Field effect tube |MOSFET|MOS tube - BYCHIP

Switching power supply is a common application of MOSFET, today we will introduce the application of MOSFET in switching power supply, where we will focus on the loss of MOSFET, and how to reduce the loss to improve efficiency.

MOSFET is mainly used for switching operation in switching power supply.

In switching power supplies, MOSFETs need to frequently switch between two states: on and off to control the on-off of current, which has the advantages of low on-resistance and fast switching speed.

MOSFET loss problem:

In switching power supply, MOSFET loss mainly includes on-off loss and switching loss.

It's easy to understand:

On-off loss is due to the power consumption of the MOSFET in the on-off state, while on-off loss is due to the power consumption of the MOSFET during the switching process.

On-off loss:

The on-loss is mainly determined by the on-resistance (RDS(ON)) and on-time of the MOSFET. When the MOSFET is on, the on-current flow over the on-resistance generates power consumption. Higher on-resistance results in higher power consumption.

Note: The longer the conduction time, the greater the conduction loss.

Switching loss: mainly caused by the switching speed and switching current of the MOSFET during the switching process.

When switching states, the MOSFET needs to overcome changes in on-resistance, from on-off to off, or from off to on-off, the process will produce energy conversion and loss. The higher the switching speed, the greater the switching loss.

Here it is suggested that the size of the switching current will also have an impact on the switching loss, and a larger switching current will lead to a larger power consumption.

Methods to reduce MOSFET loss

1. Choose a MOSFETs with low on-resistance: Lower on-resistance means lower power consumption and higher efficiency (choose MOSFETs with lower RDS(ON) values).

2. Control MOSFET switching speed: too high switching speed will increase switching loss, while too low switching speed will increase switching time and switching loss.

3. Optimize the driver circuit: it can help improve the switching performance and efficiency of MOSFET. Reasonable design of the drive circuit to ensure sufficient current and voltage to ensure stability and reliability.

4. Use thermal management measures: MOSFETs will generate heat during operation, and excessive temperatures will lead to increased power loss and decreased device reliability. A heat sink or heat sink can be used to improve the heat dissipation effect of the MOSFET, ensuring that the device is within a safe operating temperature range.

5. Current limiting and protection circuit:

In order to protect the MOSFETs from overload and overheating damage, the current limit and protection circuit must be set reasonably.

The current limiting circuit limits the maximum current of the MOSFET, preventing it from exceeding its rating.

The protection circuit can monitor the temperature and current of the MOSFET and take protective action when the set value is exceeded.

6. Increase the switching frequency: the on-time and switching time of the MOSFET can be reduced. Note: Increasing the switching frequency will also increase the complexity and cost of the switching power supply, so it needs to be considered comprehensively.