Voltage generating circuit and overcurrent detecting circuit

• US 10,281,941 B2
• Filed: 12/04/2017
• Issued: 05/07/2019
• Est. Priority Date: 12/07/2015
• Status: Active Grant

• Current Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Original Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Inventors: Mori, Takahiro, Akahane, Masashi
• Primary Examiner(s): Dole, Timothy J.
• Assistant Examiner(s): Kyaw, Htet Z
• Application Number:
  US15/830,830
• Publication Number:
  US 20180088615A1
• Time in Patent Office: 519 Days
• Field of Search: 323274
• CPC Class Codes: G05F 1/573 with overcurrent detector
• CPC Class Codes: G05F 1/575 characterised by the feedback circuit
• CPC Class Codes: H02H 3/08 responsive to excess current responsive to abnormal temperature caused by excess current H02H5/04
• CPC Class Codes: H02H 7/1227 responsive to abnormalities in the output circuit, e.g. short circuit
• CPC Class Codes: H03K 17/0828 in composite switches
• CPC Class Codes: H03K 17/60 the devices being bipolar transistors bipolar transistors having four or more electrodes H03K17/72
• CPC Class Codes: H03K 2217/0063 High side switches, i.e. the higher potential [DC] or life wire [AC] being directly connected to the switch and not via the load
• CPC Class Codes: H03K 2217/0072 Low side switches, i.e. the lower potential [DC] or neutral wire [AC] being directly connected to the switch and not via the load

Abstract

A voltage generating circuit includes a first resistance voltage dividing circuit, configured by low temperature coefficient resistors being connected in series, that generates a reference voltage by resistance-dividing a predetermined power supply voltage, one or a multiple of a second resistance voltage dividing circuit, configured by a resistor having a positive or negative resistance temperature coefficient and the low temperature coefficient resistor being connected in series, that generates a temperature-dependent divided voltage by resistance-dividing the power supply voltage, and an instrumentation amplifier that generates the comparison reference voltage in accordance with a difference between the reference voltage and the divided voltage. The voltage generating circuit includes a comparator that, when a divided voltage exceeds a predetermined voltage threshold in accompaniment to a temperature rise, changes the divided voltage generated by the second resistance voltage dividing circuit and applied to the instrumentation amplifier, or changes a gain of the instrumentation amplifier.

Claims

1. A voltage generating circuit that generates a comparison reference voltage having temperature characteristics proportional to output temperature characteristics of a current detecting element, the voltage generating circuit comprising:

a first resistance voltage dividing circuit, configured by at least two low temperature coefficient (LTC) resistors connected in series, the at least two LTC resistors have resistance temperature coefficients equal to or about zero, the first resistance voltage dividing circuit generates a reference voltage by resistance-dividing a power supply voltage;

at least two second resistance voltage dividing circuits, each of the second resistance voltage dividing circuits of the at least two second resistance voltage dividing circuits being configured by a resistor having a positive or negative resistance temperature coefficient and a third LTC resistor connected in series, each of the second resistance voltage dividing circuits of the at least two second resistance voltage dividing circuits generating a temperature-dependent divided voltage by resistance-dividing the power supply voltage;

a comparator to compare the temperature-dependent divided voltage of a first of the at least two second resistance voltage dividing circuits to the reference voltage and to select as an output,

the temperature-dependent divided voltage of the first of the at least two second resistance voltage diving circuits, when the temperature-dependent divided voltage of the first of the at least two second resistance voltage dividing circuits is less than the reference voltage, and

the temperature-dependent divided voltage of a second of the at least two second resistance voltage dividing circuits, when the temperature-dependent divided voltage of the first of the at least two second resistance voltage dividing circuits is greater than the reference voltage; and

an instrumentation amplifier that generates the comparison reference voltage based on a difference between the reference voltage and the output selected by the comparator.

2. The voltage generating circuit according to claim 1, wherein

each of the at least two second resistance voltage dividing circuits is configured by,

the resistor having the positive or negative resistance temperature coefficient has a negative resistance temperature coefficient and the third LTC resistor being connected in series with the resistor having the negative resistance temperature coefficient on a positive potential side of the power supply voltage, or,

the resistor having the positive or negative resistance temperature coefficient has a positive resistance temperature coefficient and the third LTC resistor being connected in series with the resistor having the positive resistance temperature coefficient on a negative potential side of the power supply voltage.

3. The voltage generating circuit according to claim 1, wherein

the at least two second resistance voltage dividing circuits comprise two second resistance voltage dividing circuits including a first circuit and a second circuit,

the first circuit is configured by the third LTC resistor being connected in series with a resistor having a negative resistance temperature coefficient, as the resistor having the positive or negative resistance temperature coefficient for the first circuit, on a positive potential side of the power supply voltage, and

the second circuit is configured by a fourth LTC resistor being connected in series with a resistor having a positive resistance temperature coefficient, as the resistor having the positive or negative resistance temperature coefficient for the second circuit, on a negative potential side of the power supply voltage.

