A driving power supply circuit with no output when overloaded

Abstract

The present invention discloses a driving power supply circuit with no output under overload, which includes an EMI circuit, a rectifier filter circuit, a PFC boost circuit, a PWM pulse width modulation circuit, a transformer circuit, an output synchronous rectifier circuit, a constant current and constant voltage loop, a dimming control circuit, a temperature control protection circuit, and an overload / short circuit protection circuit. The present invention has a simple circuit, reliable performance, and wide applicability. Ultra-low safety low voltage, safer, multiple sensitive protection circuits, safer and more assured for users to use. It has output overload and short circuit protection, and the output is turned off after overload and short circuit.

Description

Technical Field

[0001] The invention relates to the technical field of LED lamp driving circuits, in particular to an overloaded and no-output driving power supply circuit. Background Art

[0002] The current LED driving circuit lacks a protection circuit when the driving circuit has an output overload phenomenon, and the driving circuit still maintains the voltage output, which easily causes a safety hazard to the circuit. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a driving power supply circuit with no output when overloaded in view of the above-mentioned deficiencies in the prior art, so as to provide a safer protection for the circuit and prevent accidents when the load is abnormal.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: an overload and no-output driving power supply circuit, which includes an EMI circuit, a rectifier and filter circuit, a PFC boost circuit, a PWM pulse width modulation circuit, a transformer circuit, an output synchronous rectifier circuit, a constant current and constant voltage loop, a dimming control circuit, a temperature control protection circuit and an overload / short circuit protection circuit; the city power outputs a DC pulse voltage VIN+ through the EMI circuit and the rectifier and filter circuit, and the DC pulse voltage VIN+ outputs a boosted DC voltage HV after the power factor is corrected by the PFC boost circuit, and the DC voltage HV is transformed and output from the main primary side of the transformer circuit to the main secondary side after passing through the temperature control protection circuit, and the main and secondary sides of the transformer circuit output the load working voltage to the load through the output synchronous rectifier circuit, the PWM pulse width modulation circuit controls the on and off of the main primary side loop of the transformer circuit through the switch tube Q2, and the secondary primary side loop of the transformer circuit provides a starting voltage to the PWM pulse width modulation circuit, and the PWM pulse width modulation circuit provides a starting voltage PFC to the PFC chip in the PFC boost circuit. VCC; the constant current and constant voltage loop samples and compares the load circuit in the output synchronous rectification circuit and feeds back to the PWM pulse width modulation circuit through an optical coupler, and the PWM pulse width modulation circuit controls the output of the transformer circuit and the output synchronous rectification circuit according to the feedback and modulates the load through a switch circuit based on a switch tube group; the overload / short circuit protection circuit samples and detects the current of the load circuit and controls the output synchronous rectification circuit to turn on and off the load output through the switch circuit, and the overload / short circuit protection circuit feeds back the on and off information of the load output to the PWM pulse width modulation circuit through the optical coupler to control the output of the transformer circuit.

[0005] In the above technical solution, the constant current and constant voltage loop includes an operational amplifier U6A and an operational amplifier U6B to respectively realize voltage feedback and current feedback of the load circuit.

[0006] In the above technical solution, the output end of the operational amplifier U6A is reversely connected with a diode D21 and a pull-up resistor R61, and the output end of the operational amplifier U6B is reversely connected with a diode D22 and a pull-up resistor R59, forming a voltage follower and a current follower respectively.

[0007] In the above technical solution, the overload / short-circuit protection circuit includes a comparator, which samples the current of the load circuit and compares it with the reference current. The output terminal HP of the comparator outputs a detection voltage to indicate whether the load circuit is overloaded / short-circuited. The detection voltage controls the on / off of the switch circuit. At the same time, the detection voltage is fed back to the PWM pulse width modulation circuit via a photoelectric coupler.

[0008] In the above technical solution, the switch circuit includes a switch tube Q10, a switch tube Q9, a switch tube Q7, a switch tube Q6 and a switch tube Q4. The switch circuit obtains a working voltage AUX from the output end of the voltage conversion circuit. The working voltage AUX is connected in series with a resistor R100 and a resistor R63, and then connected in series with a resistor R101 to be electrically connected to the negative electrode of the load, and another path is electrically connected to the control end of the switch tube Q7. The input end of the switch tube Q7 is electrically connected to the control end of the switch tube Q6, and the output end of the switch tube Q6 is electrically connected to the control end of the switch tube Q4. The output end of the switch tube Q4 serves as the voltage output end VCOM+ of the load. The input ends of the switch tubes Q7, Q6 and Q4 are all electrically connected to the output end OP+ of the output synchronous rectification circuit; the control end of the switch tube Q10 is electrically connected to the output end HP of the comparator, the input end of the switch tube Q10 is electrically connected to the node CT between the resistor R100 and the resistor R63, and another path is electrically connected to the control end of the switch tube Q9, and the input end of the switch tube Q9 is electrically connected to the node CT.

