Dpwm Resonant Mode - Texas Instruments UCD3138 Technical Reference Manual

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Event 2 and Event 4 are not relevant in Multi mode.
As shown in the illustration, DPWMA is designed to turn on close to the start of the period. It can turn off
any time until the end of the period, achieving essentially 100% on-time. DPWMB is designed to start later
in the period to support a multi-phase system. Therefore DPWMB is designed to cross over the period
boundary safely, so long as it does not ever move into or out of an event update window. This makes
100% pulse width operation possible for DPWMB as well.
Since the rising edge on DPWMB is also fixed, Blanking B Begin and End can be used for blanking this
rising edge. In this mode, Blanking A works only on the falling edge of A, and Blanking B works only on
the falling edge of B.
And, of course, Cycle Adjust B is usable on DPWM B.
There is no restriction preventing the two signals from overlapping each other. The diagram shows the two
signals 180 degrees out of phase, but this is not required. They could be 90 degrees, 60 degrees or
whatever offset is desired.
2.6

DPWM Resonant Mode

The resonant mode operation depends on the status of the RESON_DEADTIME_COMP_EN bit. Setting
the RESON_DEADTIME_COMP_EN bit provides for a symmetrical waveform where DPWMA and
DPWMB have the same pulse width. As the switching frequency changes, the dead times between the
pulses remain the same. This mode is ideal for the LLC topology.
Clearing the RESON_DEADTIME_COMP_EN bit provides a mode where the pulse widths are the same
and the duty cycle percentage is constant as the period changes. This means that as the frequency
increases, the dead times shrink proportionally.
The equations for this mode are designed for a smooth transition from PWM mode to Resonant mode, as
described in Section
SNIU028A – February 2016 – Revised April 2016
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2.10.1. Here is a diagram of this mode:
Copyright © 2016, Texas Instruments Incorporated
DPWM Resonant Mode
Digital Pulse Width Modulator (DPWM)
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