LT8705 250W MPPT solar Controller CC-CV charging DC-DC buck boost 6-80V TO 1.3-80V 5V 12V 15V 24V Lithium / LiFePO4/ Battery | Электроника

250W solar MPPT CC-CV charging LT8705 automatic buck-boost DC-DC

    　   Description: Features: 


Input voltage: 6V-80V Output voltage: 1.3-80V Input current: 0.5-15A Output current: 0.5-15A

1. Module size: 103*65*24

2. Linear Technology LT8705 synchronous rectifier automatic buck-boost control scheme

3. Non-isolated BUCK-BOOST

4. Current mode control (see the difference between current mode and voltage module, the former is better than the latter)

5. Input voltage 6-80V

6. The adjustable range of input current is 0.5-15A,

7. Adjustable input voltage range: 9-60V This function is suitable for MPPT solar panels. For details, please see the detailed instructions.

8. Output voltage adjustment: 1.3-80V

9. Output current adjustment: 0.5-15A (strongly recommended to use within 15A, relatively stable point, the waveform will not jitter)



Module advantages:

1 It has a high input working voltage value above 60V and can withstand 80V pulse voltage,

2. High output current: the output current can reach 15A for long time work, the maximum current is 20A.

3. Adjustable input and output current: adjustable input current is suitable for input as a constant current source, adjustable output current is especially suitable for high-current charging of batteries, and high-current charging such as iron-lithium batteries, which basically covers all batteries.

4. With input and output voltage adjustment function: input voltage adjustment is suitable for tracking the maximum power point voltage of the solar panel, and to a certain extent realizes the function of maximum power point tracking.





Instructions:

Potentiometer adjustment: (input and output current adjustment is affected by the chip control principle. The adjustment process is not linear)

The two potentiometers are adjusted in a clockwise direction to increase the value.

1. Input voltage adjustment potentiometer: Assuming that the minimum input voltage needs to be set to 20V, the adjustment method is to connect the input terminal to a 20V power supply, and adjust the potentiometer clockwise until the module stops output. At this time, it is the 20V undervoltage shutdown value. If the input is a constant current source and the load is large, the module will reduce the input current to keep the input voltage at 20V.

3. Output voltage adjustment potentiometer: adjust the output voltage clockwise to increase, and counterclockwise to decrease.

4. Output current adjustment potentiometer: The adjustment method is to connect the multimeter and a large load in series with the positive and negative poles of the output terminal (or directly use the multimeter to short-circuit the output, this is not recommended, the accuracy will be offset) counterclockwise to adjust the potentiometer until The current value of the multimeter is reduced to the required value. (The adjustment premise is that the input power is not limited or the limited value is greater than the output power during adjustment, otherwise the correct output value cannot be obtained because the input power is limited) Use the module's own ammeter adjustment method to ensure that the output voltage is above 5V, The output terminal is connected to a large load larger than the required current value, and the potentiometer is adjusted counterclockwise until the displayed value is the required value. (The reason is that the output current detection function needs to ensure that the output voltage is above 3V. After short-circuit output, the output voltage is less than 3V and the output current value cannot be displayed).

If you need a module, please inform the use environment in detail, will evaluate the effect of use, can also give some suggestions for use, and will actually test the working conditions under this parameter before shipment.





Application note

1. Solar maximum power charging: The input current limit function is very suitable for solar panel constant current source charging. It is a good choice to purchase two 200W battery panels and charge the module. The output is directly connected to the battery for charging, no need to worry about reverse irrigation, just output The positive and negative of the battery are not reversed.

2. Car battery high-current and high-efficiency charging, car two-stage battery charging power supply system

3. Large-capacity lithium battery, iron-lithium battery, high current constant current charging

4. High-power LED constant current drive

5. Battery regulated power supply system, backup regulator for telecommunication base station.

6. It can be used as a less demanding adjustable voltage stabilizer source (response speed, accuracy, and noise are not as good as linear voltage stabilizers, but have high efficiency and high power characteristics)

7. Other adjustable constant current applications

Remarks:

1. The output voltage is different, MOS tube and capacitance are different, filtering effect, efficiency and transient capability are different, it is recommended to choose according to actual needs, input and output are lower than 40V, you can contact to use other parameter combinations.

2. When the measured Vgs=6V, the on-resistance of the MOS is only 3 milliohms, which reduces the I2R loss during the pass-through to a certain extent.

3. The input current and output current adjustment range of the module is 0.5-20A. (In the new version, in order to reduce the loss on the sampling resistor, the minimum adjustment current is 1A, and a very small current is required, please specify)

4. If the input/output ratio is less than 2 times, there is no pressure when working at 10A for a long time, and it is necessary to strengthen heat dissipation above 15A. Good heat dissipation will have a long life.

other

The difference between DC-DC controller current mode and voltage mode:

Voltage mode: There is only one voltage feedback loop, and the PWM is changed after the voltage signal is transformed. The dynamic response is poor and a larger filter capacitor is required. The system does not have a built-in current-limiting protection function, some of which may be external and do not participate in system feedback.

Current mode: fast dynamic response, good stability, real soft start of inductor current, accurate and fast current feedback, easy to realize current sharing; easy feedback design; relatively low requirement on capacitance; this mode uses inductor current signal as feedback inner loop, plus The upper voltage feedback is dual-loop control of the outer loop.

MPPT function: The module has an input voltage limit function, that is, after setting the solar maximum power point voltage, as long as the voltage is lower than this value, the module will reduce the output current, reduce the output power, and ensure that the input voltage is stable at the set value. For example, the maximum power point voltage of the solar cell is 34V, first adjust the input voltage to 30V, and adjust the input voltage potentiometer clockwise until the module has no output. At this time, the maximum input voltage of the module is 34V.

Compared with the general solar controller without MPPT function, the energy utilization rate of this module is still much higher, at least under the maximum light conditions.

It is difficult to adjust the maximum power point without suitable conditions. It is recommended to inform me of the voltage and current parameters of the maximum power of the panel to adjust it before shipment. The principle of the maximum power point is that the product of the two header values ​​of the module is maximized. According to this, the input current is adjusted first and the input voltage is adjusted.

The three working modes of the module can be selected according to the actual situation. See the following for how to choose:

1: Forced continuous mode, the inductor current is continuous, the advantage is that the output ripple is small under the same output filtering conditions, and the output current adjustment is relatively stable. However, under different output conditions, the inductor current is allowed to reverse, that is, the input will absorb current to the output. If the output voltage of the module is lower than the voltage of the battery being charged, the current will flow back to the output, resulting in a high output voltage or even damage to the module.

2: Discontinuous mode, the inductor current is discontinuous, the disadvantage is that the ripple is relatively large, and the output current adjustment range may be noisy. However, the inductor current will not be reversed, the output voltage of the module can be lower than the battery voltage, and will not be reversed to the output, which is relatively safe for battery charging. (The measured voltage is 58V directly to the output terminal of the module and the output of the module is 14V at this time)

3: Skip mode: the inductor current is intermittent, and the efficiency is higher under light load or no-load conditions. The no-load current is typically only a few milliamps, while the no-load current in other modes is tens of milliamps. The disadvantage is that it is difficult to ensure the stability of the four regulation loops.
 
 

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