US 11,870,363 B2
High-speed, accurate peak and valley sensing for secondary-controlled flyback converter
Saravanan Virunjipuram Murugesan, Bangalore (IN); Rajesh Karri, Visakhapatnam (IN); Arun Khamesra, Bangalore (IN); and Hariom Rai, Bangalore (IN)
Assigned to Cypress Semiconductor Corporation, San Jose, CA (US)
Filed by Cypress Semiconductor Corporation, San Jose, CA (US)
Filed on Jan. 14, 2022, as Appl. No. 17/576,776.
Prior Publication US 2023/0231483 A1, Jul. 20, 2023
Int. Cl. H02M 3/335 (2006.01); H02M 1/00 (2006.01)
CPC H02M 3/33592 (2013.01) [H02M 1/0058 (2021.05); H02M 3/33523 (2013.01)] 20 Claims
OG exemplary drawing
 
19. A method of operating a secondary side controller for a flyback converter that comprises a synchronous rectifier (SR) sense pin coupled to an SR transistor on a secondary side of the flyback converter, a capacitor coupled to the SR sense pin, a diode-connected transistor coupled between the capacitor and ground, a first current mirror, a first variable current source, and a peak detect transistor coupled to the diode-connected transistor and to an output of the first current mirror, wherein the method of operating the secondary side controller comprises:
allowing the capacitor to charge or discharge responsive to voltage sensed at the SR sense pin;
providing, by the first variable current source, a reference current to an input of the first current mirror, wherein the first variable current source is programmed to generate the reference current such that the peak detect transistor triggers the output at or before an actual peak of the voltage sensed at the SR sense pin;
detecting, by the peak detect transistor, current from the capacitor drop below the reference current; and
outputting, by the peak detect transistor, a peak detection signal in response to the detection.