The dead-band submodule has two groups of independent selection options as shown in Figure 12-2259.
- Input Source Selection: The input signals
to the dead-band module are the EPWMxA and EPWMxB output signals from the
action-qualifier. In this section they will be referred to as EPWMxA In and
EPWMxB In. Using the EPWM_DBCTL[5-4] IN_MODE control bits, the signal source
for each delay, falling-edge or rising-edge, can be selected:
- EPWMxA In is the
source for both falling-edge and rising-edge delay. This is the
default mode.
- EPWMxA In is the
source for falling-edge delay, EPWMxB In is the source for
rising-edge delay.
- EPWMxA In is the
source for rising edge delay, EPWMxB In is the source for
falling-edge delay.
- EPWMxB In is the
source for both falling-edge and rising-edge delay.
- Output Mode Control: The output mode is
configured by way of the EPWM_DBCTL[1-0] OUT_MODE bit fields. These bits
determine if the falling-edge delay, rising-edge delay, neither, or both are
applied to the input signals.
- Polarity Control: The polarity control
(EPWM_DBCTL[3-2] POLSEL) allows to be specified whether the rising-edge
delayed signal and/or the falling-edge delayed signal is to be inverted
before being sent out of the dead-band submodule.
Although all combinations
are supported, not all are typical usage modes. Table 12-4338 lists some classical dead-band configurations. These modes assume that the
EPWM_DBCTL[5-4] IN_MODE is configured such that EPWMxA In is the source for both
falling-edge and rising-edge delay. Enhanced, or non-traditional modes can be
achieved by changing the input signal source. The modes shown in Table 12-4338 fall into the following categories:
- Mode 1: Bypass both falling-edge delay (FED) and rising-edge delay (RED) Allows to be fully disabled the dead-band submodule from the PWM signal path.
- Mode 2-5: Classical Dead-Band Polarity Settings These represent typical polarity configurations that should address all the active high/low modes required by available industry power switch gate drivers. The waveforms for these typical cases are shown in Figure 12-2260. Note that to generate equivalent waveforms to Figure 12-2260, configure the action-qualifier submodule to generate the signal as shown for EPWMxA.
- Mode 6: Bypass rising-edge-delay and Mode 7: Bypass falling-edge-delay Finally the last two entries in Table 12-4338 show combinations where either the falling-edge-delay (FED) or rising-edge-delay (RED) blocks are bypassed.
Table 12-4338 Classical Dead-Band Operating ModesMode | Mode Description (1) | EPWM_DBCTL[3-2]
POLSEL | | EPWM_DBCTL[1-0]
OUT_MODE |
---|
S3 | S2 | | S1 | S0 |
---|
1 | EPWMxA and EPWMxB Passed Through (No Delay) | x | x | | 0 | 0 |
2 | Active High Complementary (AHC) | 1 | 0 | | 1 | 1 |
3 | Active Low Complementary (ALC) | 0 | 1 | | 1 | 1 |
4 | Active High (AH) | 0 | 0 | | 1 | 1 |
5 | Active Low (AL) | 1 | 1 | | 1 | 1 |
6 | EPWMxA Out = EPWMxA In (No Delay) | 0 or 1 | 0 or 1 | | 0 | 1 |
EPWMxB Out = EPWMxA In with Falling Edge Delay |
7 | EPWMxA Out = EPWMxA In with Rising Edge Delay | 0 or 1 | 0 or 1 | | 1 | 0 |
EPWMxB Out = EPWMxB In with No Delay |
(1) These are classical dead-band modes and assume that EPWM_DBCTL[5-4]
IN_MODE = 0b00. That is, EPWMxA in is the source for both the falling-edge and
rising-edge delays. Enhanced, non-traditional modes can be achieved by changing
the IN_MODE configuration.
Figure 12-2260 shows waveforms for typical cases where 0% < duty < 100%.
The dead-band submodule supports independent
values for rising-edge (RED) and falling-edge (FED) delays. The amount of delay is
programmed using the EPWM_DBRED and EPWM_DBFED registers. These are 10-bit registers
and their value represents the number of time-base clock, TBCLK, periods a signal
edge is delayed by. For example, the formulas to calculate falling-edge-delay and
rising-edge-delay are:
FED = EPWM_DBFED ×
TTBCLK
RED = EPWM_DBRED × TTBCLK
Where TTBCLK is the period of TBCLK, the prescaled version of FICLK.