What Is a Switched-Mode Power Supply?

Switch Mode Power Supply ( SMPS ), also known as switching power supply and switching converter , is a high-frequency power conversion device and a type of power supply. Its function is to convert a level of voltage into the voltage or current required by the user through different forms of architecture. The input of the switching power supply is mostly AC power (such as mains power) or DC power, and the output is mostly equipment that requires DC power, such as personal computers. The switching power supply converts the voltage and current between the two.

Switch Mode Power Supply ( SMPS ), also known as switching power supply , switching converter , is a high-frequency power conversion device.

Switching power supply products are widely used in industrial automation control, military equipment, scientific research equipment, LED lighting, industrial control equipment, communication equipment, power equipment, instrumentation, medical equipment, semiconductor cooling and heating, air purifiers, electronic refrigerators, liquid crystal displays, LEDs Lighting, communication equipment, audio-visual products, security monitoring, LED strips, computer cases, digital products and instruments.

There are two types of modern switching power supplies: one is a DC switching power supply; the other is an AC switching power supply.

The switching power supply is roughly composed of the main circuit,

In the field of switching power supply technology, people are developing related power electronic devices.

The high frequency of switching power supply is its development direction. The high frequency makes the switching power supply small, and makes the switching power supply enter a wider range of applications, especially in

The working process of a switching power supply is quite easy to understand. In a linear power supply, the power transistor is operated in a linear mode. Unlike a linear power supply, a PWM switching power supply is a power transistor that works in an on and off state. In the state, the volt-ampere product applied to the power transistor is very small (the voltage is low when on,

1. Switch: Power electronics work in a switched state instead of a linear state

2. High frequency: Power electronic devices work at high frequency rather than low frequency close to the power frequency

3. DC: The switching power supply outputs DC instead of AC ^[1]

1. Small size and light weight: Because there is no power frequency transformer, the volume and weight are only 20-30% of the linear power supply.

2. Low power consumption and high efficiency: The power transistor works in the on-off state, so the power consumption on the transistor is small, and the conversion efficiency is high, generally 60 to 70%, while the linear electric power supply is only 30 to 40%. ^[1]

As the name suggests, switching power supplies are the use of electronic switching devices (such as transistors, field-effect transistors, thyristors, etc.),

Switching power supply and circuit diagram

Through the control circuit, the electronic switching device is continuously on and off, and the electronic switching device is used to pulse-modulate the input voltage, thereby achieving DC / AC, DC / DC voltage conversion, and adjustable and automatic output voltage. Voltage regulation.

Switching power supplies generally have three working modes: fixed frequency, pulse width fixed mode, fixed frequency, pulse width variable mode, and frequency, pulse width variable mode. The former working mode is mostly used for DC / AC inverter power supply or DC / DC voltage conversion; the latter two working modes are mostly used for switching regulated power supply. In addition, the switching power supply output voltage also has three working modes: direct output voltage mode, average output voltage mode, and amplitude output voltage mode. Similarly, the former working mode is mostly used for DC / AC inverter power supply or DC / DC voltage conversion; the latter two working modes are mostly used for switching regulated power supply.

According to the way the switching devices are connected in the circuit, switching power supplies can be roughly divided into three categories: series switching power supplies, parallel switching power supplies, and transformer switching power supplies. Among them, transformer switching power supply (hereinafter referred to as transformer switching power supply) can be further divided into: push-pull, half-bridge, full-bridge, etc .; according to the excitation and phase of the output voltage of the transformer, it can be divided into: forward , Flyback type, single-excitation type and double-excitation type; if they are divided by purpose, they can be divided into more types. ^[1]