[0009] In the above technical solution, the output terminal HP of the comparator changes the on-off loop of the optical coupler by controlling the on-off of the switch tube Q8 to realize the feedback of the detection voltage condition of the output terminal HP to the PWM pulse width modulation circuit.

[0010] In the above technical solution, the dimming control circuit outputs a PWM control signal to control the switch circuit via the switch tube Q5 to achieve dimming.

[0011] In the above technical solution, the output synchronous rectification circuit includes a synchronous rectification chip U4 and a switch tube Q3, the input terminal VS of the switch tube Q3 is electrically connected to the output terminal of the transformer voltage, the output terminal VD of the switch tube Q3 serves as the output terminal OP+ of the output synchronous rectification circuit, and the synchronous rectification chip U4 uses the input terminal VS and the output terminal VD of the switch tube Q3 as sampling points for output rectification.

[0012] In the above technical solution, a connection terminal VSTART is provided in the EMI circuit and is electrically connected to the start terminal of the control chip U2 of the PWM pulse width modulation circuit.

[0013] In the above technical solution, the PFC boost circuit includes a PFC chip U1, an inductor T1 and a switch tube Q1, one input end of the inductor T1 is electrically connected to the DC pulse voltage VIN+, the other input end is electrically connected to the output end of the PFC chip U1, the DC pulse voltage VIN+ is electrically connected to the input end of the PFC chip U1, the control end of the switch tube Q1 is electrically connected to the control output end of the PFC chip U1, and the output end of the switch tube Q1 is electrically connected to the control end of the PFC chip U1; one output end of the inductor T1 is grounded, and the other output end is connected in series with a diode D4 and a magnetic bead FB3 to output the DC voltage HV.

[0014] The beneficial effects of the present invention are:

[0015] 1. Simple circuit, reliable performance and wide applicability.

[0016] 2. Ultra-low safety low voltage, safer, multiple sensitive protection circuits, users can use it more safely and with more confidence.

[0017] 3. With output overload and short circuit protection, the output will be shut down after overload and short circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a circuit principle schematic diagram of the driving power supply circuit of the present invention.

[0019] Figure 2 It is a circuit principle diagram of the EMI circuit, the rectifier filter circuit, and the temperature control protection circuit of the present invention.

[0020] Figure 3 It is a circuit principle schematic diagram of the PFC boost circuit and the PWM pulse width modulation circuit of the present invention.

[0021] Figure 4 It is a circuit principle schematic diagram of the voltage conversion circuit, output synchronous rectification circuit, constant current and constant voltage loop, and switch circuit of the present invention.

[0022] Figure 5 It is a circuit principle schematic diagram of the overload / short circuit protection circuit of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0024] like Figure 1-5As shown, a driving power supply circuit with no output under overload includes an EMI circuit 1, a rectifier and filter circuit 2, a PFC boost circuit 3, a PWM pulse width modulation circuit 4, a transformer circuit 5, an output synchronous rectifier circuit 6, a constant current and constant voltage loop 7, a dimming control circuit 10, a temperature control protection circuit 8, and an overload / short circuit protection circuit 9. The city power outputs a DC pulse voltage VIN+ through the EMI circuit and the rectifier and filter circuit, and the DC pulse voltage VIN+ outputs a boosted DC voltage HV after the power factor is corrected by the PFC boost circuit. The DC voltage HV is transformed and output from the main primary side of the transformer circuit to the main secondary side after passing through the temperature control protection circuit. The main and secondary sides of the transformer circuit output the load working voltage to the load through the output synchronous rectifier circuit. The PWM pulse width modulation circuit controls the on and off of the main primary side loop of the transformer circuit through the switch tube Q2. The secondary primary side loop of the transformer circuit provides a starting voltage to the PWM pulse width modulation circuit. The PWM pulse width modulation circuit provides a starting voltage PFC to the PFC chip in the PFC boost circuit. VCC; the constant current and constant voltage loop samples and compares the load circuit in the output synchronous rectification circuit and feeds back to the PWM pulse width modulation circuit through an optical coupler, and the PWM pulse width modulation circuit controls the output of the transformer circuit and the output synchronous rectification circuit according to the feedback and modulates the load through a switch circuit based on a switch tube group; the overload / short circuit protection circuit samples and detects the current of the load circuit and controls the output synchronous rectification circuit to turn on and off the load output through the switch circuit, and the overload / short circuit protection circuit feeds back the on and off information of the load output to the PWM pulse width modulation circuit through the optical coupler to control the output of the transformer circuit.

