Device for detecting short-circuits

• US 6,377,053 B1
• Filed: 02/24/1998
• Issued: 04/23/2002
• Est. Priority Date: 03/04/1997
• Status: Expired due to Term

• Current Assignee: SGS-Thomson Microelectronics, S.R.L. (STMicroelectronics NV), STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: Magneti Marelli S.p.A., SGS-Thomson Microelectronics, S.R.L. (STMicroelectronics NV)
• Inventors: Mazzucco, Michelangelo, Maggioni, Giampietro
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Hollington, Jermele M.
• Application Number:
  US09/028,731
• Time in Patent Office: 1,519 Days
• Field of Search: 324/509, 324/522, 324/523, 324/527
• US Class Current: 324/509
• 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 31/52 Testing for short-circuits, leakage current or ground faults

Abstract

The short-circuit detecting device includes a current generator for generating a current (I_IN) of predetermined intensity, selectively into or out of the terminal (IN), and a first voltage comparator connected to the terminal (IN) and connected to the current generator in a manner such that the generator generates a current (I_IN) in the inward direction and in the outward direction relative to the terminal (IN), respectively, when the voltage between the terminal (IN) and the ground is greater than a first level and less than a second level, respectively. The first level is greater than or equal to the second. The device also includes a second voltage comparator for supplying a first and a second signal, respectively, when the voltage between the terminal (IN) and the ground is close to the supply voltage (Vcc) and close to the ground potential (gnd), respectively, and a processing circuit connected to the second comparator for detecting whether the first or the second signal, respectively, persists for a predetermined period of time. In this case, an output signal (F_Vcc; F_gnd) is supplied which is indicative of a short-circuit of the terminal (IN) to the supply (Vcc) or to ground, respectively.

Claims

1. A device for detecting a condition of non-intermittent short-circuit of a desired terminal of a circuit towards ground or towards a direct-current voltage supply of the circuit, the device comprising:

current-generating means connected to the desired terminal and for generating a current of predetermined intensity selectively into or out of the desired terminal;

first voltage-comparator means connected to the desired terminal and connected to the current-generating means in a manner such that the current-generating means generates a current in the inward direction relative to the desired terminal when a voltage between the desired terminal and ground is greater than a first voltage threshold, and generates a current in the outward direction relative to the desired terminal when the voltage between the desired terminal and around is less than a second voltage threshold, the first voltage threshold being greater than or equal to the second voltage threshold;

second voltage-comparator means connected to the desired terminal and for supplying a first and a second signal, respectively, when the voltage between the desired terminal and ground is close to the supply voltage and close to ground, respectively; and

processing-circuit means connected to the second comparator means for detecting whether the first or the second signal, respectively, lasts for a predetermined period of time and, responsive thereto, for supplying an output signal indicative of a short-circuit of the terminal towards the voltage supply or towards ground, respectively.

2. A device according to claim 1, wherein said current-generating means comprises, between the voltage supply and ground:

a reference resistor;

a first circuit branch comprising a first transistor having a collector-emitter path in series with said reference resistor;

circuit means for applying to the reference resistor a voltage of predetermined value less than that of the supply;

a first and a second current mirror connected to the desired terminal and coupled to the first transistor in a manner such that the first and second current mirrors can conduct currents substantially equal to and double a current flowing in the first transistor, respectively; and

an electronic switch connected to the first and second current mirrors and controlled by the first voltage-comparator means in a manner such that, when the voltage between the desired terminal and ground is below the second voltage threshold, the electronic switch is conductive and disables the second current mirror and the current flowing in the first current mirror flows in the outward direction relative to the desired terminal and, when the voltage between the desired terminal and ground is greater than the first voltage threshold, the electronic switch is cut off and a current substantially equal to a difference between the currents flowing in the first and second current mirrors flows into the desired terminal in the inward direction.

3. A device according to claim 2, wherein said circuit means comprises:

a resistive divider which is connected between the voltage supply and ground; and

amplifier means with substantially unitary gain connected between an output of the resistive divider and the reference resistor so that current flowing in the first circuit branch depends essentially solely on the voltage supply and on the resistance values of the resistive divider and on the reference resistor.

4. A device according to claim 1, wherein said first voltage-comparator means comprises a threshold comparator circuit with hysteresis.

