A two-stage excitation controlled constant frequency electronic ignition circuit

Abstract

The application belongs to the field of ignition of aviation and aerospace engines, and particularly relates to a two-stage control fixed-frequency electronic ignition circuit, which comprises a filter circuit, a voltage stabilizing circuit, an inverter voltage-boosting circuit, a rectification energy storage circuit, a high-voltage discharge circuit and a control circuit, wherein a direct current input is used as the input of the filter circuit, two outputs of the filter circuit are respectively connected with a first input end of the inverter voltage-boosting circuit and an input end of the voltage stabilizing circuit, an output of the voltage stabilizing circuit is connected with a first input end of the control circuit, an output of the control circuit is connected with a second input end of the inverter voltage-boosting circuit, two output ends of the inverter voltage-boosting circuit are respectively connected with an input end of the rectification energy storage circuit and a second input end of the control circuit, an output end of the rectification energy storage circuit is connected with an input end of the high-voltage discharge circuit, and two outputs of the high-voltage discharge circuit are respectively connected with an ignition electrode and a third input end of the control circuit.

Description

Technical Field

[0001] This invention belongs to the field of aviation and aerospace engine ignition, specifically relating to a two-stage self-excited control fixed-frequency electronic ignition circuit. Background Technology

[0002] Currently, most domestic aero-engine electric ignition devices adopt two methods: self-excited transistor-controlled ignition circuit and single-stage externally excited transistor-controlled ignition circuit.

[0003] The self-excited transistor-controlled ignition circuit uses a feedback winding with a center tap added to the primary winding of an inverter step-up transformer. During circuit operation, an induced electromotive force is generated in the feedback winding through the primary winding of the transformer to generate an oscillating signal that controls the switching on and off of the transistor. The voltage is then boosted by the secondary winding of the transformer and rectified to achieve a high-voltage pulse output. Its circuit structure is simple and requires fewer electronic components. However, because it has fewer control and feedback circuits, it places high demands on the performance, durability, and reliability of the components in the ignition circuit. As a result, the overall circuit reliability is relatively low and the service life is short. It is often used under operating voltage conditions of (24-30) VDC. When the input voltage range is large, the output ignition frequency and input power vary greatly. Especially when the input voltage is low, the spark frequency is too low to meet the design requirements for engine starting, affecting engine starting.

[0004] The self-excited transistor ignition control circuit uses a timer circuit to provide the transistor with a PWM control signal with a fixed or variable duty cycle. The low-voltage DC power is converted into high-voltage AC power by a boost inverter circuit, and then rectified to output high-voltage pulse power. Compared with the self-excited transistor ignition control circuit, the signal controlling the transistor switch is provided by the timer circuit, which reduces the feedback winding in the primary winding of the transformer and improves the reliability and service life of the transformer and transistor used in the circuit. However, the input voltage range that the circuit can operate in is still relatively narrow. It is often used for input voltage ranges of (18~30)VDC. When the dynamic range of the input voltage is large, the output ignition frequency varies greatly. When the input voltage is low, the ignition frequency drops more severely, which has a greater impact on engine starting and ignition. Summary of the Invention

[0005] Summary of the invention: A two-stage self-excited control fixed-frequency electronic ignition circuit is provided to provide a stable output discharge frequency under different input voltages with large dynamic range variations, and to ensure that the input voltage power of the ignition device remains stable under different input voltages.

[0006] Technical solution:

[0007] A two-stage self-excited control fixed-frequency electronic ignition circuit includes: a filter circuit, a voltage regulator circuit, an inverter boost circuit, a rectifier energy storage circuit, a high-voltage discharge circuit, and a control circuit. The control circuit includes a first-stage time base circuit, a second-stage time base circuit, a D flip-flop, an OR gate, a current sampling circuit, and a voltage sampling circuit. The DC input serves as the input to the filter circuit. The two outputs of the filter circuit are connected to the first input terminal of the inverter boost circuit and the input terminal of the voltage regulator circuit, respectively. The output of the voltage regulator circuit is connected to the first input terminal of the control circuit. The output of the control circuit is connected to the second input terminal of the inverter boost circuit. The two output terminals of the inverter boost circuit are connected to the input terminals of the rectifier energy storage circuit and the second input terminal of the control circuit, respectively. The output terminal of the rectifier energy storage circuit is connected to the input terminal of the high-voltage discharge circuit. The two outputs of the high-voltage discharge circuit are connected to the ignition nozzle and the third input terminal of the control circuit, respectively.

