| 摘要 |
<p>The power supply apparatus, comprises positive and negative input terminals (1, 3) for receiving an input voltage, a first series connection (7) which interconnects the input terminals, and consists of at least one coil (9) and a controllable switching element (11), and a peak-limiting circuit (29) for limiting the maximum voltage across the switching element. The peak-limiting circuit (29) comprises a capacitor (31) and a second series connection of a first rectifier element (33) and a resistor (135), as well as a second rectifier element (41) which connects one end of the second series connection to the positive input terminal (1). In the part of the peak-limiting circuit (29) which is formed by the first and the second rectifier elements (33, 41) and the resistor (135) the forward directions of the rectifier elements are the same. The other end of the second series connection (33, 135) is connected to the negative input terminal (3) and the capacitor (31) is connected between the anode of the second rectifier element (41) and the junction (37) of the coil (9) and the switching element (11). As a result of these steps, the energy dissipation in the resistor (135) is dependent on the duty cycle of the switching element (11). This duty cycle itself is dependent on the load of the power supply apparatus. As a result, in the case of a small load the dissipation of the apparatus will be substantially lower.</p> |
