How to reduce the internal loss of switching power supply
The main losses inside the switching power supply To improve the efficiency of the switching power supply, it is necessary to distinguish and roughly estimate the various losses. Losses within a switching power supply can be roughly divided into four areas: switching losses, conduction losses, additional losses, and resistance losses. These losses usually occur simultaneously in lossy components and are discussed separately below.
Losses associated with power switches
Power switches are one of the two most significant sources of loss within a typical switching power supply. Losses can basically be divided into two parts: conduction losses and switching losses. Conduction loss is when the power device has been turned on, and drive and switching waveforms have been stabilised after the power switch is in the on-state loss; switching loss occurs when the power switch is driven into a new operating state, drive and switching waveforms are in the transition process loss.
The typical method of controlling this loss is to minimise the voltage drop during power switch conduction. To achieve this, the designer must operate the switch in saturation. These conditions are given by equations (2a) and (2b) and are driven by base or gate overcurrent, ensuring that the collector or drain current is controlled by an external component rather than by the power switch itself.
Switching losses during power switching transitions are even more complex, both by themselves and by the components involved. Loss-related waveforms can only be measured by The waveforms associated with the losses can only be observed by an oscilloscope with a voltage probe connected to the drain-source (collector) end, and an AC current probe can measure the drain or collector current. Measurement of the loss at each switching instant When measuring the loss at each switching instant, it is important to use a short lead probe with a shield, as any unshielded lead of any length may introduce noise from other power sources and thus not accurately display the true waveform. show the true waveform. Once a good waveform has been obtained, the area enclosed by the two curves can be roughly calculated by simple summation of the triangular and rectangular segments. area surrounded by the two curves.
