Laboratory for LowPower Management

1
Power Stage Parameter Estimation and Digital
Controller Design for SMPS with the Use of Limit
Cycle Oscillation Zhenyu Zhao, Aleksandar
Prodic
Energy System Group University of Toronto
2

• Fast design programming flexibility in
  digitally controlled SMPS
• Controller auto-tuning

Project Introduction
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Limit-Cycle Oscillations (LCO) in SMPS

• Reason for LCO in SMPS
• Resolution mismatch of two quantizers
• analog-to-digital converter (ADC)
• digital pulse width modulator (DPWM)

4
Limit-Cycle Oscillations (LCO) in SMPS

• System parameters can be extracted from LCO
  features
• LCO Features amplitude, frequency etc.
• System parameters load, output capacitance,
  input voltage and inductance etc.
• Practical implementation
• Look-up tables

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Construction of Look-up tables from relationship
Diagram (1)
LCO Amplitude
LCO Frequency
R
C
R
C
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Experimental vs Theoretical (1)
LCO Frequency
LCO Amplitude
R
R
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Experimental results

• Output voltage during auto-tuning upon sudden
  change of output capacitance

8
Bandwidth Controlled PID Auto-tuning for SMPS

• Two test phases to meet bandwidth requirements
• Tuning PID zeros
• Tuning PID gain

9
Conclusions

• A new digital system that allows introduction of
  auto-tuning in low-power dc-dc switching
  converters is presented.
• System parameters are identified using
  information of limit cycle oscillations that is
  intentionally introduced.
• Effective auto-tuning of PID controller provides
  fast control over a large range of system
  parameters.