Galvanically isolated DC-DC circuit converter with data communication, corresponding system and corresponding method

Patent metadata

Field	Value
Publication number	US-11128221-B2
Application number	US-202016748328-A
Country	US
Kind code	B2
Filing date	Jan 21, 2020
Priority date	Jan 12, 2018
Publication date	Sep 21, 2021
Grant date	Sep 21, 2021

Abstract

A DC-DC converter includes a transformer having primary and secondary windings, a power oscillator applying an oscillating signal to the primary winding to transmit a power signal to the secondary winding, a rectifier obtaining an output DC voltage by rectifying the power signal at the secondary winding, and comparison circuitry generating an error signal representing a difference between the output DC voltage and a reference voltage value. A transmitter connected to the secondary winding performs an amplitude modulation of the power signal at the secondary winding to transmit an amplitude modulated power signal to the primary winding, the amplitude modulation based upon the error signal and modulating a stream of data to the primary winding. A receiver coupled to the primary winding demodulates the amplitude modulated power signal to recover the error signal and the stream of data. An amplitude of the oscillating signal is controlled by the error signal.

First claim

The invention claimed is:

1. A DC-DC converter circuit, comprising:
a single isolation transformer having a primary winding and a secondary winding magnetically coupled to the primary winding through a single core of the single isolation transformer;
a power oscillator connected to apply an oscillating signal to the primary winding of the single isolation transformer to thereby transmit a power signal to the secondary winding;
a rectifier connected to the secondary winding of the single isolation transformer and configured to obtain an output DC voltage by rectification of the power signal at the secondary winding;
comparison circuitry configured to generate an error signal representing a difference between the output DC voltage and a reference voltage value;
a transmitter connected to the secondary winding of the single isolation transformer to apply an amplitude modulation to the power signal at the secondary winding of the single isolation transformer in response to the error signal to thereby produce an amplitude modulated signal at the primary winding;
a receiver connected to the primary winding and configured to demodulate the amplitude modulated signal to recover the error signal; and
a control circuit configured to control an amplitude of the oscillating signal as a function of the recovered error signal.

2. The DC-DC converter circuit of claim 1 , further comprising a common mode transient (CMT) rejection circuit connected between the primary winding and the receiver and configured to reduce effects of common mode transients in the amplitude modulated signal.

3. The DC-DC converter circuit of claim 1 , further comprising a de-multiplexing circuit configured to receive a stream of data from the receiver and de-multiplex the stream of data to produce n-data channels representing data transmitted by the transmitter, wherein one of the n-data channels is a power control bit stream responsive to the error signal, wherein n is an integer greater than zero.

4. The DC-DC converter circuit of claim 3 , further comprising a digital to analog converter configured to convert the power control bit stream to a regulation voltage for the power oscillator; and wherein the power signal transmitted by the power oscillator is based upon the regulation voltage.

5. The DC-DC converter circuit of claim 4 , further comprising an analog to digital converter configured to convert the error signal to a power control value, and a multiplexer receiving as input the power control value and data to be transmitted and to output therefrom the stream of data as the power control value and data to be transmitted in a multiplexed fashion.

6. The DC-DC converter circuit of claim 5 , further comprising:
a switch arrangement to feed a given digital value to the multiplexer under control of a timing signal based on a reference clock signal; and
a corresponding switch arrangement to feed the given digital value to a circuit arrangement performing a reset of the de-multiplexing circuit based upon occurrence of the given digital value in the stream of data, the timing signal identifying a clock training phase to synchronize the multiplexer and demultiplexer.

7. The DC-DC converter circuit of claim 6 , wherein the analog to digital converter comprises a pulse width modulation (PWM) generator generating a PWM output signal that is sampled and multiplexed with the stream of data.

8. The DC-DC converter circuit of claim 7 , wherein the digital to analog converter comprises a filter configured to extract a DC component from the PWM output signal, the DC component serving to regulate power transmitted by the power oscillator.

9. The DC-DC converter circuit of claim 1 , wherein the single isolation transformer is integrated within a dedicated stand-alone chip.

10. The DC-DC converter circuit of claim 1 , wherein the single isolation transformer is within a same chip as the power oscillator.

11. The DC-DC converter circuit of claim 1 , wherein the power oscillator comprises a cross-coupled pair of transistors.

12. The DC-DC converter circuit of claim 11 , wherein the cross-coupled pair of transistors is connected to a bias regulating circuit for regulating biasing of the cross-coupled pair of transistors, the bias regulating circuit including a bias MOSFET configured to provide a bias current for operation of the power oscillator under control of a bias voltage and a regulation MOSFET configured to adjust the bias current.

13. A DC-DC converter circuit, comprising,
a single isolation transformer having a primary winding and a secondary winding magnetically coupled to the primary winding;
a power oscillator connected to apply an oscillating signal to the primary winding of the single isolation transformer to thereby transmit a power signal to the secondary winding;
a rectifier connected to the secondary winding of the single isolation transformer and configured to obtain an output DC voltage by rectification of the power signal at the secondary winding;
comparison circuitry configured to generate an error signal representing a difference between the output DC voltage and a reference voltage value;
a transmitter connected to the secondary winding of the single isolation transformer to apply an amplitude modulation to the power signal at the secondary winding of the single isolation transformer in response to the error signal to thereby produce an amplitude modulated signal at the primary winding; and
a receiver connected to the primary winding and configured to demodulate the amplitude modulated signal to recover the error signal;
a common mode transient (CMT) rejection circuit connected between the primary winding and the receiver and configured to reduce effects of common mode transients in the amplitude modulated signal; and
a control circuit configured to control an amplitude of the oscillating signal as a function of the recovered error signal;
wherein the primary winding has a first central tap connected to a power supply on a chip containing the power oscillator; and wherein the secondary winding has a second central tap connected to a ground on a chip containing the rectifier, the first and second central taps providing a low impedance path for current injected by common mode transient (CMT) events.

14. The DC-DC converter circuit of claim 13 , further comprising a de-multiplexing circuit configured to receive a stream of data from the receiver and de-multiplex the stream of data to produce n-data channels representing data transmitted by the transmitter, wherein one of the n-data channels is a power control bit stream responsive to the error signal, wherein n is a positive, non-zero integer.

15. The DC-DC converter circuit of claim 14 , further comprising a digital to analog converter configured to convert the power control bit stream to a regulation voltage for the power oscillator; and wherein the power signal transmitted by the power oscillator is based upon the regulation voltage.

16. The DC-DC converter circuit of claim 15 , further comprising an analog to digital converter configured to convert the error signal to a power control value, and a multiplexer receiving as input the power control value and data to be transmitted and to output therefrom the stream of data as the power control value and data to be transmitted in a multiplexed fashion.

17. A method for performing an isolated DC-DC conversion, the method comprising:
transmitting a power signal from a DC-DC converter comprising a power oscillator connected to a primary winding of an isolation transformer, and implementing at least one data

Assignees

• St Microelectronics Srl

Inventors

• Parisi Alessandro
• Greco Nunzio
• Spina Nunzio
• Ragonese Egidio
• Palmisano Giuseppe

Classifications

• H02M3/337

  in push-pull configuration {(H02M3/33576 takes precedence; with self-oscillating arrangements H02M3/3382, H02M3/3385)} · CPC title

• H02M3/01

  Resonant DC/DC converters · CPC title

• H02M3/33515

  with digital control · CPC title

• H02M3/33507

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M3/33523 Primary

  with galvanic isolation between input and output of both the power stage and the feedback loop · CPC title