Transmitting and receiving digital and analog signals across an isolator

• US 8,847,503 B2
• Filed: 04/08/2013
• Issued: 09/30/2014
• Est. Priority Date: 09/21/2010
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Inventors: Chang, Kwee Chong, Ng, Gek Yong, Lum, Richard Kok Keong
• Primary Examiner(s): Hammond, Crystal L
• Application Number:
  US13/858,789
• Publication Number:
  US 20130264961A1
• Time in Patent Office: 540 Days
• Field of Search: None
• US Class Current: 315/201
• CPC Class Codes: H04B 1/48 in circuits for connecting transmitter and receiver to a common transmission path, e.g. by energy of transmitter H04B1/46 takes precedence
• CPC Class Codes: H04B 10/802 for isolation, e.g. using optocouplers
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: H05B 47/24 Circuit arrangements for protecting against overvoltage
• CPC Class Codes: H05B 47/25 Circuit arrangements for protecting against overcurrent
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

Various embodiments of systems for transmitting and receiving digital and Various embodiments of systems for transmitting and receiving digital and/or analog signals across a single isolator, solid state lighting systems, or DC/DC converter feedback regulation control systems are disclosed. In one embodiment, the digital and analog signals may be modulated into a frequency modulated signal, and each pulse of the frequency modulated signal may be further encoded into a major pulse and a minor pulse. At least some of the circuits, systems and methods disclosed herein may be implemented using conventional CMOS design and manufacturing techniques and processes to provide, for example, a single integrated circuit or ASIC.

Claims

1. An isolation system, comprising:

a modulator, wherein the modulator is configured to modulate at least one analog signal corresponding to logic state of at least one digital signal to form a frequency-modulated signal;

a transmitter electrically coupled to the modulator;

a signal isolator electrically coupled to the transmitter, wherein the transmitter is configured to transmit the frequency-modulated signal across the signal isolator;

a receiver electrically coupled to the signal isolator configured to detect and reproduce the frequency-modulated signal into a reproduced frequency-modulated signal;

a frequency discriminator electrically coupled to the receiver configured to decode the reproduced frequency-modulated signal and configured to reconstruct the at least one digital signal; and

a filtering circuit electrically coupled to the receiver configured to filter the reproduced frequency-modulated signal and to reconstruct the at least one analog signal,

wherein the signal isolator is configured to electrically isolate the transmitter and the receiver.

2. The system of claim 1, wherein the modulator further comprises a wave generator circuit configured to generate a wave signal.

3. The system of claim 2, wherein the modulator further comprises a comparator electrically coupled to the wave generator and the at least one analog signal.

4. The system of claim 3, wherein the wave generator circuit is configured to generate the wave signal in a first frequency when the at least one digital signal is in one logic state and is configured to generate the wave signal in a second frequency when the at least one digital signal is in other logic state.

5. The system of claim 1, wherein the filtering circuit further comprises a charge pump circuit having switches that open and close according to the reproduced frequency-modulated signal.

6. The system of claim 1, wherein the filtering circuit further comprises a charge pump circuit configured to provide current that varies in accordance with the frequency of the reproduced frequency-modulated signal received thereby.

7. The system of claim 1, wherein the modulator is configured such that the frequency-modulated signal comprises a pulse width modulated signal formed in accordance to the at least one analog signal.

8. An isolator, comprising:

a first circuit, the first circuit having a first analog signal and a first digital signal;

a second circuit;

a signal isolator isolating the first circuit from the second circuit;

a modulator of the first circuit, the modulator configured to modulate the first analog signal corresponding to logic state of the first digital to form a modulated signal as output of the modulator;

a transmitter of the first circuit configured to transmit the modulated signal across the signal isolator from the first circuit to the second circuit;

a receiver electrically coupled to the signal isolator configured to detect and reproduce the modulated signal into a reproduced modulated signal; and

a retrieval circuit of the second circuit configured to reconstruct the digital signal and the analog signal from the reproduced modulated signal.

