Abstract: With the progress of society and the development of science and technology, power switching devices are also progressing, in which the important technology of DC/DC converter has also been greatly improved. This paper analyses the development and application of the main technologies such as soft switching, synchronous rectification, phase-shifted PWM technology and multilevel technology in DC/DC converters, and discusses the future development trend of DC/DC converters.

The application of soft switching and synchronous rectification technology makes DCDC converter more efficient and smaller.jpg

　　DC/DC converter is to convert the unregulated non-directly usable DC voltage into a DC voltage that can be adjusted to the size of the voltage, or converted to a fixed DC voltage, DC/DC converter is usually used in switching power supply and DC speed control, with the continuous development and progress of technology, and DC/DC related technologies are also developing, the development of these technologies is also to a certain extent, affecting the DC /DC converter development.

　　First, soft switching technology

　　The development direction of the switch is high-frequency, and high-frequency switches are used more and more frequently in daily life. Higher switching frequency makes the circuit by electromagnetic interference stronger, interference enhancement to a certain extent also affects the stability of the circuit control and circuit drive. So in the high-frequency at the same time should also strive to reduce the loss caused by the switch, the emergence of soft switching technology to a certain extent to solve this problem.

　　Because soft switching technology has the advantages of low loss, high efficiency, reduce electromagnetic interference, high frequency, so in the DC/DC converter has been widely used, the development of soft switching technology to promote the DC/DC converter becomes smaller, more efficient, Dillon new energy DC/DC converter, the application of soft switching technology for production.

　　Second, synchronous rectification technology

　　With the continuous development of science and technology, communications and computer-related industry products in the need for devices and power consumption is also increasing, so that low-voltage, high-current DC/DC converter, device loss at high frequencies is very large, the emergence of synchronous rectification technology to a certain extent, to solve the problem of high loss, reduce the switching loss.

　　Synchronous rectification technology has achieved the ZVS and ZCS two ways, which further reduces the switching loss, and in this regard there has been a great progress, in which digital technology and synchronous rectification technology combined, and also developed for symmetrical topology synchronous rectification circuits, and the use of composite topology makes the synchronous rectification of the effect is better.

　　For example, Dillon new energy vehicle DC/DC converter production combines soft switching technology, fully digital modules and synchronous rectification technology, making the product performance more efficient, smaller, more stable, is widely used in new energy vehicles.

　　Third, phase-shifting PWM technology

　　Phase shifted PWM technology has been well developed in recent years, the technology usually uses bipolar control or limited bipolar control, by adjusting the phase shift angle to adjust the size of the voltage, usually used in high-power full-bridge converter circuits.

　　This technique also has some disadvantages, the rectifier diode is still hard switched under this technique, which increases the loss of the system, in order to change this disadvantage, it is possible to expand the load by connecting an inductor in series in the circuit, which also reduces the loss of duty cycle, suppresses voltage overshoots and oscillations, and enlarges the change of the zero-voltage switched load.

　　This method above usually add an inductor, which will make the control of synchronous rectification becomes complex, but not series inductance will have the phenomenon of loss of duty cycle.

　　Fourth, multi-level technology

　　Multilevel technology refers to circuits with multiple levels of output, at the beginning of the design, multilevel circuits are spliced into the output voltage with multiple levels, this approach can reduce the harmonic content, improve system performance.

　　Multilevel has a great advantage over traditional circuits in the field of high-voltage and high-power, part of the rectifier circuit output voltage is very high, and the resulting voltage stress is also relatively high, this situation can be used in order to reduce the voltage stress, but there are still a lot of shortcomings, one of them is the use of multilevel technology will make the circuit complex, so far, the multilevel technology of DC/DC converter is still still in the process of development. So far, multilevel technology for DC/DC converters is still under development.

　　Because of the complexity of the circuit so the modelling is relatively difficult, how to overcome this problem, simplify the circuit to get a simple topology of the converter, to find a suitable modelling method and a suitable control method is the multilevel technology now to solve the problem.

　　V. Development trend

　　From the current technology development trend, DC/DC converter towards high efficiency, high power density direction, improve the conversion efficiency and power density can reduce the loss in the circuit, high reliability and high performance is also the direction of the development trend of DC/DC converter, the use of soft switching technology can reduce the size of the DC/DC converter, increase the switching frequency, and improve the conversion efficiency.