COMPARISON BETWEEN ISOLATED AND NON-ISOLATED DC-DC CONVERTER

Courtesy: Md. Dehan Rahman, Lecturer, Dept. of EEE, European University of Bangladesh, Email: dehanrahman@iut-dhaka.edu    

In modern day power system, the use of renewable systems are on the rise. It is required to convert the fixed source to a variable one. This voltage conversion can be done by using DC-DC converter. DC-DC converter is a power electronic circuit which is used to step up or step down a fixed DC source, depending on the duty cycle of the switch.  

The construction of DC-DC converters is done in one of two ways.

1.      Non-isolated converters

2.      Isolated converter.

Non-isolated converter

The conventional DC-DC converters which are normally used, falls under this classification. Converters like Buck, Boost and Buck-Boost converter are non-isolated DC-DC converter. 

 

Fig. 1: Non-isolated DC-DC converter

Isolated converter

Isolation is an important component when designing electrical circuits. It provides an electrical isolation between input and output. Isolation ensures safety and a stable power supply with lower noise levels. The reduction in noise is obtained by breaking of ground loops. Isolation can be done by using transformer or by using a coupled inductor.

 

Fig. 2: Isolated DC-DC converter

Benefits of non-isolated converter

Non-isolated converters are cost-effective. Isolated converters tend to be expensive. This is usually due to the use of transformer for isolation. Addition of transformer for isolation also causes a loss in output power. Due to power loss in transformer, efficiency also decreases in isolated converter. Circuit size of isolated converter also increases due to additional components used for isolation. The circuit becomes bulky. 

Advantages of isolated converters

There are many instances when isolation is required. Isolation electrically separates input and output side. This provides safety against high and potentially hazardous voltage in DC-DC converter. Isolation also helps in reduction of noise. This is done by breaking of ground loop. This is achieved by the separation of ground, done by isolation.        

 

The choice between non-isolated and isolated converter depends on some factors. If safety is concerned then isolated converters are preferred. However if efficiency, cost and circuit size is prioritized then non-isolated converters are preferable.