| 摘要 |
PURPOSE:To protect a switching element against overheat by providing a counter electromotive force absorbing circuit for lowering peak voltage to be applied to each switching element below avalanche breakdown voltage. CONSTITUTION:A high level set reference signal Vref is set using a current value setting means 30 and a step motor 10 is operated with high current through chopping constant current control. When surge voltage generated from coils La to Ld exceeds a preset level, constant voltage elements 41acto 41bd constituting a counter electromotive force absorbing circuit 40 function to lower the peak voltage to be applied to switching elements 21a to 21d. This constitution protect the switching elements 21a to 21d against overheat. |
