| 摘要 |
<p>A pulse width modulated voltage converter is proposed, which converts a direct voltage to a sinusoidal alternating voltage with low frequency for use as a ringing signal generator for telephone exchanges. The converter includes a power stage comprising a ferrite core transformer (T) with two switches (Pf, Pr) on the primary side (battery side) and two switches (S1, S2) on the secondary side (load side). The switches are controlled by control pulses from a pulse width modulator (PM) with a variable pulse rate so that they are switched with a frequency which is much higher than the frequency of the sinusoidal alternating current and so that a pulsing of the nergy flow between battery and load side is obtained.</p> |
