Solid state relay

• US 20090195082A1
• Filed: 02/04/2008
• Published: 08/06/2009
• Est. Priority Date: 02/04/2008
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Chen, Baoxing
• Granted Patent: US 8,084,894 B2
• Time in Patent Office: Days
• US Class Current: 307/125
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: H01F 2019/085 Transformer for galvanic isolation
• CPC Class Codes: H03K 17/6874 in a symmetrical configuration
• CPC Class Codes: H03K 17/691 using transformer coupling

Abstract

A solid state relay includes: an oscillator circuit responsive to a control signal for generating an a.c. signal; an isolation transformer having a primary winding which forms a part of the tank circuit of the oscillator circuit and a secondary winding; a rectifier responsive to the a.c. signal from the oscillator circuit for providing a d.c. drive signal; and a switch circuit responsive to the drive signal to open and close the relay.

Claims

1. A solid state relay comprising:

an oscillator circuit responsive to a control signal for generating an a.c. signal;

an isolation transformer having a primary winding which forms a part of the tank circuit of said oscillator circuit and a secondary winding;

a rectifier responsive to said a.c. signal from said oscillator circuit for providing a d.c. drive signal; and

a switch circuit responsive to said drive signal to open and close the relay.

2. The solid state relay of claim 1 in which said oscillator circuit includes a cross-coupled, bi-stable oscillator.

3. The solid state relay of claim 1 in which said oscillator circuit includes a dual, cross-coupled, bi-stable oscillator.

4. The solid state relay of claim 1 in which the parasitic capacitance of said oscillator circuit forms a part of the tank circuit.

5. The solid state relay of claim 1 in which the rectifier is a full wave rectifier.

6. The solid state relay of claim 1 in which the switch circuit is a bi-directional switch.

7. The solid state relay of claim 2 in which the single wave cross coupled bi stable oscillator includes a pair of MOSFET oscillator switches.

8. The solid state relay of claim 7 in which the pair of MOSFET oscillator switches are NMOS transistors.

9. The solid state relay of claim 7 in which the dual, cross coupled, bistable oscillator includes a pair of PMOS transistors, and a pair of NMOS transistors.

10. The solid state relay of claim 1 in which said switch circuit includes MOSFET switch transistors.

11. The solid state relay of claim 1 in which the MOSFET switch transistors include NMOS transistors.

12. The solid state relay of claim 1 in which said oscillator circuit, isolation transformer, rectifier and switch circuit are all on an integrated circuit chip.

13. The solid state relay of claim 1 in which the integrated circuit chip is a CMOS chip.

14. The solid state relay of claim 1 in which said isolation transformer is a micro-transformer.

15. The solid state relay of claim 1 in which said rectifier includes Schottky diodes.

16. A fully integrated solid state transformer isolated relay on a CMOS integrated chip comprising:

an oscillator circuit responsive to a control signal for generating an a.c. signal;

a micro-transformer having a primary winding which forms a part of the tank circuit of said oscillator circuit and a secondary winding;

a rectifier responsive to said a.c. signal from said oscillator circuit for providing a d.c. drive signal; and

a switch circuit responsive to said drive signal to open and close the relay.

17. A multi-channel solid state relay comprising:

a plurality of relay channels on an integrated circuit chip, each channel including;

an oscillator circuit responsive to a control signal for generating an a.c. signal;

an isolation transformer having a primary winding which forms a part of the tank circuit of said oscillator circuit and a secondary winding;

a rectifier responsive to said a.c. signal from said oscillator circuit for providing a d.c. drive signal; and

a switch circuit responsive to said drive signal to open and close the relay.

18. The multi-channel solid state relay of claim 17 in which said isolation transformer is a micro-transformer.