Self-powered switch driving circuit and driving system

Abstract

The invention discloses a self-powered switch driving circuit and a driving system, and relates to the field of switching power supplies. The self-powered switch drive circuit comprises an undervoltage locking circuit, a constant current drive circuit, a self-powered circuit, a current detection circuit, a first switch tube, a second switch tube and a third switch tube. The under-voltage locking circuit comprises a first comparator; the first comparator outputs a driving signal according to the voltage of the power supply and the reference voltage so as to adjust the on-off state of the third switching tube and further adjust the working state of the constant current driving circuit; the current detection circuit obtains a current sampling signal and transmits the current sampling signal to the constant current driving circuit; the constant-current driving circuit comprises a biasing circuit; the constant current driving circuit outputs an adjusting signal according to the current sampling signal based on the biasing circuit, and is used for adjusting the working states of the self-powered circuit, the first switching tube and the second switching tube. The circuit structure is simplified, the manufacturing cost is reduced, and the circuit reliability is improved.

Description

Technical Field

[0001] The present application relates to the field of switching power supplies, and particularly to a self-powered switch driving circuit and a driving system. Background Art

[0002] With the rapid development of consumer electronics, LED devices have been widely used, and the demand for switching power supply chips supporting LED devices has also increased day by day. In the power supply method of traditional switching power supply control circuits, an independent power supply is usually used to supply power to the internal control circuit. Therefore, two sets of windings are required, one of which is the primary winding for storing energy, and the other is the auxiliary winding for supplying power to the load. The primary modulation technology does not require a secondary sampling circuit and has the advantages of fewer peripheral components and lower circuit complexity.

[0003] In practical applications, the auxiliary winding and the inductor cannot be fully coupled. The circuit with an auxiliary winding is not only complex in structure and high in manufacturing cost, but also the output voltage V of the auxiliary winding A will fluctuate due to the influence of load changes, thus affecting the normal operation of the control circuit. Therefore, a self-powered circuit is needed to replace the auxiliary winding for power supply to maintain the normal operation of the circuit. Summary of the Invention

[0004] The purpose of the present application is to provide a self-powered switch driving circuit and a driving system, which can simplify the circuit structure, reduce the manufacturing cost, and improve the circuit reliability.

[0005] To achieve the above purpose, the present application provides the following solutions:

[0006] In a first aspect, the present application provides a self-powered switch driving circuit, which includes: an undervoltage lockout circuit, a constant current driving circuit, a self-powered circuit, a current detection circuit, a first switching transistor, a second switching transistor, and a third switching transistor;

[0007] The undervoltage lockout circuit is respectively connected to a power supply and the third switching transistor; the third switching transistor is also connected to the constant current driving circuit;

[0008] The constant current driving circuit is also respectively connected to the self-powered circuit and the current detection circuit;

[0009] The base of the first switching transistor and the base of the second switching transistor are both connected to the constant current driving circuit;

[0010] The emitter of the first switching transistor is connected to the drain of the second switching transistor;

[0011] The undervoltage lockout circuit includes a first comparator; the output end of the first comparator is connected to the third switching transistor;

[0012] The first comparator is configured to output a driving signal according to the voltage of the power supply and a reference voltage; the driving signal is used to adjust the on / off state of the third switching transistor, thereby adjusting the operating state of the constant-current driving circuit;

[0013] The current detection circuit is configured to obtain a current sampling signal and transmit it to the constant-current driving circuit;

[0014] The constant-current driving circuit includes a bias circuit; the constant-current driving circuit is configured to output an adjustment signal based on the bias circuit according to the current sampling signal; the adjustment signal is used to adjust the operating states of the self-powered circuit, the first switching transistor, and the second switching transistor respectively.

[0015] Optionally, the under-voltage lockout circuit further includes: a resistor array;

[0016] The resistor array is connected to the power supply and the first comparator respectively;

[0017] The resistor array is configured to divide the voltage of the power supply and generate a voltage signal;

[0018] The first comparator is configured to output a driving signal according to the voltage signal and the reference voltage.

[0019] Optionally, the self-powered circuit includes: a power supply circuit, a power supply voltage clamping circuit, and a charging control circuit;

[0020] The power supply voltage clamping circuit and the charging control circuit are both connected to the power supply circuit;

[0021] The first end of the power supply circuit is connected to the power supply, and the second end of the power supply circuit is grounded.

