| 摘要 |
A converter comprises a rectifying circuit (RC1) which rectifies AC power supply (Ei), a switching transistor Q, which turns on and off so that the rectified voltage is applied across the primary winding (n1) of the transformer (Tr1) to provide a high frequency voltage across the secondary winding (n2). The secondary winding voltage is rectified by circuit (D1, D3, L2, C2) connected across the secondary winding. A choke coil (L1) and a diode (D1) are interposed between the rectifying circuit (RC1) and a smoothing capacitor (C1), and a capacitor (C3) is interposed between a first junction and a second junction. The first junction connects the choke coil (L1) to the diode (D1) and the second junction connects the switching device (Q1) to the primary winding (n1) of the transformer (Tr1). A control circuit U, coupled to a detection and comparison circuit (DET1) drives the switching transistor Q1 on and off at a high frequency (100 kilohertz) relative to the supply frequency and the inductance of the choke provides effectively a constant current at the high frequency. A power factor of up to 0,98 is achieved. In further embodiments (Figures 6, 11) the power factor may be 0.996. <IMAGE> |