[0008] Furthermore, the voltage regulator circuit comprises a voltage regulator chip U1 and filter capacitors C1 to C4. The input terminal of the voltage regulator chip U1 is connected to one end of filter capacitors C1 and C2, the output terminal of the voltage regulator chip U1 is connected to one end of filter capacitors C3 and C4, and the other end of filter capacitors C1 to C4 is grounded.

[0009] Furthermore, the time base circuit chip U2, resistors R2-R4, and capacitors C9-C11 form a first-stage time base circuit; the time base circuit chip U3, resistors R5-R7, and capacitors C12-C14 form a second-stage time base circuit; and the D flip-flops include flip-flop U4B and flip-flop U4A, wherein...

[0010] The power supply pin of timer chip U2 is connected to ground via series capacitor C5. The reset pin of timer chip U2 is connected to the power supply pin via series resistor R2. The reset pin of timer chip U2 is connected to ground via series capacitor C9. The discharge pin of timer chip U2 is connected to the power supply pin via series resistor R3. The discharge pin of timer chip U2 is connected to ground via series resistor R4 and capacitor C10. The critical pin and trigger pin of timer chip U2 are both connected to the junction of series resistor R4 and capacitor C10. The control pin of timer chip U2 is connected to ground via series capacitor C11. The ground pin of timer chip U2 is grounded. The output pin of timer chip U2 is connected to the clock bit of flip-flop U4B.

[0011] The power supply pin of timer chip U3 is connected to ground via series capacitor C6. The reset pin of timer chip U3 is connected to the power supply pin via series resistor R5. The reset pin of timer chip U3 is connected to ground via series capacitor C12. The discharge pin of timer chip U3 is connected to the power supply pin via series resistor R6. The discharge pin of timer chip U3 is connected to ground via series resistor R7 and capacitor C13. The critical pin and trigger pin of timer chip U3 are both connected to the junction of series resistor R7 and capacitor C13. The control pin of timer chip U3 is connected to ground via series capacitor C14. The ground pin of timer chip U3 is grounded. The output pin of timer chip U3 is connected to the clock bit of flip-flop U4A.

[0012] The data bit of flip-flop U4A is connected to the output of voltage regulator chip U1, the power supply pin of timer chip U2, and the power supply pin of timer chip U3 after the series resistor R8. The set terminal of flip-flop U4A is grounded, and the negative output terminal of flip-flop U4A is connected to one input of OR gate U6B. The reset terminal of flip-flop U4B is connected to the output of OR gate U6B.

[0013] Furthermore, the current sampling circuit includes: a voltage comparator U5B, a potentiometer RP1, resistors R12 to R16, and a capacitor C16, wherein,

[0014] The positive input terminal of voltage comparator U5B is connected to one end of resistor R15 and one end of capacitor C16;

[0015] The negative input terminal of voltage comparator U5B is connected to one end of resistor R13 and one end of resistor R14;

[0016] The other end of resistor R13 is connected to the other end of capacitor C16;

[0017] The other end of resistor R14 is connected in series with potentiometer RP1 and then connected to one end of resistor R12.

[0018] The other end of resistor R12 is connected to the output of voltage comparator U5B;

[0019] One end of resistor R12 is connected to the power supply pin of timer circuit chip U3;

[0020] The output of voltage comparator U5B is connected to the other input of OR gate U6B.

[0021] Furthermore, the voltage sampling circuit includes a voltage comparator U5A, resistors R9-R11, resistors R25-R28, capacitors C20-C21, and diodes D8-D10, wherein...

[0022] The negative input terminal of voltage comparator U5A is connected to one end of resistor R10 and one end of resistor R11; the other end of resistor R10 is connected to the output terminal of voltage comparator U5A.

[0023] The other end of resistor R11 is connected to one end of diode D10, one end of resistor R28, one end of capacitor C21, one end of capacitor C20, one end of diode D8, and one end of resistor R25.

[0024] The other end of diode D10, the other end of resistor R28, and the other end of capacitor C21 are connected to one end of resistor R27.

[0025] The other end of resistor R27 is connected to the other end of capacitor C20 and one end of resistor R26;

[0026] One end of diode D8 is connected to the other end of diode D9 and the other end of resistor R25;

[0027] The other end of diode D8 is connected to the other end of resistor R26.

