Principle of Power Adapter

Principle of Power Adapter

Power adapter is an indispensable electronic equipment in our daily life, widely used in mobile phones, laptops, television, security cameras, routers and other small portable electronic equipment and electronic appliances. Its main role is to convert alternating current (AC) to direct current (DC) and adjust the voltage and current to a level suitable for equipment use. This article will introduce the principle of the power adapter and its working mechanism in detail.

*The basic composition of the power adapter

The power adapter is generally composed of a shell, transformer, inductor, capacitor, control IC, PCB board and other components. Its core components include transformer, rectifier circuit and voltage regulator control circuit.

*Transformer

Transformer is the core component of the power adapter, which is responsible for converting the input AC voltage into the output voltage suitable for the use of the equipment. The transformer realizes the voltage transformation through the principle of electromagnetic induction, that is, the use of two or more mutually coupled coils (one is the primary side coil, one is the secondary side coil), through the alternating magnetic field generated by the alternating current in the primary side coil, so as to induce the corresponding voltage in the secondary side coil.

*Rectifier circuit

The function of the rectifier circuit is to convert alternating current into direct current. In the power adapter, the diode bridge rectifier circuit is usually used, the circuit is composed of four diodes, through a specific connection mode, so that AC through the diode bridge, only positive half (or negative half) of the voltage can pass, so as to achieve the conversion of AC to DC. The rectifier circuit also further eliminates voltage fluctuations by filtering components such as capacitors, making the output voltage more stable.

*Voltage control circuit

The voltage control circuit is the key part to ensure the stability of the output voltage. By detecting the change of the output voltage and adjusting the control signal, it controls the ratio of the opening and closing time of the switching tube to maintain the stability of the output voltage. Voltage regulator control circuit usually adopts pulse width modulation (PWM) technology, by adjusting the duty ratio of PWM signal, the output voltage can be accurately controlled.

The working principle of the power adapter is mainly based on the principle of electromagnetic induction and power electronics technology. When the power adapter is connected to the mains, the input circuit first converts the mains (usually 220V AC) into direct current and boosts or depresses it to the voltage range suitable for the device through the transformer. The rectifier circuit further converts alternating current to direct current and eliminates voltage fluctuations through elements such as filtering capacitors. The voltage regulator control circuit realizes the precise control of the output voltage by detecting the change of the output voltage and adjusting the duty cycle of the PWM signal to ensure that the equipment can work stably.

Switching power supply technology Modern power adapters mostly use switching power supply technology, which realizes the stability of the output voltage by controlling the ratio of switching transistor on and off time. The switching power supply has the advantages of high conversion efficiency, small size, light weight and wide range of voltage regulation. In the switching power supply, the MOSFET (metal oxide semiconductor field effect transistor), as a switching component, is driven by the excitation signal, alternately working in the on-off and cut-off states, so as to achieve voltage transformation and voltage regulation control.

*Common faults and maintenance

 During the use of the power adapter, you may encounter various faults, such as unstable output voltage, no output, and serious heating. In the maintenance, the first need to check the input voltage and output voltage is normal, and then check the power line, plug, transformer, rectifier circuit, voltage regulator control circuit and other components are normal. If the power control chip is normal but the output voltage is unstable, the output end of the control chip may be faulty or the peripheral oscillating circuit components are damaged. Check and replace them one by one.

As a small portable electronic equipment and electrical and electronic power supply conversion equipment, the principle of the power adapter is based on the principle of electromagnetic induction and power electronics technology. Through the cooperative work of transformer, rectifier circuit and voltage regulating control circuit, the conversion from AC to DC and the stable voltage output are realized. Modern power adapter adopts switching power supply technology, which has the advantages of high conversion efficiency, small size, light weight and wide voltage regulation range. In the process of use, it is necessary to pay attention to inspection and maintenance to ensure the normal operation of the equipment and extend the service life.