What is the design principle of double tube forward switching power supply
The design of dual tube forward switching power supply is based on the working principle of switching power supply. A switching power supply is a power supply that uses the conduction and cut-off states of switching tubes to control the output voltage and current of a circuit. It does this by transforming the input voltage into a high-frequency pulse voltage and changing it to a DC voltage output through a filter circuit.
Compared with the traditional linear regulated power supply, switching power supply has the advantages of high efficiency, light weight and small size. The dual-tube forward switching power supply is a design that is improved and optimised on the basis of the switching power supply, and its main feature lies in the use of two switching tubes to achieve stable regulation and protection of the circuit.
The basic structure of double tube forward switching power supply includes input filter circuit, rectifier circuit, capacitor filter circuit, switching tube control circuit and output regulation circuit.
Input filter circuit: The input filter circuit is mainly used to filter out the noise and interference signal in the input voltage to ensure the stability and reliability of the circuit.
Rectifier circuit: The rectifier circuit is used to convert the input AC voltage into DC voltage, and generally adopts rectifier bridge rectifier circuit to rectify the AC voltage into pulse voltage.
Capacitor Filter Circuit: The capacitor filter circuit is used to convert the rectified pulse voltage into a smooth DC voltage. The output voltage is stabilised by selecting suitable capacitors and resistors.
Switching Tube Control Circuit: The switching tube control circuit is the core part of the dual-tube positive excitation switching power supply, which realises the regulation and protection of the input voltage and output voltage by controlling the on-state and off-state of the two switching tubes.
Output regulation circuit: the output regulation circuit is used to precisely regulate and control the output voltage. Generally, it adopts the feedback regulation mode to achieve the precise control of output voltage through sampling and comparison circuit.
The working principle of double-tube forward switching power supply can be divided into the following steps:
Conduction of switching tubes: When the input voltage is converted to DC voltage through the rectifier circuit and capacitor filter circuit, and the control circuit detects that the output voltage is lower than the set value, it will cause one switching tube to conduct and transmit the input voltage to the primary coil of the transformer.
Transformer operation: When the switching tube conducts, the magnetic field generated in the primary coil of the transformer induces a voltage in its secondary coil, which transforms the input voltage into a higher or lower voltage through the ratio relationship of the transformer.
Switching Tube Cut-off: When the output voltage is detected to be higher or equal to the set value, the control circuit will cut off the switching tube which is conducting, thus stopping the transmission of the input voltage.
Feedback regulation: The output regulation circuit samples and compares the difference between the output voltage and the set value to control the conduction and cut-off of the switching tubes, so as to realise the precise regulation and stable control of the output voltage.
Overcurrent protection: the double-tube positive excitation switching power supply also has an overcurrent protection function. When the output current exceeds the rated value, the control circuit will immediately make both switching tubes cut off to prevent damage to the power supply and load.
