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An Efficient Digital Sliding Controller for Adaptive Power-Supply Regulation

This research presents an efficient digital sliding controller for adaptive power supply regulation. The controller saves power and energy by operating at lower frequencies and lowering voltage. It has applications in microprocessors, DSPs, and high-speed I/Os.

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An Efficient Digital Sliding Controller for Adaptive Power-Supply Regulation

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  1. An Efficient Digital Sliding Controller for Adaptive Power-Supply Regulation Jaeha Kim and Mark Horowitz

  2. Adaptive Power-Supply Regulation • Operating at lower frequency saves power, but not energy. a Power ~ V2f, Energy ~ V2. • Adaptive power-supply regulation saves both by lowering voltage, too. • Applications: mPs, DSPs, and high-speed I/Os. J. Kim and M. Horowitz

  3. Adaptive Power-Supply Regulator J. Kim and M. Horowitz

  4. The Controller • Switching power supplies regulate voltage. a Analog controllers • Adaptive power-supplies regulate delay. a Digital controllers • This work presents a simpler digital controller using sliding control. J. Kim and M. Horowitz

  5. Outline • Introduction • Sliding Control • Digital Implementation • Measurement Results • Conclusions J. Kim and M. Horowitz

  6. Phase Portraits J. Kim and M. Horowitz

  7. Sliding Control (1) • Control law: dV/dt + (V-Vref)/t = 0. • Effectively a first-order system with time constant t. J. Kim and M. Horowitz

  8. Sliding Control (2) J. Kim and M. Horowitz

  9. Digital Sliding Controller (1) Digital controller needs to estimate df/dt in: df/dt + (f-fref)/t = 0. • Approach 1: measure the change in f for a fixed time duration. • Approach 2: measure the elapsed time Dt for a fixed change in f, Df. afits the digital implementation better J. Kim and M. Horowitz

  10. Digital Sliding Controller (2) • The original sliding control law was: df/dt + (f-fref)/t =? 0. • Use df/dt = Df/Dt, and rearrange: Dt =? -tDf/(f-fref) = -Nt/(f-fref). • Measure Dt using a counter clocked at |f-fref|, i.e. Dt = N/|f-fref|, then: N =? Nt. J. Kim and M. Horowitz

  11. Digital Sliding Controller (3) J. Kim and M. Horowitz

  12. Sensor Implementation J. Kim and M. Horowitz

  13. Chip Prototype • 0.25-mm CMOS • Controller area: 0.7x0.5mm2. • On-chip power transistors: 4.4mm(P), 2.2mm(N). • Off-chip components: 15.2mH (L), 21.6mF (C). J. Kim and M. Horowitz

  14. Measurement Results (1) J. Kim and M. Horowitz

  15. Measurement Results (2) • Step change in fref • Step change in load current 150MHz 370MHz 150MHz 0mA 80mA 0mA J. Kim and M. Horowitz

  16. Conclusions • Sliding control is robust and fast in transients. • The reformulated control law enables simple digital implementation. • Scalability of the controller power keeps the efficiency high under low loads. • A new sensor based on a ring-oscillator further reduces the area. J. Kim and M. Horowitz

  17. Acknowledgements • David Su, Sotirios Limotyrakis, & Wonjoon Choi • Dean Liu, Stefanos Sidiropoulos, Gu-Yeon Wei, Ken Mai, & Dan Weinlader. • Behzad Razavi & Brian Brandt • National Semiconductor • Sookyung Kim J. Kim and M. Horowitz

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