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MPPT Solar Charge Simple Structure Jun 05, 2017

This design uses the DC-DC boost circuit to provide the BQ2000 battery charging system, and the use of STC12C5204AD microcontroller programming PWM to track the maximum power (MPPT) output. The system circuit structure is simple, the waveform is good, accurate measurement results, in line with the design requirements.

System program system structure shown in Figure 1, mainly divided into four parts, DC-DC boost circuit, MPPT microcontroller control circuit, battery charging circuit.

The output voltage of the solar panel is boosted by the LM2577 chip, and then the voltage output from the DC-DC booster circuit is sent to the BQ2000 battery charging system to complete the charging of the battery. Due to the completion of MPPT, the use of resistor divider way to sample the solar panel input voltage, combined with the Hall current sensor sampling current, through the LM358 composition of the inverting ratio amplifier circuit to amplify the sampling current, sampling voltage, current through the microcontroller itself AD conversion Outputting a pulse width modulation signal to control the DC-DC boost circuit dynamic resistance, to achieve the DC-DC boost circuit control, so as to achieve the maximum power output.

1 DC-DC boost circuit and dynamic resistance adjustment circuit circuit shown in Figure 2, the use of LM1577 can constitute a step-up regulator power supply. Design examples of the input indicators are: input voltage range: 4V-20V, the output stable voltage Vo = 13V, the maximum output current Iomax = 3A. In order to achieve MPPT, in Figure A below in parallel with the dynamic resistance adjustment circuit, as shown in Figure 3.

The microcomputer generates the PWM rectified by the diode, and then is converted into the dynamic resistance of the collector and emitter of the DC voltage control transistor 9013 after the DC filter, so as to adjust the DC-DC output voltage. The potentiometer R3 accelerates the turn-on and turn-off of the transistor. 2.2 Current sampling amplifier circuit. Because the microcontroller needs to sample the input voltage and current signal to calculate the power, the voltage signal is taken by the resistor divider to obtain relatively easy, but the current sampling is more difficult, the design of the HFB06DS5 Hall current sensor conversion to obtain the current parameters, the sensor can The input current of 0-6A is converted to 0-0.625V voltage to represent the current, its linearity is less than two thousandths. As the sampling signal is in the millivolt level, and the microcontroller only 8-bit AD, low accuracy, so the use of synchronous proportional amplifier amplifier output signal amplification 21 times, and then sent to the microcontroller P1.6 port AD conversion.