Switching power supply loss analysis and pulse skipping technology: The loss of switching power supply includes conduction loss, switching loss and peripheral control circuit loss. The causes of loss in different parts of the circuit are different, so the method of suppressing loss is also different. It is necessary to quantify these losses with mathematical equations, and then to sort out the method of reducing the loss of each part, in order to obtain a specific effective reduction of the overall loss.
The conduction loss and switching loss are closely related to the converter switching frequency, while the higher frequency reduces the converter's requirements for the size of the energy storage components (inductance and capacitance). In order to reduce the loss during standby of the converter and let the converter reduce the switching frequency at low load or no load, the component volume and energy loss can be taken into account. A variety of technologies have been applied to actual power management ICs based on this concept.
When the load is reduced, the switching pulse of the driving power switch will be shielded (ie, skipped), and part of the pulse is omitted, which is equivalent to lowering the switching frequency, which can reduce the loss caused by the high frequency switch. Will cause the output voltage to drop or rise.
In the flyback converter, the energy stored in the transformer's magnetizing inductance when the primary switch is turned on, the original stored energy is released to the load side after the switch is turned off. The power stored in the magnetizing inductance can be expressed as: (fS × Vin2 × TON2) / (2 × LP).
When the load is reduced to a certain level, the pulse skipping mechanism will halve the effective switching frequency, which means that the power supplied by the converter is halved, so the flyback circuit will increase the pulse width to compensate for the power required to output the load. The output voltage will drop suddenly before the pulse width is increased to the power required by the load. The opposite situation occurs when the equivalent switching frequency increases and the output voltage will rise. The sudden rise and fall of the output voltage during such a load change is an inevitable result of a discontinuous change in the switching frequency (increasing or decreasing by an integer multiple).
Solar home energy storage power supply
SHENZHEN CHONDEKUAI TECHNOLOGY CO.LTD , https://www.szsiheyi.com