Mochuan Drives - Professional design, manufacturer HMI Touch Screen Panel & PLC Controller, provide industry solutions and system integration since 2009.

  • Professional design, manufacturer HMI Touch Screen Panel & PLC Controller, provide industry solutions and system integration since 2009.


What is Switching Power Supply?

April 28, 2023

A switched-mode power supply (SMPS) is a type of electronic power supply that uses a switching regulator to effectively transform electrical current. In the same way, conventional supplies transform voltage and current to power DC loads, switched-mode power supplies (SMPS) do the same.

A switch-mode power supply (SMPS) is a type of power supply that converts voltage and current as it transmits energy from a direct current (DC) or alternating current (AC) source to a direct current (DC) load, like a personal computer. Unlike a linear power supply, a switching-mode supply's pass transistor rapidly changes between low-dissipation, full-on and full-off states, spending little time in the high-dissipation stages.

Theoretically, a perfect switched-mode power supply would waste no energy. Voltage is regulated by adjusting the proportion of time an electric current is "on" (its "duty cycle"). As opposed to this, linear power supplies use power dissipation in the pass transistor to maintain a constant output voltage. The switched-mode power supply is advantageous because it increases electrical efficiency. Mochuan Drive is the best switching power supply manufacturer to get your product.

How Does Switching Power Supply?

Linear AC/DC power supplies have been used for quite some time, converting AC power from the utility grid into DC voltage to power electronics and lighting. Unfortunately, linear power supplies have been confined to niche applications in industry and medicine due to the necessity for smaller supplies for high-power applications. However, switching power supply had become the standard because of its compact size, great efficiency, and ability to manage large amounts of power.

Let's look at how a switching power supply typically converts alternating current (AC) to direct current (DC).

Input Rectification

Rectification is the process of transforming alternating current into direct current. The first stage of the switched-mode AC/DC power supply is rectifying the input signal. People usually picture DC voltage as a steady, unchanging line, similar to a battery's. On the other hand, the unidirectional flow of electric charge characterizes direct current (DC). This indicates a unidirectional, although not necessarily continuous, voltage flow.

A passive half-bridge rectifier uses a diode to cancel out the negative half of a sine wave, completing the rectification process. Diodes are semiconductors that allow current to flow through them during the positive half of an incoming wave but act as a barrier to current in the negative half.

The rectified sine wave will have insufficient mean power to reliably power devices. Changing the polarity of the negative half-wave to the positive is a more effective strategy. Full-wave rectification uses four diodes in a bridge design to achieve the desired result. No matter which way the input voltage is polarized, this setup keeps the direction of the current flow constant.

Although the mean output voltage of a completely rectified wave is greater than that of a half-bridge rectifier, it is still quite different from the constant DC waveform required for powering electronic equipment. Despite being a DC wave, this source of electricity is inefficient because of the voltage wave's irregular shape and frequent value shifts. Ripple refers to the periodic variation in DC voltage, and having a supply that minimizes or eliminates ripple is essential for optimal performance.

Power Factor Correction (PFC)

Power factor correction (PFC) is the next step in the design of a switching power supply. PFC circuits are an essential part of most commercial power supplies despite having little to do with the real transformation of AC power to DC power.

The charging current travels through the capacitor for only a short time, from the instant the input voltage is higher than the capacitor's charge to its maximum of the rectified signal. As a result, the capacitor experiences a cascade of brief current spikes, which poses a serious problem not only for the power supply but for the power grid due to the enormous number of harmonics introduced by these transients. As a result of distortion caused by harmonics, other power sources and devices plugged into the grid could be adversely affected.

In a switched-mode power supply architecture, the power factor correction circuit's job is to remove or at least greatly reduce these harmonics. Active and passive power factor correction are two approaches that can be taken.


The final stage in power switching, whether or not a PFC circuit is present, is to reduce the magnitude of the rectified DC voltage to a level suitable for the load. Without power factor correction (PFC), the DC voltage output from the rectifier will be around 320V since the input AC waveform has been rectified at the entry. The output of a boost converter with a power factor correction (PFC) circuit enabled will be a constant DC voltage of 400V or higher.

When deciding on a reducing-in-size procedure, prioritizing safety is of paramount importance. Because the power supply's input is hardwired into the AC mains, any device powered by the output risks being severely damaged or even destroyed in the event of a current leak. Both the input and output circuits of an electricity-connected AC/DC power supply can be magnetically isolated to ensure safety. Flyback converters and resonant LLC converters, which feature galvanic or magnetic isolation, are the most popular types of isolated AC/DC power supply circuits.


When constructing a switching power supply, there are several factors to consider, including safety, efficiency, size, weight, etc. Many designers find it helpful to use integrated components in their power supplies due to the complexity of the control circuits for switching power supply compared to the linear power supply. Do you want the best switching power supply manufacturer? Mochuan Drive is the best brand to consult for switching power supply.



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