9. The isolator of claim 8, wherein:

the modulated signal comprises a plurality of pulses;

the first circuit comprises an encoder configured to convert each pulse of the modulated signal into a major pulse and a minor pulse respectively, wherein the major pulse is substantially longer than the minor pulse; and

each of the major pulse and the minor pulse comprises a first edge transition and a second edge transition respectively.

10. The isolator of claim 9, wherein:

each of the pulses of the modulated signal has a respective duration; and

the respective duration of each of the pulses of the modulated signal is substantially similar to time duration measuring from one of the first edge transition and the second edge transition of one of the major pulse and the minor pulse, to the one of the first edge transition and the second edge transition of the other of the major pulse and the minor pulse.

11. The isolator of claim 10, wherein the encoder is further configured to encode a keep-alive pulse after a predetermined time period.

12. The isolator of claim 11, wherein the second circuit further comprises a watchdog circuit configured to detect the keep-alive pulse for a time period relatively longer than the predetermined time period.

13. The isolator of claim 12, wherein the second circuit has a filter configured to filter out the keep-alive pulse to output the major pulse and the minor pulse.

14. The isolator of claim 13, wherein:

the keep-alive pulse has a duration;

the minor pulse has a duration; and

the duration of the keep-alive pulse is relatively shorter than the duration of the minor pulse.

15. The isolator of claim 10, wherein the edge transition is one of a rising edge and a falling edge.

16. The isolator of claim 9, wherein the second circuit comprises a decoder configured to reproduce the modulated signal from the major pulse and the minor pulse.

17. The isolator of claim 16, wherein the decoder comprises a toggle flip-flop.

18. The isolator of claim 8, wherein the first analog signal is modulated using pulse width modulation and the first digital signal is modulated using frequency modulation.

19. A control system for transmitting and receiving at least one digital signal and at least one analog signal from a first circuit across to a second circuit, comprising:

a wave generator configured to generate a first modulated signal corresponding to logic state of the at least one digital signal;

a modulator configured to further modulate the at least one analog signal with the modulated signal into a second modulated signal;

a transmitter electrically coupled to the modulator;

a signal isolator electrically coupled to the transmitter, wherein the transmitter is configured to transmit the second modulated signal across the signal isolator;

a receiver electrically coupled to the signal isolator, the receiver configured to reproduce the second modulated signal into a reproduced modulated signal; and

a retrieval circuit configured to reproduce the at least one analog signal into a reproduced analog signal and to reproduce the at least one digital signal into a reproduced digital signal.

20. The system of claim 19, wherein:

the system is configured to transmit and receive an additional digital signal

the modulator is further configured to modulate the at least one analog signal into the modulated signal corresponding to logic state of the at least one digital signal and logic state of the additional digital signal.

21. The system of claim 20, wherein the retrieval circuit is further configured to decode the reproduced modulated signal and to reconstruct the additional digital signal.

22. The system of claim 21, wherein the at least one digital signal and the additional digital signal are modulated based on frequency modulation and the retrieval circuit comprises a frequency discriminator to reproduce the at least one digital signal and the additional digital signal.

23. The system of claim 19, wherein the system forms a portion of a direct current to direct current converter feedback regulation control system.

24. The system of claim 23, wherein the direct current to direct current converter feedback regulation control system comprises:

a switched mode power supply controller of the second circuit;

an isolation transformer configured to receive current from the second circuit as an input thereto and to provide an output voltage therefrom to the first circuit;

a rectifier circuit of the first circuit coupled to the isolation transformer, the rectifier circuit configured to provide an isolated DC output voltage;

a voltage monitoring circuit of the first circuit configured to generate the at least one analog signal as feedback to the second circuit; and

a comparator configured to generate the at least one digital signal as fault signal from the at least one analog signal,

wherein the switched mode power supply controller of the second circuit is electrically coupled to the reproduced digital signal and the reproduced analog signal as feedback from the first circuit.

