Bandwidth control in PLL-based power converter
A phase-locked loop (PLL)-based power converter is disclosed. A power converter includes a switch circuit having a switch node coupled to a regulated power supply node via an inductor and configured to source a supply current to the regulated power supply node using one or more control signals. A control circuit performs a phase-frequency comparison of a reference clock signal and a switching frequency of the switch circuit and generate a control voltage using results of the phase-frequency comparison. The control circuit further generates a control current using the control voltage, a voltage of the regulated power supply node, and a duty cycle of the switch circuit, and a demand current using the voltage level of the regulated power supply node and a reference voltage. Using the demand current, the control current, and a sensed version of the supply current, the control circuit generates the one or more control signals.
1 . An apparatus, comprising:
a switch circuit including a switch node coupled to a regulated power supply node via an inductor, wherein the switch circuit is configured to source a supply current to the regulated power supply node using one or more control signals; and
a control circuit configured to:
perform a phase-frequency comparison of a reference clock signal and a switching frequency of the switch circuit;
generate a control voltage using results of the phase-frequency comparison;
generate a control current using the control voltage, a voltage level of the regulated power supply node, and a duty cycle of the switch circuit;
generate a demand current using the voltage level of the regulated power supply node and a reference voltage; and
generate the one or more control signals using the demand current, the control current, and a sensed version of the supply current, wherein the control circuit includes a charge pump and the charge pump includes a sampling circuit configured to sample the voltage level of the regulated power supply node in accordance with the switching frequency of the switch circuit.
2 . The apparatus of claim 1 , wherein the sampling circuit is configured to:
generate a sampling voltage across a first capacitor based on the voltage level of the regulated power supply node during a first portion of a switching cycle;
transfer the sampling voltage to a second capacitor during a second portion of the switching cycle; and
provide the sampling voltage from the second capacitor to a transconductance amplifier to generate a charge pump current.
3 . The apparatus of claim 2 , wherein the sampling circuit is further configured to discharge the sampling voltage from the first capacitor at an end of the switching cycle.
4 . The apparatus of claim 1 , further comprising a phase-frequency detector configured to generate either a first signal or a second signal depending on results of the phase-frequency comparison, wherein the charge pump is configured to generate the control voltage using the first signal or the second signal and a charge pump current.
5 . The apparatus of claim 1 , further comprising a transconductance amplifier configured to convert the control voltage into the control current.
6 . The apparatus of claim 1 , further comprising a comparator configured to generate the demand current based on a comparison of the voltage level of the regulated power supply node and the reference voltage.
7 . The apparatus of claim 1 , further comprising:
a first comparator configured to control a high side switch of the switch circuit based on a comparison of a first sense current from the high side switch to a sum of the demand current and the control current, wherein the high side switch is coupled between an input voltage node and the switch node; and
a second comparator configured to control a low side switch of the switch circuit based on a comparison of a second sense current from the low side switch and the sum of the demand current and the control current, wherein the low side switch is coupled between a ground node and the switch node.
8 . The apparatus of claim 1 , wherein a transfer function of the control circuit is independent of a variation in the voltage level of the regulated power supply node.
9 . A method comprising:
sourcing, from a switch circuit, a supply current to a regulated power supply node, via an inductor, using one or more control signals;
performing, in a control circuit, a phase-frequency comparison of a reference clock signal and a switching frequency of the switch circuit;
generating a control voltage using results of the phase-frequency comparison, wherein generating the control voltage includes sampling, in a sampling circuit of a charge pump, a voltage level of the regulated power supply node in accordance with the switching frequency of the switch circuit;
generating a control current using the control voltage, the voltage level of the regulated power supply node, and a duty cycle of the switch circuit;
generating a demand current using the voltage level of the regulated power supply node and a reference voltage; and
generating the one or more control signals using the demand current, the control current, and at least one sensed version of the supply current.
10 . The method of claim 9 , wherein generating the control voltage further includes:
generating, in a sampling circuit, a sampling voltage across a first capacitor based on the voltage level of the regulated power supply node during a first portion of a switching cycle;
transferring the sampling voltage to a second capacitor during a second portion of the switching cycle;
generating a charge pump current by providing the sampling voltage from the second capacitor to an input of a transconductance amplifier; and
generating the control voltage in the charge pump using the charge pump current and one or more signals generated in response to the phase-frequency comparison of the reference clock signal and the switching frequency of the switch circuit.
11 . The method of claim 9 , wherein generating the demand current comprises comparing, in a comparator, the reference voltage and the voltage level of the regulated power supply node.
12 . The method of claim 9 , wherein generating the one or more control signals includes:
generating a first control signal to control a high side switch, wherein generating the first control signal comprises comparing a first sense current to a sum of the control current and the demand current; and
generating a second control signal to control a low side switch, wherein generating the second control signal, comprises comparing a second sense current to the sum of the control current and the demand current.
13 . The method of claim 9 , further comprising a transconductance amplifier receiving the control voltage and generating the control current based on the control voltage.
14 . An apparatus, comprising:
a load circuit; and
a power converter circuit coupled to the load circuit and configured to provide a regulated supply voltage to the load circuit, wherein the power converter circuit comprises:
a switch circuit including a switch node coupled to a regulated power supply node via an inductor, wherein the switch circuit is configured to source a supply current to the regulated power supply node using one or more control signals; and
a control circuit configured to:
perform a phase-frequency comparison of a reference clock signal and a switching frequency of the switch circuit;
generate a control voltage using results of the phase-frequency comparison;
generate a control current using the control voltage, a voltage level of the regulated power supply node, and a duty cycle of the switch circuit;
generate a demand current using the voltage level of the regulated power supply node and a reference voltage; and
generate the one or more control signals using the demand current, the control current, and a sensed version of the supply current, wherein the control circuit includes a charge pump and the charge pump includes a sampling circuit configured to sample the voltage level of the regulated power supply node in accordance with the switching frequency of the switch circuit.
15 . The apparatus of claim 14 , wherein the load circuit includes a system-on-a-chip (SOC), a memory coupled to the SOC, and a peripheral device coupled to the SOC and to the memory.
16 . The apparatus of claim 14 , wherein the charge pump is configured to generate the control voltage using a charge pump current and the voltage level of the regulated power supply node.
17 . The apparatus of claim 14 , further comprising a comparator configured to generate the demand current based on a comparison of the voltage level of the regulated power supply node and the reference voltage.
18 . The apparatus of claim 14 , further comprising:
a first comparator configured to control a high side switch of the switch circuit based on a comparison of a first sense current from the high side switch to a sum of the demand current and the control current, wherein the high side switch is coupled between an input voltage node and the switch node; and
a second comparator configured to control a low side switch of the switch circuit based on a comparison of a second sense current from the low side switch and the sum of the demand current and the control current, wherein the low side switch is coupled between a ground node and the switch node.