[0022] Optionally, the power supply voltage clamping circuit includes: a second comparator and a fourth switching transistor;

[0023] The first input terminal of the second comparator is connected to the power supply circuit; the output terminal of the second comparator is connected to the first end of the fourth switching transistor; the second input terminal of the second comparator is connected to a set threshold voltage;

[0024] The second end of the fourth switching transistor is connected to the power supply circuit; the third end of the fourth switching transistor is grounded.

[0025] Optionally, the charging control circuit includes: a fifth switching transistor;

[0026] The base of the fifth switching transistor is connected to the constant-current driving circuit; the source of the fifth switching transistor is connected to the power supply circuit; the drain of the fifth switching transistor is connected to the emitter of the first switching transistor.

[0027] Optionally, the fifth switching transistor is a P-type metal oxide semiconductor field effect transistor.

[0028] Optionally, the current detection circuit includes: a sampling circuit and a current limiting protection circuit;

[0029] Wherein, the current limiting protection circuit includes: a third comparator and a fourth comparator;

[0030] The sampling circuit is respectively connected to the third comparator and the fourth comparator.

[0031] Optionally, the power supply circuit includes: an energy storage element;

[0032] One end of the energy storage element is connected to the power supply; the other end of the energy storage element is grounded; the energy storage element adopts a capacitor device.

[0033] Optionally, the first switching transistor is an NPN bipolar transistor; the second switching transistor is an N-type metal oxide semiconductor field effect transistor.

[0034] In a second aspect, the present application provides a driving system based on a self-powered switch driving circuit, and the driving system based on the self-powered switch driving circuit includes: an adjustment circuit, a conversion circuit and a self-powered switch driving circuit;

[0035] The adjustment circuit is connected to the self-powered switch driving circuit; the conversion circuit is connected to the self-powered switch driving circuit;

[0036] Wherein, the adjustment circuit includes: a first diode, a second diode, a third diode, a fourth diode, a first resistor, a second resistor, a third resistor and a first capacitor;

[0037] The conversion circuit includes: a second capacitor, a third capacitor, a fourth resistor, a fifth resistor, a fifth diode, a sixth diode and an inductor;

[0038] The first diode and the second diode are connected in series to obtain a first series circuit; the third diode and the fourth diode are connected in series to obtain a second series circuit;

[0039] The first series circuit and the second series circuit are connected in parallel; the first capacitor is respectively connected in parallel with the first series circuit and the second series circuit; after the first resistor and the second resistor are connected in series, they are connected in parallel with the first capacitor, and after the first resistor and the second resistor are connected in series, they are connected to the self-powered switch driving circuit; the third resistor is connected to the self-powered switch driving circuit;

[0040] The fourth resistor and the fifth diode are connected in series, the second capacitor is connected in parallel with the fourth resistor, and one end of the second capacitor is connected to one end of the fourth resistor, and the other end of the second capacitor is connected to the connection point of the fourth resistor and the fifth diode connected in series;

[0041] One end of the inductor is connected to one end of the fourth resistor; the second end of the inductor is connected to the other end of the fifth diode; the third end of the inductor is connected to one end of the sixth diode; the fourth end of the inductor is connected to the other end of the third capacitor; one end of the third capacitor is connected to the other end of the sixth diode, and the third capacitor is in parallel with the inductor; the fifth resistor is in parallel with the third capacitor.

[0042] According to the specific embodiments provided in this application, the following technical effects are achieved:

[0043] This application provides a self-powered switch driving circuit and a driving system. The self-powered driving circuit includes an under-voltage lockout circuit, a constant-current driving circuit, a self-powered circuit, a current detection circuit, a first switching transistor, a second switching transistor, and a third switching transistor. The constant-current driving circuit is based on a bias circuit and adjusts the working states of the first switching transistor, the second switching transistor, and the self-powered circuit according to the current sampling signal fed back by the current detection circuit. The first comparator in the under-voltage lockout circuit determines whether the power supply voltage is under-voltage and thus adjusts the working state of the constant-current driving circuit. This application realizes the self-power supply of the switching power supply through the constant-current driving circuit and the self-powered circuit, can work stably without a power supply auxiliary winding, solves the defect of requiring an auxiliary winding for power supply, simplifies the circuit structure, and improves the circuit reliability; and because the circuit structure of this application is simplified, the manufacturing cost can be reduced. Description of the Drawings

[0044] In order to more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0045] Figure 1 It is a schematic diagram of a traditional topology structure with an auxiliary winding;

[0046] Figure 2 It is a schematic diagram of typical waveforms when the traditional topology structure with an auxiliary winding is working;

