Microchip Technology MA330012 데이터 시트
dsPIC33F
DS70165E-page 180
Preliminary
©
2007 Microchip Technology Inc.
15.6
Complementary PWM Operation
In the Complementary mode of operation, each pair of
PWM outputs is obtained by a complementary PWM
signal. A dead time may be optionally inserted during
device switching, when both outputs are inactive for a
short period (refer to Section 15.7 “Dead-Time
Generators”).
PWM outputs is obtained by a complementary PWM
signal. A dead time may be optionally inserted during
device switching, when both outputs are inactive for a
short period (refer to Section 15.7 “Dead-Time
Generators”).
In Complementary mode, the duty cycle comparison
units are assigned to the PWM outputs as follows:
units are assigned to the PWM outputs as follows:
• PDC1 register controls PWM1H/PWM1L outputs
• PDC2 register controls PWM2H/PWM2L outputs
• PDC3 register controls PWM3H/PWM3L outputs
• PDC4 register controls PWM4H/PWM4L outputs
The Complementary mode is selected for each PWM
I/O pin pair by clearing the appropriate PMODx bit in the
PWMCON1 SFR. The PWM I/O pins are set to
Complementary mode by default upon a device Reset.
I/O pin pair by clearing the appropriate PMODx bit in the
PWMCON1 SFR. The PWM I/O pins are set to
Complementary mode by default upon a device Reset.
15.7
Dead-Time Generators
Dead-time generation may be provided when any of the
PWM I/O pin pairs are operating in the Complementary
Output mode. The PWM outputs use push-pull drive cir-
cuits. Due to the inability of the power output devices to
switch instantaneously, some amount of time must be
provided between the turn-off event of one PWM output
in a complementary pair and the turn-on event of the
other transistor.
PWM I/O pin pairs are operating in the Complementary
Output mode. The PWM outputs use push-pull drive cir-
cuits. Due to the inability of the power output devices to
switch instantaneously, some amount of time must be
provided between the turn-off event of one PWM output
in a complementary pair and the turn-on event of the
other transistor.
The PWM module allows two different dead times to be
programmed. These two dead times may be used in
one of two methods, described below, to increase user
flexibility:
programmed. These two dead times may be used in
one of two methods, described below, to increase user
flexibility:
• The PWM output signals can be optimized for
different turn-off times in the high side and low
side transistors in a complementary pair of tran-
sistors. The first dead time is inserted between
the turn-off event of the lower transistor of the
complementary pair and the turn-on event of the
upper transistor. The second dead time is inserted
between the turn-off event of the upper transistor
and the turn-on event of the lower transistor.
side transistors in a complementary pair of tran-
sistors. The first dead time is inserted between
the turn-off event of the lower transistor of the
complementary pair and the turn-on event of the
upper transistor. The second dead time is inserted
between the turn-off event of the upper transistor
and the turn-on event of the lower transistor.
• The two dead times can be assigned to individual
PWM I/O pin pairs. This operating mode allows
the PWM module to drive different transistor/load
combinations with each complementary PWM I/O
pin pair.
the PWM module to drive different transistor/load
combinations with each complementary PWM I/O
pin pair.
15.7.1
DEAD-TIME GENERATORS
Each complementary output pair for the PWM module
has a 6-bit down counter that is used to produce the
dead-time insertion. As shown in Figure 15-4, each
dead-time unit has a rising and falling edge detector
connected to the duty cycle comparison output.
has a 6-bit down counter that is used to produce the
dead-time insertion. As shown in Figure 15-4, each
dead-time unit has a rising and falling edge detector
connected to the duty cycle comparison output.
FIGURE 15-4:
DEAD-TIME TIMING DIAGRAM
Duty Cycle Generator
PWMxH
PWMxL
Time Selected by DTSxA bit (A or B)
Time Selected by DTSxI bit (A or B)