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Figure 19-13: Channel Outputs Controlled Independently
Switched Reluctance Motors Application
In typical power converter configurations for switched or variable reluctance motors, motor winding is connected
between the two power switches of a given inverter leg. To allow for a complete circuit in the motor winding, turn
on both switches at the same time.
PWM uses switched reluctance motors in the following configurations: hard chop, alternate chop, soft chop—bot-
tom on, and soft chop— top on.
The Four SR Mode Types, Active High PWM Output Signals figure shows the four SR mode types as active high
PWM output signals.
Hard chop mode contains independently programmed rising edges of the high and low signals of a channel in the
same PWM half cycle. Both signals contain independently programmed falling edges in the next PWM half cycle.
The PWM_CHANCFG.POLAH and PWM_CHANCFG.POLAL bits are programmed to same values.
Alternate chop mode is similar to normal PWM operation except that the PWM channel high and low signal edges
are always opposite and are independently programmed. The PWM_CHANCFG.POLAH and
PWM_CHANCFG.POLAL bits are programmed to opposite values. The low-side invert is the only difference be-
tween hard chop mode and alternate chop mode.
Soft chop - bottom on uses a 100% duty on the low side of the channel. Soft chop - top on uses a 100% duty on the
high side of the channel. Similar to hard chop mode, PWM uses the
and the
PWM_AL0
duty register for the low channel.
ADSP-SC58x/ADSP-2158x SHARC+ Processor Hardware Reference
+PWM_TM/2
0
COUNT
PWM_CH0
PWM_AH
PWM_AL
2 × DT
PWM_SYNC_OUT
PWM_TM
PWM_PHASE
-PWM_TM/2
+PWM_TM/2
0
PWM_CH0
2 × DT
PWM_TM
duty register for the high channel
PWM_AH0
Channel Timing Control Unit
19–19
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