Switching power supply is a common application of MOSFET. Today, we will introduce the application of MOSFET in switching power supply, focusing on the issue of MOSFET losses and how to reduce losses to improve efficiency.

MOSFET is mainly used for switching operations in switching power supplies.

In switching power supplies, MOSFET needs to switch between two states: on and off, to control the on and off of the current. It has the advantages of low on-state resistance and fast switching speed.

Losses of MOSFET:

In switching power supplies, the losses of MOSFET mainly include conduction losses and switching losses.

It can be well understood:

Conduction loss is due to the power dissipation of MOSFET in the on-state, while switching loss is due to the power dissipation of MOSFET in the switching process.

Conduction loss:

Conduction loss mainly depends on the on-state resistance (RDS(ON)) of MOSFET and the on-state time. When MOSFET is on, the conduction current passing through the on-state resistance will generate power loss. A higher on-state resistance will result in higher power loss.

Note: The longer the on-state time, the greater the conduction loss.

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

When switching state, MOSFET needs to overcome the change of on-state resistance, which will result in energy conversion and loss during the transition from on to off or from off to on. The higher the switching speed, the greater the switching loss.

It is worth mentioning that the magnitude of the switching current will also affect the switching loss, and a larger switching current will result in greater power loss.

Methods to reduce MOSFET losses

1. Select MOSFET with low on-state resistance: Lower on-state resistance means lower power loss and higher efficiency (choose MOSFET with lower RDS(ON) value).

2. Control MOSFET switching speed: Excessive switching speed will increase switching loss, while too low switching speed will increase on-state time and conduction loss.

3. Optimize the drive circuit: It can help improve the switching performance and efficiency of MOSFET. Design the drive circuit reasonably to ensure sufficient current and voltage to ensure stability and reliability.

4. Use thermal management measures: MOSFET generates heat during operation, and excessive temperature will increase power loss and reduce device reliability. Heat sinks or heat sinks can be used to improve the heat dissipation effect of MOSFET and ensure that the device operates within a safe temperature range.

5. Current limiting and protection circuits:

To protect MOSFET from overload and overheating damage, it is necessary to set up current limiting and protection circuits reasonably.

The current limiting circuit can limit the maximum current of MOSFET to prevent it from exceeding its rated value.

The protection circuit can monitor the temperature and current of MOSFET and take protective measures when they exceed the set value.

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

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Disclaimer: The information provided in this article is for reference only. Readers must carefully evaluate and follow relevant technical specifications and guidelines in actual applications. Thank you for your attention and support!