A self-powered switch drive circuit and drive system

Abstract

This application discloses a self-powered switch driver circuit and driving system, relating to the field of switching power supplies. The self-powered switch driver circuit includes: 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. The undervoltage lockout circuit includes a first comparator; the first comparator outputs a drive signal based on the power supply voltage and a reference voltage to adjust the on / off state of the third switching transistor, thereby adjusting the operating state of the constant current drive circuit. The current detection circuit acquires a current sampling signal and transmits it to the constant current drive circuit. The constant current drive circuit includes a bias circuit; based on the bias circuit, the constant current drive circuit outputs an adjustment signal according to the current sampling signal to adjust the operating states of the self-powered circuit, the first switching transistor, and the second switching transistor. This application aims to simplify the circuit structure, reduce manufacturing costs, and improve circuit reliability.

Description

Technical Field

[0001] This application relates to the field of switching power supplies, and in particular to a self-powered switch drive circuit and drive system. Background Technology

[0002] With the rapid development of consumer electronics, LED devices have been widely used, leading to a surge in demand for switching power supply chips to support them. Traditional switching power supply control circuits typically use an independent power supply for the internal control circuitry. This requires two sets of windings: a primary winding for energy storage and an auxiliary winding for powering the load. Primary-side modulation technology eliminates the need for secondary sampling circuits, offering advantages such as fewer external components and lower circuit complexity.

[0003] In practical applications, the auxiliary winding and the inductor cannot be completely coupled. Circuits with auxiliary windings are not only structurally complex and costly to manufacture, but also have a high output voltage V of the auxiliary winding. A The circuitry is susceptible to fluctuations due to load changes, which can affect the normal operation of the control circuit. Therefore, a self-powered circuit is needed to replace the auxiliary winding for power supply and maintain normal circuit operation. Utility Model Content

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

[0005] To achieve the above objectives, this application provides the following solution:

[0006] In a first aspect, this 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 switch transistor, a second switch transistor, and a third switch transistor.

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

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

[0009] The bases of both the first and second switching transistors are connected to the constant current drive 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 of the first comparator is connected to the third switching transistor.

[0012] The first comparator is used to output a drive signal based on the voltage of the power supply and the reference voltage; the drive signal is used to adjust the on / off state of the third switch, thereby adjusting the working state of the constant current drive circuit.

[0013] The current detection circuit is used to acquire the current sampling signal and transmit it to the constant current drive circuit;

[0014] 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 and the current sampling signal; the adjustment signal is used to adjust the operating state of the self-powered circuit, the first switching transistor, and the second switching transistor.

[0015] Optionally, the undervoltage 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 used to divide the voltage of the power supply and generate a voltage signal;

[0018] The first comparator is used to output a drive signal based on the voltage signal and the reference voltage.

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

[0020] Both the power supply voltage clamping circuit and the charging control circuit are connected to the power supply circuit.

[0021] The first terminal of the power supply circuit is connected to the power source, and the second terminal 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 terminal of the fourth switching transistor; the second input terminal of the second comparator is connected to the set threshold voltage.

[0024] The second terminal of the fourth switching transistor is connected to the power supply circuit; the third terminal 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 drive circuit; the source of the fifth switching transistor is connected to the power supply circuit; and the drain of the fifth switching transistor is connected to the emitter of the first switching transistor.

[0027] Optionally, the fifth switch 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] The current limiting protection circuit includes a third comparator and a fourth comparator.

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

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

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

[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] Secondly, this application provides a driving system based on a self-powered switch driving circuit, 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 drive circuit; the conversion circuit is connected to the self-powered switch drive circuit.

[0036] 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 form the first series circuit; the third diode and the fourth diode are connected in series to form the second series circuit.

[0039] The first series circuit and the second series circuit are connected in parallel; the first capacitor is connected in parallel with both the first series circuit and the second series circuit; the first resistor and the second resistor are connected in series and then 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 drive circuit; the third resistor is connected to the self-powered switch drive circuit.

[0040] 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 the connection point of the fourth resistor and the fifth diode connected in series.

