Working principle switching power supply
2018-11-08 23:18:25
Working principle and characteristics of switching power supply
Switching power supply uses circuit to control switching tube for high-speed pass-through and cut-off. It converts direct current into high-frequency alternating current and provides transformer with transformer for voltage conversion, thus generating one or more sets of voltage needed. The reason for converting to HVAC is that the efficiency of HVAC in transformer voltage conversion circuit is much higher than that of 50HZ. So the switching transformer can do very little, and the work is not very hot. The cost is very low. If 50HZ is not changed to high frequency, switching power supply will be meaningless. Switching transformers are also not mysterious. It's a common transformer. This is the switching power supply. Switching power supply can be divided into isolation and non insulation.
Switching power supply uses circuit to control switching tube for high-speed pass-through and cut-off. It converts direct current into high-frequency alternating current and provides transformer with transformer for voltage conversion, thus generating one or more sets of voltage needed. The reason for converting to HVAC is that the efficiency of HVAC in transformer voltage conversion circuit is much higher than that of 50HZ. So the switching transformer can do very little, and the work is not very hot. The cost is very low. If 50HZ is not changed to high frequency, switching power supply will be meaningless. Switching transformers are also not mysterious. It's a common transformer. This is the switching power supply. Switching power supply can be divided into isolation and non-isolation, isolation type must have switching transformer, but not isolation may not necessarily have.
To put it simply, the switching power supply works by:
1. AC power input is rectified and filtered into DC.
2. The switch is controlled by high frequency PWM (pulse width modulation) signal, and the DC is added to the primary stage of the switching transformer.
The 3. switch transformer secondary induces high-frequency voltage and supplies load by rectification and filtering.
4. The output part is fed back to the control circuit through a certain circuit to control the duty cycle of PWM in order to achieve stable output.
When AC power is input, it usually passes through something like an eccentric current circle to filter out the interference on the power grid, and at the same time to filter out the interference from the power supply on the power grid.
When the power is the same, the higher the switching frequency, the smaller the volume of the switching transformer, but the higher the requirement of the switching transistor.
switch
The secondary part of the transformer can have multiple windings or a winding with multiple taps to get the required output.
Generally, some protective circuits should be added, such as no-load, short-circuit protection, or the switching power supply may be burnt down.
The above is about the general working principle of switching power supply.
In fact, now there are special chips with very high integration, which can make the peripheral circuit very simple and even debug-free.
The development of computer switching power supply has gone through three stages of development: AT, ATX and ATX12V. AT standard is proposed by IBM when it first introduced PC/AT. It provides + 5V, - 5V, +12V, - 12V four groups of voltage with hard switch. The generation of ATX standard has epoch-making significance. It realizes soft switch-on and can wake up through remote network, adding + 3. 3V, +5VSB output. ATX12V is the product of CPU and other hardware development, mainly increasing the output capacity of +12V.
