Ⅰ. What is a switching power supply

Switching power supply technology is constantly evolving along with power electronic technology's growth and advancement. Switching power supplies are currently utilized extensively in practically all electronic equipment due to their small size, light weight, and great efficiency. Given the current electronic information industry's rapid development, it is an essential power supply technique.

Modern power electronics technology is used by switching power supplies to regulate the time ratio of switching on and off in order to maintain a constant output voltage. PWM control ICs and MOSFETs are the most common components of switching power supplies.

The switching power supply and the linear power supply are related. The switching tube is used to control the on-off of the current to create a high-frequency pulse current after its input terminal directly rectifies the alternating current into direct current while operating under the influence of the high-frequency oscillation circuit. An inductor (high frequency transformer) is used to provide a steady low-voltage direct current.

Since the magnetic core of a transformer has a size that is inversely proportional to the square of the switching power supply's operating frequency, the smaller the core, the higher the frequency. By doing this, the weight and volume of the power supply can be decreased along with the transformer's size. Additionally, this power supply is even more effective than a linear power supply because it directly controls DC. People appreciate this since it saves energy. But it also has drawbacks, including a circuit that is complicated, challenging to maintain, and seriously polluted; a power supply that is noisy and unsuitable for some low-noise circuits.

Ⅱ.  Features of switching power supply

Typically, a MOSFET and a pulse width modulation (PWM) control IC make up the switching power supply. Because of its small size, light weight, and high efficiency, switching power supplies have become increasingly common with the advancement and invention of power electronic technology. Its significance is clear.

Ⅲ.  Classification of switching power supplies

The switching power supply can be broadly categorized into three groups based on how the switching devices are connected in the circuit: series switching power supply, parallel switching power supply, and transformer switching power supply.

The transformer switching power supply among them can be further broken down into push-pull, half-bridge, full-bridge, and other configurations. It can be separated into forward excitation, flyback type, single excitation type, and double excitation type depending on the excitation of the transformer and the phase of the output voltage.

Ⅳ. The difference between switching power supply and ordinary power supply

Ordinary power supplies are typically linear power supplies; by this term, we mean power supplies in which the adjustment tube operates in a linear fashion. In a switching power supply, things are different. The switching tube operates in two states: on and off (with switching power supplies, we typically refer to the adjusting tube as a switching tube): On, the resistance is quite low, and off, it is very high and enormous.

A relatively recent kind of power supply is the switching power supply. It benefits from being highly effective, lightweight, step-up, step-down, and having a powerful output. But because the circuit operates in a switching mode, the noise is quite significant.

■ Example: step-down switching power supply

Let's briefly discuss the step-down switching power supply's operating principle: the circuit is made up of switches (really, transistors or field effect transistors), freewheeling diodes, energy storage inductors, filter capacitors, etc.

When the switch is closed, the power supply sends electricity through the switch and the inductor to the load while also storing some of the electricity in the capacitor and inductor. The inductor's self-inductance causes the current to grow relatively slowly once the switch is activated, preventing the output from quickly reaching the power supply voltage value.

The switch turns off after a set amount of time. The current in the circuit will remain unaltered, that is, it will keep flowing from left to right due to the inductor's self-inductance effect (it can be seen that the current in the inductor has an inertial effect). This current circulates through the load, emerges from the ground wire, travels to the anode of the freewheeling diode, flows through the diode, and then loops back around to the left end of the inductor.

The output voltage can be altered by adjusting how quickly the switch closes and opens (PWM, or pulse width modulation). The goal of voltage regulation is accomplished if the ON and OFF timings are managed by sensing the output voltage to maintain the output voltage.

The voltage regulation tube used in both the switching power supply and the common power supply regulates voltage using the feedback concept. In contrast, switching power supplies use less energy, have a wider application range for AC voltage, and have better output DC ripple coefficient. However, switching pulse interference is a drawback.

An conventional half-bridge switching power supply operates primarily by turning on the switches of the upper bridge and lower bridge in sequence (the switch is VMOS when the frequency is high). In order to collect the electric energy, the inductance coil's storage capability is used after the current enters through the upper bridge switch. The coil's inductor coil and capacitor continue to supply power to the outside while the upper bridge switch tube is eventually turned off and the lower bridge switch tube is switched on. The switching power supply is known as such because the two switches are turned on and off, so turn off the lower bridge switch, then turn on the upper bridge to let the current in, and continue this procedure.

Different is the linear power supply. The higher water pipe continuously releases water since there is no switch involvement. It will leak if there is too much of it. This is what we frequently observe in some linear power supply' adjustment tubes. All of the limitless electrical energy is transformed into thermal energy. From this perspective, the linear power supply's conversion efficiency is extremely low, and when the heat is high, the component life will inevitably shorten and have an impact on the ultimate usage effect.

■ The main difference: the way it works

The linear power supply's power regulating tube always operates in the amplification area, and a continuous current flows through it. A larger power adjustment tube and a large radiator are installed because of the adjustment tube's significant power loss. There is significant heat generation and very little efficiency. power source).

A step-down device is necessary for the linear power supply's working technique to transition from high voltage to low voltage. Typically, it is a transformer, though there are others like the KX power supply. After rectification, DC voltage is then output. This results in a huge volume, a lot of bulk, low efficiency, and a lot of heat generation, but it also has benefits: small ripple, good adjustment rate, small external interference, suitable for analog circuits/various amplifiers, etc.

When the voltage is altered, the power device of a switching power supply operates in the switching mode and temporarily stores energy through an inductive coil, resulting in minimal loss, high efficiency, and minimal heat dissipation requirements. There are also higher standards, which call for materials with high magnetic permeability and low loss. Transformator is a brief word. The overall efficiency ranges from 80% to 980%. Although the switching power supply has a low volume and a high efficiency, it offers a slight reduction in terms of voltage and current regulation compared to linear power supplies.