Pulse signal delay circuit and LED drive circuit

An LED drive circuit for driving an LED circuit where a plurality of circuit units, in which an LED series circuit where a plurality of LEDs are connected in series in the same direction and a drive transistor for driving the LED series circuit are connected in series, are connected in parallel and one end of each of the circuit units is connected to a predetermined drive voltage, the LED drive circuit comprising

• a pulse signal delay circuit, the pulse signal delay circuit comprising:
• a first pulse edge delay circuit for generating a first delay timing signal for sequentially outputting a first edge detection delay timing gained by detecting a rising edge of an input pulse signal and delaying a detection timing of the rising edge by a preset delay time a predetermined number of times within one period of the input pulse signal;
• a second pulse edge delay circuit for generating a second delay timing signal for sequentially outputting a second edge detection delay timing gained by detecting a falling edge of the input pulse signal and delaying a detection timing of the falling edge by the delay time the predetermined number of times within one period of the input pulse signal;
• and
• a delay pulse signal generating circuit for generating delay pulse signals, of which a number is the same as the predetermined number of times of delays, from the first delay timing signal and the second delay timing signal for each combination of the first edge detection delay timing and the second edge detection delay timing delayed the same number of times, the delay pulse signals rising according to the first edge detection delay timing and falling according to the second edge detection delay timing, and for outputting the generated delay pulse signals, wherein
• the first pulse edge delay circuit and the second pulse edge delay circuit in the pulse signal delay circuit accept a pulse width modulating signal for driving and controlling the LED circuit as the input pulse signal,
• the delay pulse signals of which a number is the same as the predetermined number of times of delays outputted from the delay pulse signal generating circuit in the pulse signal delay circuit are respectively inputted into gates of the drive transistors in the circuit units in the LED circuit, and
• the predetermined number of times of delays in the pulse signal delay circuit is set to the same number as a number of the circuit units in the LED circuit or smaller than the number of the circuit units by one.