| 摘要 |
<p>A power supply (20) incorporates a switching regulator circuit and a flyback transformer (26) having diodes (42) for unidirectional current flow from an output circuit of the transformer to a load (24). Substantially noise-free sensing of currents in both input (32) and output (34) windings of the transformer is provided by a sensing circuit composed of a sense winding (46) on the transformer and an integrator (50) coupled to the sense winding. The integrator provides an output signal proportional to volt seconds or flux which, in turn, is proportional to either the input current or the output current. The input current and the output current flow alternately due to a switching action of the regulator circuitry. The regulator circuitry includes an electronic switch (38) coupled via a comparator to an output terminal of the integrator so as to initiate a pulse of current in the input winding when the output currents drop below a preset value, and to terminate the input current when the input current exceeds a preset value. A bank of capacitors (54) connected to the input winding (32) stores electric energy in the intervals between pulses for subsequent discharge into the transformer during the current pulses. The foregoing arrangement of the power supply circuitry provides for isolation of input and output sections of the power supply to prevent the coupling of noise. An overvoltage sensing circuit may also be coupled to the output winding (34) for acting via a logic unit to terminate input current during intervals of excessively high output voltage.</p> |
