Abstract: A switching control circuit for use in controlling a resonant flyback power converter generates a first driving signal and a second driving signal. The first driving signal is configured to turn on the first transistor to generate a first current to magnetize a transformer and charge a resonant capacitor. The transformer and charge a resonant capacitor are connected in series. The second driving signal is configured to turn on the second transistor to generate a second current to discharge the resonant capacitor. During a power-on period of the resonant flyback power converter, the second driving signal includes a plurality of short-pulses configured to turn on the second transistor for discharging the resonant capacitor. A pulse-width of the short-pulses of the second driving signal is short to an extent that the second current does not exceed a current limit threshold.

Abstract: A resonant flyback power converter includes: a first and a second transistors which form a half-bridge circuit for switching a transformer and a resonant capacitor to generate an output voltage; a current-sense device for sensing a switching current of the half-bridge circuit to generate a current-sense signal; and a switching control circuit generating a first and a second driving signals for controlling the first and the second transistors. The turn-on of the first driving signal controls the half-bridge circuit to generate a positive current to magnetize the transformer and charge the resonant capacitor. The turn-on of the second driving signal controls the half-bridge circuit to generate a negative current to discharge the resonant capacitor. The switching control circuit turns off the first transistor when the positive current exceeds a positive-over-current threshold, and/or, turns off the second transistor when the negative current exceeds a negative-over-current threshold.

Abstract: A rotating shaft of a shutter louver is provided, which is inserted into a louver mounting hole and frame mounting hole, so as to connect the louver to the frame. The rotating shaft is formed by a shaft bushing and shaft, wherein a shaft hole is formed through the body of the shaft bushing, a flange is disposed on the body and a gripping portion is protruded from the body. The shaft is accommodated within the shaft hole, and a fin is protruded from the shaft tail. When the rotating shaft is inserted into the frame mounting hole, the gripping portion is used to bear against the inner side of the frame mounting hole and thereby applying a force to grip the rotating shaft, and cooperating with the operation of gripping the louver mounting hole by the fin, the louver is positioned on the frame quickly and firmly.