off of the constant-current load driving circuit 100, thereby turning off the second power switch Q2. This causes the compensation voltage V-comp to drop rapidly, halting operation of the constant-current control circuit 110 and the charge-discharge control circuit 130, thereby reducing power consumption of the constant-current load driving circuit 100. When power is turned on again, because the compensation voltage V-comp has already dropped to a relatively low level during power-off, and the circuits between the constant-current load 230, the bus 240, and the ground terminal GND are disconnected, and the circuits between the energy storage capacitor 220, the bus 240, and the ground terminal GND are disconnected, the higher voltage and current on the bus 240 will not affect the charge-discharge control circuit 130, thereby enhancing the safety of the constant-current load driving circuit 100 during power-on. By using the second switch circuit 142, the loop can be quickly shut down when the power is off, and the constant current control circuit 110 can be prevented from being triggered by mistake to turn on the loop of the constant current load 230, the bus 240 and the ground terminal GND, thereby greatly improving safety.

[0064] See also Figure 5 As shown, the power-on and power-off protection circuit 140 also includes a delayed start module 143. The delayed start module includes a delay input terminal 1431 and a delay output terminal 1432. The delay input terminal 1431 is connected to the output terminal of the detection control circuit 120 and is used to receive the compensation voltage V-comp. Specifically, 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. The protection control circuit includes a start input terminal, and the delay output terminal is connected to the start input terminal.

[0065] When powered on, the protection control circuit 144 controls the constant current control circuit 110 to connect the circuits of the constant current load 230, the busbar 240, and the ground terminal GND. The delayed start module 143 outputs a start signal via the delay output terminal 1432 when the compensation voltage V-comp exceeds the third voltage threshold V-set3. In response to the start signal, the protection control circuit 144 controls the charge and discharge control circuit 130 to connect the circuits of the energy storage capacitor 220, the busbar 240, and the ground terminal GND.

[0066] After power is turned off, the energy storage capacitor 220 discharges, and the amount of charge in the energy storage capacitor 220 decreases. When power is turned 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 setting, the compensation voltage V-comp is greater than the third voltage threshold V-set3, and the voltage of the energy storage capacitor 220 can be used to power the constant current load 230, 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 passing through the constant current load 230 to be constant, reducing the risk of stroboscopic constant current load 230.

[0067] For details, see Figure 3 As shown, 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 is configured to compare the drain voltage of the first power switch Q1 with a first reference voltage V-ref1 and a second reference voltage V-ref2, respectively, and output a detection signal. The compensation control module 122 is configured to output a compensation voltage V-comp based on the detection signal. Taking the example of the first reference voltage V-ref1 being less than the second reference voltage V-ref2, when the constant current load 230 is in operation and 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, thereby increasing the charging current of the energy storage capacitor 220 and thereby 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 .

[0068] For details, see Figure 3As shown, 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 obtain a detection signal and generate an oscillation signal of different frequencies according to different detection signals. The counter 1222 includes a counting input terminal 1224 and a carry and borrow input terminal 1225. The counting input terminal 1224 is connected to the oscillator 1221, and the carry and borrow input terminal 1225 is connected to the detection module 121. The counter 1222 is used to count according to the oscillation signal and perform carry and borrow operations according to the detection signal. The oscillator 1221 is used to obtain a detection signal and generate an oscillation signal 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 oscillation signal generated by the oscillator 1221 according to different detection signals can be set according to different constant current load drive circuits 100.

[0069] For details, see Figure 3 As shown, 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, which is in turn connected to the charge-discharge control circuit 130. The digital-to-analog converter 1223 is configured to convert the count result of the counter 1222 into an analog signal, which serves as the compensation voltage V-comp. The digital-to-analog converter 1223 decodes the count result of the counter 1222 and generates a corresponding analog signal as the compensation voltage V-comp.