5. A device according to claim 1, wherein said second voltage-comparator means comprises:

a chain of three resistors connected between the voltage supply and ground; and

a pair of threshold comparators each having a respective first input connected to a respective terminal of an intermediate resistor of the chain of three resistors and a second input connected to the desired terminal.

6. A device according to claim 5, wherein said processing-circuit means comprises a logic circuit including flip-flops;

and wherein said logic circuit has an input for an external control signal a duration of which defines the predetermined period of time.

7. A device according to claim 6, wherein said logic circuit has two inputs connected to outputs of the threshold comparators, and said logic circuit has two outputs;

and wherein said logic circuit is arranged to supply signals corresponding to outputs of the threshold comparators at its outputs only when there is no change in a level of these signals during the predetermined period of time.

8. A device for detecting a condition of non-intermittent short-circuit of a desired terminal of a circuit towards a first voltage supply or a second voltage supply of the circuit, the device comprising:

a current-generator connected to the desired terminal and for generating a current of predetermined intensity selectively into or out of the desired terminal;

a first voltage-comparator connected to the desired terminal and connected to the current-generator in a manner such that the current-generator generates a current in the inward direction relative to the desired terminal when a voltage between the desired terminal and the first voltage supply is greater than a first voltage threshold, and generates a current in the outward direction relative to the desired terminal when the voltage between the desired terminal and the first voltage supply is less than a second voltage threshold, the first voltage threshold being greater than or equal to the second voltage threshold;

a second voltage-comparator connected to the desired terminal and for supplying a first and a second signal, respectively, when the voltage between the desired terminal and the first voltage supply is close to the second supply voltage and close to the first voltage supply, respectively; and

a processing circuit connected to the second comparator for detecting whether the first or the second signal, respectively, lasts for a predetermined period of time and, responsive thereto, for supplying an output signal indicative of a short-circuit of the terminal towards the second voltage supply or towards the first voltage supply, respectively.

9. A device according to claim 8, wherein said current-generator comprises, between the second voltage supply and the first voltage supply:

a reference resistor;

a first circuit branch comprising a first transistor having a collector-emitter path in series with said reference resistor;

a second circuit for applying to the reference resistor a voltage of predetermined value less than that of the second voltage supply;

a first and a second current mirror connected to the desired terminal and coupled to the first transistor in a manner such that the first and second current mirrors can conduct currents substantially equal to and double a current flowing in the first transistor, respectively; and

an electronic switch connected to the first and second current mirrors and controlled by the first voltage-comparator in a manner such that, when the voltage between the desired terminal and second voltage supply is below the second voltage threshold, the electronic switch is conductive and disables the second current mirror and the current flowing in the first current mirror flows in the outward direction relative to the desired terminal and, when the voltage between the desired terminal and the first voltage supply ground is greater than the first voltage threshold, the electronic switch is cut off and a current substantially equal to a difference between the currents flowing in the first and second current mirrors flows into the desired terminal in the inward direction.

10. A device according to claim 9, wherein said second circuit comprises:

a resistive divider which is connected between the second voltage supply and the first voltage supply; and

an amplifier with substantially unitary gain connected between an output of the resistive divider and the reference resistor so that current flowing in the first circuit branch depends essentially solely on the second supply voltage and on the resistance values of the resistive divider and on the reference resistor.

11. A device according to claim 8, wherein said first voltage-comparator comprises a threshold comparator circuit with hysteresis.

12. A device according to claim 8, wherein said second voltage-comparator comprises:

a chain of three resistors connected between the second voltage supply and the first voltage supply; and

a pair of threshold comparators each having a respective first input connected to a respective terminal of an intermediate resistor of the chain of three resistors and a second input connected to the desired terminal.

13. A device according to claim 12, wherein said processing circuit comprises a logic circuit including flip-flops;

and wherein said logic circuit has an input for an external control signal a duration of which defines the predetermined period of time.

14. A device according to claim 13, wherein said logic circuit has two inputs connected to outputs of the threshold comparators, and said logic circuit has two outputs;

and wherein said logic circuit is arranged to supply signals corresponding to outputs of the threshold comparators at its outputs only when there is no change in a level of these signals during the predetermined period of time.