25. The system of claim 24, further comprising an insulated gate bipolar transistor and a current monitoring circuit, wherein the current monitoring circuit is configured to generate an additional digital signal as an over current fault signal.

26. The system of claim 19 forms a portion of a solid state lighting system.

27. The system of claim 26, wherein the solid state lighting system comprises:

a switched mode power supply controller of the second circuit;

an isolation transformer configured to receive current from the second circuit as an input thereto and to provide an output voltage therefrom to the first circuit;

a rectifier circuit of the first circuit coupled to the isolation transformer, the rectifier circuit configured to provide an isolated DC output voltage;

a voltage monitoring circuit of the first circuit configured to generate a voltage sense signal;

a comparator of the first circuit to generate the at least one digital signal as a fault signal from the voltage sense signal;

a plurality of light sources of the first circuit coupled to the isolated DC output voltage; and

a current sensing circuit of the first circuit coupled to the plurality of light sources, the current sensing circuit configured to provide the at least one analog signal as analog feedback to the switched mode power supply controller of the second circuit,

wherein the switched mode power supply controller of the second circuit is electrically coupled to the reproduced digital signal and the reproduced analog signal as feedback from the first circuit.

28. An isolator, comprising:

an encoder, the encoder coupled to a digital signal having a plurality of pulses as inputs thereto, and the encoder being configured to encode each pulse of the digital signal into an encoded signal respectively such that the respective pulse of the digital signal is converted into a major pulse and a minor pulse, wherein duration of the major pulse is longer than duration of the minor pulse;

a transmitter electrically coupled to the encoder configured to transmit the encoded signal;

a receiver formed proximate to the transmitter to receive the encoded signal;

an isolation barrier formed proximate to the transmitter and the receiver providing an electrical isolation between the transmitter and the receiver while allowing the encoded signal from the transmitter to transmit through the isolation barrier; and

a decoder electrically coupled to the receiver, the decoder being configured to decode the encoded signal into a reproduced digital signal that is substantially similar to the digital signal.

29. The isolator of claim 28, wherein the encoder comprises:

a transistor configured to control a first charging/discharging current;

a capacitor electrically coupled to the transistor;

a switch electrically coupled to the digital signal and configured such that the charging current from the transistor charges up the capacitor depending on logic state of the digital signal; and

a comparator coupled to the capacitor configured to detect voltage across the capacitor.

30. The isolator of claim 28, wherein the encoder is configured to generate one of the major pulse and the minor pulse in response to the digital signal after a waiting time period, and the minor pulse has a pulse duration that is approximately equal to the waiting time period.

31. The isolator of claim 28, wherein the encoder comprises a delay circuit and a logic circuit such that the delay circuit and the logic circuit are configured to generate the minor pulse.

32. The isolator of claim 28, wherein:

each pulse of the encoded signal has a respective encoded pulse duration;

the major pulse has a major pulse duration;

a delay between the major pulse and the minor pulse has a delay duration; and

the respective encoded pulse duration is approximately equal to sum of the major pulse duration, and the delay duration.

33. A method for conveying a first digital signal and a first analog signal across an isolator, comprising:

modulating the first analog signal corresponding to logic state of the first digital signal to form a modulated signal;

transmitting the modulated signal across the isolator;

receiving and reproducing the modulated signal;

reconstructing the first digital signal into a reconstructed first digital signal; and

reconstructing the analog signal into a reconstructed first analog signal.

34. The method of claim 33, wherein the first analog signal is modulated through pulse width modulation, and the first digital signal is modulated through frequency modulation.

35. The method of claim 33 wherein the modulated signal comprises a plurality of pulses, and wherein the method further comprising encoding the modulated signal by converting each of the pulses of the modulated signal into one major pulse and one minor pulse respectively prior to transmitting the modulated signal across the isolator such that duration of major pulse is substantially longer than duration of minor pulse.