OVERCURRENT DETECTION CIRCUIT FOR SWITCHES

• US 20190310290A1
• Filed: 03/28/2019
• Published: 10/10/2019
• Est. Priority Date: 04/04/2018
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: ARARAGI, Akifumi
• Granted Patent: US 10,823,768 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 19/16528 using digital techniques or performing arithmetic operations using digital techniques to measure a voltage or a current, see G01R19/25
• CPC Class Codes: G01R 19/16547 voltage or current in AC supplies switching for protection H02H; circuits for emergency power supply H02J9/00
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/088 for the simultaneous control of series or parallel connected semiconductor devices
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/219 in a bridge configuration
• CPC Class Codes: H02M 7/5387 in a bridge configuration
• CPC Class Codes: H03K 17/08 Modifications for protecting switching circuit against overcurrent or overvoltage
• CPC Class Codes: H03K 17/0828 in composite switches
• CPC Class Codes: H03K 17/127 in composite switches

Abstract

In an overcurrent detection circuit for switches parallely connected to each other, sense detectors are respectively provided for the switches. Each of the sense detectors detects a sense voltage of the corresponding one of the switches. The sense voltage of each of the switches is based on a sense current associated with a current flowing through the corresponding one of the switches. A parameter calculator calculates, based on the sense voltages calculated by the respective sense detectors, a determination parameter that is less subject to imbalance between currents flowing through the respective switches. A determiner determines whether a value of the determination parameter is higher than an overcurrent threshold, and determines that there is an overcurrent flowing through at least one of the switches upon determining that the value of the determination parameter is higher than the overcurrent threshold.

Claims

1. An overcurrent detection circuit for a plurality of switches parallely connected to each other, the overcurrent detection circuit comprising:

a plurality of sense detectors respectively provided for the switches, each of the sense detectors being configured to detect a sense voltage of the corresponding one of the switches, the sense voltage of each of the switches being based on a sense current associated with a current flowing through the corresponding one of the switches;

a parameter calculator configured to calculate, based on the sense voltages calculated by the respective sense detectors, a determination parameter that is less subject to imbalance between currents flowing through the respective switches; and

a determiner configured to;

determine whether a value of the determination parameter is higher than an overcurrent threshold; and

determine that there is an overcurrent flowing through at least one of the switches upon determining that the value of the determination parameter is higher than the overcurrent threshold.

2. The overcurrent detection circuit according to claim 1, wherein:

the determination voltage calculator is configured to calculate, as the determination parameter, a determination voltage that comprises at least one of;

an average value of the sense voltages calculated by the respective sense detectors;

the sum of the sense voltages calculated by the respective sense detectors; and

a product of K and the sum of the sense voltages calculated by the respective sense detectors, K being a positive integer that is unequal to 1; and

the determiner configured to;

determine whether the determination voltage is higher than the overcurrent threshold; and

determine that there is an overcurrent flowing through at least one of the switches upon determining that the determination voltage is higher than the overcurrent threshold.

3. The overcurrent detection circuit according to claim 2, wherein:

the determination voltage calculator includes a plurality of resistors that are connected to the respective sense detectors and respectively have resistors, the determination voltage calculator being configured to calculate the product of the sum of the sense voltages and a predetermined ratio among the resistors to thereby calculate the average value of the sense voltages.

4. The overcurrent detection circuit according to claim 2, wherein:

the determination voltage calculator is configured to;

calculate the sum of the sense voltages; and

divide the sum of the sense voltages by the number of sense voltages to thereby calculate the average value of the sense voltages.

5. The overcurrent detection circuit according to claim 1, wherein:

the determiner is configured to;

determine whether the value of the determination parameter is higher than a short-circuit threshold that is set to be higher than the overcurrent threshold; and

determine that there is a short-circuit fault associated with the switches upon determining that the value of the determination parameter is higher than the short-circuit threshold.

6. The overcurrent detection circuit according to claim 1, wherein:

the determiner is configured to;

determine whether at least one of the sense voltages respectively detected by the sense detectors is higher than a short-circuit threshold that is set to be higher than the overcurrent threshold; and

determine that there is a short-circuit fault associated with the switches upon determining that at least one of the sense voltages respectively detected by the sense detectors is higher than the short-circuit threshold.

7. The overcurrent detection circuit according to claim 1, wherein:

each of the switches has a control terminal, charging the control terminals of the switches causes the switches to be turned on, and discharging the control terminals of the switches causes the switches to be turned off; and

the determiner is configured to determine whether the value of the determination parameter is higher than the overcurrent threshold during the switches being on,

the overcurrent detection circuit further comprising;

a fail-safe unit configured to discharge the control terminal of each of the switches upon it being deter mined that there is an overcurrent flowing through at least one of the switches due to it being determined that the value of the determination parameter is higher than the overcurrent threshold.

8. A drive circuit for a plurality of switches parallely connected to each other and each having a control terminal, the drive circuit comprising:

a charging and discharging unit configured to;

charge the control terminals of the switches to thereby cause the switches to be turned on; and

discharge the control terminals of the switches to cause the switches to be turned off;

a plurality of sense detectors respectively provided for the switches, each of the sense detectors being configured to detect a sense voltage of the corresponding one of the switches, the sense voltage of each of the switches being based on a sense current associated with a current flowing through the corresponding one of the switches;

a parameter calculator configured to calculate, based on the sense voltages calculated by the respective sense detectors, a determination parameter that is less subject to imbalance between currents flowing through the respective switches;

a determiner configured to;

determine whether a value of the determination parameter is higher than an overcurrent threshold during the switches being on; and

determine that there is an overcurrent flowing through at least one of the switches upon determining that the value of the determination parameter is higher than the overcurrent threshold; and

a fail-safe unit configured to discharge the control terminal of each of the switches upon it being determined that there is an overcurrent flowing through at least one of the switches due to it being determined that the value of the determination parameter is higher than the overcurrent threshold.