[0028] Furthermore, the inverter boost circuit includes an inverter boost transformer T1, diodes D2 to D4, switching transistors Q1 to Q4, resistors R16 to R20, and capacitor C17.

[0029] One end of resistor R18 is connected to the negative output terminal of flip-flop U4B;

[0030] The other end of resistor R18 is connected to the base of switching transistor Q1;

[0031] The collector of switching transistor Q1 is connected to the base of switching transistor Q2 and one end of resistor R20;

[0032] The emitter of switch Q1 is connected to the base of switch Q3;

[0033] The collector of the switching transistor Q2 is connected to the other end of the resistor R18 and the cathode of the diode D2;

[0034] The emitter of switch Q2 is connected in series with resistor R19, and then connected to the collector of switch Q3, the cathode of diode D5, one end of resistor R17, and the gate of switch Q4.

[0035] The emitter of the switching transistor Q3 is connected to the positive terminal of the diode D5, the other end of the resistor R17, one end of the resistor R16, and one end of the capacitor C17.

[0036] The other end of resistor R16 is connected to the source of switching transistor Q4;

[0037] The cathode of diode D2 is connected in reverse series with diode D3 and in the same-direction series with diode D4, and then connected to the drain of switching transistor Q4.

[0038] The other end of capacitor C17 is connected to the negative terminal of diode D2;

[0039] The two input terminals of the inverter step-up transformer T1 are connected to the negative terminals of diode D2 and diode D4, respectively.

[0040] Furthermore, the rectifier-energy storage circuit includes diodes D6-D7 and energy storage capacitors C18-C19, wherein...

[0041] One output terminal of the inverter step-up transformer T1 is connected to one end of energy storage capacitor C18 and one end of energy storage capacitor C19.

[0042] The other output terminal of the inverter step-up transformer T1 is connected to the positive terminals of diodes D6 and D7;

[0043] The negative terminal of diode D6 is connected to the other end of energy storage capacitor C18;

[0044] The positive terminal of diode D7 is connected to the other end of energy storage capacitor C19.

[0045] Furthermore, the high-voltage discharge circuit includes a discharge tube V1, output inductors L1 and L2, and resistors R21 to R24, wherein...

[0046] One end of the discharge tube V1 is connected to one output terminal of the inverter step-up transformer T1;

[0047] The other end of the discharge tube V1 is connected to the other end of the resistor R25;

[0048] One end of resistor R21 is connected to the negative terminal of diode D7 and one end of inductor L1;

[0049] The other end of resistor R21 is connected in series with resistor R22, and then connected to one end of resistor R25.

[0050] One end of resistor R23 is connected to the negative terminal of diode D6 and one end of inductor L2;

[0051] The other end of resistor R23 is connected in series with resistor R24 ​​and then connected to one end of resistor R25;

[0052] The other end of inductor L1 and the other end of inductor L2 are used as two positive output terminals, respectively.

[0053] Beneficial effects:

[0054] This invention has been used in a newly developed ignition system. Currently, the ignition circuit has been verified through functional performance tests, environmental tests, and life tests along with the ignition system. The ignition circuit achieves a spark frequency tolerance of 1Hz under full input voltage conditions, and its performance is good. Attached Figure Description

[0055] Figure 1 This is a topology diagram of the two-stage self-excited control fixed-frequency electronic ignition circuit of the present invention.

[0056] Figure 2 This is a schematic diagram of the two-stage self-excited control fixed-frequency electronic ignition circuit of the present invention.

[0057] Figure 3 This is a measured waveform of the voltage sampling signal at the positive input terminal of the U5A. Detailed Implementation

[0058] This invention belongs to the field of aviation and aerospace engine ignition, and relates to the ignition circuit of an engine DC input capacitor energy storage type electric ignition device.

[0059] Under mature domestic ignition systems, the spark frequency tolerance under full input voltage conditions is approximately 4Hz. The technical protocol requires a spark frequency of (2±0.5)Hz, with a tolerance of 1Hz under full input voltage conditions. Mature technologies cannot meet these requirements. Therefore, a two-stage self-excited control circuit based on D flip-flops and OR gates is proposed. A first-stage timer circuit provides a fixed-duty-cycle PWM switching control signal to the transistor. A combinational logic feedback circuit composed of a control circuit (including the PWM control signal from the second-stage timer circuit and the feedback control signal from the MOSFET source current sampling circuit) and D flip-flops and OR gates adjusts the duty cycle and switching frequency of the MOSFET switching control signal. This allows for a stable output discharge frequency under varying input voltages (10–32)VDC with a wide dynamic range, ensuring stable input voltage and power for the ignition device. This ignition circuit offers advantages such as good dynamic response, stable output ignition frequency, stable power input, wide input voltage dynamic range, high reliability, and long service life.

