Power adapter is known as high-efficiency and energy-saving power supply. It represents the development direction of regulated power supply. At present, monolithic power adapter integrated circuit has been widely used because of its significant advantages of high integration, high cost performance, the simplest peripheral circuit and the best performance index. It has become the preferred product of medium and low-power power power adapter in design.
Pulse width modulation
A modulation control mode commonly used in power adapter. Pulse width modulation is an analog control mode, which modulates the bias of transistor base or MOS gate according to the change of corresponding load to change the conduction time of transistor or MOS, so as to change the output of switching regulated power supply. Its characteristic is to keep the switching frequency constant, that is, the switching cycle remains unchanged, and change the pulse width to minimize the change of the output voltage of the power adapter when the grid voltage and load change
Cross load adjustment rate
Cross load regulation rate refers to the change rate of output voltage caused by a change of load in a multi-channel output power adapter. The change of power load will cause the change of power output. When the load increases, the output decreases. On the contrary, when the load decreases, the output increases. The output change caused by good power load change is small, and the general index is 3% – 5%. It is an important index to measure the voltage stabilizing performance of multi-channel output power adapter.
Parallel operation
In order to improve the output current and output power, multiple power adapters can be used in parallel. During parallel operation, the output voltage of each power adapter must be the same (their output power is allowed to be different), and the current sharing method (hereinafter referred to as current sharing method) is adopted to ensure that the output current of each power adapter is distributed according to the specified proportional coefficient.
Electromagnetic interference filter
Electromagnetic interference filter, also known as “EMI filter”, is an electronic circuit equipment used to suppress electromagnetic interference, especially noise in power line or control signal line. It is a filtering device that can effectively suppress the noise of power grid and improve the anti-interference ability of electronic equipment and system reliability. Electromagnetic interference filter belongs to bidirectional RF filter. On the one hand, it should filter out the external electromagnetic interference introduced from AC power grid;
On the other hand, it can also avoid the external noise interference of its own equipment, so as not to affect the normal operation of other electronic equipment in the same electromagnetic environment. The EMI filter can suppress both series mode interference and common mode interference. The EMI filter shall be connected to the AC incoming end of the power adapter.
radiator
A heat dissipation device used to reduce the working temperature of semiconductor devices, which can avoid the tube core temperature exceeding the maximum junction temperature due to poor heat dissipation, so that the power adapter can be protected from overheating. The way of heat dissipation is from the tube core, small heat dissipation plate (or tube shell) > radiator → finally to the surrounding air. There are many types of radiators, such as flat plate type, printed board (PCB) type, rib type, interdigital type and so on. The radiator shall be kept away from heat sources such as power frequency transformer and power switch tube as far as possible.
Electronic load
The utility model relates to an electronic device specially used as a power output load. The electronic load can be dynamically adjusted under the control of a computer. Electronic load is a device that consumes electric energy by controlling the internal power (MOSFET) or the conduction flux (duty cycle) of the transistor and relying on the dissipated power of the power tube.
power factor
The power factor is related to the load nature of the circuit. It represents the ratio of active power to apparent power.
power factor correction
PFC for short. The definition of power factor correction technology is: power factor (PF) is the ratio of active power P to apparent power s. Its function is to keep the AC input current in phase with the AC input voltage, filter out current harmonics, and increase the power factor of the equipment to a predetermined value close to 1
Passive power factor correction
Passive power factor correction is referred to as PPFC (also known as passive PFC). It uses passive component inductance for power factor correction. Its circuit is simple and low cost, but it is easy to produce noise and can only increase the power factor to about 80%. The main} advantages of passive power factor correction are: simplicity, low cost, reliability and small EMI. The disadvantages are: large size and weight, difficult to obtain high power factor, and the working performance is related to frequency, load and input voltage
Active power factor correction
Active power factor correction is referred to as APFC (also known as active PFC). Active power factor correction refers to increasing the input power factor through the active circuit (active circuit), and controlling the switching device to make the input current waveform follow the input voltage waveform. Compared with the passive power factor correction circuit (passive circuit), adding inductance and capacitance is more complex, and the improvement of power factor is better, but the cost is higher and the reliability will be reduced. A power conversion circuit is added between the input rectifier bridge and the output filter capacitor to correct the input current into a sine wave with the same phase as the input voltage and no distortion, and the power factor can reach 0.90 ~ 0.99.
Post time: Apr-12-2022
