Control of a half resonant converter for avoiding capacitive mode

摘要

This invention relates to improved methods of preventing MOSFET damage in a resonant switched mode power converter (1) by preventing or limiting capacitive mode operation. A combination of response actions (respectively delaying MOSFET switch-on, adjusting switching phase, forcing a switch-on, and increasing frequency) is utilized. In the preferred embodiment, the voltage slope at the half-bridge node (5) is monitored, and in alternative embodiments the same or similar set of response actions is triggered by monitoring different signals, including: the resonant current polarity at switch-off or after the non-overlap time; the voltage of the to-be-switched-on” switch; and the voltage of the “just-switched-off” switch.

主权项

1. A method for controlling an energy converter having a switching frequency and a switching phase, a first switch, a second switch, a half-bridge node therebetween, and an oscillator, the method comprising
opening the first switch whilst the second switch is open, monitoring a parameter indicative of a state of the energy converter, including monitoring the slope of the voltage at the half-bridge node,and both
(a) delaying closing the second switch; (b) retarding the switching phase by interrupting oscillation of the oscillator in response to the parameter exhibiting a first characteristic when the first switch is opened; (c) closing the second switch at the end of a first predetermined timeout period which starts immediately after the first switch is opened in response to the parameter exhibiting the first characteristic throughout the first predetermined timeout period, wherein the first characteristic is no voltage slope at the half-bridge node; and (d) increasing the switching frequency in response to the parameter exhibiting the first characteristic throughout a second predetermined period which starts immediately after the first switch is opened.