Techniques for controlling a single-inductor multiple-output switched-mode power supply
Certain aspects of the present disclosure generally relate to methods and apparatus for operating a switched-mode power supply (SMPS). One example method generally includes selecting a first output of a plurality of outputs of the SMPS based on a power demand associated with each of the plurality of outputs if a voltage at the first output is less than a reference voltage associated with the first output, by selecting as the first output one of the plurality of outputs having the highest power demand, and based on an amount of overcharge associated with the first output if the voltage at the first output is greater than the reference voltage, by selecting as the first output one of the plurality of outputs having the lowest amount of overcharge. The method may also include directing current across an inductive element of the SMPS to the first output based on the selection.
1. A method for controlling a switched-mode power supply (SMPS), comprising:
selecting a first output of a plurality of outputs of the SMPS based on:
a power demand associated with each of the plurality of outputs if a voltage at one of the plurality of outputs is less than a reference voltage associated with the one of the plurality of outputs, by selecting as the first output the one of the plurality of outputs having the highest power demand; and
an amount of overcharge associated with each of the plurality of outputs if the voltage at the one of the plurality of outputs is greater than the reference voltage, by selecting as the first output the one of the plurality of outputs having the lowest amount of overcharge; and
directing current across an inductive element of the SMPS to the first output based on the selection.
2. The method of claim 1 , further comprising comparing a first error voltage associated with the first output with a second error voltage associated with a second output of the plurality of outputs, wherein the selection of the first output is based on the comparison.
3. The method of claim 2 , further comprising determining an error voltage difference parameter, the error voltage difference parameter representing a difference between the first error voltage and the second error voltage, wherein the selection of the first output is based on the error voltage difference parameter.
4. The method of claim 3 , wherein the determination of the error voltage difference parameter comprises applying a weight factor to the first error voltage or the second error voltage.
5. The method of claim 3 , wherein the current across the inductive element is directed to the first output when the error voltage difference parameter is less than a first hysteresis threshold, the method further comprising directing the current across the inductive element to the second output when the error voltage difference parameter is greater than a second hysteresis threshold, the second hysteresis threshold being greater than the first hysteresis threshold.
6. The method of claim 2 , wherein the first output is selected if the first error voltage associated with the first output is higher than the second error voltage associated with the second output, the voltage at the first output and a voltage at the second output being less than the reference voltage.
7. The method of claim 2 , wherein the first output is selected if the first error voltage associated with the first output is greater than the second error voltage associated with the second output, the voltage at the first output and a voltage at the second output being greater than the reference voltage.
8. The method of claim 2 , wherein:
the first error voltage comprises a difference between the reference voltage associated with the first output and the voltage at the first output; and
the second error voltage comprises a difference between a reference voltage associated with the second output and a voltage at the second output.
9. The method of claim 1 , wherein the selecting as the first output the one of the plurality of outputs having the highest power demand comprises selecting as the first output the one of the plurality of outputs having a highest current draw of the plurality of outputs.
10. The method of claim 9 , further comprising:
determining a derivative of the voltage at the first output when the current across the inductive element is not directed to the first output; and
determining the current draw of the first output based on the derivative of the voltage.
11. The method of claim 1 , wherein the power demand of the first output comprises a product of the voltage at the first output and a current draw of the first output.
12. The method of claim 1 , wherein the first output is configured to provide power to one or more circuits coupled to the first output, the method further comprising:
receiving an indication corresponding to a power demand of the one or more circuits; and
determining the power demand associated with the first output based on the indication.
13. A power supply system, comprising:
a switched-mode power supply (SMPS); and
a controller configured to:
select a first output of a plurality of outputs of the SMPS based on:
a power demand associated with each of the plurality of outputs if a voltage at one of the plurality of outputs is less than a reference voltage associated with the one of the plurality of outputs, by selecting as the first output the one of the plurality of outputs having the highest power demand and
an amount of overcharge associated with the first output if the voltage at the one of the plurality of outputs is greater than the reference voltage, by selecting as the first output the one of the plurality of outputs having the lowest amount of overcharge; and
configure the SMPS to direct current across an inductive element of the SMPS to the first output based on the selection.
14. The power supply system of claim 13 , wherein the controller is further configured to compare a first error voltage associated with the first output with a second error voltage associated with a second output of the plurality of outputs, wherein the selection of the first output is based on the comparison.
15. The power supply system of claim 14 , wherein the controller is further configured to determine an error voltage difference parameter, the error voltage difference parameter representing a difference between the first error voltage and the second error voltage, wherein the selection of the first output is based on the error voltage difference parameter.
16. The power supply system of claim 15 , wherein the determination of the error voltage difference parameter comprises applying a weight factor to the first error voltage or the second error voltage.
17. The power supply system of claim 15 , wherein the current across the inductive element is directed to the first output when the error voltage difference parameter is less than a first hysteresis threshold, the controller being further configured to configure the SMPS to direct the current across the inductive element to the second output when the error voltage difference parameter is greater than a second hysteresis threshold, the second hysteresis threshold being greater than the first hysteresis threshold.
18. The power supply system of claim 14 , wherein the first output is selected if the first error voltage associated with the first output is higher than the second error voltage associated with the second output, the voltage at the first output and a voltage at the second output being less than the reference voltage.
19. The power supply system of claim 14 , wherein the first output is selected if the first error voltage associated with the first output is greater than the second error voltage associated with the second output, the voltage at the first output and a voltage at the second output being greater than the reference voltage.
20. An apparatus for controlling a switched-mode power supply (SMPS), comprising:
means for selecting a first output of a plurality of outputs of the SMPS based on:
a power demand associated with each of the plurality of outputs if a voltage at one of the plurality of outputs is less than a reference voltage associated with the one of the plurality of outputs, by selecting as the first output the one of the plurality of outputs having the highest power demand; and
an amount of overcharge associated with the one of the plurality of outputs if the voltage at the one of the plurality of outputs is greater than the reference voltage, by selecting as the first output the one of the plurality of outputs having the lowest amount of overcharge; and
means for directing current across an inductive element of the SMPS to the first output based on the selection.