Main circuit of the high-frequency switching power supply unit
High-frequency switching power supply circuit, on the one hand, sampling from the output, by comparing with the set standard, and then go to control the inverter, change its frequency or pulse width, to achieve output stability, on the other hand, according to the information provided by the test circuit, by the protection circuit to identify, and to provide the control circuit of the whole machine to carry out a variety of protective measures.
High-frequency switching power supply circuit main circuit
From the AC grid input, DC output of the whole process, including:
1, input filter: its role is to filter the presence of power grid clutter, but also impede the machine generated clutter feedback to the public power grid.
2, rectification and filtering: the grid AC power supply directly rectified into a smoother DC power for the next level of conversion.
3, inverter: rectified DC into high-frequency alternating current, which is the core part of the high-frequency switching power supply, the higher the frequency, volume, weight and output power ratio is smaller.
4, output rectification and filtering: according to the load needs, to provide a stable and reliable DC power supply.
High frequency switching power supply circuit modulation
First, pulseWidthModulation (pulseWidthModulation, abbreviated as pWM) switching period is constant, by changing the pulse width to change the duty cycle.
Second, the pulse frequency modulation (pulseFrequencyModulation, abbreviated as pFM) conduction pulse width is constant, by changing the switching frequency to change the duty cycle.
Hybrid modulation
On-pulse width and switching frequency are not fixed, each can change the way, it is a mixture of the above two ways.
Switching control voltage regulator principle
Switch K to a certain time interval repeatedly on and off, in the switch K on, the input power supply E through the switch K and filter circuit to provide the load RL, in the whole switch on period, power supply E to the load to provide energy; when the switch K off, the input power supply E will interrupt the provision of energy. It can be seen that the input power supply to the load to provide energy is intermittent, in order to enable the load to get continuous energy supply, switch C2 and D circuit, has this function. The inductor L is used to store energy and when the switch is disconnected, the energy stored in the inductor L is released to the load through the diode D, so that the load is provided with continuous and stable energy, because the diode D makes the load current continuous, so it is called a continuity diode. The average value of voltage EAB between AB can be expressed by the following equation
EAB=TON/T*E
Where TON for each switch on time, T for the switch on and off the operating cycle (i.e., switch on time TON and off time TOFF sum).
As can be seen from the formula, change the switch on time and the ratio of the operating cycle, the average value of the voltage between the AB also changed, therefore, with the load and the input power supply voltage changes automatically adjust the ratio of TON and T will be able to make the output voltage V0 to maintain the same. Changing the on-time TON and the proportion of the operating cycle is also to change the duty cycle of the pulse, this method is called "time ratio control" (TimeRatioControl, abbreviated as TRC).