[0041] 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 and the inductor are connected in parallel; the fifth resistor and the third capacitor are connected in parallel.

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

[0043] This application provides a self-powered switch driver circuit and driving system. The self-powered driver circuit includes an undervoltage lockout circuit, a constant current drive circuit, a self-powered circuit, a current detection circuit, a first switch transistor, a second switch transistor, and a third switch transistor. The constant current drive circuit, based on a bias circuit, adjusts the operating states of the first switch transistor, the second switch transistor, and the self-powered circuit according to the current sampling signal fed back from the current detection circuit. The first comparator in the undervoltage lockout circuit determines whether the power supply voltage is undervoltage, thereby adjusting the operating state of the constant current drive circuit. This application achieves self-powering of the switching power supply through the constant current drive circuit and the self-powered circuit, enabling stable operation without the need for an auxiliary power supply winding. This solves the defect of requiring an auxiliary winding for power supply, simplifies the circuit structure, and improves circuit reliability. Furthermore, because this application simplifies the circuit structure, it can reduce manufacturing costs. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of a traditional topology with auxiliary windings;

[0046] Figure 2 This is a typical waveform diagram of a traditional topology with auxiliary windings in operation.

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

[0048] Figure 4 This is a partial structural diagram of the undervoltage lockout circuit;

[0049] Figure 5 This is a partial structural diagram of the constant current drive circuit;

[0050] Figure 6This is a partial structural diagram of a self-powered circuit.

[0051] Figure 7 This is a partial structural diagram of the current detection circuit;

[0052] Figure 8 Here is a flowchart of the self-powered control algorithm;

[0053] Figure 9 This is a circuit structure diagram of a drive system based on a self-powered switch drive circuit.

[0054] Figure 10 This is a schematic diagram of the waveform for starting operation;

[0055] Figure 11 The waveform diagram shows the operation of the drive system based on the self-powered switch drive circuit. Detailed Implementation

[0056] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0057] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] Traditional flyback primary-side detection AC-DC topology, such as Figure 1 As shown. Its specific working process is as follows:

[0059] When the switching control circuit turns on the internal MOSFET, the input voltage V IN Applying to the primary inductor L P This causes the current I flowing through the MOSFET to... DS The voltage increases linearly from 0. During this stage, the inductor stores energy through the power supply. When the switching control circuit turns off the internal MOSFET, the inductor begins to release energy, and the voltage across rectifier diode D1 begins to increase. Once rectifier diode D1 turns on, the output voltage V... O With the forward voltage drop V of the diode F Together they act on the secondary inductor L S The current I flowing through rectifier diode D1 is... D From peak current I DMAX It decreases linearly to 0. Peak current I DMAX The calculation formula is:

[0060]

[0061] Among them, M P M is the number of turns of the primary inductor. S This represents the number of turns in the secondary inductor. PEAK This represents the peak current of the primary inductor.

[0062] When the inductor current discharges to the end, all the energy stored in the inductor is released to the load. When the diode current I... D When reduced to 0, the primary inductance L P The resonance caused by the parasitic capacitance of the MOSFET leads to the auxiliary winding L of the transformer. A oscillation.

[0063] During inductor discharge, the voltage drop V generated across the auxiliary winding is... A for:

[0064]

[0065] Where, N A For auxiliary winding L A The number of turns in the coil.

[0066] The output voltage information can be obtained by sampling the voltage across the auxiliary winding when rectifier diode D1 stops conducting. Its typical operating waveform is as follows: Figure 2 As shown.

[0067] To address the problems of complex external circuitry, high manufacturing costs, and susceptibility to load variations in traditional switching power supply circuits that rely on auxiliary windings, this application proposes a self-powered drive circuit that eliminates the need for auxiliary windings. This application incorporates a constant current drive circuit and a current detection circuit within the switching power supply chip. During normal system operation, the current detection circuit converts the sampled current signal into a control signal, which is then fed back to the constant current drive circuit. Each switching transistor periodically turns on and off under the control of the constant current drive circuit. The self-powered drive circuit also includes an energy storage element, which is charged by an external power source after power-on and discharges when the power supply voltage is insufficient. When the energy storage element provides insufficient power, the self-powered control module controls the switching transistors within the self-powered circuit to turn on, allowing current to flow through the switching transistors controlled by the constant current drive circuit and the internal switching transistors of the self-powered circuit to charge the power supply. This enables a self-powered switching power supply that eliminates the need for auxiliary windings.