15. A device according to claim 8, wherein the first supply voltage is ground.

16. A device for detecting a condition of non-intermittent short-circuit of a desired terminal of a circuit towards a first voltage supply or a second voltage supply of the circuit, the device comprising:

a current-generator connected to the desired terminal and for generating a current of predetermined intensity selectively into or out of the desired terminal, said current-generator comprising between the second voltage supply and the first voltage supply

a reference resistor,

a first circuit branch comprising a first transistor having a collector-emitter path in series with said reference resistor,

a second circuit for applying to the reference resistor a voltage of predetermined value less than that of the second voltage supply, and

a first and a second current mirror connected to the desired terminal and coupled to the first transistor in a manner such that the first and second current mirrors can conduct currents substantially equal to and double a current flowing in the first transistor, respectively;

a first voltage-comparator connected to the desired terminal and connected to the current-generator in a manner such that the current-generator generates a current in the inward direction relative to the desired terminal when a voltage between the desired terminal and the first voltage supply is greater than a first voltage threshold, and generates a current in the outward direction relative to the desired terminal when the voltage between the desired terminal and the first voltage supply is less than a second level, the first voltage threshold being greater than or equal to the second voltage threshold;

a second voltage-comparator connected to the desired terminal and for supplying a first and a second signal, respectively, when the voltage between the desired terminal and the first voltage supply is close to the second supply voltage and close to the first voltage supply, respectively; and

a processing circuit connected to the second comparator for detecting whether the first or the second signal, respectively, lasts for a predetermined period of time and, responsive thereto, for supplying an output signal indicative of a short-circuit of the terminal towards the second voltage supply or towards the first voltage supply, respectively.

17. A device according to claim 16, wherein said current generator further comprises an electronic switch connected to the first and second current mirrors and controlled by the first voltage-comparator in a manner such that, when the voltage between the desired terminal and second voltage supply is below the second voltage threshold, the electronic switch is conductive and disables the second current mirror and the current flowing in the first current mirror flows in the outward direction relative to the desired terminal and, when the voltage between the desired terminal and the first voltage supply ground is greater than the first voltage threshold, the electronic switch is cut off and a current substantially equal to a difference between the currents flowing in the first and second current mirrors flows into the desired terminal in the inward direction.

18. A device according to claim 17, wherein said second circuit comprises:

a resistive divider which is connected between the second voltage supply and the first voltage supply; and

an amplifier with substantially unitary gain connected between an output of the resistive divider and the reference resistor so that current flowing in the first circuit branch depends essentially solely on the second supply voltage and on the resistance values of the resistive divider and on the reference resistor.

19. A device according to claim 16, wherein said first voltage-comparator comprises a threshold comparator circuit with hysteresis.

20. A device according to claim 16, wherein said second voltage-comparator comprises:

a chain of three resistors connected between the second voltage supply and the first voltage supply; and

a pair of threshold comparators each having a respective first input connected to a respective terminal of an intermediate resistor of the chain of three resistors and a second input connected to the desired terminal.

21. A device according to claim 20, wherein said processing circuit comprises a logic circuit including flip-flops;

and wherein said logic circuit has an input for an external control signal a duration of which defines the predetermined period of time.

22. A device according to claim 21, wherein said logic circuit has two inputs connected to outputs of the threshold comparators, and said logic circuit has two outputs;

and wherein said logic circuit is arranged to supply signals corresponding to outputs of the threshold comparators at its outputs only when there is no change in a level of these signals during the predetermined period of time.

23. A device according to claim 16, wherein the first supply voltage is ground.

24. A method for detecting a condition of non-intermittent short-circuit of a desired terminal of a circuit towards a first voltage supply or a second voltage supply of the circuit, the method comprising the steps of:

generating a current of predetermined intensity selectively into or out of the desired terminal;

providing a first voltage-comparator connected to the desired terminal and to the current-generator in a manner such that the current generator generates a current in the inward direction relative to the desired terminal when a voltage between the desired terminal and the first voltage supply is greater than a first voltage threshold, and generates a current in the outward direction relative to the desired terminal when the voltage between the desired terminal and the first voltage supply is less than a second voltage threshold, the first voltage threshold being greater than or equal to the second voltage threshold;

providing a second voltage-comparator connected to the desired terminal and for supplying a first and a second signal, respectively, when the voltage between the desired terminal and the first voltage supply is close to the second supply voltage and close to the first voltage supply, respectively; and

detecting whether the first or the second signal, respectively, lasts for a predetermined period of time and, responsive thereto, for supplying an output signal indicative of a short-circuit of the terminal towards the second voltage supply or towards the first voltage supply, respectively.

25. A method according to claim 24, wherein the first supply voltage is ground.