Isolated error amplifier for isolated power supplies

• US 9,293,997 B2
• Filed: 03/14/2013
• Issued: 03/22/2016
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Analog Devices Global Unlimited Company (Analog Devices, Inc.)
• Inventors: Chen, Baoxing, Ma, Shaoyu, Zhao, Tianting
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): DEMISSE, AFEWORK S
• Application Number:
  US13/803,833
• Publication Number:
  US 20140268917A1
• Time in Patent Office: 1,104 Days
• Field of Search: 330/9, 330/10, 330/136, 330/151, 330/188, 330/207.A, 363/13, 363/16, 363/17, 363/21.12, 363/21.15, 363/97
• US Class Current: 1/1
• CPC Class Codes: H02M 3/33515 with digital control
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A power converter may include an amplifier that generates an error signal, a modulator that generates a modulated error signal, an isolator that generates an isolated modulated error signal, and a demodulator that generates an isolated error signal, which may be substantially proportional to the difference between the output signal and the reference signal, and a controller that controls a power stage to generate the output signal of the power converter.

Claims

1. A power converter, comprising:

an amplifier, based on an output signal of the power converter and a reference signal, generating an analog error signal;

a modulator, based on the analog error signal, generating a digital modulated error signal;

an isolator, based on the digital modulated error signal, generating a digital isolated modulated error signal;

a demodulator, based on the digital isolated modulated error signal, generating an analog isolated error signal; and

a controller, based on the analog isolated error signal, controlling a power stage to generate the output signal of the power converter,

wherein a gain in generating the analog isolated error signal from the analog error signal is set by a ratio between a first reference signal generated by the modulator and a second reference signal generated by the demodulator.

2. The power converter according to claim 1, wherein the isolator comprises a primary coil receiving the digital modulated error signal and a secondary coil generating the digital isolated modulated error signal.

3. The power converter according to claim 2, wherein the primary coil is coupled to the secondary coil in an induction coupling configuration.

4. The power converter according to claim 1, wherein the controller comprises an error comparator that controls the power stage based on the digital isolated error signal.

5. The power converter according to claim 1, wherein the controller controls the power stage via a control signal having one of pulse width modulation and pulse density modulation.

6. The power converter according to claim 1, wherein:

the modulator includes a first operational amplifier connected to a first resistor;

the demodulator includes a second operational amplifier connected to a second resistor; and

the gain is further set by a ratio between the first resistor and the second resistor.

7. The power converter according to claim 6, wherein the first operational amplifier is connected in a negative feedback path to a first digital-to-analog converter, and wherein the first reference signal is a reference current applied to the first digital-to-analog converter.

8. An isolated error amplifier, comprising:

an amplifier, based on an output signal of a power converter and a reference signal, generating an analog error signal;

a modulator, based on the analog error signal, generating a digital modulated error signal;

an isolator, based on the digital modulated error signal, generating a digital isolated modulated error signal; and

a demodulator, based on the digital isolated modulated error signal, generating an analog isolated error signal, that is substantially proportional to the difference between the output signal and the reference signal,

wherein a gain in generating the analog isolated error signal from the analog error signal is set by a ratio between a first reference signal generated by the modulator and a second reference signal generated by the demodulator.

9. The isolated error amplifier according to claim 8, wherein the isolator comprises a primary coil receiving the digital modulated error signal and a secondary coil generating the digital isolated modulated error signal.

10. The isolated error amplifier according to claim 9, wherein the primary coil is coupled to the secondary coil in an induction coupling configuration.

11. The isolated error amplifier according to claim 8, wherein the amplifier comprises a wide band amplifier.

12. A linear isolator, comprising:

a modulator, based on an analog input signal, generating a digital modulated input signal;

an isolator, passing the digital modulated input signal across an isolation barrier to generate a digital isolated modulated input signal; and

a demodulator, based on the digital isolated modulated input signal, generating an analog isolated output signal, that is substantially proportional to the analog input signal,

wherein the linear isolator has a gain, that is a ratio of the analog isolated output signal and the analog input signal, and

wherein the gain of the linear isolator is set by a ratio between a first reference signal generated by the modulator and a second reference signal generated by the demodulator.

13. A method, comprising:

generating, by an amplifier, an analog error signal based on an output signal of the power converter and a first reference signal;

generating, by a modulator, a digital modulated error signal based on the analog error signal;

generating, by an isolator, a digital isolated modulated error signal based on the digital modulated error signal;

generating, by a demodulator, an analog isolated error signal based on the digital isolated modulated error signal; and

controlling, by a controller, a power stage based on the analog isolated error signal, to generate the output signal of the power converter,

wherein a gain in generating the analog isolated error signal from the analog error signal is set by a ratio between a second reference signal generated by the modulator and a third reference signal generated by the demodulator.

14. The method according to claim 13, wherein the modulator modulates via one of amplitude modulation, frequency modulation, pulse width modulation, and pulse density modulation.

15. The method according to claim 13, wherein the demodulator demodulates via one of amplitude demodulation, frequency demodulation, pulse width demodulation, and pulse density demodulation.

16. The method according to claim 13, wherein the isolator comprises a primary coil receiving the digital modulated error signal and a secondary coil generating the digital isolated modulated error signal.

17. The method according to claim 16, wherein the primary coil is coupled to the secondary coil in an induction coupling configuration.

18. The method according to claim 13, wherein the controller comprises an error comparator that controls the power stage based on the isolated error signal.

19. The method according to claim 13, wherein:

the modulator includes a first operational amplifier connected to a first resistor;

the demodulator includes a second operational amplifier connected to a second resistor; and

the gain is further set by a ratio between the first resistor and the second resistor.

20. The method according to claim 19, wherein the first operational amplifier is connected in a negative feedback path to a first digital-to-analog converter, and wherein the first reference signal is a reference current applied to the first digital-to-analog converter.