A different category of stable power supply, distinct from linear voltage regulators, is the switching DC voltage regulator. Its circuit types primarily include single-ended flyback, single-ended forward, half-bridge, push-pull, and full-bridge configurations. The fundamental difference between it and linear power supplies lies in the transformer, which operates not at the power frequency but at frequencies ranging from several tens of kilohertz to several megahertz. The switching transistors are not operating in the saturation and cutoff regions, i.e., in the switching state; hence, the name "switching power supply."
The advantages of switching power supplies include their compact size, lightweight, and stable and reliable performance; however, they have a higher ripple compared to linear power supplies (generally ≤1% VO(P-P), with good ones achieving several dozen mV(P-P) or less). They come in power ratings from a few watts to several thousand watts, and the prices range from 3 yuan to tens of thousands of yuan per watt. Below, we introduce several types of switching power supplies according to general industry practices:
AC/DC Power Supply
This type of power source, also known as primary power, draws energy from the power grid and, after high-voltage rectification and filtering, produces a DC high-voltage output. It supplies DC/DC converters to obtain one or more stable DC voltages at the output, with power ratings ranging from a few watts to several thousand watts, catering to various applications. There is a wide variety of specifications and models for such products. The primary power sources in communication power systems (with AC220 input and DC48V or 24V output) also fall into this category.
② DC/DC Power Supply
The secondary power supply, also known as a secondary power in communication systems, is a DC input voltage provided by a primary power source or a DC battery pack, which, after DC/DC conversion, yields one or several DC voltages at the output end.
③ Communication Power Supply
Communication power supply is essentially a DC/DC converter power supply, which is typically powered by DC-48V or -24V and backed up by a battery for DC power supply. It converts the DC power supply voltage into the working voltage of the circuit. Generally, it is divided into three types: central power supply, hierarchical power supply, and single-board power supply, with the latter having the highest reliability. Aviation ground power: 2 x 2,36V aviation power, 1 x 400HZ variable frequency power supply, 2 x 115/200V power supply, 5 x 27V DC power supply, 12 x 400HZ power supply, aviation power supply.
④ Radio Power Supply
This radio power supply inputs AC 220V/110V and outputs DC 13.8V, with power varying according to the radio's specifications, offering models ranging from a few to several amperes. To prevent radio operation from being affected by AC grid power outages, a battery pack is required as a backup. Therefore, this type of power supply not only outputs a 13.8V DC voltage but also features an automatic switching function for charging the battery.
⑤ Module Power Supply
With the rapid development of science and technology, there is an increasing demand for power reliability and a higher capacity/volume ratio. Modular power supplies are increasingly demonstrating their superiority due to their high operating frequencies, compact sizes, and high reliability. They are also easy to install and expand, making them more widely adopted. Currently, although there are domestic modular production capabilities, the relatively high failure rates are due to the manufacturing processes not keeping pace with international standards.
Although the DC/DC module power supply is currently expensive, considering the overall cost over the long-term product lifecycle, especially when accounting for the high repair costs and reputation loss due to system failures, opting for this power module is still cost-effective. It's also worth mentioning the Roche transformer circuit, which boasts an exceptional advantage of simple circuit structure, high efficiency, and near-zero ripple values for output voltage and current.
