| 摘要 |
PROBLEM TO BE SOLVED: To reduce a ripple voltage while suppressing output voltage variation due to a load variation in a power supply unit consisting of a discontinuous operation chopper power supply constituted of discrete components. SOLUTION: The power supply unit is equipped with: a choke coil L51; a main switching element Q52 which controls the power supply output; a regeneration diode D52; a comparator I51 which turns the Q52 on or off by comparing a voltage proportional to the output voltage with a reference voltage; an overload protective element Q51 which performs overload protection when the current passing through the Q52 exceeds a threshold; a Zener diode ZD11 and a diode D11 which change the reference voltage input to the I51; an operational amplifier I21 which detects the state of the load current; and a switching element Q11 which switches the operation of the ZD11 and D11 based on the state of the load current. The problem is solved by controlling the on/off state of the Q11 according to the load current and changing the reference voltage inputted to the I51. COPYRIGHT: (C)2011,JPO&INPIT
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