[0047] Figure 3 It is a partial circuit structure diagram of the self-powered driving control circuit of this application;

[0048] Figure 4 It is a partial structure diagram corresponding to the under-voltage lockout circuit;

[0049] Figure 5 It is a partial structure diagram corresponding to the constant-current driving circuit;

[0050] Figure 6Partial structural diagram corresponding to the self-powered circuit;

[0051] Figure 7 Partial structural diagram corresponding to the current detection circuit;

[0052] Figure 8 Flow chart of the self-powered control algorithm;

[0053] Figure 9 Circuit structural diagram of the drive system based on the self-powered switch drive circuit;

[0054] Figure 10 Schematic diagram of the start-up working waveform;

[0055] Figure 11 Working waveform diagram of the drive system based on the self-powered switch drive circuit. Specific implementation manners

[0056] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0057] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0058] The traditional flyback primary-side detection AC-DC topology is as Figure 1 shown. Its specific working process is as follows:

[0059] When the switch control circuit controls the internal MOS transistor to conduct, the input voltage V IN is applied to the primary inductor L P , causing the current I DS flowing through the MOS transistor to linearly increase from 0. In this stage, the inductor stores energy from the power supply. When the switch control circuit controls the internal MOS transistor to turn off, the inductor starts to release energy, and the voltage across the rectifier diode D1 starts to increase. When the rectifier diode D1 starts to conduct, the output voltage V O and the forward voltage drop V F of the diode act together on the secondary inductor L S . The current I D flowing through the rectifier diode D1 linearly decreases from the peak current I DMAX to 0. The calculation formula for the peak current I DMAX is:

[0060]

[0061] Among them, N P is the number of turns of the primary inductance coil; N S is the number of turns of the secondary inductance coil. I PEAK is the peak current of the primary inductance.

[0062] When the inductive current discharge ends, all the energy stored in the inductor is released to the load. When the diode current I D decreases to 0, the primary inductance L P and the parasitic capacitance of the MOS transistor generate resonance, causing oscillation in the auxiliary winding L A of the transformer.

[0063] During the inductor discharge process, the voltage drop V A generated by the output voltage across the two ends of the auxiliary winding is:

[0064]

[0065] Among them, N A is the number of turns of the auxiliary winding L A coil.

[0066] By sampling the voltage across the two ends of the auxiliary winding when the rectifier diode D1 ends conduction, the output voltage information can be obtained. Its typical working waveform is as Figure 2 shown.

[0067] In order to solve the problems of complex peripheral circuits, high manufacturing costs, and easy influence of circuit output by load changes caused by using an auxiliary winding for power supply in traditional switching power supply circuits, this application proposes a self-powered drive circuit without an auxiliary winding. This application adds a constant current drive circuit and a current detection circuit inside the switching power supply chip. When the entire system is working normally, the current detection circuit converts the sampled current signal into a control signal and feeds it back to the constant current drive circuit. Each switching transistor conducts and turns off periodically under the control of the constant current drive circuit. The self-powered drive circuit also includes an energy storage element. The energy storage element is charged through an external power supply after power-on and discharges when the power supply voltage is insufficient. When the power supply of the energy storage element is insufficient, the self-powered control module controls the switching transistor inside the self-powered circuit to turn on, and the current flows through the switching transistor controlled by the constant current drive circuit and the switching transistor inside the self-powered circuit to charge the power supply. Thus, a self-powered switching power supply without an auxiliary winding for power supply can be realized.

[0068] Embodiment 1

[0069] The embodiment of this application provides a self-powered switch drive circuit, including: an undervoltage lockout circuit, a constant current drive circuit, a self-powered circuit, a current detection circuit, a first switching transistor, a second switching transistor, and a third switching transistor.

[0070] The undervoltage lockout circuit is respectively connected to the power supply and the third switching transistor; the third switching transistor is also connected to the constant current drive circuit. The constant current drive circuit is also respectively connected to the self-powered circuit and the current detection circuit; the bases of the first switching transistor and the second switching transistor are both connected to the constant current drive circuit; the emitter of the first switching transistor is connected to the drain of the second switching transistor.

[0071] The undervoltage lockout circuit includes a first comparator; the output terminal of the first comparator is connected to the third switching transistor.

[0072] The first comparator is used to output a drive signal according to the voltage of the power supply and the reference voltage; the drive signal is used to adjust the on / off state of the third switching transistor, and further adjust the working state of the constant current drive circuit.

