About Single Phase Half Bridge Inverter | New Topic 2025

In this note, we are going to know about Single Phase Half Bridge Inverter, and about its specifications, circuit diagram, operation, advantages, disadvantages, and applications. Welcome to Poly Notes Hub, a leading destination for engineering notes for diploma and degree engineering students.

Author Name: Arun Paul.

What is Single Phase Half Bridge Inverter?

A single-phase half-bridge inverter is a type of power inverter that converts a direct current (DC) input into a single-phase AC output. It is commonly utilized in low-power applications and acts as a foundation for more complicated inverter setups.

📌 Specifications of Single Phase Half Bridge Inverter

• The total DC supply to the circuit is typically between 12V to 48V for small applications.
• Diode ratings should be same as the switches.
• The equal value capacitors are used, typically 10µF to 100µF, rated for Vs​.
• The resistance of the load is vary between 10Ω to 100Ω.
• The switching frequency is from 50Hz to several kHz, depending on the application.

Single Phase Half Bridge Inverter Circuit Diagram

Here is the circuit diagram of single-phase half-bridge inverter –

• Power Supply: The DC input is separated into two equal halves using capacitors, denoted as (Vs/2) resulting in a neutral reference point in the center.
• Switches (S1 and S2): To generate an alternating current waveform across the load, the inverter uses two switches (often IGBTs or MOSFETs or Thyristors) that are turned on and off alternately.
• Diodes (D1 and D2): Freewheeling diodes are connected anti-parallel to the switches. These offer a current path when the switches are turned off, allowing the circuit to handle reactive loads.
• Load: The load is connected between the midpoint of the voltage sources and the midpoint of the switches. It could be resistive (R), inductive (L), or a combination of both (R-L).
• Neutral Point: The neutral point is established through the two capacitors, ensuring that the output voltage swings between +Vs/2 and -Vs/2.

Single Phase Half Bridge Inverter Working

Here is the operation of single-phase half-bridge inverter circuit –

• Mode 1 (S1 ON, S2 OFF):
  • When switch S1 is turned ON, current flows from the upper voltage source (+Vs/2) through S1​, the load, and back to the neutral point.
  • The load voltage (Vo​) is +Vs/2.
  • The current direction through the load is from left to right.
• Mode 2 (S1 OFF, S2 ON):
  • When switch S2​ is turned ON, current flows from the lower voltage source (-Vs/2) through S2​, the load, and back to the neutral point.
  • The load voltage (Vo) is −Vs/2.
  • The current direction through the load is reversed (right to left).
• Freewheeling States:
  • During dead time (when both switches are turned off to avoid short circuiting), the load current continues to flow due to inductance. The current flows freely through the diodes (D1 and D2), depending on the direction of the current.

Output Voltage Equation

The output voltage alternates between +Vs/2 and -Vs/2 based on the states of the switches (S1 and S2) –

• When S1​ is ON and S2 OFF –

• When S1​ is OFF and S2 ON –

• During the freewheeling period (both switches OFF) – The output voltage is determined by both the load and the freewheeling diode operation. For a totally resistive load, it becomes zero. Inductive loads are dictated by the inductor’s stored energy. However, typically, the inverter generates a square wave output voltage –

Output Current Equation

The output current (io) depends on the load impedance (Z) and the nature of the load (resistive, inductive, or a combination). For a purely resistive load (R), the output current equation is –

Advantages of Single Phase Half Bridge Inverter

Here are the advantages of Single Phase Half Bridge Inverter –

• The circuit diagram is very simple.
• To make this, requires less amount of components which reduces price.
• This circuit is suitable for low power applications.

Drawback of Single Phase Half Bridge Inverter

Here are the disadvantages of Single Phase Half Bridge Inverter –

• It has limiting power handling capability in compare with full bridge inverter circuit.
• It has high harmonic distortion due to square wave output.
• It requires precise capacitor balancing for stable operation.

Applications of Single Phase Half Bridge Inverter

Here are the lists of applications of single-phase half-wave inverter –

• UPS Systems: For small uninterruptible power supplies.
• Motor Drives: Low-power AC motor control.
• Renewable Energy: Solar inverters for small-scale systems.
• Lighting: Powering AC lamps from DC sources.
• Educational Purposes: Teaching and lab experiments for power electronics.

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