Isolated error amplifier for isolated power supplies
View Patent ↗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.
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.