Working characteristics and selection of switching power supplies
Switching power supply is a type of power supply that uses modern power electronics technology to control the time ratio of the on and off of the switching transistor, maintaining a stable output voltage. Switching power supply is generally composed of pulse width modulation (PWM) control IC and MOSFET. The working principle of a switching power supply is that when the switching element is in an open circuit state, the current in the circuit cannot flow, resulting in zero voltage and power in the circuit; When the switching element is in the closed state, the current in the circuit can flow, thereby causing the voltage and power in the circuit to reach predetermined values.
Compared to linear power supplies, the cost of both switching power supplies increases with the increase of output power, but their growth rates are different. The cost of a linear power supply is actually higher than that of a switching power supply at a certain output power point, which is called the cost reversal point. With the development and innovation of power electronics technology, the technology of switching power supplies is constantly innovating, and this cost reversal point is increasingly moving towards the low output power end, providing broad development space for switching power supplies.
The working characteristics of switch mode power supply:
1. Small size and light weight: Due to the absence of power frequency transformers, the volume and weight are only 20-30% of linear power supplies.
2. Low power consumption and high efficiency: Power transistors work in a switching state, so the power consumption on the transistor is low and the conversion efficiency is high, generally 60-70%, while linear power supplies only have 30-40%.
3. Simple structure, high reliability: easy to maintain, and the current ripple rate can be easily achieved at a relatively low level.
The advantage of a switch power supply is that it can quickly and conveniently control the power switch, and can effectively save energy. The disadvantage is that switch mode power supplies have a short lifespan and are easily affected by external factors such as humidity, temperature, etc.
Selection of Switching Power Supply:
1) Select appropriate input voltage specifications;
2) Choose the right power supply: To extend the lifespan of the power supply, you can choose a model with a 30% increase in rated output power.
3) Consider load characteristics: If the load is a motor, light bulb, or capacitive load, when the current is high when powered on, a suitable power source should be selected to avoid overload. If the load is a motor, voltage backfilling should be considered when shutting down.
4) It is necessary to consider the working environment temperature of the power supply and whether there are additional auxiliary cooling devices. In power supplies with excessively high ambient temperatures, it is necessary to reduce the output. The derating curve of output power with respect to ambient temperature.
5) Select each function based on application requirements
6) Select the required safety regulations and electromagnetic compatibility (EMC) certification.