[0025] Specifically, the EMI circuit 1 is used to filter out the interference of high-frequency pulses of the external power grid on the power supply, and also reduces the electromagnetic interference of the switching power supply itself to the outside world. The EMI circuit includes a series fuse F1, a parallel varistor VR1, a parallel capacitor C3, a series common mode inductor LF1 and a series common mode inductor LF2, a parallel resistor R10 and a resistor R11, a series common mode inductor LF4, a resistor R10 is forward-connected in parallel with a diode D2, a resistor R11 is reverse-connected in parallel with a diode D3, and the node between the resistor R10 and the resistor R11 is used as a connection terminal VSTSRT. A connection terminal VSTART is provided in the EMI circuit and is electrically connected to the start terminal of the control chip U2 of the PWM pulse width modulation circuit.

[0026] Specifically, the rectifier and filter circuit 2 is used to step down, rectify, and filter the AC power supply into a suitable DC voltage. The rectifier and filter circuit includes a rectifier BD1, an inductor L1, a capacitor C10, a capacitor C11, and a resistor R9. The output end of the rectifier BD1 is connected in series with the inductor L1 to output a DC pulse voltage VIN+. The input end of the inductor L1 is connected in series with the capacitor C10 and then grounded. The output end of the inductor L1 is connected in series with the capacitor C11 and then grounded. The two ends of the inductor L1 are connected in parallel with the resistor R9.

[0027] Specifically, the PFC boost circuit 3 is used to perform power factor correction on the DC pulse voltage VIN+ output by the rectifier and filter circuit to boost and output a stable and reliable DC voltage HV. The PFC boost circuit includes a PFC chip U1, an inductor T1 and a switch tube Q1. One input end of the inductor T1 is electrically connected to the DC pulse voltage VIN+, and another input end is electrically connected to the output end of the PFC chip U1. The DC pulse voltage VIN+ is electrically connected to the input end of the PFC chip U1. The control end of the switch tube Q1 is electrically connected to the control output end of the PFC chip U1, and the output end of the switch tube Q1 is electrically connected to the control end of the PFC chip U1. One output end of the inductor T1 is grounded, and the other output end is connected in series with a diode D4 and a magnetic bead FB3 to output the DC voltage HV. The DC pulse voltage VIN+ is electrically connected in series with resistors R2 and R4 to the MULT end of the PFC chip U1. The switch tube Q1 is a MOS tube. The control end of the switch tube Q1 is connected in series with resistors R3 and R49 and then electrically connected to the control output end of the PFC chip U1. The resistor R3 is connected in parallel with a diode D1. The output end of the switch tube Q1 is connected in series with a magnetic bead FB1 and then connected in series with resistors R20, R21, R22 and then grounded. The resistors R20, R21, R22 are in parallel, and the resistors R20, R21, R22 are connected in parallel with diodes D16 and D19.

[0028] Specifically, the PWM pulse width modulation circuit 4 is used to control the input and output of the transformer circuit according to the feedback signal collected by the feedback end. The PWM pulse width modulation circuit includes a control chip U2, the control output end of the control chip U2 is electrically connected to the control end of the switch tube Q2 after being connected in series with resistors R27 and R39, the resistor R27 is reversely connected in parallel with a diode D6, the output end of the switch tube Q2 is connected in series with a magnetic bead FB2, and then connected in series with resistors R47, R46, R99, R45, R44, and then grounded, the resistors R47, R46, R99, R45, R44 are in a parallel relationship, and the resistors R47, R46, R99, R45, R44 are also connected in parallel with a series diode D17 and a diode D20; the control end and the output end of the switch tube Q2 are connected in parallel with a resistor R40. The feedback end of the control chip U2 is electrically connected to the optical coupler receiving end U3B of the optical coupler, and the input and output ends of the optical coupler receiving end U3B are connected in parallel with a capacitor C24. The secondary primary loop of the transformer circuit is connected in series with a diode D7, a resistor R13, a diode D5, and a polar capacitor C15 and then grounded, and the cathode end of the diode D5 is electrically connected to the start-up end VCC of the control chip U2.

