Electromagnetic coupling galvanic isolated solid state relay with output feedback

• US 7,554,827 B2
• Filed: 05/19/2006
• Issued: 06/30/2009
• Est. Priority Date: 05/19/2006
• Status: Expired due to Fees

• Current Assignee: Netio Technologies Co., Ltd.
• Original Assignee: Netio Technologies Co., Ltd.
• Inventors: Wang, Tom
• Primary Examiner(s): Jackson; Stephen W
• Assistant Examiner(s): PATEL, DHARTI HARIDAS
• Application Number:
  US11/436,605
• Publication Number:
  US 20070268649A1
• Time in Patent Office: 1,138 Days
• Field of Search: None
• US Class Current: 363/125
• CPC Class Codes: H03K 17/687 the devices being field-effect transistors
• CPC Class Codes: H03K 17/6871 the output circuit comprising more than one controlled field-effect transistor
• CPC Class Codes: H03K 17/691 using transformer coupling

Abstract

A solid state relay is provided herein, which utilizes an electromagnetic coupling device for galvanic isolation and providing feedback from the output side to the system side. The solid state relay contains a system-side driving circuit, an electromagnetic coupling device, and an output-side control circuit. The electromagnetic coupling device contains at least a system-side electromagnetic coupling element, a first output-side electromagnetic coupling element, and a second output-side electromagnetic coupling element. The system-side driving circuit is connected to the system-side electromagnetic coupling element, and takes the ON/OFF digital control signals from a digital system as input to turn on and off its driving to the system-side electromagnetic coupling element. The electromagnetic coupling device converts and transmits the electrical energy from the system side to the output side and thereby provides the working energy to the output control circuit connected to the first output-side electromagnetic coupling element. The second output-side electromagnetic coupling element forms a feedback circuit, through which the electrical status at the output side is fed back to the system side via the electromagnetic coupling device.

Claims

1. A solid state relay having a plurality of system-side terminals for connecting to a digital system and a plurality of output-side terminals for connecting to a load and an external power source, said solid state relay comprising:

an electromagnetic coupling device having a system-side electromagnetic coupling element, a first output-side electromagnetic coupling element and a second output-side electromagnetic coupling element, all of which have magnetic flux pass through each other, said system-side electromagnetic coupling element capable of transferring an electrical signal of said system-side electromagnetic coupling element to a correspond electrical signal across said first and second output-side electromagnetic coupling elements, and vice versa;

an output-side control circuit connecting to said first output-side electromagnetic coupling element in a parallel connection and to said second output-side electromagnetic coupling element in a series connection, said output-side control circuit and said second output-side electromagnetic coupling element in turn, via said output-side terminals, connecting to said load in a series connection and jointly forming a load circuit to said external power source; and

a system-side driving circuit positioned between said system-side terminals and said system-side electromagnetic coupling element, said system-side driving circuit being powered by an internal power source of said digital system and receiving a digital control signal from said digital system, said system-side driving circuit providing a feedback signal corresponding to an electrical status of said load circuit to said digital system, said system-side driving circuit connecting to said system-side electromagnetic coupling element in a parallel connection;

wherein, when said digital system outputs an ON digital control signal, said system-side driving circuit periodically applies said internal power source to said system-side electromagnetic coupling element, said first output-side electromagnetic coupling element is thereby induced to generate a corresponding electrical signal, and said electrical signal drives said output-side control circuit to turn said load circuit into a closed circuit;

when said digital system outputs an OFF digital control signal, said system-side driving circuit separates said internal power source and said system-side electromagnetic coupling element, said first output-side electromagnetic coupling element thereby cannot generates an electrical signal to turn said load circuit into a closed circuit, said load circuit thereby is therefore open-circuited; and

during when said digital system outputs an ON digital control signal and during the periods when said internal power source is not applied to said system-side electromagnetic coupling element, said feedback signal is produced by said system-side driving circuit by sampling an electrical signal across said system-side electromagnetic coupling element induced by said electrical status of said load circuit via said second output-side electromagnetic coupling element.

2. The solid state relay according to claim 1, wherein said system-side driving circuit comprises:

a switch device, said switch device and said system-side electromagnetic coupling element series-connected to said internal power source;

a switch control device, said switch control device accepting said digital control signal from said digital system and a clock signal to periodically control the conduction of said switch device; and

a feedback sampling device connected to said system-side electromagnetic coupling element in parallel, said feedback sampling device producing said feedback signal by sampling said system-side electromagnetic coupling element at appropriate times.

3. The solid state relay according to claim 2, wherein said switch device is an electronic switch having a current input terminal, a current output terminal, and a control terminal determining the conduction between said current input and output terminals;

said current input and output terminals and said system-side electromagnetic coupling element are series-connected to said internal power source; and

said control terminal is connected to the output of said switch control device.

4. The solid state relay according to claim 2, wherein said switch control device is a logic circuit accepting said digital control signal from said digital system and said clock signal as input and whose output is connected to said switch device;

and said logic circuit is controlled by said digital control signal to determine the application of said clock signal on said switch device.

5. The solid state relay according to claim 4, wherein the output of said switch control device is connected to said feedback sampling device so that said clock signal control said feedback sampling device to sample at appropriate times.

6. The solid state relay according to claim 2, wherein said feedback sampling device is a low-pass sample and hold filter.

7. The solid state relay according to claim 1, wherein said clock signal is provided by said digital system via one of said system-side terminals.

8. The solid state relay according to claim 1, wherein said clock signal is provided by an oscillator of said system-side driving circuit.

9. The solid state relay according to claim 1, wherein said output-side control circuit comprises:

a switch device, said switch device and said second output-side electromagnetic coupling element and said load series-connected to said external power source to form said load circuit; and

a switch control device connected to said first output-side electromagnetic coupling element in parallel, said switch control being device driven by an electrical signal induced across said first output-side electromagnetic coupling element to control the conduction of said switch device.

10. The solid state relay according to claim 9, wherein said switch device is an electronic switch having a current input terminal, a current output terminal, and a control terminal determining the conduction between said current input and output terminals;

said current input and output terminals, said second output-side electromagnetic coupling element, and said load are series-connected to said external power source; and

said control terminal is connected to the output of said switch control device.

11. The solid state relay according to claim 9, wherein said switch control device is an energy conversion circuit storing an energy induced across said first output-side electromagnetic coupling element as an energy required for the conduction of said switch device.

12. The solid state relay according to claim 9, further comprising:

a current sensing device series-connected to said load circuit, said current sensing device delivering an electrical signal corresponding to the current of said load circuit; and

a protection device, said protection device taking said electrical signal from said current sensing device as input, said protection device connected to said switch control device in parallel so as to control whether a control signal output by said switch control device reaches said switch device.

13. The solid state relay according to claim 12, wherein said current sensing device is a current-to-voltage or a voltage-to-current device.

14. The solid state relay according to claim 12, wherein said protection device is an electronic switch having a current input terminal, a current output terminal, and a control terminal determining the conduction between said current input and output terminals;

said current input and output terminals are connected to said switch control device in parallel;

said control terminal is connected to the output of said current sensing device so as to control whether said control signal output by said switch control device reaches said switch device.