| 摘要 |
PROBLEM TO BE SOLVED: To protect an element constituting a single phase current type power converter for feeding an AC power to a capacitive load against breakdown caused by overvoltage while allowing high frequency operation of power converter. SOLUTION: When the switch elements 6U, 6Y of a single phase current type inverter are turned on and the output voltage increases to reach a peak set voltage Vp, switch elements 6V, 6X are turned on to bring about a state where all switch elements are turned on. Consequently, a circulation current flows between the switch elements of upper and lower arms and the load voltage drops quickly. The state where all switch elements are turned on is sustained until a zero voltage detection circuit 30 detects the voltage drop to zero or the voltage detection circuit detects voltage drop to a predetermined level V0 . Subsequently, the switch elements 6U, 6Y are turned off and only the switch elements 6V, 6X are turned on thus increasing the load voltage in reverse direction. |
