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Lamp Frequency (Hz)
Designing With D355B
I. Lamp Frequency Capacitor (CLF) Selection
Selecting the appropriate value of capacitor for the low frequency oscillator (CLF) will set the output frequency
of the D355 inverter. Figure 1 graphically represents the inversely proportional relationship between the
CLF capacitor value and the oscillator frequency. In this example at V+=3.0V, LF = 1600 nF-Hz/CLF.
Alternatively, the lamp frequency may also be controlled with an external clock signal with a 50% duty
cycle. The output lamp frequency will be the same frequency as the input clock signal. For example, if a
250Hz input clock signal is used, the resulting lamp frequency will be 250Hz. The clock signal input voltage
should not exceed V+.
The selection of the CLF value can also affect the brightness of the EL lamp because of its control of the
lamp frequency (LF). Although input voltage and lamp size can change EL lamp frequency as well, LF
mainly depends on the CLF value selected or the frequency of the input clock signal to CLF. The luminance
of various sizes of
Durel 3 Blue-green EL lamp driven by a D355B at V+ = 3.0V using the same inductor
value is shown in Figure 2 with respect to lamp frequency.
Figure 1: Typical Lamp Frequency vs. CLF Capacitor
4in
2
EL Lamp
2in
2
EL Lamp
6in
2
EL Lamp
Figure 2: Typical Lamp Luminance vs. Lamp Frequency
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CLF5