An inverter is used to convert direct current (DC) to alternating current (AC). Using different transformers, or switching circuits, you can get the desired value of voltage and frequency. This post will explain the design of an inverter.
To understand the designing process of an inverter, we will go step by step.
Step 1: Oscillator Circuit of an Inverter
The oscillator circuit is the first and the most straightforward part of an inverter. Oscillator circuits can build this astable multivibrator configuration in several ways. You can make an oscillator circuit by using one of the following:
Step 2: Decide the NAND gates
Some of the common NAND gates include:
- NOR gates
- IC 4060, IC LM567 (These integrated circuits have built-in oscillators)
- IC 555
- Transistors, Capacitors in standard stable mode
The output signal of an oscillator circuit is a square wave or positive pulses. The pulses typically have a specific voltage level, and the distance or space between the pulses denotes the period for which the voltage level is maintained. This voltage level is usually the same as the supply voltage applied to the IC.
Step 3: Output Stage of an Inverter
You can design the output stage of an inverter in three ways. These are:
- Push-Pull Stage: This configuration of an inverter has a center tap transformer. The outer ends of the center tap are hot ends of output devices, such as MOSFETs. Based on the type of device used, i.e., P-type or N-type, the center tap of the transformer either goes to the positive or negative DC supply.
- Push-Pull Half-Bridge Stage: A half-bridge configuration has better efficiency and is a bit more compact than the center tap push-pull circuit. This configuration necessitates capacitors of significant value to implement the desired functions.
- Push-Pull Full-Bridge: This configuration is called the H-bridge stage. Similar to a half-bridge network, an H-bridge inverter also includes a standard two-tap transformer. This configuration does not need a center tap transformer.
The only difference between a full-bridge configuration and a half-bridge configuration is that the capacitors are eliminated, and two more power devices are added to the circuit. A full-bridge inverter circuit includes four transistors, which are arranged such that the configuration resembles the letter “H.” Based on the external driver oscillator stage, the four devices can either be N channel type or can be two P channel and two N channel devices.
Similar to a half-bridge configuration, a full-bridge configuration also necessitates discrete alternating oscillating outputs. These outputs are responsible for triggering the device. The result? The primary of the transformer is exposed to reverse forward switching of the DC. This switching then produces the desired stepped-up voltage on the secondary output winding of the transformer. It is recommended to use this design to get the best output and increase its efficiency.