PIC18F-LF1XK50 MICROCHIP [Microchip Technology], PIC18F-LF1XK50 Datasheet - Page 132

• Manufacturer Part Number: PIC18F-LF1XK50
• Description: 20-Pin USB Flash Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F/LF1XK50
14.4.6
In Half-Bridge applications where all power switches
are modulated at the PWM frequency, the power
switches normally require more time to turn off than to
turn on. If both the upper and lower power switches are
switched at the same time (one turned on, and the
other turned off), both switches may be on for a short
period of time until one switch completely turns off.
During this brief interval, a very high current
(shoot-through current) will flow through both power
switches, shorting the bridge supply. To avoid this
potentially destructive shoot-through current from
flowing during switching, turning on either of the power
switches is normally delayed to allow the other switch
to completely turn off.
In Half-Bridge mode, a digitally programmable
dead-band delay is available to avoid shoot-through
current from destroying the bridge power switches. The
delay occurs at the signal transition from the non-active
state to the active state. See
illustration. The lower seven bits of the associated
PWM1CON register
period in terms of microcontroller instruction cycles
(T
FIGURE 14-15:
DS41350E-page 132
CY
Standard Half-Bridge Circuit (“Push-Pull”)
or 4 T
OSC
PROGRAMMABLE DEAD-BAND
DELAY MODE
).
(Register
EXAMPLE OF HALF-BRIDGE APPLICATIONS
14-3) sets the delay
Figure 14-14
P1A
P1B
Preliminary
for
FET
Driver
FET
Driver
FIGURE 14-14:
P1A
P1B
td = Dead-Band Delay
Note 1: At this time, the TMR2 register is equal to the
(2)
(2)
V+
V-
(1)
2: Output signals are shown as active-high.
td
Pulse Width
PR2 register.
Load
Period
td
EXAMPLE OF
HALF-BRIDGE PWM
OUTPUT
 2010 Microchip Technology Inc.
+
V
-
+
V
-
(1)
Period
(1)