[0068] Example 1

[0069] This application provides a self-powered switch driving circuit, including: an undervoltage lockout circuit, a constant current driving circuit, a self-powered circuit, a current detection circuit, a first switch transistor, a second switch transistor, and a third switch transistor.

[0070] The undervoltage lockout circuit is 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 connected to the self-powered circuit and the current detection circuit; the bases of the first and second switching transistors 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 of the first comparator is connected to a third switching transistor.

[0072] The first comparator outputs a drive signal based on the power supply voltage and the reference voltage; the drive signal is used to adjust the opening and closing state of the third switch, thereby adjusting the operating state of the constant current drive circuit.

[0073] The current detection circuit is used to acquire the 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 and the current sampling signal; the adjustment signal is used to adjust the operating state 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 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 to output a drive signal based on 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. Both the power supply voltage clamping circuit and the charging control circuit are connected to the power supply circuit; the first terminal of the power supply circuit is connected to the power source, and the second terminal 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 terminal of the fourth switching transistor; the second input terminal of the second comparator is connected to a set threshold voltage; the second terminal of the fourth switching transistor is connected to the power supply circuit; and the third terminal 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; and 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. The current limiting protection circuit includes a third comparator and a fourth comparator; the sampling circuit is connected to both the third and fourth comparators.

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

[0080] As an optional 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 Figures 3-7 The self-powered switch drive circuit mentioned in this application is further described below. The undervoltage lockout circuit is connected to the voltage pin of the power supply VCC and controls the third switch S1. The undervoltage lockout circuit detects whether the power supply voltage is undervoltage and controls the conduction state of the third switch S1 according to the voltage state. When the power supply voltage drops to the undervoltage lockout threshold Vth1, a control signal is generated to turn off the third switch S1; when the power supply voltage rises to the exit undervoltage lockout threshold Vth2, a control signal is generated to turn off the third switch S1.

[0082] The constant current drive 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 drive circuit is regulated by the undervoltage lockout circuit and the current detection circuit.

[0083] The self-powered circuit is connected to the constant current drive 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 drive circuit and the current sampling CS pin. The circuit detection circuit converts the sampled current value into a voltage value and compares it with the comparator inside the current detection circuit, thereby outputting a control signal to control the constant current drive circuit.

[0085] The self-powered switch drive circuit mentioned in this application also includes a self-powered control module. The self-powered control module 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 a self-powered operation in the current cycle.

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

[0087] The second switch M1 is an N-type metal-oxide-semiconductor field-effect transistor, i.e., an NMOS field-effect transistor. The first terminal (base) of the second switch M1 is connected to the constant current drive circuit, and the second terminal (drain) is connected to the third terminal (emitter) of the first switch Q1. The source of the second switch M1 is grounded.

[0088] The first terminal of the third switching transistor S1 is connected to the power supply VCC, and the second terminal is connected to the constant current drive circuit. The third switching transistor S1 is controlled by the undervoltage 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] like Figure 4 As shown, the undervoltage 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 generation of voltage signal Vref1; the first input terminal of the first comparator Comp1 is connected to the voltage signal Vref1, and the second terminal 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 power supply voltage drops, the voltage signal generated after voltage division by the resistor array also drops. When the voltage signal Vref1 drops to the reference voltage signal Vref at the second terminal of the first comparator Comp1, the first comparator Comp1 is triggered to flip and generate a control signal, which controls the third switch S1 to turn off and enter the undervoltage lockout state.

