| 摘要 |
<p>For charging a battery (6) from different input voltages use is made of a flyback converter in which during the forward interval a linearily increasing current flows through a transformer primary winding (n1), which current is turned off by a first switch (S1) at a value which is dictated by switching means (3). During the flyback interval the energy stored in the transformer (Tr) is then supplied to the battery in the form of a charging current via the secondary winding (n2) and a diode (D1). The voltage pulses appearing across the secondary winding (n2) during the forward intervals are applied to an integrator (11) via a third switch (S3), which integrator integrates these voltage pulses. If the output voltage of this integrator (11) exceeds a first threshold value a threshold circuit (12) is activated and turns on a second switch (S2) to disable the flyback converter. If subsequently the output voltage of the integrator (11) decreases below a second threshold value, the second switch (S2) is turned off again by the threshold circuit (12), so that the flyback converter can be restarted. In this way the average value of the voltage across the secondary winding during the forward intervals is maintained substantially constant. Thus, the flyback converter constitutes a constant-power source, the power supplied to the battery (6) being constant and independent of the input voltage. </p> |
