Why do switching power supplies use high-frequency transformers?
Switching power supply is a kind of power supply that uses modern power electronic technology to control the time ratio of switching on and off to maintain a stable output voltage. Switching power supply is generally composed of pulse width modulation (PWM) control IC and MOSFET. With the development and innovation of power electronics technology, switching power supply technology is constantly innovating. So why do switching power supplies use high-frequency transformers?
Reasons why switching power supplies use high-frequency transformers:
1. For safety, regardless of high frequency or low frequency, the high voltage must be isolated with a transformer.
2. The high-magnet transformer saves material and copper wire, and is small in size.
3. Low-frequency transformers made of materials such as silicon steel sheets are bulky and uneconomical, and are only suitable for isolation of low-frequency pulse power supplies.
4. Why not use transformer isolation at the rectifier? Because you want the switching power supply to be material-saving and compact, you can’t use a large-volume power-frequency transformer at the low-frequency rectifier of the front stage, and because the high-frequency rectifier diode can’t reach the switch tube, The high-frequency transformer outputs a high-frequency square wave of tens of thousands of KHz.
5. The old-fashioned mobile phone charger uses a power frequency transformer, which can only output 500mA, because the low frequency of 50Hz cannot induce a larger electric field on the secondary side coil. If you want to change the output power, it is limited by the diameter and number of turns of the primary primary coil. If you use If the wire is thicker, the number of turns around it will make the transformer hot without load. Therefore, only when the switching tube emits high-frequency oscillation and then outputs it through a small high-frequency transformer, after rectification and filtering and then voltage stabilization, can a safe low-voltage large output be output. Current (such as 5V4A).
The above reasons for the use of high-frequency transformers for switching power supplies are shared here. I hope this article will be helpful to everyone.
