Method and apparatus for conveying bidirectional data, power and timing signals using a single transformer
Transformer driven by data modulated signal provides isolated power. Outbound data is extracted from the data modulated signal received from the transformer. Inbound data received in isolated circuitry modulates the load presented to transformer. Inbound data perceived in non-isolated circuitry by sensing load experienced by the transformer.
1. A method for conveying bidirectional data over a transformer comprising the steps of:
modulating an alternating current signal with outbound data;
driving a first side of the transformer with the modulated signal;
receiving the modulated signal from a second side of the transformer;
extracting outbound data from the received modulated signal using a comparator;
modulating according to inbound data the load presented to the second side of the transformer using a switch connected to ground when the alternating current signal is not modulated; and
receiving inbound data by sensing said load modulation.
2. The method of claim 1 wherein modulating the alternating current signal with outbound data comprises switching the phase of an alternating current signal according to a serial bit stream coincident with a clock.
3. The method of claim 1 wherein extracting outbound data comprises:
extracting a clock signal from the received modulated signal; and
sampling the received modulated signal according to the extracted clock signal.
4. The method of claim 3 wherein extracting a clock signal comprises:
sensing transitions in the received modulated signal;
generating an independent clock signal; and
synchronizing the independent clock with the transitions.
5. The method of claim 1 wherein modulating the load presented to the second side of the transformer comprises:
varying the impedance presented to the transformer according to a serial data stream coincident with an extracted clock signal.
6. The method of claim 1 further comprising:
generating an analog signal according to the extracted outbound data signal; and
varying the impedance of a circuit load according to the analog signal.
7. The method of claim 1 wherein modulating the load presented to the second side of the transformer comprises:
generating a digital value according to the voltage across a circuit load coincident with an extracted clock signal; and
varying the impedance presented to the second side of the transformer according to the digital value.
8. An apparatus for conveying bidirectional data across a galvanic barrier comprising:
a signal generator;
a signal modulator for modulating with outbound data a signal produced by the signal generator;
a transformer having a first side for receiving a modulated signal from the signal modulator and a second side;
a data extractor for extracting outbound data from a modulated signal received from the second side of the transformer, the data extractor further comprising a comparator;
a transformer load modulator for modulating the load on the second side of the transformer utilizing a switch configured to be coupled to ground, according to inbound data; and
an inbound data recovery unit for determining inbound data by sensing load modulations induced by the transformer load modulator.
9. The apparatus of claim 8 wherein the signal modulator comprises a phase modulator for altering the phase of the signal coincident with a clock.
10. The apparatus of claim 8 wherein the data extractor comprises:
a clock extractor for extracting a clock from a received modulated signal; and
a sampling device for sampling the received modulated signal according to the extracted clock.
11. The apparatus of claim 10 wherein the clock extractor comprises:
a controllable oscillator for generating a clock according to a control signal; and
the comparator is for generating the control signal by comparing transitions in a received modulated signal with transitions in the generated clock.
12. The apparatus of claim 8 wherein the transformer load modulator comprises:
an impedance element;
a synchronizer for synchronizing inbound data with an extracted clock signal; and
the switch for attaching the impedance element to the second side of the transformer according to the synchronized inbound data.
13. The apparatus of claim 8 further comprising:
a digital-to-analog converter for capable of generating an analog signal according to extracted outbound data;
a line circuit load for presenting a load to a communications channel;
an impedance element; and
an analog gate for linearly imparting the impedance element across the line circuit load according to the analog signal.
14. The apparatus of claim 8 further comprising:
a line circuit load for presenting a load to a communications channel;
an analog-to-digital converter for generating a digital value according the voltage present across the line circuit load;
an impedance element; and
a switch for attaching the impedance element to the second side of the transformer according to the digital value.
15. A system-side isolation controller comprising:
a signal generator;
a signal modulator for modulating a signal produced by the signal generator, the signal modulator comprising an exclusive OR gate and an exclusive NOR gate; and
an inbound data recovery unit for determining inbound data by sensing load modulations exhibited by a transformer, wherein the load modulations are generated using a switch coupled to ground.
16. The system-side isolation controller of claim 15 further comprising a transformer driver for driving the transformer with the modulated signal.
17. A line-side isolation controller comprising:
a data extractor for extracting outbound data from a modulated signal received from a second side of a transformer, the data extractor comprising a comparator; and
a transformer load modulator utilizing a switch coupled to ground for modulating the load presented to the second side of the transformer according to inbound data.
18. The line-side isolation controller of claim 17 wherein the data extractor comprises:
a clock extractor for extracting a clock signal from a received modulated signal; and
a sampling device for sampling the received modulated signal according to the extracted clock signal.
19. The line-side isolation controller of claim 18 wherein the clock extractor comprises:
a controllable oscillator for generating a clock according to a control signal; and
the comparator is for generating the control signal by comparing transitions in a received modulated signal with transitions in the generated clock.
20. The line-side isolation controller of claim 17 further comprising:
a digital-to-analog converter for generating an analog signal according to extracted outbound data;
an analog gate for linearly imparting a first impedance element across a line circuit load according to the analog signal;
an analog-to-digital converter for generating a digital value according the voltage present across the line circuit load;
an impedance element; and
the switch configured for attaching a second impedance element of the second side of the transformer to ground according to the digital value.