Single-phase Half Bridge Inverter

The single-phase half-bridge inverter converts DC power to AC power using two switches and two diodes.

Components

1.  Power Switches: Typically, Thyristors or MOSFETs or IGBTs are used.

2.  Diodes: Two diodes (D1 and D2) are placed in anti-parallel with each switch to allow for freewheeling current paths when the switches are off.

3.  DC Source: A DC voltage source V_dc.

4.  Load: Connected between the midpoint of the switches and the neutral point of the DC source.

 

Working Principle

1.  Switching States:

·         State 1 (S₁ ON, S₂ OFF):

·           When S₁ is turned ON by i_g1 for a period of 0<t≤(T/2), and S₂ is turned OFF, current flows from the positive terminal of the DC source, through S1, through the load, and returns to the midpoint of the DC source.

·         During the time S₁ conducts, load is directly connected to source +𝑉𝑑𝑐/2

State 2 (S₁ OFF, S₂ ON):

·         When S₁ is turned OFF and S₂ is turned ON by i_g2 for a period of (T/2)<t≤T , current flows from the midpoint of the DC source, through the load, through S₂, and returns to the negative terminal of the DC source.

·         During the time S₂ conducts, load is directly connected to source −𝑉𝑑𝑐/2

2.    AC Output Generation:

·         By alternately switching S1 and S2 at a high frequency, the output voltage across the load alternates between +𝑉_𝑑𝑐/2  and −V_dc/2, creating an alternating square voltage output waveform.

 

 

3.    Diode Function:

When the load is purely resistive, there is no need of diode D1 & D2, if the loads other than purely resistive, diodes are required.

·         During S1 ON (State 1):

·         D1 is reverse-biased and does not conduct.

·         D2 is forward-biased and allows any freewheeling current from inductive loads to pass through it when S2 is off.

·         During S2 ON (State 2):

·         D2 is reverse-biased and does not conduct.

·         D1 is forward-biased and allows any freewheeling current from inductive loads to pass through it when S1 is off.

Applications:-

·       Small Motor Drives: Used for driving small AC motors in applications like household appliances.

·       Uninterruptible Power Supplies (UPS): Provides AC power in backup systems for small loads.

·       Renewable Energy Systems: Converts DC from solar panels or batteries to AC for residential or small commercial use.