Pre-filtering in a power supply control circuit
A hybrid power supply circuit includes a digital circuit, a digital-to-analog converter circuit, and an analog compensator circuit (analog control circuit). According to one configuration, the digital circuit includes a digital pre-filter that substantially matches settings of analog filter circuitry present in the analog compensator circuit. During operation, the digital circuit receives control input indicating how to control a magnitude of an output voltage produced by the power supply circuit. The digital circuit passes the received through the digital pre-filter to produce a (filtered) digital reference voltage. The digital-to-analog converter circuit converts the received digital reference voltage into an analog reference voltage (a filtered rendition of the received control input). The analog compensator circuit receives and uses the digitally pre-filtered analog reference voltage as a basis to control the magnitude of the output voltage produced by the power supply circuit.
1. A hybrid switching power supply circuit comprising:
a digital circuit, the digital circuit operable to pass received command signal through a digital pre-filter to produce a digital reference voltage, the digital pre-filter substantially matching analog filter circuitry in an analog control circuit;
a digital-to-analog converter circuit to convert the digital reference voltage into an analog reference voltage; and
the analog control circuit operable to control generation of an output voltage of the hybrid switching power supply circuit based on the analog reference voltage and feedback of the output voltage through the analog filter circuitry.
2. The hybrid switching power supply circuit as in claim 1 , wherein the received command signal indicates a setting in which to control a magnitude of the output voltage, the digital pre-filter filtering the command signal in a substantially similar manner that the analog filter circuitry filters the feedback of the output voltage.
3. The hybrid switching power supply circuit as in claim 1 , wherein the analog filter circuitry resides in an analog control loop of the hybrid switching power supply circuit.
4. The hybrid switching power supply circuit as in claim 1 , wherein the analog control circuit includes:
an amplifier, the amplifier having an inverting input and a non-inverting input, the amplifier operable to produce a command signal that controls switching of power supply switches that generate the output voltage through an inductor.
5. The hybrid switching power supply circuit as in claim 4 , wherein the non-inverting input of the amplifier receives the analog reference voltage from the digital-to-analog converter circuit; and
wherein the inverting input of the amplifier receives the feedback of the output voltage through the analog filter circuitry.
6. The hybrid switching power supply circuit as in claim 1 , wherein the digital pre-filter is a reduced order filter in comparison to an order of the analog filter circuitry, the digital pre-filter representing an approximation of the analog filter circuitry.
7. The hybrid switching power supply circuit as in claim 1 , wherein filtering of the command signal using the digital pre-filter reduces overshoot and undershoot transients on the output voltage during respective conditions in which a magnitude of the command signal varies over time.
8. The hybrid switching power supply circuit as in claim 1 further comprising:
a configurable register, the configurable register storing attributes of the digital pre-filter, the digital circuit including a processor to access the configurable register to implement the digital pre-filter.
9. The hybrid switching power supply circuit as in claim 1 , wherein the digital pre-filter is of a same order as and substantially matches the analog filter circuitry.
10. The hybrid switching power supply circuit as in claim 1 further comprising:
a control switch;
a synchronous switch; and
a pulse width modulator resource, the pulse width modulator resource producing a pulse width control signal based on a control signal produced by the analog control circuit, the pulse width control signal controlling switching of the control switch and the synchronous switch between ON states and OFF states to produce the output voltage in accordance with a magnitude as specified by the digital reference voltage.
11. The hybrid switching power supply circuit as in claim 1 , wherein a voltage magnitude as specified by the received command signal varies over time.
12. The hybrid switching power supply circuit as in claim 1 , wherein the analog control circuit includes compare circuitry to compare the output voltage to the analog reference voltage.
13. The hybrid switching power supply circuit as in claim 1 , wherein the received command signal indicates settings in which to control a magnitude of the output voltage which varies over time, the digital pre-filter providing substantially similar filter attributes as those of the analog filter circuitry; and
the hybrid switching power supply circuit further comprising:
a control switch;
a synchronous switch; and
a pulse width modulator resource, the pulse width modulator resource operable to produce a pulse width control signal based on a control signal produced by the analog control circuit, the pulse width control signal controlling switching of the control switch and the synchronous switch between ON states and OFF states to produce the output voltage in accordance with a magnitude as specified by the digital reference voltage.
14. A method comprising:
receiving a command signal;
passing the command signal through a digital pre-filter to convert the received command signal into a digital reference voltage, filter settings of the digital pre-filter substantially matching filter settings of an analog filter circuitry of an analog control circuit;
converting the digital reference voltage into an analog reference voltage; and
controlling generation of an output voltage based on the analog reference voltage and feedback of the output voltage through the analog filter circuitry.
15. The method as in claim 14 , wherein controlling generation of the output voltage based on the analog reference voltage and the feedback of the output voltage through the analog filter circuitry includes:
amplifying a difference between the output voltage received on the feedback path through the analog filter circuitry and the analog reference voltage.
16. The method as in claim 15 , wherein amplifying the difference includes:
receiving the feedback of the output voltage through the analog filter circuitry on an inverting input of an amplifier;
receiving the digital reference voltage on a non-inverting input of the amplifier; and
outputting an output signal from the amplifier, the output signal controlling settings of switches in a power supply circuit to produce the output voltage at a desired magnitude as specified by the received command signal.
17. The method as in claim 14 , wherein the command signal indicates a setting in which to control a magnitude of the output voltage, the digital pre-filter filtering the command signal in a substantially similar manner that the analog filter circuitry filters the feedback of the output voltage.
18. The method as in claim 14 , wherein filtering of the command signal using the digital pre-filter reduces an overshoot/undershoot of the output voltage during conditions in which a magnitude of the command signal varies over time.
19. The method as in claim 14 further comprising:
storing attributes of the digital pre-filter in a register; and
accessing the register to implement the digital pre-filter.
20. The method as in claim 19 , wherein the digital pre-filter is of a same filter order as the analog filter circuitry.
21. The method as in claim 14 , wherein the digital pre-filter is a reduced order filter in comparison to an order of the analog filter circuitry.
22. The method as in claim 14 , wherein controlling generation of the output voltage based on a combination of the analog reference voltage and the feedback of the output voltage through the analog filter circuitry includes:
producing an output signal, the output signal controlling switching of a control switch and a synchronous switch between ON states and OFF states to produce the output voltage in accordance with a magnitude as specified by the digitally pre-filtered analog reference voltage.
23. Computer-readable storage hardware having instructions stored thereon, the instructions, when carried out by computer processor hardware, causes the computer processor hardware to perform operations of:
receiving a command signal;
implementing a digital pre-filter to convert the received command signal into a digital reference voltage, attributes of the digital pre-filter substantially matching filter attributes of an analog filter circuitry in a feedback path of an analog power supply control circuit; and
outputting the digital reference voltage to a digital-to-analog converter circuit that converts the digital reference voltage into an analog reference voltage, the analog reference voltage inputted to the analog power supply control circuit to control generation of an output voltage.