Microchip Technology APGRD004 数据表
4
LED Lighting Solutions Design Guide
www.microchip.com/lighting
LED Lighting Solutions
Driving LEDs with a Boost Regulator
A boost regulator topology is used when the output voltage
of the converter must be equal to or greater than the input
voltage. A boost regulator is useful for driving a chain of
LEDs connected in series. It is beneficial to drive multiple
LEDs in series. This ensures that all LEDs receive the same
amount of current and will have the same brightness level.
Using a coupled inductor in the boost circuit reducing the
switching voltage requirements of the MOSFET switch.
of the converter must be equal to or greater than the input
voltage. A boost regulator is useful for driving a chain of
LEDs connected in series. It is beneficial to drive multiple
LEDs in series. This ensures that all LEDs receive the same
amount of current and will have the same brightness level.
Using a coupled inductor in the boost circuit reducing the
switching voltage requirements of the MOSFET switch.
The MCP1640 synchronous boost regulator can provide
a stable operating voltage for an LED from a single cell
alkaline battery.
a stable operating voltage for an LED from a single cell
alkaline battery.
The MCP1650 Boost Regulator uses an external switch
so that it can be used for any type of load. An additional
advantage of the MCP1650 in battery applications is the
Gated Oscillator Architecture which provides 2 duty cycles
reducing high-peak inductor current and output ripple
voltages. Input voltages above 3.8V engage a 56% duty
cycle and an 80% duty cycle when the input voltage drops
below 3.8V, extending battery life in these applications.
so that it can be used for any type of load. An additional
advantage of the MCP1650 in battery applications is the
Gated Oscillator Architecture which provides 2 duty cycles
reducing high-peak inductor current and output ripple
voltages. Input voltages above 3.8V engage a 56% duty
cycle and an 80% duty cycle when the input voltage drops
below 3.8V, extending battery life in these applications.
Driving LEDs with a Charge Pump
A charge pump power supply does not have inductors that
are required in other SMPS topologies. This provides a
more compact and less expensive circuit. The downside is
that charge pumps cannot supply large amounts of current
compared to the other topologies. Charge pump circuits
are most useful for backlighting applications. Common
applications include PCs, LCD displays and automotive
instrumentation.
are required in other SMPS topologies. This provides a
more compact and less expensive circuit. The downside is
that charge pumps cannot supply large amounts of current
compared to the other topologies. Charge pump circuits
are most useful for backlighting applications. Common
applications include PCs, LCD displays and automotive
instrumentation.
MCP1252 Charge Pump Backlight
Demonstration Board
Demonstration Board
(MCP1252DM-BKLT)
Demonstrates the use of a charge
pump device in an LED application
and acts as a platform to evaluate
the MCP1252 device in general.
Light intensity is controlled
uniformly through the use of ballast
resistors. A PIC10F206 MCU
pump device in an LED application
and acts as a platform to evaluate
the MCP1252 device in general.
Light intensity is controlled
uniformly through the use of ballast
resistors. A PIC10F206 MCU
provides an enable signal to the MCP1252 and accepts a
push-button input that allows the white LEDs to be adjusted
to five different light intensities.
push-button input that allows the white LEDs to be adjusted
to five different light intensities.
Literature on the Web
■
MCP1252/3 Data Sheet, DS21572
■
MCP1252 Charge Pump Backlight Demo Board
User’s Guide, DS51551
■
MCP1252/3 Evaluation Kit User’s Guide, DS51313
■
DG10 – Power Solutions Design Guide, DS21913
Charge Pump LED Driver Using the MCP1252
3
1
7
8
2
4
5
6
C-
FB
GND
PG
V
IN
V
OUT
C+
SHDN
Single
Li-Ion
Cen
Li-Ion
Cen
PWM Brightness
Control
Control
MCP1252-ADJ
V
IN
0.9V to 1.7V
V
OUT
3.3V @ 100 mA
C
OUT
10 μF
976 KΩ
562 KΩ
C
IN
4.7 μF
L
1
4.7 μH
V
OUT
V
FB
V
IN
SW
EN
GND
Alkaline
MCP1640
MCP1640 Single Cell Synchronous Boost Regulator