CPC6826
4. Functional Description
L1
D1
COUT
VIN +
5 (LX)
6 (CS)
1 (VDD
)
)
CPC6826
RSW
2 (RSW-osc
Switch
Osc
Q
Q
8 (VA)
Vsen
+
-
REL
EL Lamp
3 (REL-osc
)
Output
Osc
Disable
Vref
Q
Q
CIN
7 (VB)
VIN -
4 (GND)
4.1 Overview
When power is applied to V , the internal feedback
DD
The CPC6826 is an EL lamp driver designed for
battery applications operating from an input supply
voltage range of 1.8V to 3.5V and generating an AC
voltage V
is less than V
causing the
SEN
REF
comparator output to go low, which enables the
switching power MOSFET oscillator. When turned on,
the internal low impedance switching MOSFET
causes current to flow through the external inductor.
With current flowing in the inductor, the switching
MOSFET is turned off causing a flyback voltage to
develop across the inductor. As the inductor's flyback
voltage increases to a level greater than a diode drop
output voltage of 180V . The device is capable of
p-p
2
2
driving lamp panels ranging from 1 in to 5 in .
The CPC6826 IC main block architecture is made up
of two independent oscillators, which control the
switching of a power MOSFET and an H-bridge.
above the voltage across the capacitor on the C pin,
Adjustment of two external resistors, R
and R ,
S
SW
EL
charge stored in the inductor is transferred into the
sets the frequencies of the oscillators, thus allowing
the designer to maximize efficiency and to increase
the brightness of the lamp.
C
capacitor. This operating cycle continues until
OUT
the V
voltage is above the V
in which case the
SEN
REF
comparator disables the Switch Oscillator.
To conserve supply power and extend battery life, the
CPC6826 automatically shuts down the switcher
circuit whenever switcher output power exceeds load
requirements. Supply power can also be conserved
manually by disabling the switching circuit: pull pin 2,
The internal high voltage H-Bridge section is enabled
by external resistor R at pin 3 and V on pin 1. The
EL
DD
H-bridge operation is controlled by output oscillator
waveforms driving H-bridge high-side and low-side
R
, to ground.
SW
MOSFETs. Selecting the value of R allows the
EL
designer to set the frequency of the internal oscillator
to meet design requirements. By alternately switching
the terminals of the lamp between high voltage supply
4.2 Regulation
The circuit configuration is based on simple boost
converter topology. This method provides excellent
efficiency, minimizes loss of energy, and allows
smaller components to be used in the design. Only a
few passive components (an inductor, a capacitor, two
resistors, and a diode) are required to complete the
simple boost switcher circuit.
and ground the 180V
potential develops across the
P-P
EL lamp.
R00C
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