Inverter circuit diagram and maintenance brief

1. Main indicators of common car inverter products on the market

Input voltage: DC 10V～14.5V; output voltage: AC 200V～220V±10%; output frequency: 50Hz±5%; output power: 70W～150W; conversion efficiency: greater than 85%; inverter operating frequency: 30kHz～50kHz.

The output power of the most popular and most common vehicle inverter on the market is 70W-150W. The inverter circuit mainly uses pulse width modulation circuits based on TL494 or KA7500 chips. The schematic diagram of the most common vehicle inverter circuit is shown in Figure 1. The entire circuit of the vehicle inverter can be roughly divided into two parts. Each part uses a TL494 or KA7500 chip to form a control circuit. The function of the first part of the circuit is to convert the 12V DC power provided by the car battery into 30kHz-50kHz, 220V AC power through high-frequency PWM (pulse width modulation) switching power supply technology; the function of the second part of the circuit is to use bridge rectification, filtering, pulse width modulation and switching power output technologies to convert 30kHz~50kHz, 220V AC power into 50Hz, 220V AC power.

2. Maintenance points of vehicle inverter products

Since the vehicle inverter circuit generally has a power-on soft start function, it takes 5s-30s after the power is turned on before there is an AC 220V output and the LED indicator lights up. When the LED indicator is not on, it means that the inverter circuit is not working.

When the LED indicator does not light up after being powered on for more than 30 seconds, it is necessary to measure the AC voltage value at the XAC output socket. If the voltage value is around the normal 220V, it means that only the circuit of the LED indicator part is faulty; if the AC voltage value at the XAC output socket is 0, it means that the cause of the fault is that the inverter circuit of the front stage of the inverter is not working, and the protection circuit inside the chip IC1 may be activated.

The method to determine whether the internal protection circuit of chip IC1 is activated is: use the DC voltage block of the multimeter to measure the DC voltage value of pin 3 of chip IC1 to ground. If the voltage is above 1V, it means that the protection circuit inside the chip has been activated. Otherwise, it means that the cause of the fault is due to the action of the non-protection circuit.

If the voltage value of the chip IC1's 3rd pin to the ground is above 1V, indicating that the protection circuit inside the chip has been activated, it is necessary to further use the DC voltage block of the multimeter to test the DC voltage between the 15th and 16th pins of the chip IC1, as well as the DC voltage between the 1st and 2nd pins of the chip IC1. Under normal circumstances, the DC voltage of the chip IC1's 15th pin to the ground in the circuit of Figure 1 should be higher than the DC voltage of the 16th pin to the ground, and the DC voltage of the 2nd pin to the ground should be higher than the DC voltage of the 1st pin to the ground. Only when these two conditions are met at the same time, the DC voltage of the chip IC1's 3rd pin to the ground can be normal 0V, and the inverter circuit can work normally. If it is found that a certain test voltage does not meet the above relationship, just find the cause of the fault according to the corresponding branch to solve the problem.