What is the principle of peak absorption circuit?

The principle of the peak absorption circuit is that the reverse peak voltage generated on the collector of the switch tube forms a charging loop through C 1 and R 1 at the moment when the switch tube VT is turned off, and the charging current keeps the peak voltage within a certain range to prevent the switch tube from being broken down. When C 1 is charged, C 1 forms a discharge loop through the primary winding of switching transformer T, 300V filter capacitor ground and R 1. Therefore, when the value of R 1 is small, it is beneficial to absorb the peak voltage, but it increases the turn-on loss of the switch tube.

Interpretation of peak absorption circuit

In switching power supply, when the switch tube is turned off, the primary of the switching transformer will induce high pulse voltage in the opposite direction, which is easy to damage the switch tube. Therefore, a pulse absorption loop consisting of a high voltage capacitor and a fast recovery diode is connected in parallel at the primary of the transformer, which provides a discharge path for this reverse high pulse voltage and protects the switch tube. This loop is called the peak absorption loop.