What is a switching power supply
1, switching power supply is the use of modern power electronic technology, control switch tube opening and closing time ratio, to maintain a stable output voltage of a power supply, switching power supply is generally composed of pulse width modulation control IC and MOSFET. Compared with linear power supply, the cost of switching power supply and linear power supply both increase with the increase of output power, but their growth rates are different.
2, the general power supply is generally linear power supply, linear power supply, refers to the adjustment tube work in the linear state of the power supply, switching power supply is a relatively new type of power supply. It has the advantages of high efficiency, light weight, high and low voltage, high output power and so on. High-frequency switching power supply is the direction of its development, which miniaturizes the switching power supply and makes the switching power supply enter a wider application field. In addition, the development and application of switching power supply have important significance in saving energy, saving resources and protecting the environment.
3, switching power supply is to use electronic switching device (e.g., field effect transistor, SCR thyratron, etc.), through the control circuit, the electronic switch devices constantly "on" and "off", make electronic switching device to pulse modulation of the input voltage, so as to realize the DC/AC, DC/DC voltage conversion, and output voltage harmonic voltage automatically.
4, switching power supply generally has three operating modes: frequency, pulse width fixed mode, frequency fixed, pulse width variable mode, frequency, pulse width variable mode. It is composed of main circuit, switching power supply control circuit, detection circuit and auxiliary power supply.
Maintenance essentials of switching power supply
1. When repairing the switching power supply, firstly use the multimeter to detect whether the power components break down the short circuit, such as power rectifier bridge reactor, switching tube and high-frequency high-power rectifier tube; Whether the high - power resistance to inrush current is burnt out. Then check whether the resistance of each output voltage port is abnormal or not. If the above parts are damaged, they need to be replaced.
2. After the power supply is switched on, the power factor module (PFC) and pulse width modulation module (PWM) should be tested, and relevant
information should be consulted to get familiar with the functions of each pin of PFC and PWM modules and the necessary conditions for their normal operation. For power supply with PFC circuit, it is necessary to measure whether the voltage at both ends of the filter capacitor is around 380VDC. If there is around 380VDC voltage, it indicates that the PFC module works normally.
3. In the maintenance practice of switching power supply, many switching power supply adopts UC38×× series 8-pin PWM module, and most of the power supply cannot work because of the damage of the starting resistance of the power supply, or the chip performance degradation, and the increase of starting current. In this case, the external circuit connected with the VR terminal is disconnected, the VR changes from 0V to 5V, the PWM module works normally, and the output voltage is normal.
4, switching power circuit is easy to difficult, power is large and small, output voltage is varied. As long as grasp the core of the thing, fully familiar with the basic structure of switching power supply and module characteristics and, you can quickly eliminate the fault of switching power supply.
Switching power supply for a lot of household appliances, is very important, and is often prone to problems. As ordinary consumers, we may not be familiar with the switching power supply, so that electrical equipment failure, sometimes do not know where the problem. Above saw what is the introduction of switch power supply, as well as the maintenance essentials of switch power supply, make clear to everybody the action of switch power supply to home appliance is helpful.