Ampilfier with VCO-based ADC
View Patent ↗An amplifier includes an input circuit configured to receive an analog input signal and a feedback signal, and output an analog error signal based on the analog input signal and the feedback signal. An ADC is configured to convert the analog error signal into a digital signal in a phase domain. A digital control circuit is configured to generate a digital control signal based on the digital signal in the phase domain. An output circuit is configured to generate an amplified output signal based on the digital control signal, and a feedback circuit is configured generate the feedback signal based on the amplified output signal.
1. An amplifier, comprising:
an input circuit configured to receive an analog input signal and a feedback signal, and output an analog error signal based on the analog input signal and the feedback signal;
an analog-to-digital converter (ADC) configured to convert the analog error signal into a digital signal in a phase domain;
a digital control circuit configured to generate a digital control signal based on the digital signal in the phase domain;
an output circuit configured to generate an amplified output signal based on the digital control signal;
a feedback circuit configured to generate the feedback signal based on the amplified output signal, and
wherein the ADC includes a voltage controlled oscillator (VCO) configured to output a frequency signal based on the analog error signal.
2. The amplifier of claim 1 , wherein the digital control signal is a pulse width modulated (PWM) signal.
3. The amplifier of claim 1 , wherein the ADC includes a Delta-Sigma ADC.
4. The amplifier of claim 1 , wherein the ADC includes a phase quantizer configured to convert the frequency signal output by the VCO to a phase signal.
5. The amplifier of claim 4 , wherein the phase quantizer is configured to compare the phase signal to a reference frequency.
6. The amplifier of claim 5 , wherein the phase quantizer includes an exclusive OR (XOR) gate configured to receive the phase signal and the reference signal as inputs.
7. The amplifier of claim 1 , wherein the digital control circuit includes a digital filter configured to receive the phase signal.
8. The amplifier of claim 7 , wherein the digital filter includes a loop filter having an equivalent Laplace transfer function with at least one zero and one pole.
9. The amplifier of claim 1 , wherein the feedback circuit includes a voltage divider.
10. The amplifier of claim 9 , wherein the feedback circuit includes a filter.
11. The amplifier of claim 3 , wherein the ADC includes a digital-to-analog converter (DAC) configured to convert the digital signal in the phase domain into an analog feedback signal received by the VCO.
12. The amplifier of claim 1 , wherein the analog input signal is a differential input signal, and wherein the amplified output signal is a differential output signal.
13. The amplifier of claim 1 , wherein the VCO is configured to receive the analog error signal directly from the input circuit.
14. The amplifier of claim 1 , wherein the amplifier is a Class D amplifier.
15. A circuit, comprising:
an input circuit configured to receive an analog input signal and a feedback signal, and output an analog error signal based on the analog input signal and the feedback signal;
an analog-to-digital converter (ADC) including a voltage controlled oscillator (VCO) configured to receive the analog error signal and output a frequency signal based on the analog error signal;
a quantizer configured to receive the frequency signal and compare the frequency signal to a reference signal to output a phase signal based on the frequency signal; and
a digital control circuit configured to receive the phase signal and output a pulse width modulated (PWM) signal based on the phase signal.
16. The circuit claim 15 , further comprising an output driver configured to generate an output signal based on the PWM signal.
17. The circuit claim 15 , wherein the ADC includes a Delta-Sigma ADC, and wherein the Delta-Sigma ADC includes a digital-to-analog converter (DAC) configured to convert the phase signal into an analog feedback signal.
18. The circuit claim 15 , wherein the quantizer includes an exclusive OR (XOR) gate configured to receive the phase signal and the reference signal as inputs.
19. A method, comprising:
receiving an analog input voltage signal;
comparing the analog input signal to a feedback signal to determine an analog error signal;
converting the analog error signal into a frequency signal with a voltage controlled oscillator (VCO) based on the analog error signal;
converting the frequency signal into a phase signal, including comparing the frequency signal to a reference signal;
converting the phase signal into a digital control signal based on the phase signal; and
generating an output signal based the digital control signal.
20. The method of claim 19 , further comprising filtering the output signal to generate the feedback signal.