LIGHT EMITTING DIODE DRIVING CIRCUIT

PROBLEM TO BE SOLVED: To enable use of electrically conductive material having large resistivi ty as an electrically conductive material to be formed in a flexible printed circuit board by impressing the voltage obtained by boosting a system voltage on light emitting diodes while connecting the light emitting diodes in series and driving the light emitting diodes with a constant current. SOLUTION: In a light emitting diode driving circuit, in lighting a liquid crystal display, a transistor Q2 is controlled to be in an operating state and the output voltage from a voltage boosting circuit 21 is impressed on one end of serially connected light emitting diodes 11-14. The constant current of 7mA is made to flow into a constant current circuit 22 and the constant current made to flow into the constant current circuit 22 is made to flow in the light emitting diodes 11-14 and they are made to emit lights. In this case, the serially connected light emitting diodes 11-14 are driven with the constant current of 7mA. Thus, the variation of brightness in lighting is eliminated in spite of the variation of resistivities of electrically conductive material 32.