US 2014/0192569 A1 · OVERVOLTAGE PROTECTION CIRCUIT

Abstract

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.

Claims29

Dependent claims

An overvoltage detection circuit for a power converter, the circuit comprising:

a threshold 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 threshold circuit is operable 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 from the threshold circuit, wherein the filter circuit is operable to filter the level shifted sense signal to output a filtered level shifted sense signal;
and
a detection circuit coupled to an input terminal for receiving the filtered level shifted sense signal from the filter circuit and a power signal representative of a rectified version of the sense signal, 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.

1 more element

A power converter, comprising:

a power switch;
a controller for controlling the power switch to regulate the power converter;
and
an overvoltage detection circuit comprising:
a threshold 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 the power switch, wherein the threshold circuit is operable 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 from the threshold circuit, wherein the filter circuit is operable to filter the level shifted sense signal to output a filtered level shifted sense signal;
and
a detection circuit coupled to an input terminal of the controller for receiving the filtered level shifted sense signal from the filter circuit and a power signal representative of a rectified version of the sense signal, 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.

5 more elements

A method for detecting an overvoltage condition at an output of a power converter, the method comprising:

receiving a sense signal from a bias winding of a transformer representative of an output voltage of a power converter only during a portion of an off time of a power switch of the power converter;
reducing a voltage of the sense signal by a threshold circuit to generate a level shifted sense signal;
filtering the level shifted sense signal by a filter circuit to generate a filtered level shifted sense signal;
generating an augmented sense signal based on the filtered level shifted sense signal;
receiving, at an input terminal, the augmented sense signal and a power signal representative of a rectified version of the sense signal, wherein the power signal is used to at least partially power a controller of the power converter;
and
generating an overvoltage signal based at least in part on to the augmented sense signal, the overvoltage detection signal being representative of an overvoltage condition in the output voltage of the power converter.

4 more elements

Dependencies are inferred from the claim text.

Overvoltage protection circuit

Life of this patent

Overvoltage protection circuit

Life of this patent

Abstract

Claims29