III. Lamp Frequency Control with an External Clock Signal
An external clock signal may be used to control the EL lamp frequency (LF) of the D371A instead of using a capacitor.
There is an internal frequency divider in the IC so that the output lamp frequency will be half of the input clock signal.
Forexample,ifa500Hzinputclocksignalisused,theresultinglampfrequencywillbe250Hz. Theclocksignalvoltage
should not exceedV+. Atypicaldutycyclefortheclock input is +75%, butit canalso beadjusted withinarangeof20%
to 99% to control brightness and discharge level. A higher positive duty cycle allows for longer charge time and peak
voltage, at the expense of a faster discharge slope and higher noise.
11
IV. EL Brightness Control Through HF Clock Pulse Width Modulation
The inductor oscillating frequency may also be controlled on the D371A EL driver IC using an external clock input to
CHF. In addition, pulse-width modulation of the external HF clock signal to the D371 may be used to regulate the
brightness of the EL lamp load. High frequency input is typically in the range of 10kHz to 40kHz, with duty cycle in the
range of 15% to 100%. In general, a lower HF frequency results in higher brightness and using a lower duty cycle
results in higher brightness. The clock signal voltage should not exceed V+. Prior to finalization of the circuit, contact
Durel to verify that the frequency, duty cycle, and setup chosen are acceptable for EL driver performance.
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
D371A
Vbat
0.1 uF
OFF
ON
EL Lamp
1.0V Min
0.2V Max
200Hz - 2KHz
20%-99% +Duty
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
D371A
Vbat
0.1 uF
OFF
ON
EL Lamp
1.0V Min
0.2V Max
10KHz - 40KHz
15%-100% Duty
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
