vbh and vbl there are various other methods to control the currents iled 1 iledn to achieve the same purpose such as by varying the resistance of the resistor r e g through series or parallel connection with another resistor or by providing another current source connected in parallel with the current source as shown as another example one can insert a circuit which does not affect the primary meaning of its input signal such as a delay circuit between any two devices shown to be in direct connection in the embodiments as yet another example the definition of high low level of signals inputted to or outputted from a digital device is not limited by what is shown in the forgoing embodiments the signals can be inverted as long as proper rearrangement is made to corresponding circuitry moreover in the forgoing embodiments the backlight control circuit is shown as one integrated circuit but it can be divided into two or more integrated circuits or integrated with other circuit devices further the present invention can be applied not only in the circuit with light emitting devices connected partially in series and partially in parallel but also in the circuit with light emitting devices connected all in series or all in parallel and although the light emitting devices are shown to be leds they can be other light.