[0060] To achieve the above-mentioned functional circuit, the circuit topology and circuit principle were analyzed and designed, and finally the circuit was built and the actual waveform was measured to verify it.

[0061] 1. Circuit topology design

[0062] The invented circuit topology mainly consists of a filter circuit, a voltage regulator circuit, an inverter boost circuit, a rectifier energy storage circuit, a high-voltage discharge circuit, and a control circuit (including a first-stage time base circuit, a second-stage time base circuit, a D flip-flop, an OR gate, a current sampling circuit built with a voltage comparator, and a high-voltage discharge feedback voltage sampling circuit). The filter circuit is used to filter out the parasitic electromagnetic noise introduced into the power supply circuit by other electrical devices during operation, while also reducing the electromagnetic influence of high-frequency pulses from the ignition circuit on other recording devices, ensuring the stability of the ignition circuit's function and performance. The voltage regulator circuit boosts the DC power supplied by the power source after voltage regulation. The various modules of the supply control circuit are as follows: the inverter boost circuit converts the input low-voltage DC power into high-voltage pulsed power; the rectifier energy storage circuit rectifies the high-voltage pulsed power and stores it in the energy storage capacitor; the high-voltage discharge circuit releases the energy stored in the capacitor, breaking down the discharge gap of the ignition nozzle to form an electric spark; the control circuit, through signals generated by the first-stage time base circuit, the second-stage time base circuit, the current sampling circuit, and the voltage sampling circuit, processes the signals through D flip-flops and OR gates to control the inverter boost circuit, adjusting the PWM duty cycle of the switching transistors and the peak current in the circuit, thereby stabilizing the discharge frequency. The circuit topology design diagram is shown below. Figure 1 As shown.

[0063] 2. Circuit schematic design

[0064] To implement the invented circuit, the circuit schematic is as follows: Figure 2 As shown, it mainly consists of functional circuits such as a filter circuit, a first- and second-stage time base circuit, a D flip-flop and an OR gate, a current sampling circuit, a voltage sampling circuit, an inverter boost circuit, a rectifier energy storage circuit, and a high-voltage discharge circuit. The main focus is on the analysis and design of the control circuit, as detailed below:

[0065] 2.1 Filtering, time base circuit, D flip-flop and OR gate.

[0066] FL in the diagram represents the filter module, used to filter out parasitic electromagnetic noise from other airborne equipment entering the power supply circuit besides the ignition circuit. It also reduces the electromagnetic influence of high-frequency pulses from the ignition circuit on other recording equipment, ensuring the stability of the ignition circuit's function and performance. The voltage regulator circuit consists of voltage regulator chip U1 and filter capacitors C1-C4, regulating the low-voltage DC power (10VDC-32VDC) supplied by the power supply to power the chips and devices in the control circuit. The timer circuit chip U2, resistors R2-R4, and capacitors C9-C11 form a primary timer circuit. 3. Resistors R5-R7 and capacitors C12-C14 form a two-stage time base circuit. U2 and U3 provide PWM control signals for the main oscillation frequency and discharge frequency of the D flip-flops U4B and U4A, respectively, serving as the clock signals for the D flip-flops U4B and U4A. The D flip-flops are triggered on the rising edge of the clock. The logic level applied to the D input is transmitted to the Q output. The set and reset are independent of the clock and are determined by the high level on the set and reset bits, respectively. The truth table is shown in Table 1. U6B is an OR gate, and its truth table is shown in Table 2. It converts different combinations of input signal levels to drive the subsequent circuits. The pin relationships of U2 and U3 are as follows: pin 1 GND is the ground pin, pin 2 TRI is the trigger pin, pin 3 OUT is the output pin, pin 4 RST is the reset pin, pin 5 CON is the control pin, pin 6 THR is the critical pin, pin 7 DIS is the discharge pin, and pin 8 VDD is the power supply pin.

