FEEDBACK CONTROLLER

PURPOSE:To execute the control with high precision by supplying data of a difference of data of a given target value and data of the present value of a controlled system to a D/A converter, and using an inexpensive one in which the number of input bits is small for the converter, at the time of controlling the controlled system to an arrival state by an analog control signal of this converter. CONSTITUTION:The controller is provided with an input side coefficient multiplier 9 for compressing data of a difference to 1/K (K is a constant) and supplying it to a D/A converter, an output side coefficient multiplier 10 for multiplying a control signal outputted from the converter 4 by K and amplifying and correcting a controlled variable, an input side changeover switch 11 which is provided on the input side of the converter 4 and switches input data of the converter 4 to data of a difference from output data of the input side coefficient multiplier 9, when a controlled system is in to a state within a prescribed range from an arrival state, and an output side changeover switch 12 which is provided on the output side of the converter 4, and switches the control of a controlled system to the control of high accuracy by a control signal from the control of a wide range by an output signal of the output side coefficient multiplier 10, when the input side switch 11 is switched.