SLYY205A March   2021  – October 2022 TPS562211 , TPS562212 , TPS562231 , TPS563211 , TPS563212 , TPS563231 , TPS56339

 

  1.   At a glance
  2.   Authors
  3.   What is AECM control?
  4.   PCM
  5.   D-CAP2 control scheme
  6.   AECM control benefits
  7.   How AECM control works
  8.   PWM operation mode
  9.   PFM operation mode
  10.   Smart loop-bandwidth control
  11.   Conclusion
  12.   References
  13.   Additional Resources

PFM operation mode

AECM control implements PFM mode to achieve high efficiency under light loads. With a load current decrease, the device enters into discontinuous conduction mode (DCM) from continuous conduction mode (CCM). In both modes, the switching frequency is fixed; the width of the on-pulse (Ton) depends on the load current. Lighter loads have a shorter Ton. AECM has an on-time generator like the D-CAP2 control topology, but that generator is disabled in PWM mode. With the load current further decreasing, the Ton decreases down to the internal clamped on-time, while the AECM device steps into PFM mode with the internal clock blocked and the on-time generator enabled. As shown in Figure 10, the control scheme of PFM mode issimilar to the D-CAP2 control scheme. Figure 11 on the following page shows the transition waveform between PWM mode and PFM mode.

GUID-20220324-SS0I-SS2B-9HFJ-1XXJLMNC2LH1-low.png GUID-20220324-SS0I-BTJ2-7RVK-8ZXPQ2VB3BMJ-low.png Figure 11 Duty-cycle changes with the load current: load step-up (a); load step-down (b).
Figure 12 Transition waveform between PWM mode and PFM mode of AECM: PWM mode to PFM mode (a); PFM mode to PWM mode (b).