DC/DC design principles, experience and application skills

MP24AE off-the-shelf supply

Overview:
The development trend of “green” systems not only means that environmentally-friendly components must be used, but also challenges to the electronics industry. Organizations such as EnergyStar and 80+ have issued regulations for various consumer electronics (especially computing). For current consumers, longer battery life is also a very attractive feature. As a result, longer battery life, smaller form factors, and new regulations introduced by governments require careful selection of power components, especially for on-board DC-DC converters. This means that the power density, efficiency and thermal performance of the new platform must be significantly increased.

It is well known that designing an ideal DC-DC converter involves numerous trade-offs. An increase in power density usually means an increase in overall power consumption, as well as an increase in junction temperature, case temperature, and PCB temperature. Similarly, optimizing a DC/DC power supply for medium to peak currents almost always means sacrificing light load efficiency and vice versa. I have combined my experience of DC-DC application for more than ten years to talk about the basic principles and design experience of DC-DC converters.

DC-DC is a DC-DC converter, generally has two types of boost (BOOST) and step-down (BUCK). The output current of the buck DC/DC converter is large, ranging from hundreds of milliamps to several amps, so it is suitable for applications where the output current is large. The basic working principle circuit of the step-down DC/DC converter is shown in Figure 1. VT1 is a switching transistor. When VT1 is turned on, the input voltage Vi is supplied to the load RL through the inductor L1, and at the same time, the capacitor C2 is also charged. In this process, energy is stored in capacitor C2 and inductor L1. When VT1 is turned off, the energy stored in the inductor L1 continues to supply power to the RL. When the output voltage is to be decreased, the energy in the capacitor C2 is also discharged to the RL, maintaining the output voltage unchanged. Diode VD1 is a freewheeling diode to form a circuit loop. The output voltage Vo is divided by a voltage divider composed of R1 and R2, and the output voltage signal is fed back to the control circuit, and the control circuit controls the on and off times of the switch tube to keep the output voltage constant.

Figure 1, the basic working principle circuit of the buck DC/DC converter (please read the PDF for details)