Power delivery system having cascaded buck stages
A power delivery system for a microprocessor or other ASIC. The power delivery system includes a plurality of cascaded buck stages connected in series, wherein a last buck stage in the plurality of cascaded buck stages provides an output voltage V o in response to an input voltage V in applied to a first buck stage of the plurality of cascaded stages. A duty cycle control regulates a duty cycle of each buck stage to maintain the output voltage V o . The duty cycle control sets the duty cycle of the first buck stage of the plurality of cascaded buck stages to 1 if an input-to-output voltage ratio (V in /V o ) is lower than a threshold input-to-output voltage ratio R T .
1. A power delivery system, comprising:
a plurality of cascaded buck stages connected in series, wherein a last buck stage in the plurality of cascaded buck stages provides an output voltage V o in response to an input voltage V in applied to a first buck stage of the plurality of cascaded stages; and
a duty cycle control for controlling a duty cycle of each buck stage to maintain the output voltage V o , wherein the duty cycle control sets the duty cycle of the first buck stage of the plurality of cascaded buck stages to 1 if an input-to-output voltage ratio (V in /V o ) is lower than a threshold input-to-output voltage ratio R T .
2. The power delivery system of claim 1 , wherein each of the plurality of cascaded buck stages comprises one or more interleaved synchronous buck channels arranged in parallel.
3. The power delivery system of claim 2 , wherein each buck channel includes first and second switches SW 1 , SW 2 , and wherein the first switch SW 1 of the first buck stage is always on and the second switch SW 2 is always off when the duty cycle of the first buck stage is set to 1 by the duty cycle control.
4. The power delivery system of claim 1 , wherein the first buck stage operates as an input filter when the duty cycle of the first buck stage is set to 1 by the duty cycle control.
5. The power delivery system of claim 1 , wherein the duty cycle control sets the duty cycle of the first buck stage to a value less than 1 if the input-to-output voltage ratio (V in /V o ) is higher than the threshold input-to-output voltage ratio R T .
6. The power delivery system of claim 1 , wherein two cascaded buck stages are connected in series.
7. The power delivery system of claim 1 , wherein the input voltage V in comprises a bus voltage of about 12 V or a battery voltage of 6-24 V, and the output voltage V o is a voltage of 0.x-1.x V.
8. The power delivery system of claim 1 , wherein the system is operated at a switching frequency of at least one MHz.
9. A method for power delivery, comprising:
connecting a plurality of cascaded buck stages in series, wherein a last buck stage in the plurality of cascaded buck stages provides an output voltage V o in response to an input voltage V in applied to a first buck stage of the plurality of cascaded stages; and
controlling a duty cycle of each buck stage to maintain the output voltage V o , wherein the duty cycle of the first buck stage of the plurality of cascaded buck stages is set to 1 if an input-to-output voltage ratio (V in /V o ) is lower than a threshold input-to-output voltage ratio R T .
10. The power delivery method of claim 9 , wherein each of the plurality of cascaded buck stages comprises one or more interleaved synchronous buck channels arranged in parallel.
11. The power delivery method of claim 10 , wherein each buck channel includes first and second switches SW 1 , SW 2 , and wherein the first switch SW 1 of the first buck stage is always on and the second switch SW 2 is always off when the duty cycle of the first buck stage is set to 1.
12. The power delivery method of claim 9 , wherein the first buck stage operates as an input filter when the duty cycle of the first buck stage is set to 1.
13. The power delivery method of claim 9 , wherein the duty cycle of the first buck stage is set to a value less than 1 if the input-to-output voltage ratio (V in /V o ) is higher than the threshold input-to-output voltage ratio R T .
14. The power delivery method of claim 9 , wherein two cascaded buck stages are connected in series.
15. The power delivery method of claim 9 , wherein the input voltage V in comprises a bus voltage of about 12 V or a battery voltage of 6-24 V, and the output voltage V o is a voltage of 0.x-1.x V.
16. The power delivery method of claim 9 , further comprising:
operating the system at a switching frequency of at least one MHz.
17. A quasi-single-stage power delivery system, comprising:
first and second cascaded buck stages connected in series, wherein the second buck stage provides an output voltage V o in response to an input voltage V in applied to the first buck stage; and
a duty cycle control for controlling duty cycles of the first and second buck stages to maintain the output voltage V o , wherein the duty cycle of the first buck stage is set to 1 if an input-to-output voltage ratio (V in /V o ) is lower than a threshold input-to-output voltage ratio R T , and wherein the duty cycle of the first buck stage is set to a value less than 1 if the input-to-output voltage ratio (V in /V o ) is higher than the threshold input-to-output voltage ratio R T .
18. The quasi-single-stage power delivery system of claim 17 , wherein the first and second buck stages each comprise one or more interleaved synchronous buck channels arranged in parallel.
19. The quasi-single-stage power delivery system of claim 18 , wherein each buck channel includes first and second switches SW 1 , SW 2 , and wherein the first switch SW 1 of the first buck stage is always on and the second switch SW 2 of the first buck stage is always off when the duty cycle of the first buck stage is set to 1 by the duty cycle control.
20. The quasi-single-stage power delivery system of claim 17 , wherein the first buck stage operates as an input filter when the duty cycle of the first buck stage is set to 1 by the duty cycle control.