[0070] Specifically, taking the case where the first reference voltage V-ref1 is 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 detection signal controls the counter 1222 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 detection signal controls the counter 1222 to perform a borrow operation. The oscillator 1221 is used to obtain the detection signal and generate oscillation signals of different frequencies based on different detection signals. The counter 1222 performs a carry or borrow operation based on the number of pulses in the oscillation signal generated by the oscillator 1221. The frequencies of the oscillation signals generated by the oscillator 1221 based on 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 frequency of an oscillating signal at a specific frequency based on the detection signal, controls the counter 1222 to perform a carry operation based on the number of pulses in the oscillating signal, and 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, reduces the charging current of the energy storage capacitor 220, and thus reduces the discharge voltage of the energy storage capacitor 220. In this way, the current through the constant current load 230 is maintained constant. The counting result of the counter 1222 is decoded by the digital-to-analog converter 1223, so that a corresponding relationship exists between the counting result of the counter 1222 and the compensation voltage V-comp output by the digital-to-analog converter 1223. By setting the corresponding relationship between the counting result of the counter 1222 and the compensation voltage V-comp output by the digital-to-analog converter 1223, when the compensation voltage V-comp output by the digital-to-analog converter 1223 is greater than the third voltage threshold V-set3, the counter 1222 can output an overflow signal A0 = 1.

[0071] It should be noted that the counting logic of the counter 1222 and the manner in which the DAC 1223 decodes the counting result of the counter 1222 are adjustable and are not limited to this embodiment.

[0072] The counter 1222 includes an overflow signal output terminal 12221 . The overflow signal output terminal 12221 is connected to the power-on and power-off protection circuit 140 . The overflow signal output terminal 12221 is used to output an overflow signal A0 of the counter 1222 .

[0073] When power is turned off, the drain voltage of the first power switch Q1 continues to decrease, the oscillator 1221 continues to output an oscillation signal based on the detection signal, and the counter 1222 performs a carry operation based on the number of pulses in 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 and the bus voltage V-in is less than the first voltage threshold V-set1, the power-on / off protection circuit 140 determines that the constant current load 230 is in the power-off state. The power-on / off protection circuit 140 controls the constant current control circuit 110 to disconnect the circuit between the constant current load 230, the bus 240, and the ground terminal GND, and controls the charge-discharge control circuit 130 to disconnect the circuit between the energy storage capacitor 220, the bus 240, and the ground terminal GND, thereby rapidly decreasing the compensation voltage V-comp. The constant current control circuit 110 and the charge-discharge control circuit 130 stop operating, and the counter 1222 is reset to zero.

[0074] For details, see Figure 3 As shown, the gate of the first power switch Q1 is connected to the input terminal of the oscillator 1221. According to the comparison result between the gate voltage of the first power switch Q1 and the third reference voltage V-ref3, the oscillation frequency output by the oscillator 1221 is controlled. The third reference voltage V-ref3 can be an internal fixed value or provided externally.

[0075] Through the above configuration, the detection control circuit 120 obtains the current operating current of the constant current load 230. When the constant current load 230 is controlled to operate at a relatively low current, the risk of the detection control circuit 120 misjudging that the circuit is powered off is reduced, thereby reducing the risk of the constant current load driving circuit 100 being mistriggered.

[0076] For details, see Figure 3 As shown, the detection module 121 includes a first amplifier CMP1 and a second amplifier CMP2. One input of the first amplifier CMP1 is connected to the drain of the first power switch Q1, and the other input of the first amplifier CMP1 is used to receive a first reference voltage V-ref1. In the illustrated embodiment, the inverting input of the first amplifier CMP1 is connected to the drain of the first power switch Q1, and the positive input of the first amplifier CMP1 is used to receive the first reference voltage V-ref1. When the voltage of the drain of the first power switch Q1 after the voltage is divided by the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 is less than the first reference voltage V-ref1, the output of the first amplifier CMP1 outputs a high level. When the voltage of the drain of the first power switch Q1 after the voltage is divided by the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 is greater than the first reference voltage V-ref1, the output of the first amplifier CMP1 outputs a low level.

