Patent ID: 6860576

Claim:
A drive circuit comprising: a resistor having one end thereof connected to a first power supply; drive control means, which is connected to the other end of said resistor, for controlling drive of said resistor, said drive control means having a control terminal; and a power driving circuit, which is connected to a second power supply, for controlling power consumed by said resistor based upon a value of current supplied to the control terminal of said drive control means; said power driving circuit including: a first voltage-to-current converting circuit, to which are input (a) a first voltage value corresponding to voltage across both ends of said resistor prevailing when power consumed by said resistor has attained a predetermined value at such time that the resistance value of said resistor is a set value, (b) a second voltage value corresponding to voltage across both ends of said resistor prevailing when power consumed by said resistor becomes substantially equal to said predetermined value at such time that the resistance value of said resistor fluctuates from the set value, and (c) a current value corresponding to current that flows through said resistor, for controlling an output current value by a control signal that corresponds to a value of voltage across both ends of said resistor; and a second voltage-to-current converting circuit for controlling an output current value based upon the control signal, having a voltage-to-current converting characteristic similar to that of said first voltage-to-current converting circuit, and outputting a current to the control terminal of said drive control means.