Drive circuit fault detection drive

• US 5,623,254 A
• Filed: 01/03/1995
• Issued: 04/22/1997
• Est. Priority Date: 07/31/1991
• Status: Expired due to Term

• Current Assignee: SGS-Thomson Microelectronics, S.R.L. (STMicroelectronics NV)
• Original Assignee: SGS-Thomson Microelectronics, S.R.L. (STMicroelectronics NV)
• Inventors: Brambilla, Massimiliano, Maggioni, Giampietro
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Lefkowitz, Edward
• Application Number:
  US08/367,746
• Time in Patent Office: 840 Days
• Field of Search: 340/635, 340/638, 340/639, 340/644, 340/654, 340/642, 361/101, 361/93, 364/483
• US Class Current: 340/644
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: H03K 17/0822 in field-effect transistor switches

Abstract

A drive circuit fault detection device comprising a discriminating circuit generating a digital signal, the level of which indicates a fault; and an identifying circuit generating a binary-coded signal indicating the type of fault, i.e. ground shorting of the drive circuit or an open load. The discriminating circuit comprises a resistive network connected to the output of the drive circuit, for generating a voltage indicating correct connection of the load or a fault on the drive circuit and a comparator for comparing the generated voltage with a reference voltage and supplying the digital signal at its output. The identifying circuit comprises a current mirror circuit generating an output voltage having two different logic levels in the event of short circuiting or an open load, respectively, and a combination circuit for generating the binary-coded output signal.

Claims

1. A fault detection device for a drive circuit having a control terminal that receives a control signal, an output terminal capable of establishing a connection to a load, and a third terminal coupled to a ground reference, the fault detection device comprising:

a fault discriminating circuit that determines whether a fault exists in the connection between the drive circuit and the load, the fault discriminating circuit having;

an input coupled to the output terminal of the drive circuit, and an output providing a condition signal indicative of a condition of the connection between the drive circuit and the load when the drive circuit is disabled to prevent current from passing through the drive circuit;

a voltage generator for generating a voltage representing the condition of the connection between the drive circuit and the load;

a comparator, coupled to and responsive to the voltage generated by the voltage generator, that compares the voltage generated by the voltage generator with a reference voltage and that provides the output signal, at least a portion of the voltage generator and the comparator forming a short-to-ground detector that detects a short circuit between the output terminal and the ground reference; and

an AND circuit having a first input responsive to the output signal of the comparator, a second input, responsive to the drive circuit control signal, and an output, responsive to the signals at the first and second inputs, providing the condition signal only when the drive circuit control signal is at a level that disables the drive circuit;

a fault identification circuit, coupled to the output of the fault discriminating circuit including circuitry responsive to the condition signal provided by the fault discriminating circuit that provides a type signal indicative of a type of fault detected by the fault discriminating circuit, and a combinatorial circuit generating a binary-coded output signal having a first state when the drive circuit and the load are connected, a second state when the output terminal of the drive circuit is short-circuited to the ground reference, and a third state when the drive circuit and the load are disconnected.

2. The fault detection device of claim 1, wherein the circuitry responsive to the condition signal includes a current mirror having an input coupled to and controlled by the output terminal of the drive circuit and an output, responsive to the input, that provides a first signal if the load is disconnected and a second signal if the output terminal of the drive circuit is short-circuited to the ground reference.

3. The fault detection device of claim 2, wherein the voltage generator circuit comprises a resistive network.

4. The fault detection device of claim 3, further comprising a delay circuit, responsive to the drive control signal, to disable the output signal of the comparator for a predetermined time after the drive circuit control signal has disabled the drive circuit.

5. The fault detection device of claim 4, further comprising an inverter circuit coupling the drive circuit control signal to the second input of the AND circuit.

6. A fault detection device for a drive circuit having a control terminal that receives a control signal, an output terminal capable of establishing a connection to a load, and a third terminal coupled to a ground reference, the fault detection device comprising:

fault discriminating circuit means for determining when a fault exists in the connection between the drive circuit and the load, the fault discriminating circuit means having;

an input coupled to the output terminal of the drive circuit and an output providing a condition signal indicative of a condition of the connection between the drive circuit and the load when the drive circuit is disabled to prevent current from passing through the drive circuit;

a voltage generating means for generating a voltage representing the condition of the connection between the drive circuit and the load;

a comparator means, coupled to and responsive to the voltage generating means, for comparing the voltage generated by the voltage generating means with a reference voltage, and for providing an output signal, at least a portion of the voltage generating means and the comparator means forming a means for detecting a short circuit between the output terminal and the ground reference; and

an AND circuit means having a first input responsive to the output signal of the comparator means and a second input, responsive to the drive circuit control signal, and an output, responsive to the signals at the first and second inputs, for providing the condition signal only when the drive circuit control signal is at a level that disables the drive circuit; and

a fault identification circuit means, responsive to the condition signal, for providing a type signal indicative of a type of fault detected by the fault discriminating circuit means, including a combinatorial circuit means for generating a binary-coded output signal having a first state when the drive circuit and the load are connected, a second state when the output terminal of the drive circuit is short-circuited to the ground reference, and a third state when the drive circuit and the load are disconnected.

7. The fault detection device of claim 6, wherein the fault identification circuit means includes a current mirror circuit means, having an input coupled to and controlled by the output terminal of the drive circuit and an output responsive to the input, for providing a first signal if the load is disconnected and a second signal if the output terminal of the drive circuit is short-circuited to the ground reference.

8. The fault detection device of claim 7, further comprising a delay circuit means, responsive to the drive circuit control signal, for disabling the output signal of the comparator means for a predetermined time after the drive circuit control signal has disabled the drive circuit.

9. The fault detection device of claim 8, wherein the voltage generating means comprises a resistive network means for providing a voltage representing the condition of the connection between the drive circuit and the load.

10. A drive circuit, comprising:

a control element having an output terminal capable of establishing a connection to a load to supply a drive signal to the load, a control terminal that receives a drive circuit control signal, and a third terminal coupled to a reference potential;

a first fault discriminating circuit having an input coupled to the output terminal of the control element, a short-to-reference detector that detects a short circuit between the output terminal and the reference potential, an output providing a condition signal indicative of a condition of the connection between the control element and the load, and a detector for determining when a fault exists at the output terminal of the drive circuit; and

a fault identification circuit, coupled to the output of the fault discriminating circuit, including circuitry, responsive to the condition signal provided by the fault discriminating circuit, that provides a type signal indicative of a type of fault detected by the fault discriminating circuit, wherein the fault identification circuit further comprises a combinatorial circuit that generates a binary-coded output signal having a first state when the control element and the load are connected, a second state when the output terminal of the control element is short-circuited to the reference potential, and a third state when the control element and the load are disconnected, wherein the fault identification circuit further includes a current mirror circuit having an input coupled to and controlled by the output terminal of the control element, and an output, responsive to the input, that provides a first signal if the load is disconnected and a second signal if the output terminal of the control element is short-circuited to the reference potential.

11. The drive circuit of claim 10, wherein the detector comprises a voltage generator for generating a voltage representing the condition of the connection between the control element and the load, and a comparator, coupled to and responsive to the voltage generated by the voltage generator, for comparing the voltage generated by the voltage generator with a reference voltage and for providing an output signal indicative of the condition of the connection between the control element and the load.