| 摘要 |
PROBLEM TO BE SOLVED: To sustain high efficiency over a wide temperature range by varying the part constants of a high voltage conversion circuit to compensate each other through temperature variation. SOLUTION: A primary inductance is formed in a high voltage transformer T1 by providing a gas and when an FET Q1 is turned on, drain current is increased linearly by the primary inductance. When the FET Q1 is turned off, a current is fed from the secondary of the high voltage transformer T1 to a load L and it also flows into the stray capacity Cp of the transformer T1. A gap material having a coefficient of thermal expansion larger than that of a core is employed in the transformer T1 in order to lower primary inductance when the temperature rises. According to the arrangement, rising rate of the drain voltage can be kept constant when the FET Q1 is turned off even if the drain current is increased and the stray capacity Cp is increased when the FET Q1 is turned on upon temperature rise. An ideal switching operation is thereby effected over a wide temperature range and high efficiency can be sustained.
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