[0092] like Figure 5 As shown, the constant current drive circuit includes an internal reference voltage and bias circuit (i.e., bias circuit), which is connected to the second terminal of the third switch S1, thereby controlling the operating state of the internal reference voltage and bias circuit. When the voltage potential of the power supply VCC is lower than the undervoltage lockout threshold Vth1, the internal reference voltage and bias circuit is turned off by the third switch S1.

[0093] That is, the internal reference voltage and bias circuit is connected to the power supply VCC through the third switch S1. When the undervoltage lockout function is triggered, the internal reference voltage and bias circuit disconnects from the power supply VCC.

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

[0095]

[0096] like Figure 6 As 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 the fifth switching transistor S3. That is, in Figure 6 In the diagram, after removing the constant current drive circuit, the remaining part within the dashed box is the self-powered circuit.

[0097] The first terminal of the power supply circuit is connected to the power supply VCC, and the second terminal 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, the power supply circuit obtains energy from 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 switch 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 switch S2 to turn on and discharge 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, preventing the power supply voltage from becoming too high when the energy storage element C1 fails or the charging control circuit fails. The first terminal of the second comparator Comp2 is connected to the voltage signal obtained by voltage division of the power supply voltage, namely the power supply voltage divider signal VCC1, and the second terminal of the second comparator Comp2 is connected to the threshold voltage Vth3. When the power supply voltage VCC rises, the power supply voltage divider signal VCC1 rises along with the power supply voltage. When the power supply voltage divider signal VCC1 rises to the threshold voltage Vth3, the second comparator Comp2 generates a control signal to control the fourth switch S2 to turn on. The first terminal of the fourth switch S2 is connected to the power supply voltage. When the fourth switch S2 is turned on, it can discharge the power supply voltage, preventing the power supply voltage from becoming too high.

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

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

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

[0103] The current sampling circuit is used to generate the 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, and the second terminal of the third comparator Comp3 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.

[0104] The current sampling circuit has its first terminal connected to the current sampling pin CS of the switching power supply chip, and its second terminal connected to the third comparator Comp3 and the fourth comparator Comp4. The current sampling circuit samples the current and converts it into a voltage signal Vcs, which is then compared by the third comparator Comp3 and the fourth comparator Comp4. 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 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 switch M1 to turn off. When the current sampling signal Vcs reaches the threshold voltage signal Vth5, the constant current drive circuit controls the fifth switch S3 to turn on and charge the power supply VCC.

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

[0106] The constant current drive circuit adopts a cycle-by-cycle current detection mode. The current detection circuit compares the current sampling signal Vcs with the threshold voltage signals Vth4 and Vth5. When the current sampling signal Vcs reaches the threshold voltage signal Vth4, the constant current drive circuit 2 controls the first switch 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 switch S3 to turn on to charge the power supply VCC.

[0107] Figure 8This is a flowchart of the self-powered control algorithm. The self-powered control module uses this algorithm to determine whether to perform a self-powered operation in the current cycle. First, it detects the voltage of the power supply VCC. If the voltage is greater than or equal to the reference voltage Vref2, it enters a non-self-powered cycle; if the voltage is less than the reference voltage Vref2, it enters a self-powered cycle. When entering a non-self-powered cycle, an internal counter is reset; when entering a self-powered cycle, the internal counter is incremented. The internal counter records the number of consecutive self-powered cycles. When N consecutive self-powered cycles have elapsed and N ≥ K, it forces the system to enter a non-self-powered cycle in the next cycle. K is the minimum number of self-powered cycles.

[0108] The self-powered drive circuit proposed in this application can operate stably without the need for an auxiliary power supply winding. It incorporates a built-in self-powered control algorithm that detects the VCC voltage of the power supply in each cycle to determine whether self-powering operation should be performed in that cycle. The built-in high-voltage BJT eliminates the need for the RCD circuit used to absorb leakage inductance spikes when applied to a flyback topology, thereby reducing external circuit components and lowering material costs.