[0067] Table 1 Truth Table for Flip-Flop U4A and Flip-Flop U4B

[0068]

[0069] Table 2 Truth Table for OR Gate U6B

[0070]

[0071] 2.2 Current Sampling Circuit

[0072] A voltage comparator U5B, potentiometer RP1, resistors R12-R16 (R16 is the current sampling resistor), and capacitor C16 form a current sampling circuit. Q4 is a MOSFET switch. The sampling resistor R16 converts the source-sink current signal of Q4 into a voltage signal and feeds it to pin 7 (positive input) of voltage comparator U5B. When the current flowing through the source of switch Q4 reaches the preset peak current, the voltage at pin 7 (positive input) of U5B is greater than the voltage at pin 6 (negative input) of U5B. Pin 2 (output) of U5B outputs a high level to drive an OR gate U6B. The OR gate receives a high level... When the voltage is at the specified level, pin 4 outputs a high level to pin 10 of the D flip-flop U4B reset terminal. The D flip-flop U4B outputs a high level through internal level conversion to drive Q1, Q2, and Q3, thereby turning off the switch Q4. Whenever the current flowing through the source of the switch Q4 reaches its peak value, the current sampling circuit will perform the above process. By adjusting the duty cycle of the PWM control signal of the switch Q4, the output discharge frequency can be stabilized under different input voltage conditions. The voltage value of pin 6 (negative input terminal) of U5B is set by adjusting potentiometer RP1, thereby setting the peak value of the current flowing through the source of Q4.

[0073] 2.3 Voltage Sampling Circuit

[0074] The voltage sampling circuit consists of voltage comparator U5A, resistors R9-R11, resistors R25-R28 (R28 being the voltage sampling resistor), and a filter circuit (including capacitors C20-C21 and diodes D8-D10). When the voltage in the high-voltage discharge circuit reaches the conduction voltage of the discharge tube V1, the discharge tube breaks down and discharges. The sampling resistor R25 samples the discharge signal. The sampled voltage signal is filtered by the filter circuit and then transmitted to pin 5 (positive input) of voltage comparator U5A, driving U5A to output a high level to the reset terminal of D flip-flop U4A. When the reset terminal of the D flip-flop is high... Pin 2 (output terminal) of U4A outputs a high level to pin 6 (input terminal) of OR gate U6B. When the OR gate receives a high level input, pin 4 (reset pin) of OR gate U6B outputs a high level to pin 10 (reset terminal) of D flip-flop U4B. D flip-flop U4B outputs a high level through internal level conversion to drive Q1, Q2, and Q3, thereby turning off the switch Q4. Since the circuit is a single-ended flyback discharge circuit, the high-voltage discharge circuit discharges once when the switch is turned off. Each time it discharges, the voltage sampling circuit will perform the above operation to stabilize the frequency output of the discharge circuit.

[0075] 2.4 Inverter Boost Circuit

[0076] Q4 is a MOSFET switch, and T1 is an inverter boost transformer. Through the switching signal on the switch Q4, the inverter boost transformer converts low-voltage DC power into high-voltage AC power. Q1, T1 and other peripheral circuits form a single-ended flyback inverter boost circuit. When Q4 is turned off, the transformer transmits the electrical energy stored in the magnetic core.

[0077] 2.5 Rectifier Energy Storage Circuit

[0078] The rectifier energy storage circuit consists of silicon stacks D6 to D7 and energy storage capacitors C18 to C19. Its function is to rectify the high-voltage AC power transmitted from the inverter boost circuit into high-voltage pulse power, which is then stored in the energy storage capacitors.

[0079] 2.6 High-voltage discharge circuit

[0080] The high-voltage discharge circuit consists of a discharge tube V1, output inductors L1 and L2, and a high-voltage transmission circuit. When the voltage across the energy storage capacitor reaches the discharge voltage of the discharge tube, the discharge tube breaks down and discharges, converting electrical energy into an electric spark through the ignition nozzle.

[0081] The OR gate U6B can be selected from CC4071, the voltage comparators U5A and U5B can be selected from FX139GJ(Z); the flip-flops U4A and U4B can be selected from CC4013.

[0082] from Figure 3 As can be seen, under the control of each stage of the control circuit, the input DC power is discharged through the inverter boost circuit and the rectifier energy storage circuit, and finally discharged in the high-voltage discharge circuit. The electrical signal in the high-voltage discharge circuit is sampled and filtered by the sampling resistor R25 and then transmitted to the positive input terminal 5 (positive input terminal) of the voltage comparator U5A. It can be seen that the frequency of the voltage signal at pin 5 (positive input terminal) of U5A is 2.040Hz. Therefore, the discharge signal frequency is 2.040Hz, which reaches the preset value of 2Hz.

