Control device for power conversion apparatus and power conversion apparatus

Patent metadata

Field	Value
Publication number	US-9762117-B2
Application number	US-201615199881-A
Country	US
Kind code	B2
Filing date	Jun 30, 2016
Priority date	Aug 19, 2015
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A sense voltage obtained by feeding a sense current of an IGBT into a sense resistor is input to a comparator, and as the reference voltage of the comparator, a sense voltage immediately before the IGBT is turned off is held by a sample and hold circuit for each switching, and is then divided by a voltage dividing circuit and the divided voltage is input to the comparator. The comparator compares the sense voltage with the voltage based on the sense voltage immediately before the IGBT is turned off, and therefore the comparator may accurately detect the falling edge time of the sense voltage and is used for the control for dissolving the imbalance in current with respect to the other IGBTs connected in parallel.

First claim

What is claimed is:

1. A control device for a power conversion apparatus, the control device comprising:
gate drive circuits configured to simultaneously turn on or off a plurality of power semiconductor elements connected in parallel, respectively;
timing detection comparators each configured to compare a sense voltage detected as a voltage proportional to a main current that flows when a corresponding one of the plurality of power semiconductor elements is turned on, with a reference voltage to detect turn-on and turn-off times of the corresponding power semiconductor element; and
sample and hold circuits each configured to hold the sense voltage when the power semiconductor element is turned on, divide the sense voltage being held when the corresponding power semiconductor element is turned off, and supply a resulting divided voltage as the reference voltage for detecting the turn-off times of the corresponding power semiconductor element to a corresponding one of the timing detection comparators.

2. The control device for a power conversion apparatus according to claim 1 , wherein each of the sample and hold circuits includes:
a first voltage buffer circuit configured to receive the sense voltage;
a switch having one terminal connected to an output of the first voltage buffer circuit and being configured to be conductive when the corresponding power semiconductor element is turned on and to be cut off when the corresponding power semiconductor element is turned off;
a capacitor connected to another terminal of the switch and configured to hold the sense voltage; and
a voltage dividing circuit configured to divide a voltage held in the capacitor.

3. The control device for a power conversion apparatus according to claim 2 , wherein the voltage dividing circuit includes, as the capacitor, a first and a second capacitor connected in series, and is configured to supply, as the reference voltage, a divided voltage obtained by dividing the voltage by the first and second capacitors to the corresponding timing detection comparator via a second voltage buffer circuit.

4. The control device for a power conversion apparatus according to claim 2 , wherein the voltage dividing circuit includes first and second resistors connected in series, the first and second resistors receiving a voltage of the capacitor via a second voltage buffer circuit, and is configured to supply a divided voltage obtained by dividing the voltage by the first and second resistors to the corresponding timing detection comparator as the reference voltage.

5. The control device for a power conversion apparatus according to claim 2 , wherein the switch is controlled by an input signal to the gate driver circuit, such that the switch is configured to be turned on or off in synchronization with a gate signal supplied to a corresponding one of the gate drive circuits.

6. The control device for a power conversion apparatus according to claim 1 , wherein each of the sample and hold circuits includes:
a variable gain amplifier circuit configured to receive the sense voltage,
a switch having one terminal connected to an output of the variable gain amplifier circuit and being configured to be conductive when the corresponding power semiconductor element is turned on and to be cut off when the corresponding power semiconductor element is turned off;
a capacitor configured to hold the sense voltage, the capacitor being connected to another terminal of the switch; and
a voltage dividing circuit configured to divide a voltage held in the capacitor.

7. The control device for a power conversion apparatus according to claim 6 , wherein the variable gain amplifier circuit includes:
a noninverting amplifier circuit;
a variable resistor for setting an amplification factor of the noninverting amplifier circuit; and
an amplification factor variable setting section which controls the variable resistor so that the amplification factor of the noninverting amplifier circuit becomes higher as the sense voltage becomes lower.

8. A power conversion apparatus comprising:
a plurality of power semiconductor elements connected in parallel; and
a control device for a power conversion apparatus,
wherein the control device includes
gate drive circuits configured to simultaneously turn on or off the plurality of power semiconductor elements, respectively,
timing detection comparators each configured to compare a sense voltage detected as a voltage proportional to a main current, the main current flowing when a corresponding one of the plurality of power semiconductor elements is turned on, with a reference voltage to detect turn-on and turn-off times of the corresponding power semiconductor element; and
sample and hold circuits each configured to hold the sense voltage when the corresponding power semiconductor element is turned on, and to divide, when the corresponding power semiconductor element is turned off, the held sense voltage and supply a resulting divided voltage as the reference voltage for detecting the turn-off times of the corresponding power semiconductor element to the timing detection comparator.

9. A control device for a power conversion apparatus, comprising:
at least one gate drive circuit configured to turn on and off one of a plurality of power semiconductor switch elements connected in parallel with each other;
at least one timing detection comparator configured to compare a sense voltage corresponding to a current which flows when one of the plurality of power semiconductor switch elements is turned on with a reference voltage, and configured to output a timing signal corresponding to a turn on or turn off time of one of the plurality of power semiconductor switch elements; and
at least one sample and hold circuit configured to hold the sense voltage when one of the plurality of power semiconductor switch elements is turned on, configured to divide the sense voltage being held when one of the plurality of power semiconductor switch elements is turned off, and configured to supply a resulting divided voltage as the reference voltage to the at least one timing detection comparator.

10. The control device for a power conversion apparatus according to claim 9 , wherein the at least one sample and hold circuit circuit comprises:
a first voltage buffer circuit configured to receive the sense voltage;
a voltage dividing circuit configured to divide a voltage output from the first voltage buffer circuit and to supply a divided voltage to the at least one timing detection comparator; and
a switch connected between the first voltage buffer and the voltage dividing circuit, the switch activated by an activation signal to the at least one gate drive circuit.

11. The control device for a power conversion apparatus according to claim 10 , wherein the voltage dividing circuit comprises first and second capacitors connected in series,
the at least one sample and hold circuit further comprises a second voltage buffer circuit configured to receive a divided voltage from the first and second capacitors, and
the at least one timing detection comparator is configured to receive an output from the second voltage buffer circuit as the reference voltage.

12. The control device for a power conversion apparatus according to claim 10 , wherein the voltage dividing circuit comprises:
a capacitor configured to hold the sense voltage; and
first and second resistors connected in series, the first and second resistors configured to receive a voltage of the capacitor and to supply a divided voltage obtained by dividing the voltage by the first and second resistors to the at least one timing detection comparator as the refere

Assignees

• Fuji Electric Co Ltd

Inventors

• Sasaki Masahiro

Classifications

• H03K17/18

  Modifications for indicating state of switch · CPC title

• H02M1/32 Primary

  Means for protecting converters other than automatic disconnection · CPC title

• H02M2001/0009

  Electricity · mapped topic

• H02M1/088

  for the simultaneous control of series or parallel connected semiconductor devices · CPC title

• H02M1/0009

  Devices or circuits for detecting current in a converter · CPC title