| 摘要 |
PURPOSE:To provide the title circuit with sufficient current drooping characteristics, by a method wherein the detection of switching current is effected employing only a resistor and a reference signal is provided with a quasi trapezoidal wave. CONSTITUTION:A switching power source control circuit 1 is constituted of a buffer circuit 2 for the pulse width control signal of the circuit 1, a transformer 3, a power MOS-FET Q1 and a control signal generating circuit, producing a control signal. The control circuit 1 is constituted of a comparator 11, a quasi trapezoidal wave generator 12 and a reference power source 13 while said oscillator 12 receives a reference voltage VREF and generates a quasi trapezoidal signal, which becomes a reference signal. The false trapezoidal signal and a control signal from the control signal generating circuit 4 are inputted into the comparator 11 to output a pulse width control signal. According to this constitution, the pulse width of the pulse width control signal narrows steeply when the control signal of the switching power source control circuit 1 has become higher than the peak level of the quasi trapezoidal wave, whereby sufficient drooping characteristics may be obtained in an output current.
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