[0073] The current detection circuit is used to obtain a current sampling signal and transmit it to the constant current drive circuit; the constant current drive circuit includes a bias circuit; the constant current drive circuit is used to output an adjustment signal based on the bias circuit according to the current sampling signal; the adjustment signal is used to adjust the working states of the self-powered circuit, the first switching transistor and the second switching transistor respectively.

[0074] The undervoltage lockout circuit further includes: a resistor array; the resistor array is respectively connected to the power supply and the first comparator; the resistor array is used to divide the voltage of the power supply and generate a voltage signal; the first comparator is used to output a drive signal according to the voltage signal and the reference voltage.

[0075] The self-powered circuit includes: a power supply circuit, a power supply voltage clamping circuit and a charging control circuit. The power supply voltage clamping circuit and the charging control circuit are both connected to the power supply circuit; the first end of the power supply circuit is connected to the power supply, and the second end of the power supply circuit is grounded.

[0076] The power supply voltage clamping circuit includes: a second comparator and a fourth switching transistor. The first input terminal of the second comparator is connected to the power supply circuit; the output terminal of the second comparator is connected to the first end of the fourth switching transistor; the second input terminal of the second comparator is connected to a set threshold voltage; the second end of the fourth switching transistor is connected to the power supply circuit; the third end of the fourth switching transistor is grounded.

[0077] The charging control circuit includes: a fifth switching transistor. The base of the fifth switching transistor is connected to the constant current drive circuit; the source of the fifth switching transistor is connected to the power supply circuit; the drain of the fifth switching transistor is connected to the emitter of the first switching transistor. The fifth switching transistor is a P-type metal oxide semiconductor field effect transistor.

[0078] The current detection circuit includes: a sampling circuit and a current limiting protection circuit. Among them, the current limiting protection circuit includes: a third comparator and a fourth comparator; the sampling circuit is respectively connected to the third comparator and the fourth comparator.

[0079] In one embodiment, the power supply circuit includes: an energy storage element; one end of the energy storage element is connected to the power supply; the other end of the energy storage element is grounded; the energy storage element uses a capacitor device.

[0080] As an alternative implementation, the first switching transistor is an NPN bipolar transistor; the second switching transistor is an N-type metal oxide semiconductor field effect transistor.

[0081] Specifically, in combination with Figures 3 - 7 The self-powered switch driving circuit mentioned in this application is further introduced. The under-voltage lockout circuit is connected to the voltage pin of the power supply VCC and controls the third switching transistor S1. The under-voltage lockout circuit is used to detect whether the power supply voltage is under-voltage and control the conduction state of the third switching transistor S1 according to the voltage state. When the power supply voltage drops to the under-voltage lockout threshold Vth1, a control signal is generated to control the third switching transistor S1 to turn off; when the power supply voltage rises to the under-voltage lockout release threshold Vth2, a control signal is generated to control the third switching transistor S1 to close.

[0082] The constant current driving circuit is connected to the base of the first switching transistor Q1, the base of the second switching transistor M1, and the self-powered circuit. The constant current driving circuit is regulated by the under-voltage lockout circuit and the current detection circuit.

[0083] The self-powered circuit is connected to the constant current driving circuit, the emitter of the first switching transistor Q1, and the drain of the second switching transistor M1.

[0084] The current detection circuit is connected to the constant current driving circuit and the current sampling CS pin. The circuit detection circuit converts the sampled current value into a voltage value and compares it through a comparator inside the current detection circuit, so as to output a control signal to control the constant current driving circuit.

[0085] The self-powered switch driving circuit mentioned in this application further includes: a self-powered control module. The self-powered control module internally integrates a self-powered control algorithm. The self-powered control module is connected to the self-powered circuit and is used to control whether to perform self-powered operation in the current cycle.

[0086] The first switching transistor Q1 is an NPN bipolar junction transistor BJT. The first end (base) of the first switching transistor Q1 is connected to the constant current driving circuit. The second end (collector) of the first switching transistor Q1 is connected to the collector pin of the switching power supply chip C. The third end of the first switching transistor Q1 is the emitter.

[0087] The second switching transistor M1 is an N-type metal oxide semiconductor field effect transistor, that is, an NMOS field effect transistor. The first end (gate) of the second switching transistor M1 is connected to the constant current driving circuit. The second end (drain) of the second switching transistor M1 is connected to the third end (emitter) of the first switching transistor Q1. The source of the second switching transistor M1 is grounded.

[0088] The first end of the third switching transistor S1 is connected to the power supply VCC, the second end is connected to the constant current drive circuit, and the third switching transistor S1 is controlled by the under-voltage lockout circuit.