[0109] Example 2

[0110] like Figure 9 As shown, this application provides a driving system based on a self-powered switch driving circuit. The driving system includes: an adjustment circuit, a conversion circuit, and the self-powered switch driving circuit from 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 form the first series circuit; the third diode D13 and the fourth diode D14 are connected in series to form the 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; the first resistor R1 and the second resistor R2 are connected in series and then in parallel with the first capacitor C11, and the first resistor R1 and the second resistor R2 are connected in series 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, and one end of the second capacitor C12 is connected to one end of the fourth resistor R4. The other end of the second capacitor C12 is connected to the connection point of the fourth resistor R4 and the fifth diode D15 connected in series.

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

[0117] Taking an AC-DC power supply chip with a flyback SSR topology as an example, the pins of this AC-DC power supply chip include power supply VCC, current sampling pin CS, reference ground pin GND, and collector pin C of a built-in high-voltage transistor. Because this structure incorporates a high-voltage BJT, the RCD circuit used to absorb leakage inductance spikes can be omitted when applying a flyback topology, thereby reducing the number of external components and lowering material costs.

[0118] Figure 10 This is the startup waveform. When the system is powered on, the VCC capacitor is charged through the startup resistor. Once the voltage on the VCC capacitor reaches the VCC_on startup voltage, the self-powered drive control circuit will start working. In addition, to prevent high voltage from damaging the chip, the maximum voltage of the VCC pin is clamped at VCC_clamp.

[0119] Figure 11 The diagram shows the operating waveforms of a drive system based on a self-powered switch drive circuit, combined with... Figure 9 The operation 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 performs self-powered operation 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 M1... gM1 The signal transitions from high to low, turning off the second switch M1. When the current sampling signal Vcs drops to the threshold voltage Vth5, the gate control signal V of the fifth switch S3... gS1 The transition from high to low level controls the fifth switch 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, so no self-powered operation is performed in the current cycle, and the fifth switch S3 remains 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 repeats the working process of the Nth cycle.

[0120] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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, they should be considered to be within the scope of this specification.

[0121] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

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

2. The self-powered switch drive 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 to output a drive signal based on the voltage signal and the reference voltage.

3. The self-powered switch drive circuit according to claim 1, characterized in that, The self-powered circuit includes: a power supply circuit, a power voltage clamping circuit, and a charging control circuit. Both the power supply voltage clamping circuit and the charging control circuit are connected to the power supply circuit. The first terminal of the power supply circuit is connected to the power source, and the second terminal of the power supply circuit is grounded.

4. The self-powered switch drive circuit according to claim 3, characterized in that, 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 terminal of the fourth switching transistor; the second input terminal of the second comparator is connected to the set threshold voltage. The second terminal of the fourth switching transistor is connected to the power supply circuit; the third terminal of the fourth switching transistor is grounded.

5. The self-powered switch drive circuit according to claim 3, characterized in that, 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; and the drain of the fifth switching transistor is connected to the emitter of the first switching transistor.

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

7. The self-powered switch drive circuit according to claim 1, characterized in that, The current detection circuit includes: a sampling circuit and a current limiting protection circuit; The current limiting protection circuit includes 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 drive circuit according to claim 3, characterized in that, The power supply circuit includes: an energy storage element; One end of the energy storage element is connected to the power source; the other end of the energy storage element is grounded; the energy storage element is a capacitor.

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

10. A drive system based on a self-powered switch drive circuit, characterized in that, The drive system based on the self-powered switch drive circuit includes: an adjustment circuit, a conversion circuit, and the self-powered switch drive circuit according to any one of claims 1-9; The adjustment circuit is connected to the self-powered switch drive circuit; the conversion circuit is connected to the self-powered switch drive circuit. 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 includes: 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 form the first series circuit; the third diode and the fourth diode are connected in series to form the second series circuit. The first series circuit and the second series circuit are connected in parallel; the first capacitor is connected in parallel with both the first series circuit and the second series circuit; the first resistor and the second resistor are connected in series and then 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 drive circuit; the third resistor is connected to the self-powered switch drive 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 the 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 and the inductor are connected in parallel; the fifth resistor and the third capacitor are connected in parallel.

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