Thermal protection of SMPS switch

Patent metadata

Field	Value
Publication number	US-10833500-B2
Application number	US-201815966557-A
Country	US
Kind code	B2
Filing date	Apr 30, 2018
Priority date	Apr 30, 2018
Publication date	Nov 10, 2020
Grant date	Nov 10, 2020

Abstract

A circuit for measuring temperature of an external switch is disclosed. The circuit includes a variable resistor, a switch coupled to the variable resistor in series, a fixed value resistor coupled to the variable resistor and a comparator coupled between the variable resistor and the fixed value resistor. The circuit is configured to compare voltage drop between a drain and a source of the external switch when the external switch is in ON state with voltage drop at the variable resistor and output a signal to indicate an overtemperature based on the comparing.

First claim

What is claimed is:

1. A circuit for measuring temperature of an external switch, the circuit comprising:
a variable resistor;
a switch coupled to the variable resistor in series;
a fixed value resistor coupled to the variable resistor; and
a comparator coupled between the variable resistor and the fixed value resistor;
wherein the circuit is configured to compare voltage drop between a drain and a source of the external switch when the external switch is in ON state with voltage drop at the variable resistor and output a signal to indicate an overtemperature based on the comparing.

2. The circuit of claim 1 , wherein the switch is configured to be turned on only when the external switch is turned on.

3. The circuit of claim 2 , wherein the switch is configured to be turned on via a drive signal that drives a gate of the external switch.

4. The circuit of claim 3 , wherein the drive signal is coupled to the switch via a delay circuit.

5. The circuit of claim 4 , wherein the delay circuit is configured to introduce a predetermined delay based on saturation characteristics of the external switch.

6. The circuit of claim 1 , wherein the comparator is configured to maintain an output until voltage difference at the comparator's inputs reverses.

7. The circuit of claim 1 , wherein the variable resistor is configured to change a temperature threshold.

8. An integrated circuit, comprising:
a port for receiving a drive signal for driving the switch;
a port for outputting an overtemperature signal;
a port for receiving an input from a drain of the external switch;
a port for receiving an input from a source of the external switch
a circuit for measuring temperature of an external switch, wherein the circuit includes:
a variable resistor;
a switch coupled to the variable resistor in series;
a fixed value resistor coupled to the variable resistor; and
a comparator coupled between the variable resistor and the fixed value resistor;
wherein the circuit is configured to compare voltage drop between a drain and a source of the external switch when the external switch is in ON state with voltage drop at the variable resistor and output a signal to indicate an overtemperature based on the comparing.

Assignees

• Nxp Bv

Inventors

• Effing Hermanus Johannes

Classifications

• H02M1/327

  against abnormal temperatures · CPC title

• H02H7/1203

  Circuits independent of the type of conversion · CPC title

• G01K7/01

  using semiconducting elements having PN junctions (G01K7/02, G01K7/16, G01K7/30 take precedence) · CPC title

• G01R31/2628

  for measuring thermal properties thereof · CPC title

• G01R31/42

  AC power supplies · CPC title