4. The voltage generating circuit according to claim 1, wherein

the at least two second resistance voltage dividing circuits generate a plurality of divided voltages of differing temperature gradients, and

the comparator

selects a divided voltage with a smaller temperature gradient from among the differing temperature gradients, as the temperature-dependent divided voltage, from the plurality of divided voltages at a time of normal temperature and applies the selected divided voltage to the instrumentation amplifier, and

when the divided voltage with the smaller temperature gradient exceeds the reference voltage, selects a divided voltage with a larger temperature gradient than the smaller temperature gradient, as the at least one temperature-dependent divided voltage, and applies the selected divided voltage with the larger temperature gradient to the instrumentation amplifier.

5. The voltage generating circuit according to claim 1, wherein the at least two LTC resistors are formed of polysilicon formed by being simultaneously integrated on a semiconductor circuit element substrate on which the voltage generating circuit is constructed.

6. The voltage generating circuit according to claim 1, wherein

the current detecting element is a current sensing IGBT integrally provided in a switching IGBT and mirror-connected to the switching IGBT, and

the comparison reference voltage is used in a determination of a current detecting voltage proportional to an output current of the current sensing IGBT.

7. The voltage generating circuit according to claim 6, wherein

the switching IGBT forms a half-bridge circuit and is a high side switching element in a power converter that switches the power supply voltage, and

the first resistance voltage dividing circuit and the at least one second resistance voltage dividing circuit resistance-divide a difference between the power supply voltage and an intermediate point potential of the half-bridge circuit.

8. An overcurrent detecting circuit, provided in a drive control circuit that drives a switching element that switches input power on and off, that detects a current flowing into the switching element and controls an operation of the drive control circuit, the overcurrent detecting circuit comprising:

a current detecting resistance that generates voltage proportional to a current flowing into the switching element based on an output of a current detecting element incorporated in the switching element;

a voltage generating circuit according to claim 1 that generates the comparison reference voltage having temperature characteristics proportional to output temperature characteristics of the current detecting element; and

an overcurrent detecting comparator that

compares the comparison reference voltage generated by the voltage generating circuit and a voltage detected via the current detecting resistance, and

detects an overcurrent flowing into the switching element.

9. The overcurrent detecting circuit according to claim 8, wherein

the switching element is a high side switching element in a power converter including a pair of switching elements that are connected in series to form a half-bridge circuit, switch input power by being alternately driven on and off by a drive control circuit, and output alternating current voltage to be supplied to a load from an intermediate point of the half-bridge circuit, and

the voltage generating circuit is incorporated in a high side drive control circuit that drives the high side switching element on and off.

10. A voltage generating circuit that generates a comparison reference voltage, the voltage generating circuit comprising:

a first resistance voltage dividing circuit configured to generate a reference voltage by resistance-dividing a power supply voltage;

a second resistance voltage dividing circuit configured to generate first and second temperature-dependent divided voltages by resistance-dividing the power supply voltage;

a comparator that, in response to a change in the first temperature-dependent divided voltage in response to a temperature change, compares the first temperature-dependent divided voltage with the reference voltage and selects as an output,

the first temperature-dependent divided voltage when the first temperature-dependent divided voltage is less than the reference voltage, and

the second temperature-dependent divided voltage when the first temperature-dependent divided voltage is greater than the reference voltage; and

an instrumentation amplifier that generates the comparison reference voltage based on the reference voltage and the output selected by the comparator.

11. A voltage generating circuit that generates a comparison reference voltage, the voltage generating circuit comprising:

a first resistance voltage dividing circuit configured to generate a reference voltage by resistance-dividing a power supply voltage;

a second resistance voltage dividing circuit configured to generate a first temperature-dependent divided voltage by resistance-dividing the power supply voltage;

a third resistance voltage dividing circuit configured to generate a second temperature-dependent divided voltage by resistance-dividing the power supply voltage;

a comparator that, in response to a change in the one of first temperature-dependent divided voltage or the second temperature-dependent divided voltage in response to a temperature change, compares the first temperature-dependent divided voltage with the reference voltage and selects as an output,

the first temperature-dependent divided voltage when the first temperature-dependent divided voltage is less than the reference voltage, and

the second temperature-dependent divided voltage when the first temperature-dependent divided voltage is greater than the reference voltage; and

an instrumentation amplifier that generates the comparison reference voltage in accordance with the difference between the reference voltage and the output selected by the comparator.