| 摘要 |
PURPOSE: To provide a soft start circuit which has a simple circuit configuration, without having to use a capacitor for setting a soft start time, and built LSI in the soft start circuit. CONSTITUTION: This switching power source which include a triangular wave generating circuit, an error amplifier, and a PWM comparator, and obtains a PWM pulse by comparing the triangular wave amplitude output of the triangular wave generating circuit with the output voltage of the error amplifier as a reference (comparison) voltage by the PWM comparator under normal conditions is formed out of a soft start reference value setting part of a group of resistor nets and a group of switches using the same means as an upper/lower value setting part consisting of a resistor net and a switches which set the upper/lower value of the triangular wave amplitude of the triangular wave generating circuit, when the power source starts up, and a clock circuit which calculates a triangular wave period of the triangular wave generating circuit for switching the group of switches, to obtain a plurality of arbitrary soft start time.
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