[0077] 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 positive input terminal of the second amplifier CMP2 is connected to the drain of the first power switch Q1, and the negative input terminal of the second amplifier CMP2 is used to receive the second reference voltage V-ref2. When the voltage of the drain of the first power switch Q1 after the voltage is divided by the first voltage-dividing resistor R1 and the second voltage-dividing 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 voltage of the drain of the first power switch Q1 after the voltage is divided by the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 is greater than the second reference voltage V-ref2, the output terminal of the second amplifier CMP2 outputs a high level.

[0078] 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 of the first amplifier CMP1 and the positive input of the second amplifier CMP2 are connected between the first voltage-divider resistor R1 and the second voltage-divider resistor R2. The output of the first amplifier CMP1 and the output of the second amplifier CMP2 are connected to the input of the oscillator 1221 to control the oscillation frequency output by the oscillator 1221. Either the output of the first amplifier CMP1 or the output of the second amplifier CMP2 is connected to the counter 1222 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 the voltage is divided by the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, is less than the first reference voltage V-ref1, the detection signal controls the counter 1222 to perform a carry operation. When the drain voltage of the first power switch Q1, after the voltage is divided by the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, is greater than the first reference voltage V-ref1, the detection signal controls the counter 1222 to perform a borrow operation. The carry and borrow operations of the counter 1222 may also be controlled based on a comparison result between the drain voltage of the first power switch Q1 and the second reference voltage V-ref2, and the present invention is not limited to this embodiment.

[0079] For details, see Figure 3As shown, the detection module 121 includes a third amplifier CMP3. One input of the third amplifier CMP3 is connected to the gate of the first power switch Q1, and the other input of the second amplifier CMP2 is used to receive a third reference voltage V-ref3. In the illustrated embodiment, the positive input of the third amplifier CMP3 is connected to the gate of the first power switch Q1, and the negative input 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 of the third amplifier CMP3 is connected to the input of an oscillator 1221. Oscillator 1221 controls the oscillation frequency output by the oscillator 1221 based on the output signal of the third amplifier CMP3, thereby controlling the counting result of the counter 1222. The output signal is converted into a compensation voltage V-comp via the digital-to-analog converter 1223, thereby controlling the current passing through the constant current load 230.

[0080] See also Figure 5As shown, protection control circuit 144 specifically includes a comparison and judgment module 146, a logic gate module 145, and a trigger 147. Comparison and judgment module 146 is connected to bus 240 and is configured 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, comparison and judgment module 146 outputs a low level; when the bus voltage V-in is greater than the first voltage threshold V-set1, comparison and judgment module 146 outputs a high level. The inputs of logic gate module 145 are connected to the output of delay start module 143 and the overflow signal output, respectively. When the overflow signal output terminal outputs the overflow signal A0 of the counter 1222 = 1 and the comparison and judgment module 146 outputs a high level, the trigger 147 outputs a trigger signal Load = 0 to control the first power switch Q1 and the second power switch Q2 to be turned off. 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, thereby causing the compensation voltage V-comp to drop rapidly, causing the constant current control circuit 110 and the charge and discharge control circuit 130 to stop operating, thereby reducing the power consumption of the constant current load drive circuit 100. When the overflow signal output terminal outputs the overflow signal of the counter 1222 and the comparison and judgment module 146 outputs a low level, the trigger 147 outputs a trigger signal Load = 1 to control the first power switch Q1 and the second power switch Q2 to be turned on. 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 conduction voltage of the constant current load 230, thereby controlling the current passing through the constant current load 230 to be constant, reducing the risk of flicker of the constant current load 230.

[0081] This embodiment provides a driving method for a constant current load 230, such as Figure 6 As shown, it includes step S10, step S20 and step S30.

