In 1955, G.H. Royer, a scientist in the United States, first developed a transistor DC converter which uses the saturation of the magnetic core to self oscillate. Since then, various forms of DC converters using this technology have been developed and emerged continuously, which has replaced the rotating and mechanical vibrator converter with short service life, poor reliability and low conversion efficiency. Because the power transistors in the transistor DC converter work in the on-off state, the linear regulated power supply produced by this method has many output groups, variable polarity, high efficiency, small volume and light weight, so it was widely used in aerospace and military electronic equipment at that time. At that time, due to the backward microelectronic equipment and technology, it was impossible to produce transistors with high voltage withstand, high switching speed and high power, so the DC converter in this period could only use low-voltage input, and the conversion speed could not be too high.

In the 1960s, due to the rapid development of microelectronics technology, high reverse voltage transistors appeared. From then on, DC converters can be directly input by the mains power through rectification and filtering, without the need for power frequency transformer to reduce voltage, thus greatly expanding its application scope, and on this basis, a switching power supply without power frequency step-down transformer was born. The power frequency transformer is omitted, and the volume and weight of the switching power supply are greatly reduced, so that the switching power supply can achieve high efficiency, small volume and light weight.

After the 1970s, high frequency, high back pressure power transistors, high frequency capacitors, switching diodes, switching transformer cores and other components related to this technology have been developed and produced continuously, which has made the switching power supply without power frequency transformer develop rapidly, and has been widely used in the fields of electronic computers, communications, aerospace, color TV, etc., thus enabling Switching power supply without power frequency transformer becomes the leader of all kinds of power supply.

The necessity of using regulated power supply

With the rapid development of society, the number of electric equipment is increasing. The aging and lagging development of the power transmission and distribution facilities of the linear regulated power supply, as well as the poor design and insufficient power supply and other reasons cause the terminal user's voltage to be too low, while the terminal user's voltage is often too high. There is no insurance for electric equipment, especially for high-tech and precision equipment with strict voltage requirements.

Unstable voltage will cause fatal injury or misoperation to the equipment, affect production, cause delay in delivery, unstable quality and other losses. At the same time, it can accelerate the aging of the equipment, affect the service life and even burn the accessories, which makes the owner face the trouble of maintenance or to update the equipment in a short period of time and waste resources; serious accidents even occur, causing incalculable losses.