PIC16F883 Microchip Technology Inc., PIC16F883 Datasheet - Page 145

• Manufacturer Part Number: PIC16F883
• Description: 28/40/44-pin Flash-based, 8-bit Cmos Microcontrollers With Nanowatt Technology
• Manufacturer: Microchip Technology Inc.

11.6.6
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 Figure 11-16 for
illustration. The lower seven bits of the associated
PWM1CON register (Register 11-4) sets the delay
period in terms of microcontroller instruction cycles
(T
FIGURE 11-17:
© 2007 Microchip Technology Inc.
CY
Standard Half-Bridge Circuit (“Push-Pull”)
or 4 T
OSC
PROGRAMMABLE DEAD-BAND
DELAY MODE
).
EXAMPLE OF HALF-BRIDGE APPLICATIONS
P1A
P1B
PIC16F882/883/884/886/887
Preliminary
FET
Driver
FET
Driver
FIGURE 11-16:
P1A
P1B
td = Dead-Band Delay
Note 1: At this time, the TMR2 register is equal to the
(2)
(2)
V+
V-
2: Output signals are shown as active-high.
(1)
Pulse Width
td
PR2 register.
Load
Period
td
EXAMPLE OF
HALF-BRIDGE PWM
OUTPUT
+
V
-
+
V
-
(1)
DS41291D-page 143
Period
(1)