1. The working principle of the full-control inverter: It is the commonly used single-phase output full-bridge inverter main circuit, and the AC components use IGBT tubes Q11, Q12, Q13, and Q14. And by PWM pulse width modulation control IGBT tube on or off.
When the inverter circuit is connected to the DC power supply, Q11 and Q14 are turned on first, and Q1 and Q13 are turned off, then the current is output from the positive pole of the DC power supply, through Q11, L or the primary coil of the transformer, as shown in Figure 1-2, to Q14. To the negative pole of the power supply. When Q11 and Q14 are cut off, Q12 and Q13 are turned on, and the current flows from the positive pole of the power supply through Q13 and the inductance of the transformer primary winding 2-1 to Q12 back to the negative pole of the power supply. At this time, on the primary coil of the transformer, a positive and negative alternating square wave has been formed. Using high-frequency PWM control, two pairs of IGBT tubes are alternately repeated to generate an alternating voltage on the transformer. Due to the role of the LC AC filter, a sine wave AC voltage is formed at the output.
When Q11 and Q14 are turned off, in order to release the stored energy, diodes D11 and D12 are connected in parallel at the IGBT to return the energy to the DC power supply.
2. Working principle of semi-controlled inverter: semi-controlled inverter uses thyristor components. Th1 and Th2 are thyristors that work alternately. If Th1 is first triggered and turned on, the current flows through Th1 through the transformer. At the same time, due to the induction of the transformer, the commutation capacitor C is charged to twice the power supply voltage. Pressing Th2 is triggered to turn on, because the anode of Th2 is reversely biased, Th1 is turned off and returns to the blocking state. In this way, Th1 and Th2 commutate, and then the capacitor C is charged in reverse polarity. In this way, the thyristor is triggered alternately, and the current alternately flows to the primary of the transformer, and alternating current is obtained at the secondary of the transformer.
In the circuit, the inductance L can limit the discharge current of the commutation capacitor C, extend the discharge time, and ensure that the circuit turn-off time is greater than the turn-off time of the thyristor, without the need for a large-capacity capacitor. D1 and D2 are two feedback diodes, which can release the energy in the inductance L and return the remaining energy in the commutation back to the power supply to complete the energy feedback function.
