| 摘要 |
PURPOSE:To simplify a circuit constitution and decrease the number of parts by constituting a stabilized power unit to perform switching not on a secondary side but on a primary side only. CONSTITUTION:A stabilized power unit is composed of a switching transistor (hereinafter referred to as Tr) Q1, a flyback converter transformer T3, a drive circuit DR of the TrQ1 and others and outputs a rectified and smoothed DC from secondary coils NS1,NSm of a transistor T3 while supplying an AC output from a secondary coil NS2 to a load Rl. An output V1 of this secondary coil NS1 is fed back from an error amplifier A1 via a photo-coupler PC to a pulse width modulation circuit PWM. As a result, said output V1 is compared with a triangular wave outputted by an oscillating circuit OSC to be subjected to pulse width modulation and the TrQ1 is ON-OFF controlled so that a DC output voltage V1 becomes constant via the drive circuit DR.
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