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Dongguan Jiuqi Industrial Co., Ltd.
Contact: Mr.liang
Mobile: +86-13122876672
Tel: 0769-81818179
Fax: 0769-81806179
Address: Kongwu District, Guxia, Shipai town, Dongguan city
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E-mail:haulwee@vip.163.com
A design example of passive PFC circuit
| A design example of passive PFC circuit |
| Link Switch-TN series of products LNK306P constitute a 9W constant current power adapter based on the passive circuit. The circuit has the following characteristics: (1) simple circuit, low cost. The passive valley filled rectifying filter circuit is matched with LNK306P to realize power factor correction. When the ac input voltage range is 108~132V, the power factor can be increased to more than 0.92, up to 0.965(the corresponding ac input voltage is 90V). The power adapter efficiency under full load condition exceeds 85%. (2) a complex EMI filter (C, L1, L2 and C2) is used at the ac input end, and R1 and R2 are the discharge resistors (3) undervoltage protection is realized by using transistor (VT,2N3906) circuit. (4) the passive grain filling circuit as shown in figure 42-3 is adopted. ,L3 is the energy storage inductance in buck/boost converter. The output rectifier tube VD adopts 1400V ultra-fast recovery diode BYV26B, which conducts during the MOSFET shutdown in LNK306P, and transmits the energy stored by L3 to the output filter capacitor C8 and the load. The output overvoltage protection circuit is composed of voltage regulator VDz and VD, and their voltage regulator values are respectively 39V and 36V(both are typical values). Once the load is open, the output voltage can be clamped at about 75V to protect it. When the load is open, the charge on C8 can be discharged through R13. C9 is a noise reduction capacitor, which is used to reduce the output noise. R1 is the current detection resistance, and the rated output current set is 130mA current. The voltage on R1 is applied to both ends of the LED in the optocoupler PC817A. The feedback signal can be connected to FB of LNK306P feedback terminal through the photosensitive transistor and Rs in PC817A. R12 is the setting resistor of dc gain of the feedback loop. Undervoltage protection circuit consists of R4, R7~R9, C6 and PNP transistor VT. By sampling U, we can indirectly determine whether the grid voltage is normal. U adopts R7~R9 partial voltage to obtain pulsating voltage on R, and then C6 filters out ripple to obtain dc sampling voltage UQ, which is added to the base of VT. UR also decreases significantly when ac input voltage is too low. Once U reaches the undervoltage threshold UB(uv,Ua falls below 5.v, so that VT conduction, collector current flows into the FB end, and MOSFET is turned off, thus playing an undervoltage protection role. When MOSFET is on,VD is in reverse bias and cut off. The current passes through the output filter capacitor C4, load and energy storage inductor L3. While providing constant current to the load, some electric energy is stored on L3. When MOSFET is turned off, the reverse electromotive force generated by L3 leads VD. |
| | release time：2019.10.07 Source： |
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Contact: Mr.liangTel:+86-13122876672Tel:0769-81818179Fax:0769-81806179 E-mail:haulwee@vip.163.com
Address: Kongwu District, Guxia, Shipai town, Dongguan city, China Zipcose:523,339
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