[0082] In step S10 , the current I-CH of the constant current load 230 is detected.

[0083] In step S20 , a compensation voltage V-Comp is generated based on the current of the constant current load 230 .

[0084] In step S30, when power is turned off, 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 is controlled to disconnect the loop of 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 loop of the energy storage capacitor 220, the bus 240 and the ground terminal GND.

[0085] During power-off, the bus voltage V-in continues to drop, while the compensation voltage V-comp output by the detection control circuit 120 continues to rise. 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 is controlled to disconnect the loop between the constant current load 230, the bus 240, and the ground terminal GND. The charge-discharge control circuit 130 is controlled to disconnect the loop between the energy storage capacitor 220, the bus 240, and the ground terminal GND, thereby causing the compensation voltage V-comp to drop rapidly. The constant current control circuit 110 and the charge-discharge control circuit 130 stop operating, thereby reducing the power consumption of the constant current load drive circuit 100. When the power is turned on again, the constant current control circuit 110 disconnects the loop of the constant current load 230, the bus 240 and the ground terminal GND, and the charge and discharge control circuit 130 disconnects the loop of the energy storage capacitor 220, the bus 240 and the ground terminal GND. The higher voltage and current generated by the bus 240 will not affect the constant current control circuit 110 and the charge and discharge control circuit 130. Figure 7 As shown, 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 (an LED in this embodiment) is I-LED, and the current through the energy storage capacitor 220 is I-CH. From t0 to t1, the constant current load 230 is continuously powered on; from t1 to t2, it is powered off; and after t2, it is powered on again. This configuration improves the safety of the constant current load drive circuit 100 during power-up.

[0086] See also Figure 6 As shown, the driving method of the constant current load 230 further includes step S40.

[0087] In step S40, when power is turned on, the loop of the constant current load 230, the bus 240 and the ground terminal GND is controlled to be turned on. When the bus voltage V-in is greater than the third voltage threshold V-rep3, the loop of the energy storage capacitor 220, the bus 240 and the ground terminal GND is controlled to be turned on.

[0088] After power is turned off, the energy storage capacitor 220 discharges, and the amount of charge in the energy storage capacitor 220 decreases. When power is turned 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 setting, 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. Through the above setting, the current passing through the constant current load 230 is controlled to be constant, reducing the risk of stroboscopic constant current load 230.

[0089] It should be noted that the technical solutions or technical 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 shall be included in the scope of protection of this application.

Claims

1. A constant current load driving circuit, characterized in that: Used to drive a constant current load, 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, and the constant current load driving circuit includes: A constant current control circuit, connected to the constant current load, for adjusting the current passing through the constant current load; a detection control circuit connected to the constant current load and the constant current control circuit, configured to detect the current of the constant current load adjusted by the constant current control circuit, and output a compensation voltage based on the current of the constant current load; a charge and discharge control circuit, connected to the energy storage capacitor and the detection control circuit, and configured to control the charge and discharge of the energy storage capacitor according to the compensation voltage; and The power-on and power-off protection circuit includes a first detection end, a second detection end, and a control end. The first detection end is connected to the bus for receiving the bus voltage. The second detection end is connected to the detection control circuit for receiving the compensation voltage. The control end is respectively connected to the constant current control circuit and the charge and discharge control circuit. The power-on and power-off protection circuit is used to control the constant current control circuit and the charge and discharge control circuit through the control end according to the bus voltage and the compensation voltage.

2. The constant current load driving circuit according to claim 1, wherein: The constant current control circuit includes a first power switch tube, and the first power switch tube and the constant current load are connected in series between the bus and the ground terminal; The power-on and power-off protection circuit includes a protection control circuit and a first switching circuit. The protection control circuit includes the first detection end, the second detection end and the control end. The control end is connected to the first switching circuit. The first switching circuit is connected to the gate of the first power switch tube and the ground end, and is used to control the on and off of the first power switch tube. The control end is used to control the first switching circuit.

