Patent ID: 7714523

Claim:
A load driving device for independently driving a plurality of loads connected to a power source by a PWM (pulse-width modulation) control method, the load driving device comprising control means, which is configured to: set a standard duty ratio of a PWM signal used in driving the plurality of loads to (100/n)% with “n” indicating the number of the plurality of loads; output a standard PWM signal, which is the PWM signal of the standard duty ratio outputted to one load of the plurality of loads, in a phase not to overlap in respect of energization periods with a standard PWM signal outputted to another load of the plurality of loads; output, when a voltage level of a drive instruction for the load corresponds to a level at the standard duty ratio, the standard PWM signal to each of the plurality of loads, wherein the standard PWM signal outputted to the one load is shifted in time from the standard PWM signal outputted to the another load, so that the standard PWM signal outputted to the another load rises when the standard PWM signal outputted to the one load falls; output, when the voltage level of the drive instruction corresponds to a level lower than the level of the standard duty ratio, which is defined as an under-standard level, a continuous non-energization period and the standard PWM signal by changing over the continuous non-energization period and the standard PWM signal at a ratio corresponding to the voltage level of the drive instruction, wherein the standard PWM signal outputted to the one load is shifted in time from the standard PWM signal outputted to the another load, so that the standard PWM signal outputted to the another load rises when the standard PWM signal outputted to the one load falls from the energization period, and wherein the continuous non-energization period outputted to the one load is shifted in time from the continuous non-energization period outputted to the another load, so that the standard PWM signal outputted to the another load rises when the standard PWM signal falls from the energization period; and output, when the voltage level of the drive instruction corresponds to a level higher than the level at the standard duty ratio, which is defined as an over-standard level, a continuous energization period and the standard PWM signal by changing over the continuous energization period and the standard PWM signal at a ratio corresponding to the voltage level of the drive instruction, wherein the standard PWM signal outputted to the one load is shifted in time from the standard PWM signal outputted to the another load, so that the standard PWM signal outputted to the another load rises when the standard PWM signal outputted to the one load falls from the energization period, and wherein the continuous energization period outputted to the one load is shifted in time from the continuous energization period outputted to the another load, so that the standard PWM signal outputted to the another load rises when the standard PWM signal falls from the energization period.