Protective device against excessive currents, in particular for resettable protection of a controlled switch

• US 6,342,994 B1
• Filed: 02/04/2000
• Issued: 01/29/2002
• Est. Priority Date: 12/12/1997
• Status: Expired due to Fees

• Current Assignee: Legrand (Legrand SA), Legrand Snc (Legrand SA)
• Original Assignee: Legrand (Legrand SA), Legrand Snc (Legrand SA)
• Inventors: Batongue, Serge, Cousy, Jean-Pierre
• Primary Examiner(s): Leja, Ronald W.
• Application Number:
  US09/367,351
• Time in Patent Office: 725 Days
• Field of Search: 361/23, 361/24, 361/29, 361/31, 361/57, 361/58, 361/93.1, 361/93.8, 361/93.9, 361/91.8, 361/103, 361/106
• US Class Current: 361/24
• CPC Class Codes: H02H 9/026 Current limitation using PTC resistors, i.e. resistors with a large positive temperature coefficient
• CPC Class Codes: H03K 17/08124 in thyristor switches
• CPC Class Codes: H03K 17/08144 in thyristor switches

Abstract

A protective device against excessive currents occurring in an electric circuit between a voltage source and a load mounted downstream of said device, comprising a first triggering component with high current sensitivity and adapted to be triggered, rapidly, but reversibly, in case of excessive current in the circuit, and a second triggering component, mounted in parallel with the first, capable of bearing a temporary voltage higher than the power supply voltage, when the first component is triggered, and of being triggered rapidly and reversibly thereafter. The triggering component are preferably conductive polymer components. Also, a triac switch comprising such a protective device mounted upstream of the triac and a third component is mounted on the triac trigger.

Claims

1. An electronic switch comprising:

a) a triac,

b) a device protecting against overcurrents in an electrical circuit between a voltage supply and a load downstream of said device, said device being connected in series upstream of the triac and including;

first tripping means having a high current sensitivity and adapted to be tripped (i.e. to change from a conductive state to a virtually non-conductive state) fast, but reversibly, in the event of an overcurrent in the circuit, and

second tripping means connected in parallel with the first tripping means, adapted to withstand a temporary voltage higher than a mains voltage when the first tripping means trips and trips quickly after the first tripping means; and

c) third tripping means between the trigger of the triac and the voltage supply.

2. An electronic switch according to claim 1, wherein the first, second and third tripping means are components whose resistivity increases by several orders of magnitude with temperature, reversibly, and the first tripping means has a very low resistance when in the conductive state compared to the resistance of the second tripping means when in the conductive state.

3. An electronic switch according to claim 2, wherein the first, second and third tripping means comprise respective first, second and third positive temperature coefficient charged polymer components.

4. An electronic switch according to claim 3, wherein the third tripping means has a high resistance when in the conductive state compared to the resistance of the first polymer component when in the conductive state, in order to withstand the transfer of voltage.

5. A device according to claim 3, wherein the resistance of the first polymer component when in the conductive state is approximately 200 milli-ohms and the resistance of the second polymer component when in the conductive state is approximately 13 to 26 ohms.

6. A device according to claim 3, wherein the first polymer component has a holding current of a few amperes at 20°

C.

7. A device according to claim 3, wherein the second polymer component has a holding current of approximately 0.1 ampere at 20°

C.