Switching power supply is a kind of power supply that uses modern power electronic information 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 steady development and independent innovation of power electronics technology, the promotion of switching power supply technology is also constantly independent innovation. At present, switching power supplies are widely used in almost all electronic equipment due to their advantages of small and medium-sized, light weight and high efficiency. It is a power supply method that cannot be lacked in the rapid development of the information technology industry of electronic devices nowadays. With the rapid and steady development of my country's processing and manufacturing industries, switching power supplies have slowly stepped onto the world stage, and the volume of power supplies has gradually tended to modular design and miniaturization, and the immunity level of power supplies has also improved.
1Switching power supply
Switching power supply is the general name of switching regulator tube power supply, generally refers to AC-DC rectifier circuit typed as AC current and output as AC voltage. The output power switch tube in the switching power supply is working at high frequency switching, and its own power consumption is very low. The high efficiency of the power supply can achieve 75%~90%, which is 1 higher than the general linear regulator power supply (line power supply). Times.
The difference between the linear power supply and the switching power supply is that the voltage transformation of the linear power supply can be regarded as the voltage adjustment of the resistance value, just like adjusting the sliding rheostat to change the working voltage. The switching power supply can be regarded as a change in the operating voltage according to the frequency of the adjustment switch.
Switching power supplies are classified
1. Switching power supply without power frequency transformer

The power frequency transformerless switching power supply is based on the small transformer coil to replace the heavy power frequency transformer, test and power grid protection. Since the electronic devices in the switching power supply work at high frequency switching, the power consumption of their own consumption is very low, and the high efficiency of the power supply is doubled compared with the general linear power supply.  

2. Switching power supply, regulated power supply
The switching power supply stabilized power supply is a switch-type integrated power supply stabilized power supply. It integrates the PWM control board, output power output stage, and maintenance power supply circuit into an integrated IC. The high efficiency of the power supply stabilized power supply can achieve 90%. Above %, some can continuously adjust the output voltage, suitable for the production of switching power supplies ranging from tens of watts to hundreds of watts.
3. Chip switching power supply
The chip switching power supply integrates the key power supply circuits of the switching power supply into the integrated IC, which can complete output protection, duty cycle modulation and various maintenance functions, and its processing speed is the largest. The chip switching power supply is compatible with 85~265V, 47~400Hz AC current according to the type of rectifier filter. And it has the advantages of high integration, high cost performance, simplest peripheral circuits, best performance parameters, etc. Now it has become the development and design of small and medium output power switching power supplies below 600W, high-precision switching power supplies and modular switching power supplies. Selection of integrated circuit chips.
Basic characteristics and classification of switching power supply
Switching power supply working mode
Switching power supplies are categorized according to the basic concepts of operation, and can be classified into the following 4 categories:
(1) Pulse width modulation PWM, that is, duty cycle modulation. According to adjusting the pulse width to achieve the overall goal of the voltage regulator tube, the key is the PWM control board. The application of this kind of switching power supply is more common, and its pwm duty cycle adjustment range is large, and PWM can also maintain the same pace with the digital clock of the main system software.
(2) Single pulse frequency modulation PFM, that is, pulse frequency modulation: similar to the duty cycle adjustment, it is based on adjusting the switching frequency to achieve the overall goal of the regulator tube, and the key is the PFM control board. This kind of method is suitable for portable devices, it reduces the amount of static data current for operating the integrated IC under the low PWM duty cycle and low frequency standard.
(3) Single pulse relative density modulation PDM, that is, pulse density modulation: its advantage is that the duty cycle is stable, and the overall goal of the regulator tube is achieved according to the number of pulses. It adopts zero working voltage technology, which can significantly reduce the loss of output power switch tube.
(4) Mixed modulation: it is a combination of PWM and PFM. Switching cycle time Switching cycle time and pulse width are adjustable. The PWM control board can be used as a single integrated circuit chip application, can also be integrated in the switching power supply, or integrated in the switching power supply.
Among them, the switching power supply belongs to DC-DCSPWM, and the switching power supply is generally AC-DCSPWM. Excluding part of the front rectifier filter, it can be regarded as a DC-DCSPWM, plus the part of the front rectifier filter is an AC-DCSPWM.
4Basic concept of switching power supply
The basic concept of switching power supply is composed of the following 7 parts:
(1) Key in the rectifier filter, including the rectifier tube and key in the coupling capacitor.
(2) Chip switching power supply, including output power switch tube and control board (including oscillator, standard voltage source, error amplifier and PWM voltage comparator), MOSFET.
(3) The drain clamp maintains the power supply circuit.
(4) Transformer coil.
(5) Output rectifier filter.
(6) Optocoupler integrated operational amplifier circuit.
(7) Reference point power supply circuit to bias the phototransistor of the optocoupler.
5 Basic Concept Research
The scientific research of the basic concept of Zener tube shows as follows: When V rises due to some conditions, the current on the LED rises at this moment. According to the photocoupler, the emitter current of the receiving tube rises, so that the control terminal of TOPSWITCH is electrically charged. As the flow rate increases, the pwm duty cycle decreases, resulting in a decrease in V, thereby achieving the effect of a regulator tube.
6 Summary
From the above, we can get that switching power supply, as the best in the power supply industry at this stage, also has a very long life span and has significant advantages. From the basic concept of operation, many elements will endanger the quality of the switching power supply, and the improvement of other maintenance power circuits will also make the safety performance of the switching power supply higher. The choice of protection will also endanger the response level of the power supply.
Switching power supply takes into account the power requirements of many commercial circles, whether it is power supply volume or power safety performance, it guarantees perfection, guarantees the smooth output of power supply circuits of various enterprise design boards, and applies power supply design schemes to achieve true and practical significance. Interactions between customers and manufacturers on the Internet.