Various Losses in Power Semiconductor Devices

Various Losses in Power Semiconductor Devices

The power electronics switches like IGBT, MOSFET, BJT are widely used in modern circuit designs. However, these devices have more efficiency. Then also, some losses occurred. In this article, we discuss the various losses in power semiconductor devices.

These losses are mainly classified into two types;

  • Static losses (Steady-state losses)
  • Dynamic losses (Switching losses)

Static Losses

When the power device is in ON-state or OFF-state, the losses occur in a power device. These losses are known as static losses or Steady-state losses.

The static losses are further classified into three parts;

  • Forward conduction loss
  • Forward blocking state loss
  • Reverse blocking state loss

Forward Conduction Loss

When the semiconductor device is in fully conduction mode, the loss that takes place in devices is known as forward conduction loss.

It is evaluated by the product of ON-state voltage drop and ON-state current flowing through the device.

When the device is in ON-state, the voltage drop in the device is very small. And hence, the forward conduction loss is very small.

Forward Blocking State Loss

When the device is conducting on forward blocking mode, the device withstands the entire supply voltage.

But due to blocking characteristics, the device tries to block current passes through the device. Then also, a small amount of current is flowing through the device.

As the current passes through the device is small, the power loss that occurs in this state is small. So, the forward blocking state loss is negligible.

Reverse Blocking State Loss

In the reverse blocking state, the voltage and current in the device are very small. And the loss that occurred in this state is a product of voltage and current.

Therefore, the reverse blocking state loss is very small and negligible.

Switching Losses

The switching losses are also known as dynamic losses. When the device is turned ON and OFF, switching losses occur in the device; these are the significant loss occurred in the device.

The power semiconductor device is not turned ON or OFF instantaneously, but it takes finite time in switching.

When the device is switching (turning ON or OFF), the voltage and current through the device are high.

Therefore, during this time, the losses that occurred in the device were very high, as shown in the below figure.

Switching Loss in Power Semiconductor Device
Switching Loss in Power Semiconductor Device

In the above figure, the area under the power curve represents the switching power loss.

The switching time should be reduced to its minimum value to minimise the switching loss. The switching time depends on the characteristics of a semiconductor device.

When the device is used for high frequency, the switching losses are very high.

The switching losses occurred in the device is transferred in heat. Hence, the switching loss must be minimized to avoid damage to the device.

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