The principle Of DC-AC inverter

An inverter is a device that converts direct current into alternating current. It generally consists of an inverter bridge, control logic, and filtering circuit. The main purpose is to convert various DC sources into AC for the use of AC loads. Generally, DC sources include batteries, dry batteries, solar cells, etc., which can be applied to uninterruptible power supplies (UPS), solar power conversion, etc.

This time, let's explore the working principle of the inverter bridge, which is the relevant principle of the inverter circuit.

Inverter circuits generally include half bridge inverter circuits, full bridge inverter circuits, and push-pull inverter circuits.

Half bridge inverter circuit

The schematic diagram of the half bridge inverter circuit is shown in Figure 1:

The gate signals of V1 and V2 are positively and negatively biased by half a cycle each, complementing each other. The output voltage uo is a rectangular wave with an amplitude of Um=Ud/2.

Work Engineering:

1. When V1 conducts and V2 cuts off, the current path is V1->L ->R ->C2;

2. When V1 cuts off and V2 cuts off, due to the effect of L, the value of the current cannot change suddenly. At this time, the path of the current is L ->R ->C2->VD2->L. At this time, L is the source of energy, and the current time is related to the size of L;

3. When V1 cuts off V2 conduction, the current path is C1->R ->L ->V2, and the uo value is negative;

4. When V1 and V2 are cut off again, the current path is C1->R ->L ->VD1->C1, and L still serves as the energy source.

The above is the principle of a half bridge inverter circuit.

Full bridge inverter circuit

The schematic diagram of the full bridge inverter circuit is shown in Figure 3

Four switching tubes and four freewheeling diodes form two bridge arms, which can be seen as a combination of two half bridge circuits;

Two switching devices on the same bridge arm cannot conduct simultaneously, that is, V1 and V2 cannot conduct simultaneously, V3 and V4 cannot conduct simultaneously, which will cause a short circuit in Ud;

The base signal of V3 differs from V1 θ (0)< θ< 180);

The output voltage is the input voltage Ud.

Work process:

1. When V1 and V4 conduct and V3 and V4 cut off, the current path is V1->R ->L ->V4;

2. When V1 is conducting and V2, V3, and V4 are all cut off (the base signal of V3 differs from V1) θ)， The current path is V1->R ->L-VD3->V1;

3. When V1, V2, V3, and V4 are all cut off, uo is 0;

4. When V1 and V4 are cut off and V2 and V4 are conducting, the current path is V3->L ->R ->V2;

When V2 conducts and V1, V3, and V4 are cut off, the current path is V2->VD4->L ->R ->V2;