om5448 Hendon Semiconductors, om5448 Datasheet - Page 17

• Manufacturer Part Number: om5448
• Description: Low Voltage Led Driver And Boost Converter
• Manufacturer: Hendon Semiconductors

9.10
In the circuit of the regulated boost
power supply in figure 19 the OM5448
provides drive to the output regulating
circuit until the zener diode begins to
conduct. When the zener diode
conducts, and sufficient current flows
9.11
The voltage output of the OM5448
can be multiplied to offer larger
voltages greater than the maximum
voltage allowed on pin OP. An
example of such an application circuit
is shown in figure 20.
This example circuit is not regulated,
and uses the zener ZD1 to clamp the
output pin to a safe voltage.
2007 May 28, Revision 1.0
Regulated boost power
supply
Voltage multiplier power
supply
Fig.20 Voltage multiplier boost power supply circuit using the OM5448.
through R3 to provide sufficient
voltage to start to turn on transistor
TR1, the collector of TR1 will start to
pull the enable pin EN low, turning off
the OM5448.
In this way the OM5448 only runs
when needed to provide output
current, and its input current demands
9.12
With a few additional components the
circuit in figure 20 can be given a
voltage regulated output voltage.
Zener diode ZD1 is still needed to
prevent excessive voltage on pin OP,
and a second zener provides
feedback of the output voltage to the
enable pin EN to switch off the
OM5448 when the voltage out
reaches its required value.
Regulated voltage multiplier
power supply
17
Low Voltage LED Driver
will track the load. This is a much
more efficient circuit than the circuit of
figure 18 which is not load regulated.
As in figure 18, the output voltage is
limited to 14 volts peak on pin OP
(about 12 volts regulated output
voltage).
While small signal diodes are shown
in the voltage multiplier circuit,
performance may be improved if
Schottky diodes are used, minimising
forward voltage drop.
and Boost Converter
Product Specification
OM5448