| 摘要 |
PURPOSE:To reduce switching loss and to enhance efficiency by controlling the carrier frequency low when the ambient noise level is higher than a predetermined level and canceling the noise of power converter by the ambient noise. CONSTITUTION:A noise sensor 101 detects the total ambient noise level. A filter 102 for removing the carrier frequency component detects an ambient noise level P1 where the carrier frequency component is removed from the total noise level. The relationship between the ambient noise level P1 and the carrier frequency fc is prestored in a carrier frequency control section 103 and a carrier frequency fc is set depending on the ambient noise level P1 with reference to the relationship. The carrier frequency fc is controlled low when the ambient noise level P1 is higher than a predetermined level Pd. A carrier signal having carrier frequency fc is outputted from a carrier signal generating section 104. |
