What is the difference between a switching power supply and a transformer?

Switching power supply is the DC voltage obtained after rectifying the mains, using the on and off of the switch to cut the voltage into a rectangular wave (of course, the actual waveform is not a perfect rectangular wave, but there will be overshoot). The meaning of this is to cut the high energy into countless low energy and pass it to the output end. The output end will feed back to the input end through the output voltage level (adjust the frequency of cutting, and the width of the cutting-duty cycle ) To achieve the purpose of stabilizing the output voltage

Principle of switching power supply

The principle of switching power supply is to convert the power frequency AC into DC, and then convert the DC into high-frequency AC. After the process of switching transformers, feedback and voltage stabilization, etc. become the voltage you need, it is rectified, filtered, and then converted into DC. During the whole process, the MOSFET is continuously turned on and off to transform the high-voltage direct current into high-frequency alternating current.

Switching power supplies are usually divided into AC/DC, DC/DC, DC/AC and other types. Generally speaking, it is to convert a certain voltage into a specific voltage suitable for the needs of electrical equipment. For example, the on-board switching power supply converts the on-board 12V DC voltage into 5V or other voltages for use by the equipment.

Commonly used mobile phone chargers (also switching power supplies), computer power supplies, etc. are all switching power supplies

Switching power supply function

The LED switching power supply has a circuit to control the switching tube for high-speed pass and cut-off. It converts direct current into high-frequency alternating current to transform the converter to generate one or more sets of voltages. What is the purpose of the switching power supply? The reason for converting into high-frequency alternating current is that high-frequency alternating current is in the transformer. The efficiency in the circuit is higher than the commercial power 50Hz or 60Hz. Therefore, the size of the switching power supply transformer can be very small, it will not be very hot when the switching power supply is working, the product price is lower than the power frequency DC regulated power supply, what is the switching power supply, if you don’t change 50Hz or 60Hz to high Frequency power, then the switching power supply has no meaning. Switching power supplies can be roughly divided into two types: isolation and non-isolation. Those that are isolated must have switching power converters, while those that are not isolated may not necessarily have switching power converters. What is the switching power supply? Compared with the traditional DC power supply, the switching power supply has the advantages of small size, light weight, and high efficiency.

Main purpose of switching power supply

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 refrigeration and heating, air purifiers, electronic refrigerators, liquid crystal displays, LEDs Lighting, communication equipment, audio-visual products, security monitoring, LED light bags, computer cases, digital products and instruments, etc.

Introduction to Transformers

Transformer is a kind of electrical equipment used for power conversion. It is an indispensable and important device in the power grid. It can convert AC power of one voltage and current into AC power of another voltage and current of the same frequency. Transformers are used in all electronic products. Its principle is simple, but the winding process of the transformer will have different requirements according to different use occasions (different purposes). The main functions of the transformer are: voltage transformation; impedance transformation; isolation, voltage stabilization (magnetic saturation transformer), etc., The core shapes commonly used in transformers generally have E-type and C-type cores.

In different environments, transformers have different uses, such as:

1. Increasing the voltage during long-distance transmission can reduce the power loss on the line

2. Lowering the voltage when reaching the area of ​​use can meet the electricity needs of different users

3. The use of transformer connection when impedance matching can play a role in changing the impedance

4. The use of an isolation transformer can isolate the two phases to prevent electric shock accidents

The difference between switching power supply and transformer

Switching power supply is a kind of power supply that uses modern power electronic technology to control the time ratio of switching on and off to maintain a stable output voltage. Switching power supplies are generally composed of pulse width modulation (PWM) control ICs and MOSFETs. With the development and innovation of power electronics technology, switching power supply technology is constantly innovating. At present, the switching power supply is widely used in almost all electronic equipment due to its small size, light weight and high efficiency. It is an indispensable power supply method for the rapid development of today's electronic information industry.

Transformer (Transformer) is a device that uses the principle of electromagnetic induction to change the AC voltage. The main components are the primary coil, the secondary coil and the iron core (magnetic core). The main functions are: voltage transformation, current transformation, impedance transformation, isolation, voltage stabilization (magnetic saturation transformer), etc. According to the purpose, it can be divided into: power transformers and special transformers (electric furnace transformers, rectifier transformers, power frequency test transformers, voltage regulators, mining transformers, audio transformers, intermediate frequency transformers, high frequency transformers, impact transformers, instrument transformers, electronic transformers , Reactors, transformers, etc.). Circuit symbols often use T as the beginning of the number. Example: T01, T201, etc.

Transformer is a device that transforms voltage, current and impedance based on the principle of electromagnetic induction. The primary of the transformer is used in AC circuits. Switching power supply is a kind of power supply that uses modern power electronic technology to control the time ratio of switching transistors on and off to maintain a stable output voltage. Switching power supplies can be divided into two categories: AC/DC and DC/DC; electrical isolation according to input and output Can be divided into two categories: one is isolated called isolated DC/DC converters; the other is not isolated, called non-isolated DC/DC converters. The switching power supply has overheating, overcurrent, short-circuit protection, a wide range of input voltage, input and output isolation voltage, isolation between high-voltage input and output isolation.

A transformer is a simple coil. It is used to change the voltage. The output is AC. If DC is needed, it must be rectified and stabilized. The output of the switching power supply is direct current, which usually includes components such as voltage transformation, rectification, and stabilization. It is an integrated component.

The transformer is two sets of coils. According to the principle of electromagnetic induction, the primary coil is connected to the power supply, and the secondary coil is connected to the load. The voltage and current changes of the primary coil cause the magnetic field to change. The changed magnetic field generates an induced voltage in the secondary, according to the number of turns of the two coils. Ratio, the primary is more than the secondary, it is a step-down, and the primary is less than the secondary is a step-up;

Switching power supplies use the characteristics of electronic components to rectify and filter the power supply voltage (usually AC 220V 380V), and then convert the DC voltage into high-frequency pulses, use different duty cycles to obtain different voltages, and then stabilize the output , The transformer is simpler than the switching power supply for low power requirements and low cost, but for the occasions with high requirements for power supply voltage stability, if the transformer is also required to be rectified and stabilized, the cost is better than that of the same efficiency. Switching power supplies are much higher, and the width of the transformer to the input voltage is narrow. Variations in the input voltage will cause the output voltage to follow changes, while the switching power supply has a wide input voltage range, and the input voltage changes have almost no effect on the output voltage.

The principle of the switching power supply is to first convert the alternating current into direct current, and then into higher frequency alternating current to perform voltage conversion through a high-frequency transformer. Ordinary transformers directly convert the power frequency alternating current. The difference is as follows: the switching power supply is lighter in weight, has a wider voltage range, higher power utilization efficiency, and is more environmentally friendly, but the cost is correspondingly higher (sometimes not too high), and the transformer can be used in most cases.

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