
2006 Microchip Technology Inc.
Preliminary
DS70178C-page 107
dsPIC30F1010/202X
12.0
POWER SUPPLY PWM
The Power Supply PWM (PS PWM) module on the
dsPIC30F1010/202X device supports a wide variety of
PWM modes and output formats. This PWM module is
ideal for power conversion applications such as:
DC/DC converters
AC/DC power supplies
Uninterruptable Power Supply (UPS)
12.1
Features Overview
The PS PWM module incorporates these features:
Four PWM generators with eight I/O
Four Independent time bases
Duty cycle resolution of 1.1 nsec @ 30 MIPS
Dead-time resolution of 4.2 nsec @ 30 MIPS
Phase-shift resolution of 4.2 nsec @ 30 MIPS
Frequency resolution of 8.4 nsec @ 30 MIPS
Supported PWM modes:
- Standard Edge-Aligned PWM
- Complementary PWM
- Push-Pull PWM
- Multi-Phase PWM
- Variable Phase PWM
- Fixed Off-Time PWM
- Current Reset PWM
- Current-Limit PWM
- Independent Time Base PWM
On-the-Fly changes to:
- PWM frequency
- PWM duty cycle
- PWM phase shift
Output override control
Independent current-limit and Fault inputs
Special event comparator for scheduling other
peripheral events
Each PWM generator has comparator for
triggering ADC conversions.
module hardware is partitioned for each PWM output
pair for the Complementary PWM mode. Each func-
tional unit of the PWM module is discussed in
subsequent sections.
The PWM module contains four PWM generators. The
module has eight PWM output pins: PWM1H, PWM1L,
PWM2H, PWM2L, PWM3H, PWM3L, PWM4H and
PWM4L. For complementary outputs, these eight I/O
pins are grouped into H/L pairs.
12.2
Description
The PWM module is designed for applications that
require (a) high resolution at high PWM frequencies,
(b) the ability to drive standard push-pull or half bridge
converters or (c) the ability to create multi-phase PWM
outputs.
Two common, medium-power converter topologies are
Push-Pull and Half-Bridge. These designs require the
PWM output signal to be switched between alternate
pins, as provided by the Push-Pull PWM mode.
Phase-shifted PWM describes the situation where
each PWM generator provides outputs, but the phase
relationship between the generator outputs is
specifiable and changeable.
Multi-Phase PWM is often used to improve DC-DC
converter load transient response, and reduce the size
of output filter capacitors and inductors. Multiple DC/
DC converters are often operated in parallel but phase
shifted in time. A single PWM output operating at 250
KHz has a period of 4 sec. But an array of four PWM
channels, staggered by 1 sec each, yields an effective
switching frequency of 1 MHz. Multi-phase PWM appli-
cations typically use a fixed-phase relationship.
Variable Phase PWM is useful in Zero Voltage Transi-
tion (ZVT) power converters. Here the PWM duty cycle
is always 50%, and the power flow is controlled by
varying the relative phase shift between the two PWM
generators.
Note: The PLL must be enabled for the PS PWM
module to function. This is achieved by using the
FNOSC<1:0> bits in the FOSCSEL Configuration
register.