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An Efficient Digital Sliding Controller for Adaptive Power-Supply Regulation : An Efficient Digital Sliding Controller for Adaptive Power-Supply Regulation Jaeha Kim and Mark Horowitz
Adaptive Power-Supply Regulation : 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.
Adaptive Power-Supply Regulator : Adaptive Power-Supply Regulator
The Controller : 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.
Outline : Outline Introduction
Sliding Control
Digital Implementation
Measurement Results
Conclusions
Phase Portraits : Phase Portraits
Sliding Control (1) : Sliding Control (1) Control law:
dV/dt +
(V-Vref)/t = 0.
Effectively a first-order system with time constant t.
Sliding Control (2) : Sliding Control (2)
Digital Sliding Controller (1) : 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
Digital Sliding Controller (2) : 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.
Digital Sliding Controller (3) : Digital Sliding Controller (3)
Sensor Implementation : Sensor Implementation
Chip Prototype : 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).
Measurement Results (1) : Measurement Results (1)
Measurement Results (2) : Measurement Results (2) 0mA 0mA 80mA Step change in fref
Step change in load current 370MHz 150MHz 150MHz
Conclusions : 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.
Acknowledgements : 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
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