[0029] Specifically, the voltage conversion circuit 5 is used to convert the DC voltage HV output by the PFC boost circuit into an output working voltage required by the load. The voltage conversion circuit includes a transformer T2, the input end has a primary side and a secondary side, and the output end has a primary side and a secondary side. The secondary primary loop is connected in parallel with a capacitor C12, and the secondary primary loop and the primary and secondary loops are connected in parallel with a capacitor C19.

[0030] Specifically, the output synchronous rectification circuit 6 is used to replace the rectifier diode with a power MOSFET with extremely low on-resistance, so that the loss of the rectifier can be greatly reduced, the efficiency of the DC / DC converter can be improved, and the needs of low-voltage and high-current rectification can be met. The output synchronous rectification circuit includes a switch tube Q3, polar capacitors C28, C20, C29, capacitor C26, and a common-mode inductor LF3. The input end of the common-mode inductor LF3 is connected in parallel with a resistor R83 and in series with a resistor R51 as the output voltage sampling point VD of the synchronous rectification chip U4. The output point of the common-mode inductor LF3 is connected in parallel with the point C1, and is connected in parallel with a series resistor R78 and a light-emitting diode LED1. The output end of the common-mode inductor LF3 serves as the output end OP+ of the output synchronous rectification circuit. A series capacitor C27 and a resistor R37 are connected in parallel between the input end and the output end of the switch tube Q3, and the resistor R37 is connected in parallel with a resistor R38. The input terminal VS of the switch tube Q3 is electrically connected to the output terminal of the transformed voltage, and the output terminal VD of the switch tube Q3 serves as the output terminal OP+ of the output synchronous rectification circuit. The synchronous rectification chip U4 uses the input terminal VS and the output terminal VD of the switch tube Q3 as sampling points for output rectification. The synchronous rectification chip U4 is provided with a starting voltage by the secondary side SB of the transformer circuit in series with the diode D8.

[0031] Specifically, the constant current and constant voltage loop 7 is used to sample the current and voltage signals of the output synchronous rectification circuit and feed them back to the PWM pulse width modulation circuit to facilitate the adjustment of constant current and constant voltage. The constant current and constant voltage loop includes an operational amplifier U6A and an operational amplifier U6B to respectively realize voltage feedback and current feedback of the load circuit. The output end of the operational amplifier U6A is reversely connected with a diode D21 and a pull-up resistor R61, and the output end of the operational amplifier U6B is reversely connected with a diode D22 and a pull-up resistor R59, which respectively constitute a voltage follower and a current follower. The V0 end of the output synchronous rectification circuit is connected in series with a resistor 58, a resistor R67, and a resistor R42 and then grounded, and the node voltage between the resistor R58 and the resistor R67 is used as a reference voltage source 2.5V used by a subsequent comparator.

[0032] Specifically, the temperature control protection circuit 8 is used for temperature protection of the transformer input end. The temperature control protection circuit is electrically connected to the main primary circuit of the transformer, including resistors R24, R23, R25, R32, R33, R34, R35, R36, as well as fuse F2, diode D9 and capacitor C21. It has output overload and short circuit protection, and is designed to shut down the output after overload and short circuit. After overload or short circuit, the mains power is disconnected and the fault is eliminated. Wait for about 10 seconds, and then turn on the mains power again to output normally, with ultra-low short-circuit power. When the operating temperature of F2 reaches 110±5℃, the circuit immediately cuts off the output; when the operating temperature of F2 drops by 75±15℃, the circuit automatically resumes the output. From then on, the purpose of over-temperature protection is achieved.