[0089] The energy storage element C1 is a capacitor. The first end of the energy storage element C1 is connected to the power supply VCC, and the second end of the energy storage element C1 is grounded, that is, connected to the reference ground pin GND.

[0090] As Figure 4 shown, the under-voltage lockout circuit includes a resistor array and a first comparator Comp1. The resistor array is connected to the power supply circuit for power supply voltage division and generates a voltage signal Vref1; the first input end of the first comparator Comp1 is connected to the voltage signal Vref1, and the second end is connected to the reference voltage signal Vref of the bias circuit (i.e., the reference voltage and bias circuit) for comparing the voltage signal Vref1 with the reference voltage signal Vref.

[0091] When the supply voltage of the power supply drops, the voltage signal generated after voltage division by the resistor array follows the drop. When the voltage signal Vref1 drops to the reference voltage signal Vref at the second end of the first comparator Comp1, the first comparator Comp1 is triggered to flip and generate a control signal to control the third switching transistor S1 to turn off and enter the under-voltage lockout state.

[0092] As Figure 5 shown, the constant current drive circuit includes an internal reference voltage and bias circuit (i.e., the bias circuit), which is connected to the second end of the third switching transistor S1 to control the working state of the internal reference voltage and bias circuit. When the potential of the voltage of the power supply VCC is lower than the under-voltage lockout threshold Vth1, the internal reference voltage and bias circuit is turned off by the third switching transistor S1.

[0093] That is, the internal reference voltage and bias circuit is connected to the power supply VCC through the third switching transistor S1. When the under-voltage lockout function is triggered, the internal reference voltage and bias circuit is disconnected from the power supply VCC.

[0094] The constant current drive circuit also includes a logic control circuit. When operating in the DCM discontinuous conduction mode, the average value I of the output current OUT can be calculated by the area method, where T dem is the demagnetization time, T sw is the switching cycle time, N p and N s are the number of turns of the primary inductance coil and the number of turns of the secondary inductance coil respectively. I pk That is, I PEAK , which is the primary inductance peak current. When the demagnetization time T dem and the switching cycle time T swWhen the ratio is fixed at 1 / 2 (typical value), the actual output current can be constant.

[0095]

[0096] As Figure 6 shown, the self-powered circuit includes: a power supply circuit, a power supply voltage clamping circuit, and a charging control circuit. The charging control circuit includes a fifth switching transistor S3. That is, in Figure 6 , after removing the constant current drive circuit from the dashed box, the remaining part is the self-powered circuit.

[0097] The first end of the power supply circuit is connected to the power supply VCC, and the second end is connected to the energy storage element C1 and then to the reference ground pin GND. When the switching power supply chip is powered on and working, the power supply circuit obtains energy through the power supply VCC and stores it in the energy storage element C1. When the power supply voltage is insufficient, the energy storage element discharges to ensure that the VCC voltage remains stable.

[0098] The power supply voltage clamping circuit includes a second comparator Comp2 and a fourth switching transistor S2. When the power supply voltage exceeds the threshold voltage Vth3 of the power supply voltage clamping circuit, the second comparator Comp2 controls the fourth switching transistor S2 to turn on and discharges the power supply VCC.

[0099] Specifically, the power supply voltage clamping circuit is used to detect whether the power supply voltage exceeds the threshold voltage Vth3 and avoid excessive power supply voltage when the energy storage element C1 fails or the charging control circuit fails. The first end of the second comparator Comp2 is connected to the voltage signal after dividing the power supply voltage, that is, the power supply voltage divided signal VCC1. The second end of the second comparator Comp2 is connected to the threshold voltage Vth3. When the voltage of the power supply VCC rises, the power supply voltage divided signal VCC1 follows the power supply voltage to rise. When the power supply voltage divided signal VCC1 rises to the threshold voltage Vth3, the second comparator Comp2 generates a control signal to control the fourth switching transistor S2 to turn on. The first end of the fourth switching transistor S2 is connected to the power supply voltage. When the fourth switching transistor S2 is turned on, the power supply voltage can be discharged to avoid excessive power supply voltage.

[0100] The fifth switching transistor S3 is a P-type metal oxide semiconductor field effect transistor. The first end (base) is connected to the constant current drive circuit, the second end (source) is connected to the power supply VCC, and the third end (drain) is connected to the third end (emitter) of the first switching transistor Q1. When the first switching transistor Q1 and the fifth switching transistor S3 are turned on and the second switching transistor M1 is turned off, the current charges the power supply VCC through the first switching transistor Q1 and the fifth switching transistor S3.

