The switching circuitry topology is arranged so that the transistors operate in a 1E mode, that is, the voltage across the switching transistors is no greater than the input voltage (E) and at the same time the noise voltage normally generated in regulating circuit arrangements employing transistor switching is greatly reduced. A filter inductor in the primary switching circuit protects the switching transistors from sudden current changes during overload and enables operation of the transistors below the 2E mode. Power is regulated by pulse width control of the switching transistors. One pair of switching transistors is arranged to control the direction of current through the transformer primary winding. Another pair of transistors is arranged for controlling the current in accordance with the width of applied switching pulses. The switch topology also is arranged so that no current ever attempts to flow in the reverse direction through a previously conducting primary circuit diode, hence the rectifying elements are never snapped off, and the less desirable reverse recovery effects are eliminated. Primary-to-secondary circuit isolation is afforded with interchangeable transformer coupling and optocoupling components which also improve immunity to noise.
展开▼
