Electronic control apparatus having switching element and drive circuit

Patent metadata

Field	Value
Publication number	US-9735767-B2
Application number	US-201213348951-A
Country	US
Kind code	B2
Filing date	Jan 12, 2012
Priority date	Jan 12, 2011
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

An electronic control apparatus includes a switching element; an ON-drive constant-current circuit supplying a constant current to the control terminal of the switching element thereby charging the control terminal of the switching element; an OFF-drive switching element discharging electrical charge from the control terminal of the switching element by being turned ON; and a control circuit adapted to control the ON-drive constant-current circuit and the OFF-drive switching element in response to a drive signal being inputted, thereby controlling the voltage of the control terminal of the switching element so as to drive the switching element. The control circuit controls the current control transistor based on the voltage of the current detection resistor and supplies the constant current to the control terminal of the switching element, and detects an abnormality in the ON-drive constant-current circuit based on the voltage of the current detection resistor.

First claim

What is claimed is:

1. An electronic control apparatus comprising:
a switching element driven by a voltage of a control terminal being controlled;
an ON-drive constant-current circuit connected to the control terminal of the switching element, supplying a constant current to the control terminal thereby charging the control terminal of the switching element with electrical charge, the ON-drive constant-current circuit including a current control transistor that controls the current supplied to the control terminal of the switching element, and a current detection resistor that detects a current flowing to the current control transistor and is used for detecting an abnormality in the ON-drive constant-current circuit, the current control transistor being disposed between the switching element and the current detection resistor in a current path where the constant current flows;
a drive power supply circuit connected to the ON-drive constant-current circuit, supplying the voltage for driving the switching element;
an OFF-drive switching element connected to the control terminal of the switching element, discharging electrical charge from the control terminal of the switching element by being turned ON; and
a control circuit adapted to control the ON-drive constant-current circuit and the OFF-drive switching element in response to a drive signal being inputted, thereby controlling the voltage of the control terminal of the switching element so as to drive the switching element, the control circuit being connected to the current detection resistor and detecting a voltage across the current detection resistor, representing the current flowing to the current control transistor, wherein
the control circuit, includes an operational amplifier circuit, and controls the current control transistor by using the voltage across the current detection resistor and by using the operational amplifier circuit to start driving the current control transistor in response to turning on of the drive signal, and supplies the constant current to the control terminal of the switching element, and detects the abnormality in the ON-drive constant-current circuit by using the drive signal in combination with the voltage across the current detection resistor, the abnormality detection being performed during a period in which the current supplied to the control terminal of the switching element is constant during the period, and the current supplied to the control terminal of the switching element is constant during the period regardless of a control terminal-emitter voltage of the switching element, and
the drive power supply circuit, the current detection resistor, and the current control transistor are connected in series in this order in the current path with respect to the control terminal of the switching element, one end of the current detection resistor is connected to the drive power supply circuit, and the control circuit controls the voltage across the current detection resistor to be constant with respect to the voltage supplied by the drive power supply circuit.

2. The electronic control apparatus according to claim 1 , wherein
the control circuit determines that a short circuit has occurred in the current control transistor, when the drive signal gives a command to supply constant current to the control terminal of the switching element, if the voltage across the current detection resistor increases to be greater than the voltage across the current detection resistor expected when the constant current is being supplied in response to the command given by the drive signal.

3. The electronic control apparatus according to claim 1 , wherein
the control circuit determines that an open fault has occurred in the current control transistor or a short circuit has occurred in the current detection resistor when the voltage across the current detection resistor is 0V, while the drive signal gives a command to supply the constant current from the ON-drive constant-current circuit to the control terminal of the switching element.

4. The electronic control apparatus according to claim 1 , wherein
the control circuit determines that a short circuit has occurred in the current control transistor when the voltage across the current detection resistor is greater than 0V, while the drive signal gives a command to turn ON the OFF-drive switching element.

5. The electronic control apparatus according to claim 1 , wherein
an input terminal of the current control transistor is connected to a positive terminal of a drive power circuit included in the control circuit via the current detection resistor, an output terminal of the current control transistor is connected to the control terminal of the switching element, and a connection point between the current control transistor and the current detection resistor is connected to a negative terminal of the drive power supply circuit with a reference potential connection resistor therebetween.

6. The electronic control apparatus according to claim 5 , wherein the control circuit determines that an open fault has occurred in the current detection resistor when the voltage across the current detection resistor is the voltage of the drive power supply circuit, while the drive signal gives a command to turn ON the OFF-drive switching element.

7. The electronic control apparatus according to
claim 5 , wherein the control circuit determines that an open fault has occurred in the current control transistor when the voltage across the current detection resistor is equal to a voltage where a voltage of the drive power supply circuit is divided by the current detection resistor and the reference potential connection resistor, while the drive signal gives a command to supply the constant current from the ON-drive constant-current circuit to the control terminal of the switching element.

8. The electronic control apparatus according to claim 1 , wherein the control circuit includes:
a current control circuit for controlling the current control transistor based on the voltage across the current detection resistor; and
an abnormality detection circuit for detecting an abnormality in the ON-drive constant-current circuit based on the voltage across the current detection resistor, and wiring from the current detection resistor to the current control circuit and the wiring from the current detection resistor to the abnormality detection circuit are provided separately.

9. The electronic control apparatus according to claim 8 , wherein the abnormality detection circuit is constituted by a differential amplifier that detects the voltage across the current detection resistor.

10. The electronic control apparatus according to claim 1 , wherein
the electronic control apparatus includes an OFF-holding switching element connected to the control terminal of the switching element and adapted to discharge electrical charge from the control terminal of the switching element by being turned ON, the control circuit turns OFF the switching element when an abnormality in the ON-drive constant-current circuit is detected.

11. The electronic control apparatus according to claim 10 , wherein
the control circuit is adapted to control the OFF-holding switching element such that when the voltage of the control terminal of the switching element becomes an OFF-holding threshold or less, the OFF-holding threshold being lower than an ON/OFF threshold voltage, the control circuit controls the OFF-holding switching element so as to hold the OFF-state of the switching element, and when an abnormality in the ON-drive constant-current circuit is detected, the control circuit controls the OFF-holding switching element so as to turn

Assignees

• Watanabe Kazunori
• Mizobe Shunichi
• Maebara Tsuneo
• Denso Corp

Inventors

• Watanabe Kazunori
• Mizobe Shunichi
• Maebara Tsuneo

Classifications

• H03K17/08

  Modifications for protecting switching circuit against overcurrent or overvoltage · CPC title

• H03K17/0822 Primary

  in field-effect transistor switches · CPC title