User manual

PSMC Designer User’s Guide
DS40001671B-page 30  2012-2013 Microchip Technology Inc.
2.19.11 ECCPF: ECC PWM Full-Bridge Mode, Forward Direction
ECC compatible PWM mode, forward direction, is selected by clicking on the ECCPF
tab as shown in Figure 2-19. This mode is a full-bridge driver with two of four outputs,
Channels B and C, active. The Channel B output is the PWM drive and the Channel C
output is true without Pulse-Width Modulation. This mode is intended to drive the high
side and low side of opposite sides of an H-bridge power device configuration. Such
configurations are used in brushed DC motor applications that need speed and
direction control. This mode is compatible with the Full-Bridge mode of the ECCP
peripheral.
The mode can be changed to the reverse direction mode by clicking on the direction
switch or clicking on the ECCPR tab.
When the motor is running and the direction is changed, then the change is
synchronized with the period event and dead-band time is inserted to prevent
shoot-through on either side of the H-bridge. Click on either dead-band block to open
the corresponding dead-band control. See Section 2.19.1 “Dead-Band Control” for
more information.
FIGURE 2-19: ECC PWM FULL-BRIDGE FORWARD
2.19.12 FDC: Fixed Duty Cycle Mode
Fixed Duty Cycle mode is selected by clicking on the FDC tab as shown in Figure 2-20.
The Fixed Duty Cycle mode is used to generate frequencies with a much higher
resolution than is possible with the period count alone. This mode provides only 50%
duty cycle waveforms and should be used only with synchronous period time
generation. This mode is generally used in fluorescent lamp ballast controls. Course
frequency is determined with the period count (see synchronous period control).