[0033] Specifically, the overload / short circuit protection circuit 9 is used to protect the circuit when an overload / short circuit occurs at the output. The overload / short circuit protection circuit includes a comparator, which samples the current of the load circuit and compares it with the reference current. The output terminal HP of the comparator outputs a detection voltage to indicate whether the load circuit is overloaded / short-circuited. The detection voltage controls the on / off of the switch circuit. At the same time, the detection voltage is fed back to the PWM pulse width modulation circuit via a photoelectric coupler. The switch circuit includes a switch tube Q10, a switch tube Q9, a switch tube Q7, a switch tube Q6 and a switch tube Q4. The switch circuit obtains a working voltage AUX from the output end of the voltage conversion circuit. The working voltage AUX is connected in series with a resistor R100 and a resistor R63, and then one path is connected in series with a resistor R101 and is electrically connected to the negative electrode of the load, and the other path is electrically connected to the control end of the switch tube Q7. The input end of the switch tube Q7 is electrically connected to the control end of the switch tube Q6, and the output end of the switch tube Q6 is electrically connected to the control end of the switch tube Q4. The output end of the switch tube Q4 serves as the voltage output end VCOM+ of the load. The input ends of the switch tubes Q7, Q6 and Q4 are all electrically connected to the output end OP+ of the output synchronous rectification circuit; the control end of the switch tube Q10 is electrically connected to the output end HP of the comparator, one path of the input end of the switch tube Q10 is electrically connected to the node CT between the resistor R100 and the resistor R63, and the other path is electrically connected to the control end of the switch tube Q9, and the input end of the switch tube Q9 is electrically connected to the node CT. The output terminal HP of the comparator controls the on-off of the switch tube Q8 to change the on-off loop of the optical coupler to realize the feedback of the detection voltage condition of the output terminal HP to the PWM pulse width modulation circuit.

[0034] Specifically, the dimming control circuit 10 is a control circuit that outputs a dimming signal PWM. The dimming control circuit outputs a PWM control signal to control the switch circuit via the switch tube Q5 to achieve dimming.

[0035] The working principle of the present invention: the key point is overload protection. When the output end is overloaded or short-circuited, the circuit pulls the potentials of the 3, 5, 10, and 12 pins of the comparators U8 and U9 to 0 potential through the sampling resistors R66, R70, R72, R74, and R82 respectively. At this time, the 1, 7, 8, and 14 pins of the comparators U8 and U9 output a high level of about 0.7V, and at the same time, the capacitor C34 continuously provides a high level to the base of the switch tube Q9 and the collector of the switch tube Q10 through the resistor R100. At this time, the switch tubes Q9 and Q10 are turned on, and the switch tube Q9 outputs a high level. After the voltage is divided by the resistors R63 and R101, the base of the switch tube Q7 obtains a high level, so that the switch tube Q7 is turned on. After the switch tube Q7 is turned on, the resistor R64 provides a high level to the base of the switch tube Q6, so that the switch tube Q6 is turned on. After the switch tube Q6 is turned on, the gate of the switch tube Q4 obtains a high level QP point voltage, causing the switch tube Q4 to be cut off and the output to be turned off, thereby achieving the purpose of overload and short circuit protection.

[0036] The above embodiments are only for illustration rather than limitation of the present invention, so all equivalent changes or modifications made according to the method described in the scope of the present patent application are included in the scope of the present patent application.

Claims

1. A driving power supply circuit with no output when overloaded, characterized in that: It includes an EMI circuit, a rectifier and filter circuit, a PFC boost circuit, a PWM pulse width modulation circuit, a transformer circuit, an output synchronous rectifier circuit, a constant current and constant voltage loop, a dimming control circuit, a temperature control protection circuit and an overload / short circuit protection circuit; the AC power outputs a DC pulse voltage VIN+ through the EMI circuit and the rectifier and filter circuit, the DC pulse voltage VIN+ is corrected for power factor by the PFC boost circuit and then outputs a boosted DC voltage HV, the DC voltage HV is transformed from the main primary side of the transformer circuit to the main secondary side after passing through the temperature control protection circuit, the main and secondary sides of the transformer circuit output the load working voltage to the load through the output synchronous rectifier circuit, the PWM pulse width modulation circuit controls the on and off of the main primary side loop of the transformer circuit through the switch tube Q2, the secondary primary side loop of the transformer circuit provides a starting voltage to the PWM pulse width modulation circuit, and the PWM pulse width modulation circuit provides a starting voltage PFC to the PFC chip in the PFC boost circuit. VCC; the constant current and constant voltage loop samples and compares the load loop in the output synchronous rectification circuit and feeds back to the PWM pulse width modulation circuit through the optical coupler, and the PWM pulse width modulation circuit controls the output of the voltage conversion circuit and the output synchronous rectification circuit according to the feedback and modulates the load through the switch circuit based on the switch tube group; the overload / short circuit protection circuit samples and detects the current of the load loop and controls the output synchronous rectification circuit to turn on and off the load output through the switch circuit, and the overload / short circuit protection circuit feeds back the on and off information of the load output to the PWM pulse width modulation circuit through the optical coupler to control the output of the voltage conversion circuit; The switch circuit includes a switch tube Q10, a switch tube Q9, a switch tube Q7, a switch tube Q6 and a switch tube Q4. The switch circuit obtains a working voltage AUX from the output end of the voltage conversion circuit. The working voltage AUX is connected in series with a resistor R100 and a resistor R63, and then connected in series with a resistor R101 and electrically connected to the negative electrode of the load, and another path is electrically connected to the control end of the switch tube Q7. The input end of the switch tube Q7 is electrically connected to the control end of the switch tube Q6, and the output end of the switch tube Q6 is electrically connected to the control end of the switch tube Q4. The output end of the switch tube Q4 serves as the voltage output end VCOM+ of the load. The input ends of the switch tubes Q7, Q6 and Q4 are all electrically connected to the output end OP+ of the output synchronous rectification circuit. The control end of the switch tube Q10 is electrically connected to the output end HP of the comparator of the overload / short circuit protection circuit. The input end of the switch tube Q10 is electrically connected to a node CT between the resistor R100 and the resistor R63, and another path is electrically connected to the control end of the switch tube Q9. The input end of the switch tube Q9 is electrically connected to the node CT. Among them, when the output end of the switching circuit is overloaded or short-circuited, a high level is provided to the base of the switching tube Q9 and the collector of the switching tube Q10 to turn on the switching tubes Q9 and Q10, and the switching tube Q9 outputs a high level. After voltage division by the resistor R63 and the resistor R101, the base of the switching tube Q7 obtains a high level to turn on the switching tube Q7 and provides a high level to the base of the switching tube Q6 to turn on the switching tube Q6. The gate of the switching tube Q4 obtains a high-level QP point voltage, causing the switching tube Q4 to be turned off and the output to be turned off.

