Microcomputer for driving induction motor

DETAILED DESCRIPTION The invention has been conducted in view of the above-described circumstances.
It is an object of the invention to provide a microcomputer for driving induction motor in which the load on a CPU can be reduced and the frequency of a carrier for generating a control signal can be increased when the driving of the induction motor is controlled.
The microcomputer for driving induction motor according to the invention comprises: first storing means for storing time width data of a positive phase (or a negative phase) of a control signal which is synchronized with a carrier; calculating means for subtracting a value of the time width data stored in the first storing means from a value of period data of the carrier; and second storing means for storing the calculation result.
In the microcomputer for driving induction motor of the invention, a period data output unit outputs period data of the carrier.
When a CPU controls the first storing means so as to store positive phase time width data of the control signal which is synchronized with the carrier, the calculating means subtracts the value of the time width data stored in the first storing means from the value of the period data of the carrier, and the time width data after the calculation is stored in the second storing means.
Accordingly, it is required only to write the time width data in the positive phase (or the negative phase) of the control signal into the first storing means, and hence the load on the CPU is reduced.
In addition, the control operation time of the CPU is shortened and hence the frequency of the carrier can be increased.
In a first aspect of the microcomputer for driving induction motor of the invention, a first register is used as the first storing means and a second register is used as the second storing means.
The first register (or the second register) stores the time width data in the positive phase (or the negative phase) of the control signal which is synchronized with the carrier.
An operation unit subtracts the value of the time width data stored in the first register (or the second register) from the value of the period data of the carrier