Antonelli, Terry & Wands
Drive circuit for electroluminescent element
 A drive circuit for an electroluminescent (EL) element whose brightness can be changed by changing a voltage or the frequency of the voltage applied to the EL element and can be kept constant by keeping the current flowing through the EL element constant is disclosed. The drive circuit is provided with a drive power source whose output voltage or output voltage frequency is variable by a control signal. The output of the drive power source is supplied to the EL element. The current flowing through the EL element is detected by a current detecting element and a signal related to the detected current is applied as the control signal to the drive power source to subject the EL element to a constant-current drive. 
Hitachi, Ltd.
Y H
Y02B H05B
additional inventional
Shin-ichi Katsuyuki Tohru Masakatsu
Ohashi Tanaka Sampei Saito