| 摘要 |
The switch-mode dc power supply includes a series circuit, a rectifier, an output smoothing circuit, detection circuit, an adding circuit, a triangular wave generator and a control signal generator. The series circuit includes a primary winding of a HF transformer, a semiconductor switching element and a current detection unit connected between two output terminals of a rectifier/smoothing circuit. The rectifier is connected to an end of a secondary winding of the HF transformer. The output smoothing circuit is connected between the rectifier and other end of the secondary winding. The detection circuit is connected to a connection point between the rectifier and the output smoothing circuit. The adding circuit is connected between the detection circuit and a connection point between the semiconductor switching element and the current detection unit. The adding circuit has a current mirror and a current detector. The triangular wave generator is connected to the adding circuit. And the control signal generator is connected between the adding circuit and a control electrode of the semiconductor switching element, and further is connected to the triangular wave generator. The adding circuit adds a voltage corresponding to a dc output signal at the secondary winding to a voltage corresponding to a current flowing in the semiconductor switching element so as to obtain an augmented voltage signal. The gate electrode is supplied with a drive signal keeping the "H" level until the augmented voltage signal reaches the triangular wave signal. Then, the power supply operates with good stability.
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