Overvoltage protection circuit

摘要

Apparatus and methods for generating an overvoltage signal from a bias winding signal of a power converter transformer are disclosed. In one example, an overvoltage protection circuit may include a current augmentation circuit and a detection circuit. The current augmentation circuit may be coupled to receive the bias winding signal, which may be representative of the power converter output. The current augmentation circuit may include a threshold circuit and a filter circuit that may generate a filtered level shifted signal from the bias winding signal. The current augmentation circuit may generate an augmented signal from the filtered level shifted signal. The detection circuit may be coupled to receive the augmented signal and to generate an overvoltage signal by comparing the augmented signal with a reference voltage. When high asserted, the overvoltage signal may indicate a potential overvoltage condition at the output of the power converter.

主权项

1. An overvoltage detection circuit for a power converter, the circuit comprising:
a current augmentation circuit coupled to receive a sense signal representative of an output voltage of the power converter only during a portion of an off time of a power switch of the power converter, wherein the current augmentation circuit is further coupled to output an augmented signal, wherein the current augmentation circuit includes:
a threshold circuit coupled to reduce a voltage of the sense signal to output a level shifted sense signal;a filter circuit coupled to receive the level shifted sense signal, wherein the filter circuit is further coupled to filter a transient portion of the level shifted sense signal to output a filtered level shifted sense signal; and a detection circuit coupled to receive the filtered level shifted sense signal from the filter circuit and a power signal representative of a rectified version of the sense signal at a same input terminal, wherein the detection circuit is operable to output an overvoltage detection signal based at least in part on the filtered level shifted sense signal, the overvoltage detection signal being representative of an overvoltage condition in the output voltage of the power converter.