The basic knowledge of the power adapter _

The basic knowledge of the power adapter, 2020-1986 07 - 27 10:49:20 power adapter is known as the high efficiency, energy-saving power supply, it represents the development direction of regulated power supply. At present, the monolithic power adapter integrated circuit with high integration, high cost performance, the most simple peripheral circuit, the obvious advantages of best performance, wide application, has become, in the design of small power optimization of power adapter products. Pulse width modulation power adapter that is commonly used in a way of modulation control. Pulse width modulation is a kind of analog control mode, according to the corresponding changes in load modulation transistor base or MOS tube grid bias, to achieve or MOS transistor conduction time change, so as to realize the change of a switching power supply output. Its characteristic is to keep the switching frequency constant, that is, switching cycle is constant, change the pulse width, the grid voltage and load change the power adapter output voltage when the minimum cross load regulation of cross load regulation refers to when a multiplexed output type power adapter in a certain way load changes, caused by the rate of change of output voltage of all stripes. The change of the power load will cause the change of output power, load increase, the output is reduced, opposite load decrease and increase output. Good power load changes caused by output is small, usually index for 3% - 5%. It is measure of multiplexed output power adapter voltage regulator is an important indicator of performance. Parallel operation to improve the output current and output power, can be used multiple power adapter will be connected in parallel. When parallel operation requirement of each power adapter output voltage must be the same, Allow their output power is different) Divide, and USES the current method ( Referred to as 'flow method) To ensure that each output current of the power adapter is in accordance with the provisions of proportion coefficient to allocate. Electromagnetic interference filter, electromagnetic interference filter, also known as 'EMI filter is a kind of' is used to suppress electromagnetic interference, especially the power lines or noise in the electronic circuit device control signal lines. Can effectively suppress the noise power grid, improve the anti-interference ability and the system reliability of electronic equipment a filtering device belongs to the two-way radio frequency filter of emi filter, on the one hand, to filter out from the ac power grid is introduced into the external electromagnetic interference; On the other hand also can avoid itself equipment to external noise, so as not to affect the normal work of the other electronic equipment under the same electromagnetic environment. Emi filter in series mode interference and common mode interference can play an inhibitory effect. Electromagnetic interference filter is connected in the power adapter into the terminal. Radiator is used to reduce the operating temperature of the semiconductor device of a cooling device, can avoid the bad heat dissipation led tube core temperature more than the highest junction temperature, make the power adapter for overheating protection. The cooling way from 亠 small cooling tube core board ( Or package) > The radiator and finally into the surrounding air. Radiator plate type, printed circuit board ( PCB) Type, plate, fork, refers to the type and other types. Radiator should as far as possible away from power frequency transformer, power switch tube heat source, etc. Kind of special electronic load for the power output load electronic device, the electronic load can be adjusted dynamically under the computer control. The electronic load is through the internal power of control ( MOSFET） Or transistor conduction flux ( Duty ratio, size) , rely on the power tube of the electrical energy dissipation power consumption equipment. Power factor power factor ( 功率因数) The size of the associated with the load characters of circuit. It said the ratio of active power and apparent power. The power factor correction or PFC power factor correction. A power factor correction technology is defined as the power factor ( PF) Is the ratio of active power and apparent power s P. Its purpose is to keep the ac input current and ac input voltage and phase and filter harmonic current, to increase the equipment of the power factor to close to 1 of a predetermined value of passive power factor correction of passive power factor correction (PPFC for short Also known as passive PFC) 。 Its passive components inductance is adopted to improve the power factor correction and its circuit is simple, low cost, but easy to produce noise and only to increase the power factor to around 80%. Passive power factor correction main advantages are: simple, low cost, reliable, small emi, the disadvantage is that: the large size and weight, hard to get high power factor, the working performance is related to frequency, load and input voltage active power factor correction active power factor correction APFC (for short Also called active PFC) 。 Active power factor correction refers to through the active circuit ( Active circuit) To improve the input power factor, control switch device for input current waveform follow the input voltage waveform, compared with the passive power factor correction circuit ( Passive circuit) By adding some more complex inductance and capacitance, the improvement of power factor better, but costs are higher, reliability will be reduced. It is in the input rectifier bridge between the output filter capacitor and join a power conversion circuit, the input current into the same as the input voltage and phase correction and undistorted sine wave, the power factor can reach 0. 90-0. 99.