METHOD OF FORMING AN OVER-VOLTAGE PROTECTION CIRCUIT AND STRUCTURE THEREFOR

• US 20080186644A1
• Filed: 02/05/2007
• Published: 08/07/2008
• Est. Priority Date: 02/05/2007
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Migliavacca, Paolo
• Granted Patent: US 8,649,144 B2
• Time in Patent Office: Days
• US Class Current: 361/86
• CPC Class Codes: G05F 1/571 with overvoltage detector

Abstract

In one embodiment, an over-voltage protection circuit is configured to have two control circuits that respond at different values of the input voltage.

Claims

1. An over-voltage protection circuit comprising:

an input configured to receive an input voltage;

an output;

a pass element coupled between the input and the output and configured to couple the input voltage to the output;

a first circuit configured to disable the pass element responsively to the input voltage being no less than a first value; and

a second circuit configured to disable the pass element responsively to the input voltage being no less than a second value that is less than the first value.

2. The over-voltage protection circuit of claim 1 wherein the second circuit includes a comparator configured to receive a sense signal that is representative of the input voltage and form a control signal used to disable the pass element wherein the comparator is configured to form the control signal responsively to the input voltage being no less than second value.

3. The over-voltage protection circuit of claim 2 further including a feed forward circuit coupled to receive the input voltage and form the sense signal.

4. The over-voltage protection circuit of claim 2 further including a first resistor coupled to enable the pass element.

5. The over-voltage protection circuit of claim 1 wherein the first circuit includes a zener diode coupled to receive the input voltage.

6. The over-voltage protection circuit of claim 5 further including a threshold shifting circuit coupled to the zener diode.

7. The over-voltage protection circuit of claim 6 further including a transistor coupled to the zener diode and the threshold shifting circuit and configured to form a control signal used to disable the pass element responsively to the input voltage being no less than the first value.

8. The over-voltage protection circuit of claim 1 wherein an output of the first circuit is connected to an output of the second circuit.

9. The over-voltage protection circuit of claim 1 wherein the first circuit includes a zener diode having an anode and a cathode.

10. The over-voltage protection circuit of claim 9 further including a first transistor having a first current carrying electrode coupled to the pass element, a control electrode coupled to the anode of the zener diode, and a second current carrying electrode coupled to a voltage return of the over-voltage protection circuit.

11. The over-voltage protection circuit of claim 10 further including a first resistor having a first terminal coupled to the control electrode of the first transistor and a second terminal coupled to the voltage return, and also including a second resistor having a first terminal coupled to receive the input voltage and a second terminal coupled to the cathode of the zener diode.

12. The over-voltage protection circuit of claim 1 wherein the second circuit includes a comparator having a non-inverting input, an inverting input, and an output, and also including a first transistor having a control electrode coupled to the output of the comparator, a first current carrying electrode coupled to a voltage return of the over-voltage protection circuit, and a second current carrying electrode coupled to the pass element.

13. The over-voltage protection circuit of claim 12 wherein the second circuit includes a feed-forward circuit coupled to receive the input voltage and couple a sense signal to the non-inverting input of the comparator wherein the sense signal is representative of the input voltage.

14. A method of forming an over-voltage protection circuit comprising:

configuring a pass element of the over-voltage protection circuit to couple an input voltage to an output of the over-voltage protection circuit;

configuring a first circuit of the over-voltage protection circuit to decouple the input voltage from the output responsively to a first value of the input voltage for the input voltage increasing at a first rate; and

configuring a second circuit of the over-voltage protection circuit to decouple the input voltage from the output responsively to the input voltage increasing to no less than a second value at a second rate wherein the second value is greater than the first value.

15. The method of claim 14 wherein configuring the second circuit of the over-voltage protection circuit includes configuring the second circuit to respond to the input voltage at a rate that is greater than the first circuit responds to the input voltage.

16. The method of claim 15 further including coupling a zener diode to sense the input voltage increasing to the second value and responsively form a control signal that causes disabling the pass element.

17. The method of claim 15 further including coupling the zener diode to disable the pass element responsively to the second value.

18. The method of claim 14 wherein configuring the second circuit of the over-voltage protection circuit includes configuring the second rate to be greater than the first rate.

19. The method of claim 18 further including configuring a comparator of the first circuit to sense the first value after the second circuit senses the second value.

20. The method of claim 19 further including coupling a first input of the comparator to receive a sense signal that is representative of the input voltage, coupling a second input of the comparator to receive a reference signal, and coupling an output of the comparator to form a signal that causes disabling of the pass element.