[0083] To verify that the present invention achieves a stable output spark frequency of 2Hz under a wide input voltage range (10-32) VDC, an experiment was conducted. By setting different input voltages, the spark frequency at the discharge terminal of the ignition nozzle was measured with a frequency meter. Three measurements were taken under the same input voltage, and the average value was taken (two decimal places were retained). The experimental results are shown in the table below:

[0084] Table 3 Output spark frequency under different input voltages

[0085]

[0086] The above test results show that under different input voltage conditions (10-32) VDC, the output spark discharge frequency is stable at around 2Hz, proving that the invention has achieved its objective.

Claims

1. A two-stage self-excited control fixed-frequency electronic ignition circuit, characterized in that, include: The system comprises a filter circuit, a voltage regulator circuit, an inverter / boost circuit, a rectifier / energy storage circuit, a high-voltage discharge circuit, and a control circuit. The control circuit includes a first-stage timer circuit, a second-stage timer circuit, a D flip-flop, an OR gate, a current sampling circuit, and a voltage sampling circuit. The DC input serves as the input to the filter circuit. The two outputs of the filter circuit are connected to the first input terminal of the inverter / boost circuit and the input terminal of the voltage regulator circuit, respectively. The output of the voltage regulator circuit is connected to the first input terminal of the control circuit. The output of the control circuit is connected to the second input terminal of the inverter / boost circuit. The two output terminals of the inverter / boost circuit are connected to the input terminals of the rectifier / energy storage circuit and the second input terminal of the control circuit, respectively. The output terminal of the rectifier / energy storage circuit is connected to the input terminal of the high-voltage discharge circuit. The two outputs of the high-voltage discharge circuit are connected to the ignition nozzle and the third input terminal of the control circuit, respectively. The voltage regulator circuit consists of a voltage regulator chip U1 and filter capacitors C1 to C4. The input terminal of the voltage regulator chip U1 is connected to one end of filter capacitors C1 and C2, the output terminal of the voltage regulator chip U1 is connected to one end of filter capacitors C3 and C4, and the other end of filter capacitors C1 to C4 is grounded. The time base circuit consists of chip U2, resistors R2-R4, and capacitors C9-C11 forming a first-stage time base circuit. The time base circuit consists of chip U3, resistors R5-R7, and capacitors C12-C14 forming a second-stage time base circuit. The D flip-flops include flip-flop U4B and flip-flop U4A. Specifically, the power supply pin of time base chip U2 is connected to ground via series capacitor C5; the reset pin of time base chip U2 is connected to the power supply pin via series resistor R2; the reset pin of time base chip U2 is connected to ground via series capacitor C9; the discharge pin of time base chip U2 is connected to the power supply pin via series resistor R3; the discharge pin of time base chip U2 is connected to ground via series resistor R4 and capacitor C10; the critical pin and trigger pin of time base chip U2 are both connected to the junction of series resistor R4 and capacitor C10; the control pin of time base chip U2 is connected to ground via series capacitor C11; the ground pin of time base chip U2 is grounded; and the output pin of time base chip U2 is connected to the clock bit of flip-flop U4B. The power supply pin of timer chip U3 is connected to ground after series with capacitor C6. The reset pin of timer chip U3 is connected to the power supply pin after series with resistor R5. The reset pin of timer chip U3 is also connected to ground after series with capacitor C12. The discharge pin of timer chip U3 is connected to the power supply pin after series with resistor R6. The discharge pin of timer chip U3 is also connected to ground after series with resistor R7 and capacitor C13. The critical pin and trigger pin of timer chip U3 are both connected to the junction of series resistor R7 and capacitor C13. The control pin of U3 is connected to ground via capacitor C14; the ground pin of timer chip U3 is grounded; the output pin of timer chip U3 is connected to the clock bit of flip-flop U4A; the data bit of flip-flop U4A is connected to the output of voltage regulator chip U1, the power supply pin of timer chip U2, and the power supply pin of timer chip U3 via resistor R8; the set pin of flip-flop U4A is grounded; the negative output of flip-flop U4A is connected to one input of OR gate U6B; the reset pin of flip-flop U4B is connected to the output of OR gate U6B.

