Inverter power supply: Learn about half-bridge and full-bridge inverter circuits

When a DC power source such as a battery, dry cell, or solar cell is needed to supply power to an AC load, an inverter circuit is required.

Common inverter circuits include half-bridge and full-bridge.

Compared with the half-bridge, the number of switching tubes in the full-bridge is doubled, but under the same switching current, the output power of the full-bridge circuit is twice that of the half-bridge.

What is the difference between how the two work?

The half-bridge circuit consists of two power switches connected in series and two capacitors connected in series.

When V1 is turned on and V2 is turned off , the energy on capacitor C1 is released to load R, the output voltage Uo is positive, and capacitor C2 is charged at the same time;

When VI is turned off, V2 is turned on , and the energy of capacitor C2 is released to the load R. The output voltage Uo is negative. At the same time, capacitor C1 is charged, and the switches V1 and V2 are turned on alternately to allow the load to obtain AC power.

The two capacitors are connected in series to drive the transformer load. However, it should be noted that when working at 50Hz-60Hz, the capacitance requirement of the capacitor will be relatively large, which will lead to a change in the volume of the circuit and an increase in cost.

 The full-bridge circuit, also called the H-bridge circuit, consists of four power switch tubes.

Among them, Q1 and Q4 are complementary in on-off, and Q2 and Q3 are complementary in on-off.

 When Q1 and Q3 are closed and Q2 and Q4 are open, the load voltage Uo is positive;

When Q1 and Q3 are disconnected and Q2 and Q4 are closed, the load voltage Uo is negative;

Q1, Q3 and Q2, Q4 are turned on alternately, and the load obtains AC power.

When the load is not a pure resistor, the load voltage and load current are not in phase. At this time, the parasitic diode of the switching tube plays the role of current follow-up.

Compared with half-bridge, full-bridge circuit is more suitable for high-power applications.