UCD3138 datasheet(54/99 Pages) TI2

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9.6.5 Triangular Mode

Triangular mode provides a stable phase shift in interleaved PFC and similar topologies. In this case, the PWM

pulse is centered in the middle of the period, rather than starting at one end or the other. In Triangular Mode,

only DPWM-B is available. Here is a diagram for Triangular Mode:

Start of Period

Period Counter

Start of Period

Period

Sample Trigger 1

DPWM Output A

Filter Duty/2 (High Resolution)

Period/2

DPWM Output B

Blanking A Begin

Blanking A End

Blanking B Begin

Blanking B End

Phase Trigger

Sample Trigger 2

To Other

Modules

To Other

Modules

Triangular Mode Closed Loop

Events which change with DPWM mode:

DPWM A Rising Edge = None

DPWM A Falling Edge = None

Adaptive Sample Trigger = None

DPWM B Rising Edge = Period/2 - Filter Duty/2 + Cycle Adjust A

DPWM B Falling Edge = Period/2 + Filter Duty/2 + Cycle Adjust B

Phase Trigger = Phase Trigger Register value or Filter Duty

Events always set by their registers, regardless of mode:

Sample Trigger 1, Sample Trigger 2, Blanking A Begin , Blanking A End , Blanking B

Begin, Blanking B End

Filter controlled edge

Cycle Adjust A (High Resolution)

Cycle Adjust B (High Resolution)

Figure 9-21. Triangular Mode Closed Loop

All edges are dynamic in triangular mode, so fixed blanking is not that useful. The adaptive sample trigger is not

needed. It is very easy to put a fixed sample trigger exactly in the center of the FET on-time, because the center

of the on-time does not move in this mode.

UCD3138

SLUSAP2J – MARCH 2012 – REVISED NOVEMBER 2021

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