Development and Trend of Switch Mode DC Power Supply
The self-excited oscillating push-pull transistor single-transformer DC converter invented by GH. Roger in 1955 is the beginning of the realization of high-frequency conversion control circuits. In 1957, Jen Sen of the United States invented the self-excited push-pull Double transformer, in 1964, American scientists proposed the idea of canceling the series switching power supply of the power frequency transformer, which obtained a fundamental way for the reduction of the size and weight of the power supply.
In 1969, due to the improvement of the withstand voltage of high-power silicon transistors and the shortening of diode reverse recovery time, a 25 kHz switching power supply was finally made.
At present, switching power supplies are widely used in almost all electronic equipment such as various terminal equipment and communication equipment dominated by electronic computers due to their small size, light weight and high efficiency. power mode.
Among the switching power supplies currently on the market, the 100kHz power supply made of bipolar transistors and the 500kHz power supply made of MOS-FET have been put into practical use, but their frequency needs to be further improved.
To increase the switching frequency, it is necessary to reduce switching losses, and to reduce switching losses, high-speed switching components are required.
However, as the switching speed increases, surges or noise can be generated due to the distributed inductance and capacitors in the circuit or the stored charge in the diodes. In this way, it will not only affect the surrounding electronic equipment, but also greatly reduce the reliability of the power supply itself.
Among them, in order to prevent the voltage surge that occurs with the opening and closing of the switch, R-C or L-C buffers can be used, and for the current surge caused by the stored charge of the diode, a magnetic buffer made of an amorphous magnetic core can be used .
However, for high frequencies above 1MHz, a resonant circuit should be used, so that the voltage on the switch or the current through the switch is a sine wave, which can not only reduce switching losses, but also control the occurrence of surges. This switching method is called resonant switching.
At present, the research on this kind of switching power supply is very active, because this method can theoretically reduce the switching loss to zero without greatly increasing the switching speed, and the noise is also small, which is expected to become one of the high frequencies of the switching power supply. main way.
At present, many countries in the world are working on the practical research of multi-terahertz converters.
