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Monday, July 12, 2010

How to DIY Solar Cell Phone Charger?

Use mobile phones have such an experience: when suddenly without electricity for mobile phone battery charger, because of absence or find can recharge, affects the normal use of the mobile phone. In order to solve this problem, this paper introduces a kind of solar cell phone charger, solar panels, it uses the circuit dc voltage transform to phone battery, the battery can automatically charge.

Working principle

Solar cells in the use of the sun when changes, its resistance and high output voltage instability, therefore, the output current is small, it will need to use a dc voltage transform circuit transform for mobile phone battery, after dc transform circuit (see figure 1, it is single pipe dc, using the ocl circuit transform flyback converter type. When the switch VT1 turn-on, high-frequency transformer winding NP induction T1 primary voltage is 2 to 1, secondary coil Ns for 5 is 6, VD1 rectifier diode, then in cut-off frequency transformer winding T1 through primary energy storage; NP When the switch VT1 deadline, secondary coil Ns for 5 6, high-frequency transformers are stored energy through T1 VD1 rectifier and capacitance C3 to load output filter.

Circuit principle briefly described as follows:

VT1 triode tube for switching power supply, and T1, R1, R3, etc ZiJiShi C2 oscillating circuit. After the input voltage, electric and VT1 flow through the start of passive resistance R1, make VT1 conduction.

VT1 conduction, transformer winding will add input dc voltage Np, its collector current Ic in the Np, linear increase in three positive feedback coil Nb produce inductive voltage 4, VT1 got fired for positive, base is negative, the positive feedback, the voltage to VT1 R3 C2 into the base current collector current VT1 make further increases, the positive feedback, which produces an avalanche VT1 saturated conductivity. In VT1 saturated conductivity, through primary coil Np T1 stored energy.

Meanwhile, inductive voltage to C2 charging, with the increased C2 recharging voltage potential VT1 base, when VT1 low gradually become the base current change cannot satisfy their continued saturated, VT1 exit saturated zone put into the region.

VT1 into amplification, after the collector current amplification of the maximum down before 3 negative feedback coil Nb produce inductive voltage, the four are made VT1, its base current collector current then decreases, and the positive feedback again, VT1 rapidly by an avalanche.

After the deadline, VT1 T1 stored energy of transformer winding, provide loads of secondary 5 6 Ns is VD1 diode rectifier voltage filter, get in C3 to mobile phone battery dc voltage.

In VT1 deadline, dc power supply input voltage and Nb induction of 3 and 4 are voltage by R1, R3 to reverse charge, and gradually improve C2 VT1 base, its potential to conduction, turn again reached saturation, circuit that repeated oscillation.

VD2 R5, R6, components, such as pressure, VT2 circuit, in order to protect the battery charging, here is not to 3.6 V battery charging as an example, the voltage limit 4.2 V. In the process of rechargeable battery, the battery voltage rise gradually, when recharging voltage than 4.2 V, via R5, R6 pressure stabilizing VD2 began after diode conduction, make VT2 conduction, distribution of reduced VT2 is the base of current VT1 VT1, thus reduce the collector current Ic, reached the limits of the output voltage. This circuit has stopped battery charging current, voltage, small current will maintain the batteries in 4.2 V.

Component selection and installation

VT1 requirements, hEF > Icm 0.5 for 50-100, 2SC2500 available for 2SC1008, etc, VD1 voltage stabilizing 3V for the value of the diodes.

High-frequency transformer, using self-made E16 T1 to the magnetic ferrite, Np by φ 0.21 enameled wire around 26 ratios in φ 0.21 enameled wire, Nb around 8 ratios, Ns with φ 15 turns around 0.41 enameled wire. Note that each wound up to locate the coil not make a mistake, avoid vibration or output voltage circuit can not normal. When two magnetic cushion layer thickness between about 0.03 mm plastic film for air-gap magnetic cores.

Solar panels for use 4 x 6cm 6cm area of silicon solar panels, its non-load output voltage, current 4V when working for 40mA for when the output voltage for 3V. Due to the dc converter working efficiency as the input voltage and increased, so 4 pieces of solar panels, then use after series of input voltage circuit for 12V. Readers can according to your specifications of solar panels can be bought the quantity and decided to use the method.

After the installation is complete, and will be connected to the solar panels, the sunshine on output voltage circuit, idling about 4.2 V, when the load voltage output than 4.2 V when the resistance can be appropriately reduced R5, and increasing the resistance R5). Work with the current circuit, normal light intensity is about 40mA, then charge current 85mA about.

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