Datasheet

www.microchip.com/lighting LED Lighting Solutions Design Guide 9
LED Lighting Solutions
Generating PWM Control Signals
There are multiple ways to generate PWM control signals to
control power circuits.
■
Devices with the Capture-Compare-PWM (CCP) module
can generate PWM signals to control power circuits using
an on-chip digital timebase. The signal pulse width is
controlled by the MCU clock and a duty cycle register.
■
The Enhanced CCP (ECCP) module allows one PWM signal
to control 2 or 4 output pins for half-bridge or H-bridge
control, respectively.
■
Devices that have a comparator and the ECCP module
can use the comparator signal to control the turn-off time
of the PWM signal.
■
Devices with comparators and a PWM SR latch can use
comparator signals and/or clock pulses to turn the latch
output on and off.
PIC12HV615
VDD
Buck Topology
Driver
Drive
Level
-
+
VSS
VBUS
Other Device Options:
PIC12F1822
PIC16F1823
–
+
Comparator
Buck LED Driver Using a Comparator
■
An external PWM peripheral IC may be used. This option
is useful when multiple high speed PWM channels are
required.
■
PWM signals can be generated using software and I/O
pins. This option is less costly when PWM frequency and
duty cycle resolution requirements are not too high.
A PIC microcontroller with an on-chip comparator such as
the PIC12F609 can be used to implement a simple LED
driver. The PIC12HV609 adds an internal regulator, allowing
operation from a DC bus higher than 5 volts.
Literature on the Web
■
AN874 – Buck Configuration High-Power LED Driver,
DS00874
■
AN1074 – Software PWM Generation for LED Dimming
and RGB Color Applications, DS01074
R BG
PIC12HV615
ADC Input
Color Set
RGB LED
50 mA
Other Device Options:
PIC12F1822
PIC16F1827
User
Interface
V IN
RGB Color LED Application Using PIC12HV615