A device for converting high level voltage to relatively low level DC voltage for the driving of a plurality of loads. The device utilizes a relatively small transformer with a gapped core and a single transistor to regulate the high frequency power transformer process. Controlled release of magnetic energy induced in the core prevents magnetic saturation of the core.
A forward converter circuit (FIG. 1) is provided with a transformer reset sensing circuit (FIG. 2) whereby base drive to the switching transistor TR1 is inhibited until after reset of the transformer T1. The reset sensing circuit includes a sensing winding T1d provided on the transformer for sensing the waveform at the primary winding T1a, a comparator IC1 and diodes D5, D4 connected in such a way that one input of the comparator is high when the waveform changes in one direction, and the other input of the comparator is high when the waveform changes in the other direction. The output of the comparator inhibits switching of the transistor before reset and thus allows the use of a maximum switching duty cycle of 50% without risk of transformer saturation.
A power supply provides a low-level DC voltage to one or more DC load circuits by first rectifying either of the two standard AC voltages and thereafter reducing the rectified AC voltage to the low-level DC voltage. The reduction of the rectified AC voltage to the low-level DC voltage is accomplished by a power transformer which is switched on or off by a pair of switching transistors. The switching transistors are activated by a control transformer operating in combination with a control circuit. The control circuit timely produces various pulse conditions in the control transformer which turns the switching transistors on or off in a prescribed manner.
An electric wrist watch including a case containing a timekeeping module, an electrical storage device, and a display device. The case also includes a thermoelectric generator in contact with two heat exchangers. The two heat exchangers are arranged such that they are at least temporarily at different temperatures, with one of the heat exchangers being in contact with the surrounding air.
An initial drive voltage supply control circuit for an SMPS, comprising a rectifier for rectifying and smoothing an AC voltage inputted by an AC input unit to convert it into a DC voltage, a switching transformer having a primary coil for receiving the DC voltage from the rectifier and secondary and tertiary coils for inducing desired voltages in response to the DC voltage received by the primary coil, an output power controller for supplying or blocking the DC voltage from the rectifier to the primary coil of the switching transformer, an initial drive voltage controller for supplying an initial drive voltage to the output power controller and blocking the initial drive voltage to the output power controller when a normal drive voltage is supplied to the output power controller after the lapse of a predetermined time, a load output unit for rectifying and smoothing the voltage induced in the secondary coil of the switching transformer to output an operating voltage to a load, a drive voltage supply unit for rectifying and smoothing the voltage induced in the tertiary coil of the switching transformer to supply the normal drive voltage to the output power controller, and an error detection feedback unit for detecting the operating voltage from the load output unit and feeding the detected operating voltage back to the output power controller.
The switching power supply has pulse width modulation controller 51 isolated by transformer 35, which is connected by line 33 to the output, VO, across lines 27 and 29. An alternating input is obtained from transistor 19 acting as a switch controlled by alternating signals on line 15 connected to node C. Diode 37 in series with resistor 39 provides damping. Response is very fast and effective, and the input elements, including controller 51, are fully isolated.