2. The two-stage self-excited control fixed-frequency electronic ignition circuit according to claim 1, characterized in that, The current sampling circuit includes: a voltage comparator U5B, a potentiometer RP1, resistors R12 to R16, and a capacitor C16. The positive input terminal of the voltage comparator U5B is connected to one end of resistor R15 and one end of capacitor C16; the negative input terminal of the voltage comparator U5B is connected to one end of resistor R13 and one end of resistor R14; the other end of resistor R13 is connected to the other end of capacitor C16; the other end of resistor R14 is connected in series with potentiometer RP1 and then to one end of resistor R12; the other end of resistor R12 is connected to the output terminal of voltage comparator U5B; one end of resistor R12 is connected to the power supply pin of the timer circuit chip U3; and the output terminal of voltage comparator U5B is connected to the other input terminal of OR gate U6B.

3. The two-stage self-excited control fixed-frequency electronic ignition circuit according to claim 2, characterized in that, The voltage sampling circuit includes a voltage comparator U5A, resistors R9-R11, resistors R25-R28, capacitors C20-C21, and diodes D8-D10. The negative input terminal of voltage comparator U5A is connected to one end of resistor R10 and one end of resistor R11; the other end of resistor R10 is connected to the output terminal of voltage comparator U5A; the other end of resistor R11 is connected to one end of diode D10, one end of resistor R28, one end of capacitor C21, one end of capacitor C20, one end of diode D8, and one end of resistor R25; the other end of diode D10, the other end of resistor R28, and the other end of capacitor C21 is connected to one end of resistor R27; the other end of resistor R27 is connected to the other end of capacitor C20 and one end of resistor R26; one end of diode D8 is connected to the other end of diode D9 and the other end of resistor R25; the other end of diode D8 is connected to the other end of resistor R26.

4. The two-stage self-excited control fixed-frequency electronic ignition circuit according to claim 3, characterized in that, The inverter boost circuit includes an inverter boost transformer T1, diodes D2-D4, switching transistors Q1-Q4, resistors R16-R20, and capacitor C17. One end of resistor R18 is connected to the negative output of trigger U4B; the other end of resistor R18 is connected to the base of switching transistor Q1; the collector of switching transistor Q1 is connected to the base of switching transistor Q2 and one end of resistor R20; the emitter of switching transistor Q1 is connected to the base of switching transistor Q3; the collector of switching transistor Q2 is connected to the other end of resistor R18 and the negative terminal of diode D2; the emitter of switching transistor Q2 is connected in series with resistor R19 and then connected to switching transistor Q3. The collector of transistor Q3, the cathode of diode D5, one end of resistor R17, and the gate of switching transistor Q4 are connected; the emitter of switching transistor Q3 is connected to the anode of diode D5, the other end of resistor R17, one end of resistor R16, and one end of capacitor C17; the other end of resistor R16 is connected to the source of switching transistor Q4; the cathode of diode D2 is connected in reverse series with diode D3 and in the same series with diode D4, and then connected to the drain of switching transistor Q4; the other end of capacitor C17 is connected to the cathode of diode D2; the two input terminals of inverter step-up transformer T1 are connected to the cathodes of diode D2 and diode D4, respectively.

5. The two-stage self-excited control fixed-frequency electronic ignition circuit according to claim 4, characterized in that, The rectifier energy storage circuit includes diodes D6 to D7 and energy storage capacitors C18 to C19. One output terminal of the inverter step-up transformer T1 is connected to one end of energy storage capacitor C18 and one end of energy storage capacitor C19. The other output terminal of the inverter step-up transformer T1 is connected to the positive terminals of diodes D6 and D7. The negative terminal of diode D6 is connected to the other end of energy storage capacitor C18. The positive terminal of diode D7 is connected to the other end of energy storage capacitor C19.

6. The two-stage self-excited control fixed-frequency electronic ignition circuit according to claim 5, characterized in that, The high-voltage discharge circuit includes a discharge tube V1, output inductors L1 and L2, and resistors R21 to R24. One end of the discharge tube V1 is connected to one output terminal of the inverter step-up transformer T1; the other end of the discharge tube V1 is connected to the other end of resistor R25; one end of resistor R21 is connected to the cathode of diode D7 and one end of inductor L1; the other end of resistor R21 is connected in series with resistor R22 and then connected to one end of resistor R25; one end of resistor R23 is connected to the cathode of diode D6 and one end of inductor L2; the other end of resistor R23 is connected in series with resistor R24 ​​and then connected to one end of resistor R25; the other ends of inductors L1 and L2 serve as two positive output terminals.

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