[0101] Specifically, when the constant-current drive circuit controls the fifth switching transistor S3 to turn on, a path is generated from the second terminal (collector) to the third terminal (emitter) of the first switching transistor Q1, through the fifth switching transistor S3 to the power supply VCC, thereby charging the power supply VCC.

[0102] As Figure 7 shown, the current detection circuit includes: a current sampling circuit (i.e., a sampling circuit) and a current limiting protection circuit.

[0103] The current sampling circuit is used to generate a current sampling signal Vcs; the current limiting protection circuit includes a third comparator Comp3 and a fourth comparator Comp4. The first terminal of the third comparator Comp3 is connected to the current sampling signal Vcs, the second terminal of the third comparator Comp3 is connected to a threshold voltage signal Vth4, the first terminal of the fourth comparator Comp4 is connected to the current sampling signal Vcs, and the second terminal of the fourth comparator Comp4 is connected to a threshold voltage signal Vth5.

[0104] The first terminal of the current sampling circuit is connected to the current sampling pin CS of the switching power supply chip, and the second terminal is connected to the third comparator Comp3 and the fourth comparator Comp4. The current sampling circuit samples and converts the sampled current into a voltage signal Vcs, which is transmitted to the third comparator Comp3 and the fourth comparator Comp4 for comparison. The first terminal of the third comparator Comp3 is connected to the current sampling signal Vcs, and the second terminal is connected to the threshold voltage signal Vth4. The first terminal of the fourth comparator Comp4 is connected to the current sampling signal Vcs, and the second terminal of the fourth comparator Comp4 is connected to the threshold voltage signal Vth5. The signals generated by the third comparator Comp3 and the fourth comparator Comp4 are fed back to the constant-current drive circuit. When the current sampling signal Vcs reaches the threshold voltage signal Vth4, the constant-current drive circuit controls the second switching transistor M1 to turn off. When the current sampling signal Vcs reaches the threshold voltage signal Vth5, the constant-current drive circuit controls the fifth switching transistor S3 to conduct to charge the power supply VCC.

[0105] In one embodiment, the working process of the constant-current drive circuit is as follows:

[0106] The constant-current drive circuit adopts a working mode of cycle-by-cycle current detection. The current detection circuit compares the current sampling signal Vcs with the threshold voltage signal Vth4 and the threshold voltage signal Vth5. When the current sampling signal Vcs reaches the threshold voltage signal Vth4, the constant-current drive circuit 2 controls the first switching transistor Q1 to turn off until the next turn-on cycle arrives. When the current sampling signal Vcs reaches the threshold voltage signal Vth5, the constant-current drive circuit controls the fifth switching transistor S3 to conduct to charge the power supply VCC.

[0107] Figure 8It is a flowchart of the self-powered control algorithm. The self-powered control module controls whether to perform self-powered operation in the current cycle based on the self-powered control algorithm. First, it detects the voltage of the power supply VCC. When the voltage is greater than or equal to the reference voltage Vref2, it enters the non-self-powered cycle; when the voltage is less than the reference voltage Vref2, it enters the self-powered cycle. When entering the non-self-powered cycle, it triggers the reset of the internal counter. When entering the self-powered cycle, it triggers the increment of the internal counter. The internal counter is used to record the number of consecutive self-powered cycles. When there are N consecutive self-powered cycles and N≥K, it forces the entry into the non-self-powered cycle in the next cycle. K is the minimum number of self-powered cycles.

[0108] The drive circuit with self-powered function proposed in this application can operate stably without a power supply auxiliary winding. It has a built-in self-powered control algorithm, and detects the voltage of the power supply VCC in each cycle to determine whether to perform self-powered operation in that cycle. It has a built-in high-voltage BJT. When applied to a flyback topology, the RCD circuit for absorbing leakage inductance spikes can be omitted, thereby reducing peripheral circuit components and lowering the material cost.

[0109] Embodiment 2

[0110] As Figure 9 shown, the embodiment of this application provides a drive system based on a self-powered switch drive circuit. The drive system includes: an adjustment circuit, a conversion circuit, and the self-powered switch drive circuit in Embodiment 1.

[0111] The adjustment circuit is connected to the self-powered switch drive circuit; the conversion circuit is connected to the self-powered switch drive circuit; wherein, the adjustment circuit includes: a first diode D11, a second diode D12, a third diode D13, a fourth diode D14, a first resistor R1, a second resistor R2, a third resistor R3, and a first capacitor C11.

