Switching power supply controller and switching power supply containing same

Abstract

The invention provides a switching power supply controller and a switching power supply containing the same. The switching power supply controller comprises a zero-cross detection circuit for performing zero-cross detection on input feedback signals and generating zero-cross signals, an input voltage detection circuit for detecting input voltage, an output voltage detection circuit for detecting input voltage, a connection time length control module and a radio station (RS) trigger. The connection time length control module generates turn-off signals according to the input voltage, the output voltage and offset voltage so as to enable connection time of a switching tube to be relevant to the input voltage and the output voltage, and the connection time is prolonged when the input voltage rises and shortened when the output voltage rises. The setting input end of the RS trigger receives the zero-cross signals, the resetting input end of the RS trigger receives the turn-off signals, and the output end of the RS trigger generates driving signals to control connection and disconnection of the switching tube of the switching power supply. The switching power supply controller and the switching power supply containing the switching power supply controller can optimize power factors of the switching power supply controlled by a critical connection mode and reduce total harmonic distortion.

Description

technical field [0001] The invention relates to switching power supply technology, in particular to a switching power supply controller with power factor adjustment function and critical conduction mode control, and a switching power supply including the switching power supply controller. Background technique [0002] Traditional AC power supply, with power factor adjustment (PFC) function, critical conduction mode isolated LED constant current drive circuit such as figure 1 As shown, it mainly includes: AC input rectifier circuit 101, AC input source 102, input capacitor Cin, resistor 104, capacitor 105, diode 106, isolation transformer T1, power switch 112, sampling resistor Rs, resistor 113, output rectifier diode D1, Output capacitor Cbulk, constant current switching power supply controller 100 . Wherein, the controller 100 is used to receive the feedback signal FB from the auxiliary winding L3 of the isolation transformer T1, the sampling resistor Rs samples the primar...

AI Technical Summary

Problems solved by technology

With a fixed on-time (T on constant), critical conduction mode control, the input current I in cannot fully follow the input voltage V in changes, the power factor becomes worse, the total harmonic distortion increas

Images