3. The constant current load driving circuit according to claim 2, wherein: The charge and discharge control circuit includes a second power switch tube, and the second power switch tube and the energy storage capacitor are connected in series between the bus and the ground terminal; The power-on and power-off protection circuit includes a second switching circuit, the control end is connected to the second switching circuit, the second switching circuit is connected to the gate of the second power switch tube and the ground end, and is used to control the on and off of the second power switch tube. The control end is used to control the second switching circuit.

4. The constant current load driving circuit according to claim 2, wherein: The first power switch tube and the constant current load are connected in series between the bus and the ground terminal; The detection control circuit includes a detection module and a compensation control module. The detection module is connected between the first power switch tube and the compensation control module. The detection module is used to generate a detection signal based on the magnitude relationship between the drain voltage of the first power switch tube and the first reference voltage, as well as the magnitude relationship between the drain voltage of the first power switch tube 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 driving circuit according to claim 4, wherein: The compensation control module includes an oscillator and a counter. The oscillator is connected to the detection module and is used to obtain the detection signal and generate oscillation signals of different frequencies according to different detection signals. The counter includes a counting input terminal and a carry and borrow input terminal. The counting input terminal is connected to the oscillator, and the carry and borrow input terminal is connected to 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 upper and lower power protection circuit. The overflow signal output terminal is used to output the overflow signal of the counter. The upper and lower power protection circuit is used to control the constant current control circuit and the charge and discharge control circuit according to the overflow signal.

6. The constant current load driving circuit according to claim 5, wherein: The compensation control module also includes a digital-to-analog converter, the output end of the counter is connected to the digital-to-analog converter, the output end of the digital-to-analog converter is connected to the charge and discharge control circuit, and 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 driving circuit according to claim 5, wherein: The detection module includes a first amplifier and a second amplifier, wherein one input end of the first amplifier is connected to the drain of the first power switch tube, and the other input end of the first amplifier is used to receive the first reference voltage; one input end of the second amplifier is connected to the drain of the first power switch tube, and the other input end of the second amplifier is used to receive the second reference voltage; The output end of the first amplifier and the output end of the second amplifier are connected to the input end of the oscillator, so as to control the oscillation frequency output by the oscillator; Any one of the output end of the first amplifier and the output end of the second amplifier is connected to the counter and is used to control the carry and borrow operations of the counter.

8. The constant current load driving circuit according to claim 7, wherein: The detection module includes a third amplifier, one input end of the third amplifier is connected to the gate of the first power switch tube, the other input end of the third amplifier is used to receive a third reference voltage, and the output end of the third amplifier is connected to the input end of the oscillator for controlling the oscillation frequency output by the oscillator.

9. The constant current load driving circuit according to claim 2, wherein: The power-on and power-off protection circuit includes a delayed start module, which includes a delay input terminal and a delay output terminal. The delay input terminal is connected to the output terminal of the detection control circuit and is used to receive the compensation voltage. The protection control circuit includes a start input terminal, and the delay output terminal is connected to the start input terminal. The protection control circuit is used to control the constant current control circuit to connect the loop of the constant current load, the bus and the ground terminal when the constant current load drive circuit is powered on; the delayed start module is used to output a start signal through the delayed output terminal when the compensation voltage is greater than the third voltage threshold when the constant current load drive circuit is powered on; the protection control circuit is used to control the charge and discharge control circuit to connect the loop of the energy storage capacitor, the bus and the ground terminal in response to the start signal.

10. A constant current load circuit, characterized in that: It includes a busbar, an energy storage capacitor, a constant current load and a ground terminal, the constant current load is connected between the busbar and the ground terminal, and is connected to the energy storage capacitor, the energy storage capacitor is connected between the busbar and the ground terminal, the constant current load circuit also includes the constant current load driving circuit according to any one of claims 1 to 9, and the constant current load driving circuit is used to drive the constant current load.

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