Power Integrations, Inc.
Electronic circuit for fast temperature sensing of a power switching device

Abstract:

An electronic circuit for sensing a temperature rise in a power transistor device, the temperature rise caused by a current flow in the power transistor device. The power transistor device and a sense-FET are disposed on a substrate. The sense-FET senses a fractional portion of the current flow and outputs a current signal. A JFET has its drain connected to the drain of the power transistor device. The gate of the JFET is connected to the source of the power transistor device, such that when the power transistor device is on, the JFET is also turned on, and a drain voltage signal of the power transistor device is output at a second node of the JFET. A detection circuit receives the drain voltage signal and the current signal and outputs an alarm signal when the drain-source resistance of the power transistor device exceeds a combined threshold limit.