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Hanumolu, Pavan Kumar Hanumolu, Pavan Kumar Krein, Philip T. Shanbhag, Naresh R. Pilawa-Podgurski, Robert Kim, Seong Joong 2017-03-01T17:01:13Z 2017-03-01T17:01:13Z 2019-03-02T10:15:33Z 2016-11-09 2016-12 Time-based control techniques for the design of high switching frequency buck converters are presented. Using time as the processing variable, the proposed controller operates with CMOS-level digital-like signals but without adding any quantization error. A ring oscillator is used as an integrator in place of conventional opamp-RC or Gm-C integrators while a delay line is used to perform voltage-to-time conversion and to sum time signals. A simple flip-flop generates a pulse-width modulated signal from the time-based output of the controller. Hence time-based control eliminates the need for a wide bandwidth error amplifier, pulse width modulator (PWM) in analog controllers or high-resolution analog-to-digital converter (ADC) and digital PWM in digital controllers. As a result, it can be implemented in a small area and with minimal power. First, a time-based single-phase buck converter is proposed and fabricated in a 180nm CMOS process, the prototype buck converter occupies an active area of 0.24mm^2, of which the controller occupies only 0.0375mm^2. It operates over a wide range of switching frequencies (10-25 MHz) and regulates output to any desired voltage in the range of 0.6V to 1.5V with 1.8V input voltage. With a 500mA step in the load current, the settling time is less than 3.5us and the measured reference tracking bandwidth is about 1MHz. Better than 94% peak efficiency is achieved while consuming a quiescent current of only 2uA/MHz. Second, the techniques are extended to a high switching frequency multi-phase buck converter. Efficiency degradation due to mismatch between the phases is mitigated by generating precisely matched duty-cycles by combining a time-based multi-phase generator (MPG) with a time-based PID compensator (T-PID). The proposed approach obviates the need for a complex current sensing and calibration circuitry needed to implement active current sharing in an analog controller. It also eliminates the need for a high-resolution analog-to-digital converter and digital pulse width modulator needed for implementing passive current sharing in a digital controller. Fabricated in a 65nm CMOS process, the prototype multi-phase buck converter occupies an active area of 0.32mm^2, of which the controller occupies only 0.04mm^2. The converter operates over a wide range of switching frequencies (30-70 MHz) and regulates output to any desired voltage in the range of 0.6V to 1.5V from 1.8V input voltage. With a 400mA step in the load current, the settling time is less than 0.6us and the measured duty-cycle mismatch is less than 0.48%. Better than 87% peak efficiency is achieved while consuming a quiescent current of only 3uA/MHz. Finally, light load operation is discussed. The light load efficiency of a time-based buck converter is improved by adding proposed PFM control. At the same time, the proposed seamless transition techniques provide a freedom to change the control mode between PFM and PWM without deteriorating output voltage which allows for a system to manage its power efficiently. Fabricated in a 65nm CMOS, the prototype achieves 90% peak efficiency and > 80% efficiency over an ILOAD range of 2mA to 800mA. VO changes by less than 40mV during PWM to PFM transitions. Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-12-01 The student, Seong Joong Kim, accepted the attached license on 2016-11-08 at 17:34. The student, Seong Joong Kim, submitted this Dissertation for approval on 2016-11-08 at 17:35. This Dissertation was approved for publication on 2016-11-09 at 15:08. 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No. of bitstreams: 3 KIM-DISSERTATION-2016.pdf: 8999524 bytes, checksum: f88db28fbf6fd779a58053a484e2c954 (MD5) LICENSE.txt: 4212 bytes, checksum: d88400bc9d1b5475baef16c642a8e83c (MD5) PROQUEST_LICENSE.txt: 4558 bytes, checksum: 2af6689c4451637eb110cb32e29e6c69 (MD5) Previous issue date: 2016-11-09 Embargo set by: Seth Robbins for item 98682 Lift date: 2019-03-01T17:02:22Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Embargo set by: Seth Robbins for item 98682 Lift date: 2019-03-01T17:03:32Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Embargo set by: Seth Robbins for item 98682 Lift date: 2019-03-01T17:05:02Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Embargo set by: Seth Robbins for item 98682 Lift date: 2019-03-01T17:06:55Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Limited Restriction Lifted for Item 98682 on 2019-03-02T10:15:33Z. application/pdf http://hdl.handle.net/2142/95566 en Copyright 2016 Seong Joong Kim time-based DC-DC buck Proportional-Integral-Derivative (PID) Pulse-width modulator (PWM) Pulse frequency modulation (PFM) Time-based control techniques for integrated DC-DC conversion text text Electrical & Computer Eng Electrical & Computer Engr University of Illinois at Urbana-Champaign Dissertation Ph.D.