DSPIC30F2023 Microchip Technology Inc., DSPIC30F2023 Datasheet - Page 140

• Manufacturer Part Number: DSPIC30F2023
• Description: 28/44-pin Dspic30f1010/202x Enhanced Flash Smps 16-bit Digital Signal Controller
• Manufacturer: Microchip Technology Inc.

dsPIC30F1010/202X
12.34.3 APPLICATION OF PUSH-PULL PWM
Push-Pull PWM mode is typically used in transformer
coupled circuits to ensure that no net DC currents flow
through the transformer. Push-Pull mode ensures that
the same duty cycle PWM pulse is applied to the
transformer windings in alternate directions, as shown
in Figure 12-24.
FIGURE 12-24:
DS70178C-page 138
PWM1H
PWM1L
+V
+V
PWH1H
PWH1L
PWM1H
+
IN
+V
IN
PWM1L
+
IN
PWM1L
PWM1H
Dead Time
MODE
PWH1L
PWH1H
T
ON
Period
APPLICATIONS OF PUSH-
PULL PWM MODE
T1
T1
T
OFF
Dead Time
Half Bridge Converter
Push-Pull Buck Converter
T1
Full Bridge Converter
T
ON
Period
L1
L1
T
Dead Time
L1
OFF
V
OUT
+
V
V
OUT
+
OUT
+
Preliminary
12.34.4 APPLICATION OF MULTI-PHASE PWM
Multi-Phase PWM mode is often used in DC/DC con-
verters that must handle very fast load current tran-
sients and fit into tight spaces. A multi-phase converter
is essentially a parallel array of buck converters that
are operated slightly out of phase of each other, as
shown in Figure 12-25. The multiple phases create an
effective switching speed equal to the sum of the indi-
vidual converters. If a single phase is operating with a
333 KHz PWM frequency, then the effective switching
frequency for the circuit is 1 MHz. This high switching
frequency greatly reduces output capacitor size
requirements and improves load transient response.
FIGURE 12-25:
PWM1H
PWM1L
PWM1H
PWM1L
PWM2H
PWM2L
PWM3H
PWM3L
+
V
IN
MODE
PWM2H
PWM1L
L1
APPLICATIONS OF MULTI-
PHASE PWM MODE
© 2006 Microchip Technology Inc.
PWM3H
PWM1L
L2
Multiphase DC/DC
L3
Converter
V
+
OUT