Galvanic isolation circuit, corresponding system and method

• US 10,193,581 B2
• Filed: 03/24/2017
• Issued: 01/29/2019
• Est. Priority Date: 08/30/2016
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Ragonese, Egidio, Spina, Nunzio, Parisi, Alessandro, Lombardo, Pierpaolo, Greco, Nunzio, Palmisano, Giuseppe
• Primary Examiner(s): Takaoka, Dean
• Application Number:
  US15/468,306
• Publication Number:
  US 20180062678A1
• Time in Patent Office: 676 Days
• Field of Search: 333 24 R, 375219
• CPC Class Codes: H01F 19/04 Transformers or mutual inductances suitable for handling frequencies considerably beyond the audio range resonant circuits H03H
• CPC Class Codes: H01F 2019/085 Transformer for galvanic isolation
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H03F 2203/45084 the common mode signal circuit comprising one or more inductive or capacitive elements, e.g. filter circuitry
• CPC Class Codes: H03F 2203/45621 the IC comprising a transformer for phase splitting the input signal
• CPC Class Codes: H03F 2203/45642 the LC, and possibly also cascaded stages following it, being (are) controlled by the common mode signal derived to control a dif amp
• CPC Class Codes: H03F 2203/45704 the LC comprising one or more parallel resonance circuits
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence
• CPC Class Codes: H03F 3/45632 in differential amplifiers with FET transistors as the active amplifying circuit H03F3/4578 takes precedence
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04L 25/02 Details ; arrangements for supplying electrical power along data transmission lines systems for transmitting signals via power distribution lines H04B3/54
• CPC Class Codes: H04L 25/0266 Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission

Abstract

A galvanic isolation circuit is formed by a differential transformer having primary and secondary windings for transmission of signals over a carrier between the primary and the secondary windings of the transformer. A galvanic isolation oxide layer is provide between the primary and secondary windings. Each winding includes include a center tap providing a low-impedance paths for dc and low frequency components of common-mode currents through the differential transformer. A pass-band stage is coupled to the secondary winding of the transformer and configured to permit propagation of signals over said carrier through the pass-band amplifier stage while providing for a rejection of common-mode noise.

Claims

1. A system, comprising:

a differential transformer having a primary winding and a secondary winding configured to transmit signals over a carrier between the primary and secondary windings, wherein the primary and secondary windings have a galvanic isolation oxide layer therebetween, and wherein the primary and secondary windings each include a center tap providing low-impedance paths for dc and low frequency components of common-mode currents through the differential transformer; and

a pass-band circuit coupled to the secondary winding of the transformer, said pass-band circuit configured to permit propagation of signals over said carrier through the pass-band circuit while providing for a rejection of common-mode noise.

2. The system of claim 1, further including a transmitter circuit coupled to the primary winding and a receiver coupled to the pass-band circuit.

3. The circuit of claim 1, wherein said pass-band circuit includes a pass-band amplifier stage.

4. The circuit of claim 2, wherein the pass-band amplifier stage is a differential amplifier stage.

5. The circuit of claim 1, wherein said pass-band circuit includes a LC resonant load.

6. The circuit of claim 5, wherein said LC resonant load includes at least one Q-factor adjusting resistance element.

7. The circuit of claim 1, wherein said pass-band circuit is coupled to terminals of the secondary winding of the transformer.

8. A system, comprising:

a transmitter configured for transmitting signals over a carrier;

a receiver configured for receiving said signals over a carrier transmitted by said transmitter; and

a circuit positioned between said transmitter and said receiver, said circuit providing a galvanically isolated transmission path for said signals over the carrier between said transmitter and said receiver;

wherein said transmitter is coupled with the primary winding of said transformer; and

a pass-band circuit coupled with said receiver and configured to permit propagation of signals over said carrier through the pass-band circuit while providing for a rejection of common-mode noise.

9. The system of claim 8, wherein said pass-band circuit includes a LC resonant load.

10. The system of claim 9, wherein said LC resonant load includes at least one Q-factor adjusting resistance element.

11. The system of claim 8, wherein said pass-band circuit is coupled to terminals of the secondary winding of the transformer.

12. The system of claim 8, wherein said transmitter and said receiver include respective distinct grounds.

13. The system of claim 12, wherein the primary winding has a center tap coupled to the distinct ground of the transmitter and wherein the secondary winding has a center tap coupled to the distinct ground of the receiver.

14. The system of claim 8, further including an automatic gain control circuit active on said pass-band circuit to provide automatic gain control of said signals over the carrier.

15. A system, comprising:

a transmitter referenced to a first ground voltage and having an output;

a transformer having a primary winding and a secondary winding, wherein the primary winding is coupled to the output of the transmitter and has a center tap coupled to the first ground voltage;

a receiver referenced to a second ground voltage isolated from the first ground voltage and having an input coupled to the secondary winding, wherein the secondary winding has a center tap coupled to the second ground voltage; and

a differential amplifier circuit including a differential pair of input transistors coupled to terminals of the secondary winding and a differential pair of output terminals coupled to the input of the receiver;

wherein the differential amplifier circuit further includes an LC resonant load and at least one Q-factor adjusting resistance element.

16. The system of claim 15, wherein the resistance element is coupled between the differential pair of output terminals.