Overcurrent detection circuit

Patent metadata

Field	Value
Publication number	US-9671437-B2
Application number	US-201514794891-A
Country	US
Kind code	B2
Filing date	Jul 9, 2015
Priority date	Jun 11, 2013
Publication date	Jun 6, 2017
Grant date	Jun 6, 2017

Abstract

An overcurrent detection circuit includes a current detection resistor that generates a voltage in proportion to current flowing through a switching element and a comparator that compares the voltage detected via the current detection resistor and a reference voltage generated by a reference voltage generation circuit to thereby detect overcurrent flowing through the switching element. In particular, the reference voltage generation circuit includes: a first resistance voltage dividing circuit that resistance-divides a standard voltage by connecting, in series, two types of resistors having different temperature characteristics; a second resistance voltage dividing circuit that resistance-divides the standard voltage by connecting, in series, resistors having the same temperature characteristics; and an instrumentation amplifier that generates the reference voltage according to the difference between the divided output voltages of the first and second resistance voltage dividing circuits.

First claim

The invention claimed is:

1. An overcurrent detection circuit for use in a driver circuit that turns a switching element ON/OFF to switch input power and that controls operation of the driver circuit by detecting current flowing through the switching element, the switching element having a current detection element incorporated therein, said overcurrent detection circuit comprising:
a current detection resistor that generates voltage in proportion to the current flowing through the switching element, based on the output of the current detection element incorporated into the switching element;
a reference voltage generation circuit that generates a reference voltage having a temperature characteristic that is in proportion to an output temperature characteristic of the current detection element, by resistance-dividing a predetermined standard voltage; and
a comparator that detects overcurrent of the current flowing through the switching element by comparing the reference voltage generated by the reference voltage generation circuit and the voltage detected via the current detection resistor,
wherein the reference voltage generation circuit includes a first resistance voltage dividing circuit comprising a first resistor and a second resistor connected in series between the standard voltage and an output voltage output from the switching element,
wherein the first resistor has a resistance temperature coefficient such that a resistance of the first resistor rises and falls proportionally to a rise and fall of a temperature of the first resistor, and
wherein the second resistor has a resistance temperature coefficient such that a resistance of the second resistor is independent of a temperature of the second resistor.

2. The overcurrent detection circuit according to claim 1 , wherein the reference voltage generation circuit further includes:
a second resistance voltage dividing circuit that resistance-divides the standard voltage by connecting, in series, third resistors having the same temperature characteristics such that a resistance of the third resistors rises and falls proportionally to a rise and fall of a temperature of the third resistors; and
an instrumentation amplifier that generates the reference voltage according to the difference between the divided output voltages of the first and second resistance voltage dividing circuits.

3. The overcurrent detection circuit according to claim 2 , wherein the instrumentation amplifier includes a resistor for gain adjustment and a resistor for offset adjustment, the reference voltage having a temperature characteristic that varies according to resistance values of the resistor for gain adjustment and the resistor for offset adjustment.

4. The overcurrent detection circuit according to claim 2 , wherein the instrumentation amplifier further comprises:
a first operational amplifier (op-amp) configured to receive as first input a first voltage output from the first resistance voltage dividing circuit;
a second op-amp configured to receive as a first input a second voltage output from the second resistance voltage dividing circuit; and
a third op-amp configured to receive as inputs a first amplified voltage output from the first op-amp and second amplified voltage output from the second op-amp, and
wherein the reference voltage generator further comprises a fourth op-amp configured to output the reference voltage, and configured to receive as inputs the reference voltage and an output from the third op-amp.

5. The overcurrent detection circuit according to claim 4 , wherein the instrumentation amplifier further comprises:
a gain-setting resistor connected between a second input of the first op-amp and a second input of the second op-amp, the gain-setting resistor being a variable resistor having an adjustable resistance value.

6. The overcurrent detection circuit according to claim 5 , wherein the instrumentation amplifier further comprises:
an offset-adjustment resistor having one end connected to an output of the first op-amp and an opposite end connected to ground, the offset-adjustment resistor being a variable resistor having an adjustable resistance value.

7. The overcurrent detection circuit according to claim 1 , wherein the second resistor is a low temperature coefficient resistor, and the resistance temperature coefficient of the second resistor is zero.

8. The overcurrent detection circuit according to claim 1 , wherein the switching element is an insulated-gate bipolar transistor (IGBT), and the current detection element is a current sensing IGBT that is integrated with the IGBT and is mirror-connected to the IGBT.

9. An overcurrent detection circuit for use in a driver circuit that turns a switching element on/off to switch input power and that controls operation of the driver circuit by detecting current flowing through the switching element, said overcurrent detection circuit comprising:
current detection means for generating a detected voltage that is proportional to the current flowing through the switching element;
reference voltage generation means for generating a reference voltage having a temperature characteristic that is proportional to a temperature characteristic of the switching element; and
overcurrent detection means for detecting overcurrent of the current flowing through the switching element by comparing the detected voltage and the reference voltage,
wherein the reference voltage generation means includes a first resistance voltage dividing circuit comprising a first resistor and a second resistor connected in series between the standard voltage and an output voltage output from the switching element,
wherein the first resistor has a resistance temperature coefficient such that a resistance of the first resistor rises and falls proportionally to a rise and fall of a temperature of the first resistor, and
wherein the second resistor has a resistance temperature coefficient such that a resistance of the second resistor is independent of a temperature of the second resistor.

10. The overcurrent detection circuit according to claim 9 , wherein the reference voltage generation means further comprises:
a second resistance voltage dividing circuit that resistance-divides the predetermined voltage to provide a second divided voltage, the second resistance dividing circuit including third resistors having the same temperature characteristics, such that a resistance of the third resistors rises and falls proportionally to a rise and fall of a temperature of the third resistors; and
means for generating the reference voltage according to the difference between the first and second divided voltages.

11. The overcurrent detection circuit according to claim 10 , wherein the means for generating the reference voltage comprises an instrumentation amplifier.

12. The overcurrent detection circuit according to claim 11 , wherein the instrumentation amplifier includes a resistor for gain adjustment and a resistor for offset adjustment, the reference voltage having a temperature characteristic that is set by adjusting these resistors.

13. The overcurrent detection circuit according to claim 10 , wherein the second resistor is a low temperature coefficient resistor.

14. The overcurrent detection circuit according to claim 9 , wherein the switching element is an IGBT.

Assignees

• Fuji Electric Co Ltd

Inventors

• Akahane Masashi

Classifications

• H02H1/0007

  concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445) · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H02H3/08

  responsive to excess current (responsive to abnormal temperature caused by excess current H02H5/04) · CPC title

• H02H6/00

  Emergency protective circuit arrangements responsive to undesired changes from normal non-electric working conditions using simulators of the apparatus being protected, e.g. using thermal images · CPC title

• H02M3/33507

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title