Single inductor, multiple output DC-DC converter
A single-inductor DC-DC converter generates two DC output voltages at two capacitors. The converter selectively transfers energy from a battery to the inductor or from the inductor to a selected capacitor. While the converter is still settling, the converter is regulated based on only the more deficient DC output voltage. After the converter has already settled, the converter is regulated based on the common-mode voltage for both DC output voltages. By regulating the still-settling converter based on only the more deficient DC output voltage, instead of the common-mode voltage, even greater deficiencies in that already more-deficient DC output voltage are avoided.
1. A single-inductor, multiple-output, DC-DC converter for generating at least two DC output voltages, wherein the converter is connectable to a DC power supply, an inductor, and different capacitors corresponding to each different DC output voltage, the converter comprising:
a switching module configured to selectively transfer energy (i) from the DC power supply to the inductor or (ii) from the inductor to a selected one of the capacitors based on switch-control signals; and
control circuitry configured to determine whether the converter is still settling or has already settled, wherein:
if the control circuitry determines that the converter is still settling, then the control circuitry generates the switch-control signals based on only a selected one of the at least two DC output voltages; and
if the control circuitry determines that the converter is already settled, then the control circuitry generates the switch-control signals based on the at least two DC output voltages,
wherein the control circuitry comprises:
a settling-detection module that determines whether the converter is still settling or has already settled;
a control module that generates the switch-control signals based on a load select signal and a duty cycle control signal;
a load-select module that generates the load select signal based on a comparison of two scaled voltage signals based respectively on the at least two DC output voltages; and
a feedback module that generates the duty cycle control signal, wherein the feedback module is configurable in (i) a still-settling mode if the settling-detection module determines that the converter is still settling and (ii) an already-settled mode if the settling-detection module determines that the converter has already settled, wherein in the still-settling mode, the feedback module generates the duty cycle control signal based on only the selected one of the at least two DC output voltages, and in the already-settled mode, the feedback module generates the duty cycle control signal based on the at least two DC output voltages.
2. The converter of claim 1 , wherein, in the still-settling mode, the feedback module generates the duty cycle control signal based on the DC output voltage that is relatively most deficient of the at least two DC output voltages.
3. The converter of claim 1 , wherein, in the already-settled mode, the feedback module generates the duty cycle control signal based on a common-mode voltage for the at least two DC output voltages.
4. The converter of claim 1 , wherein the settling-detection module determines that the converter has already settled after (i) detecting a specified number of oscillations in the duty cycle control signal and (ii) determining that each capacitor has been charged at least one time.
5. The converter of claim 1 , wherein the load-select module and the feedback module share common resistor-divider circuitry.
6. The converter of claim 1 , wherein the feedback module comprises a switched, resistor-divider network having a different resistor-divider leg for each different DC output voltage, wherein each resistor-divider leg comprises a switch that is (i) turned on to enable the feedback module to generate the duty cycle control signal based on the corresponding DC output voltage and (ii) turned off to enable the feedback module to generate the duty cycle control signal independent of the corresponding DC output voltage.
7. The converter of claim 1 , wherein the converter operates as at least one of a boost converter and a buck converter.
8. The converter of claim 7 , wherein the converter is selectively configurable to operate as either the boost converter or the buck converter.