2. The overload-no-output driving power supply circuit according to claim 1, characterized in that: The constant current and constant voltage loop includes an operational amplifier U6A and an operational amplifier U6B, which respectively implement voltage feedback and current feedback to the load loop.

3. The overload-no-output driving power supply circuit according to claim 2, characterized in that: The output end of the operational amplifier U6A is reversely connected with a diode D21 and a pull-up resistor R61, and the output end of the operational amplifier U6B is reversely connected with a diode D22 and a pull-up resistor R59, forming a voltage follower and a current follower respectively.

4. The overload-no-output driving power supply circuit according to claim 1, characterized in that: The overload / short-circuit protection circuit includes a comparator, which samples the current of the load circuit and compares it with the reference current. The output terminal HP of the comparator outputs a detection voltage to indicate whether the load circuit is overloaded / short-circuited. The detection voltage controls the on / off of the switch circuit. At the same time, the detection voltage is fed back to the PWM pulse width modulation circuit via a photoelectric coupler.

5. The overload-no-output driving power supply circuit according to claim 4, characterized in that: The output terminal HP of the comparator controls the on-off of the switch tube Q8 to change the on-off loop of the optical coupler to realize the feedback of the detection voltage condition of the output terminal HP to the PWM pulse width modulation circuit.

6. The overload-no-output driving power supply circuit according to claim 1, characterized in that: The dimming control circuit outputs a PWM control signal through the switch tube Q5 to control the switch circuit to achieve dimming.

7. The overload-no-output driving power supply circuit according to claim 1, characterized in that: The output synchronous rectification circuit includes a synchronous rectification chip U4 and a switch tube Q3. The input terminal VS of the switch tube Q3 is electrically connected to the output terminal of the transformed voltage. The output terminal VD of the switch tube Q3 serves as the output terminal OP+ of the output synchronous rectification circuit. The synchronous rectification chip U4 uses the input terminal VS and the output terminal VD of the switch tube Q3 as sampling points for output rectification.

8. The overload-no-output driving power supply circuit according to claim 1, characterized in that: A connection terminal VSTART is provided in the EMI circuit and is electrically connected to a start terminal of the control chip U2 of the PWM pulse width modulation circuit.

9. The overload-no-output driving power supply circuit according to claim 1, characterized in that: The PFC boost circuit includes a PFC chip U1, an inductor T1 and a switch tube Q1. One input end of the inductor T1 is electrically connected to a DC pulse voltage VIN+, and another input end is electrically connected to an output end of the PFC chip U1. The DC pulse voltage VIN+ is electrically connected to the input end of the PFC chip U1, the control end of the switch tube Q1 is electrically connected to a control output end of the PFC chip U1, and the output end of the switch tube Q1 is electrically connected to a control end of the PFC chip U1; one output end of the inductor T1 is grounded, and the other output end is connected in series with a diode D4 and a magnetic bead FB3 to output the DC voltage HV.

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