[0112] The conversion circuit includes: a second capacitor C12, a third capacitor C13, a fourth resistor R4, a fifth resistor R5, a fifth diode D15, a sixth diode D16, and an inductor L.

[0113] The first diode D11 and the second diode D12 are connected in series to obtain a first series circuit; the third diode D13 and the fourth diode D14 are connected in series to obtain a second series circuit.

[0114] The first series circuit and the second series circuit are connected in parallel; the first capacitor C11 is connected in parallel with both the first series circuit and the second series circuit; after the first resistor R1 and the second resistor R2 are connected in series, they are connected in parallel with the first capacitor C11, and after the first resistor R1 and the second resistor R2 are connected in series, they are connected to the self-powered switch drive circuit. The third resistor R3 is connected to the self-powered switch drive circuit.

[0115] The fourth resistor R4 and the fifth diode D15 are connected in series. The second capacitor C12 is connected in parallel with the fourth resistor R4. One end of the second capacitor C12 is connected to one end of the fourth resistor R4, and the other end of the second capacitor C12 is connected to the connection point of the fourth resistor R4 and the fifth diode D15 in series.

[0116] The first end of the inductor L is connected to one end of the fourth resistor R4; the second end of the inductor L is connected to the other end of the fifth diode D15; the third end of the inductor L is connected to one end of the sixth diode D16; the fourth end of the inductor L is connected to the other end of the third capacitor C13; one end of the third capacitor C13 is connected to the other end of the sixth diode D16, and the third capacitor C13 is connected in parallel with the inductor L; the fifth resistor R5 is connected in parallel with the third capacitor C13.

[0117] Taking the AC-DC power supply chip with a flyback SSR topology as an example, the pins of the AC-DC power supply chip include the power supply VCC, the current sampling pin CS, the reference ground pin GND, and the collector pin C of the built-in high-voltage triode. Since this structure has a built-in high-voltage BJT, the RCD circuit for absorbing the leakage inductance spike voltage can be omitted when applying the flyback topology in applications, thereby reducing the number of peripheral components and lowering the material cost.

[0118] Figure 10 This is the starting working waveform. When the system starts to power on, the VCC capacitor is charged through the starting resistor. Once the voltage on the VCC capacitor reaches the VCC_on starting voltage, the self-powered drive control circuit will start to work; in addition, to prevent the chip VCC pin from being damaged by breakdown due to a higher voltage, the maximum voltage will be clamped at VCC_clamp.

[0119] Figure 11 This is the working waveform diagram of the drive system based on the self-powered switch drive circuit. Combining Figure 9 The working process of the self-powered drive control circuit is described as follows. In the Nth cycle (N < K), the self-powered control algorithm detects that the power supply voltage is less than the reference voltage Vref2, and self-powered operation is performed in the current cycle. When the current sampling signal Vcs drops to the threshold voltage Vth4, the gate control signal V of the second switch tube M1 gM1 jumps from high level to low level, controlling the second switch tube M1 to turn off. When the current sampling signal Vcs drops to the threshold voltage Vth5, the gate control signal V of the fifth switch tube S3 gS1 jumps from high level to low level, controlling the fifth switch tube S3 to turn on and charge the power supply voltage; in the (N + 1)th cycle, the self-powered control algorithm detects that the power supply voltage is greater than the reference voltage Vref2, and no self-powered operation is performed in the current cycle, and the fifth switch tube S3 is always off; in the (N + 2)th cycle, the self-powered control algorithm detects that the power supply voltage is less than the reference voltage Vref2, and the working process of the Nth cycle is repeated.

[0120] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0121] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A self-powered switch driving circuit, characterized in that: The self-powered switch driving circuit comprises: an undervoltage lockout circuit, a constant current driving circuit, a self-powered circuit, a current detection circuit, a first switch tube, a second switch tube and a third switch tube; The undervoltage lockout circuit is connected to the power supply and the third switch tube respectively; the third switch tube is also connected to the constant current drive circuit; The constant current driving circuit is also connected to the self-power supply circuit and the current detection circuit respectively; The base of the first switch tube and the base of the second switch tube are both connected to the constant current drive circuit; The emitter of the first switch tube is connected to the drain of the second switch tube; The undervoltage lockout circuit comprises a first comparator; the output end of the first comparator is connected to the third switch tube; The first comparator is used to output a driving signal according to the voltage of the power supply and the reference voltage; the driving signal is used to adjust the on / off state of the third switch tube, thereby adjusting the working state of the constant current driving circuit; The current detection circuit is used to obtain a current sampling signal and transmit it to the constant current driving circuit; The constant current driving circuit includes a bias circuit; the constant current driving circuit is used to output an adjustment signal according to the current sampling signal based on the bias circuit; the adjustment signal is used to adjust the respective working states of the self-powered circuit, the first switch tube and the second switch tube.

