Patent ID: 8890554
Filing Date: 2014-11-18
Classification: H02J,H02M

Abstract:
1. A current control device for an electric load comprising: a power supply circuit part in which a switching element, a current detection resistor, and the electric load, to which power is supplied from a drive power supply, are connected in series to each other; and a control circuit part which controls an on/off ratio of the switching element on the basis of a target load current Is wherein the control circuit part includes a microprocessor having a nonvolatile program memory, an RAM memory for arithmetic processing, and a multichannel AD converter, an amplifier circuit part for current detection, a temperature detection circuit, and a drive signal circuit, the nonvolatile program memory includes temperature characteristic data which is one of an approximation formula and a data table regarding temperature-to-resistance value of the current detection resistor, the amplifier circuit part for current detection amplifies a voltage across the current detection resistor, and generates a monitored voltage Ef which is based mainly on a current proportional component proportional to the load current Im for the electric load and includes an error component, when the temperature close to the current detection resistor is a normal-temperature ambient temperature Ta, control characteristic data which represents the correspondence relationship between an actually measured load current Im measured by an external ammeter for calibration and the target load current Is the temperature detection circuit includes a temperature sensor and generates measured voltages Sa and Sb corresponding to the normal-temperature ambient temperature Ta of the current detection resistor and an actual operation ambient temperature Tb in operation, respectively, and the measured voltages Sa and Sb are input to the microprocessor through the multichannel AD converter, the control circuit part generates a corrected signal voltage Es proportional to a corrected target current Is obtained by correcting the target load current Is the corrected target current Is corresponds to the target load current Is one of the converted monitored voltage Efb and the converted target current Isb is calculated on the basis of a comparison value of normal-temperature resistance Ra and actual operation resistance Rb of the current detection resistor obtained from the temperature characteristic data in response to the normal-temperature ambient temperature Ta when the control characteristic data is obtained and the actual operation ambient temperature Tb in operation.