In the PCB copy board technology, the inverse is the basis for PCB schematic diagram or document directly Anti-kind product launch PCB schematics, circuit board designed to illustrate the principles and working conditions, product commissioning, maintenance and improvement process based on the same play indispensable role. This paper introduces according PCB back to the schematic circuit diagram of a solar cell phone charger, to help you make your own kind of solar cell phone charger that uses solar panels by DC voltage conversion circuit to the phone after charging the battery, and can charge the battery automatically stop charging after completion.
When using solar cells due to the larger changes in sunlight, its resistance and relatively high, so the output voltage is unstable, the output current is also small, which requires using a DC voltage conversion circuit transformation after charging the battery for the phone, the DC conversion circuit Figure 1, it is a single tube DC conversion circuit, single-ended flyback converter circuit form. When the switch VT1 conduction, high-frequency transformer T1 primary coil induced voltage NP 2 is a positive negative, positive secondary winding Ns 5 and 6 losses, rectifier diode VD1 is off, then the high-frequency transformer T1 through the primary coil Np stored energy; VT1 when the switch is turned off, the secondary winding Ns 5 6 positive negative energy stored in the high-frequency transformer T1 through the VD1 rectifier and filter capacitor C3 to the load output.
Circuit works briefly as follows:
Switching power transistor VT1 tube, which, T1, R1, R3, C2 composed of self-excited oscillation circuit. Plus the input supply current to flow through the startup resistor R1 VT1 base, so that VT1 conduction.
VT1 conduction, the transformer primary winding Np plus the DC input voltage, the collector current Ic in a linear increase in the Np, a positive feedback winding Nb 3 4 losses generated induced voltage VT1 obtained that the base is extremely positive, the emitter to the negative Positive feedback voltage, this voltage through C2, R3 to inject VT1 VT1 base current so that the collector current is further increased, the positive feedback generated an avalanche process so that VT1 saturated conduction. In VT1 saturated conduction period, T1 through the primary coil Np stored magnetic energy.
At the same time, the induced voltage is charged to C2, C2 with higher charging voltage, VT1 base potential gradually decreases, the current change when the base can not meet the continued VT1 saturated, VT1 exit saturated zone into the enlarged area.
VT1 into the enlarged state, the collector current is decreased by the maximum value before the enlarged state, generating the feedback winding Nb 3 L four positive induced voltage VT1 base current is reduced so that the collector current decreases, n Feedback avalanche process occurs again, VT1 rapidly closing.
After VT1 deadline, the energy stored in the transformer T1 to the load, 5 negative 6 positive voltage is rectified and filtered by diode VD1 secondary winding Ns generated after the C3 DC voltage to charge the phone battery.
When VT1 deadline, the DC power supply input voltage and Nb 3 induced a positive voltage and a negative 4 by R1, R3 to C2 reverse charge, a gradual increase in VT1 base potential to re-conduction, flip again reach saturation, So go on repeating the oscillation circuit.
R5, R6, VD2, VT2 composed voltage limiter circuit to protect the battery is not overcharged, here to 3.6V cell phone battery, for example, limiting the charging voltage is 4.2V. In the process of charging the battery, the battery voltage is gradually increased, when the charging voltage is greater than 4.2V, by R5, R6 partial pressure after the beginning of the Zener diode VD2 conduction, so VT2 conduction, streaming effect of reducing the VT1 VT2 base Current-VT1 to reduce the collector current Ic, thus limiting the output voltage. Then the circuit stops the large current charging the battery, with a small current to the battery voltage is maintained at 4.2V.
Component selection and installation
VT1 requirements Icm> 0.5A, hEF 50-100, available 2SC2500, 2SC1008, etc., VD1 is a Zener diode voltage is 3V.
High-frequency transformer T1 to self-control, with E16 ferrite core, Np around 26 turns enameled with φ0.21, Nb 8 turns around with φ0.21 enameled, Ns 15 turns enameled with φ0.41. Note that when the winding starting end of each coil no mistake, so the output voltage of the circuit can not afford to vibration or abnormal. When the pad assembly having a thickness of about 0.03mm for plastic film between the two cores in the core gap.
Solar panels using four area of 6cm × 6cm silicon solar panels, the no-load output voltage of 4V, when the operating current of 40mA when the output voltage is 3V. Because of the efficiency of the DC-DC converter with input voltage increases and higher, so after four solar panels in series, then the input voltage of the circuit is 12V. Readers can determine the number and connectivity method according to which you can purchase solar panel specifications.
Parameters other elements in Figure 1.
The printed circuit board shown in Figure 2, the size of 45 × 26mm2.
After installation is complete, connect the solar panels, and put it under the sun, when the load circuit output voltage is approximately 4.2V, the output voltage when the load is higher than 4.2V may be appropriate to reduce the resistance R5, whereas the increase R5 resistance. Circuit operating current with the strength of the sun related to the normal of about 40mA, then the charging current is about 85mA.
Its inverse schematics and PCB were made strict network proofreading, complete and clear and easy to figure check component position number, model number, network name, etc., and a "functional modules related components relative concentration" and "modular" rendering , readability and design comparable to the original image. Customers can easily grasp the idea of product design, the bright spot to capture some of the high-end design to help electronic engineers for product technical analysis, as well as to upgrade the secondary development of applied research, in order to develop a more high-end products.