2. The self-powered switch driving circuit according to claim 1, characterized in that: The undervoltage lockout circuit further includes: a resistor array; The resistor array is connected to the power supply and the first comparator respectively; The resistor array is used to divide the voltage of the power supply and generate a voltage signal; The first comparator is used for outputting a driving signal according to the voltage signal and a reference voltage.

3. The self-powered switch driving circuit according to claim 1, characterized in that: The self-powered circuit comprises: a power supply circuit, a power supply voltage clamping circuit and a charging control circuit; The power supply voltage clamping circuit and the charging control circuit are both connected to the power supply circuit; A first terminal of the power supply circuit is connected to the power supply, and a second terminal of the power supply circuit is grounded.

4. The self-powered switch driving circuit according to claim 3, characterized in that: The power supply voltage clamping circuit comprises: a second comparator and a fourth switch tube; The first input terminal of the second comparator is connected to the power supply circuit; the output terminal of the second comparator is connected to the first terminal of the fourth switch tube; the second input terminal of the second comparator is connected to the set threshold voltage; The second end of the fourth switch tube is connected to the power supply circuit; the third end of the fourth switch tube is grounded.

5. The self-powered switch driving circuit according to claim 3, characterized in that: The charging control circuit comprises: a fifth switch tube; The base of the fifth switch tube is connected to the constant current drive circuit; the source of the fifth switch tube is connected to the power supply circuit; and the drain of the fifth switch tube is connected to the emitter of the first switch tube.

6. The self-powered switch driving circuit according to claim 5, characterized in that: The fifth switch tube is a P-type metal oxide semiconductor field effect tube.

7. The self-powered switch driving circuit according to claim 1, characterized in that: The current detection circuit comprises: a sampling circuit and a current limiting protection circuit; Wherein, the current limiting protection circuit comprises: a third comparator and a fourth comparator; The sampling circuit is connected to the third comparator and the fourth comparator respectively.

8. The self-powered switch driving circuit according to claim 3, characterized in that: The power supply circuit comprises: an energy storage element; One end of the energy storage element is connected to the power supply; the other end of the energy storage element is grounded; and the energy storage element is a capacitor device.

9. The self-powered switch driving circuit according to claim 1, characterized in that: The first switch tube is an NPN bipolar transistor; the second switch tube is an N-type metal oxide semiconductor field effect transistor.

10. A driving system based on a self-powered switch driving circuit, characterized in that: The driving system based on the self-powered switch driving circuit comprises: an adjustment circuit, a conversion circuit and the self-powered switch driving circuit according to any one of claims 1 to 9; The adjustment circuit is connected to the self-powered switch driving circuit; the conversion circuit is connected to the self-powered switch driving circuit; Wherein, the adjustment circuit includes: a first diode, a second diode, a third diode, a fourth diode, a first resistor, a second resistor, a third resistor and a first capacitor; The conversion circuit comprises: a second capacitor, a third capacitor, a fourth resistor, a fifth resistor, a fifth diode, a sixth diode and an inductor; The first diode and the second diode are connected in series to obtain a first series circuit; the third diode and the fourth diode are connected in series to obtain a second series circuit; The first series circuit and the second series circuit are connected in parallel; a first capacitor is connected in parallel with the first series circuit and the second series circuit respectively; a first resistor and a second resistor are connected in series and then connected in parallel with the first capacitor, and the first resistor and the second resistor are connected in series and then connected to the self-powered switch driving circuit; a third resistor is connected to the self-powered switch driving circuit; The fourth resistor and the fifth diode are connected in series, the second capacitor is connected in parallel with the fourth resistor, one end of the second capacitor is connected to one end of the fourth resistor, and the other end of the second capacitor is connected to a connection point of the fourth resistor and the fifth diode connected in series; The first end of the inductor is connected to one end of the fourth resistor; the second end of the inductor is connected to the other end of the fifth diode; the third end of the inductor is connected to one end of the sixth diode; the fourth end of the inductor is connected to the other end of the third capacitor; one end of the third capacitor is connected to the other end of the sixth diode, and the third capacitor is connected in parallel with the inductor; the fifth resistor is connected in parallel with the third capacitor.

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