copyright 2011 controltrix corpwww. controltrix.com Digitally controlled power supply Perspective on Slope Compensation
copyright 2011 controltrix corpwww. controltrix.com
copyright 2011 controltrix corpwww. controltrix.com In depth analysis :
copyright 2011 controltrix corpwww. controltrix.com Expected duty: 83.3%, ripple: 1A, valley current =4A, duty max = 95%
copyright 2011 controltrix corpwww. controltrix.com
copyright 2011 controltrix corpwww. controltrix.com MeritsDe-Merits m = m 2 / 2 Behaves like average current mode control Convergence issues at higher duty ratios (~ 0.9) m = 2 * m 2 Guaranteed convergence Voltage mode control equivalent Poor dynamic line regulation m = m 2 Fastest single cycle convergence Not true current mode control. Poor dynamic line regulation
copyright 2011 controltrix corpwww. controltrix.com Analog circuit with switch or extra DSP PWM Fixed slope value (m) Wide range input and output fixed slope m is suboptimal Finding m 1, m 2 hard with inductance changes with load
copyright 2011 controltrix corpwww. controltrix.com Find intersection point of slope m1 and m in Software Defeats peak current mode control Sub harmonic oscillations still present Needs noise free ADC measurement of valley current (hard)
copyright 2011 controltrix corpwww. controltrix.com Only Software / firmware no extra hardware Few extra mips (<1us extra execution per mips / 40MHz proc) Wide input / output voltage acceptable Maintains nearly stable effective duty
copyright 2011 controltrix corpwww. controltrix.com Supports all duty ratios Reduces instability (current ripple deviation) by factor of 10X or more Higher duties more improvement factor True peak current mode control dynamics Patent pending
copyright 2011 controltrix corpwww. controltrix.com May need extra PWM channel. (Depends on DSC peripheral availability) Bounded overshoot above current limit. Periodic sub harmonics still present (smaller amplitude)
copyright 2011 controltrix corpwww. controltrix.com 4A valley expected at steady state. 5A peak (current reference). 83.3% duty. 95% max duty. 1 unit period. Figure of merit : minimum valley current.
copyright 2011 controltrix corpwww. controltrix.com Simulation Results Baseline : valley min 0.5 A (ideal 4A) Proposed : valley min 3.8 A (ideal 4A)
copyright 2011 controltrix corpwww. controltrix.com Thank You