Say Goodbye to Overheating: An Introduction to the Junction Box of QC Solar's "Low-Temperature Module Diode"

In the field of photovoltaic new energy, with the continuous advancement of technology and the ever-increasing market demand for high-efficiency and low-cost solutions, innovation has become a crucial driving force for the development of the industry. QC Solar (stock code: 301278.sz) has launched an ideal diode junction box with higher current specifications, low temperature, and low power loss.

Introduction to the Ideal Diode

Ideal Diode

Functional Block Diagram

Traditional high-current three-piece junction boxes adopt six 165 or 180 Schottky wafers, which are prone to generating significant voltage drops and power dissipation under heavy loads. Expensive heat dissipation solutions are required, increasing the design complexity and size. In contrast, the ideal diode junction box uses one MOSFET to replace two Schottky wafers. It has a smaller reverse leakage current and is more likely to pass the 30A thermal runaway test, significantly reducing the junction temperature. When part of the photovoltaic cell string fails, the MOSFET ideal diode photovoltaic bypass protection module will provide a relatively lower impedance path for the string current after detecting such an imbalance, ensuring that the remaining normal parts can continue to generate electricity.

The ideal diode consists of a MOSFET, a capacitor, and a controller. Compared with traditional Schottky diodes, it demonstrates significant advantages in aspects such as forward voltage drop, heat generation, reverse voltage withstand capability, and reverse leakage current control.

Advantages of the Ideal Diode

1.Significantly Enhanced Safety
The forward conduction voltage VF of the ideal diode is five times lower than that of the Schottky diode, and the power consumption of the ideal diode is also five times lower than that of the Schottky diode. Under the environment of 30A @ 75℃, the temperature of the ideal diode is greatly reduced. It can effectively reduce the risks of junction box deformation and high-temperature occurrence. The ideal diode is designed based on the 3QXY module platform and can replace the Schottky diode module without causing any damage.

2.Substantially Extended Service Life
The long-term high-temperature working environment will accelerate the aging of electronic components and shorten their service life. However, in the hot spot protection mode, the service life of the ideal diode is more than 15 times that of the traditional Schottky diode.

Under a reverse voltage of 30V, the leakage current of the ideal diode is 1/2000 of that of the Schottky diode.

3.Smaller Reverse Leakage Current
The ideal diode has an extremely low reverse leakage current, fundamentally avoiding the risk of high-temperature reverse bias breakdown and effectively solving the problem of diode thermal runaway failure.

Schottky diodes have the risk of high-temperature reverse bias breakdown in practical applications. However, the MOS photovoltaic bypass switch circuit has no such risk and completely solves the problem of diode thermal runaway (meeting the requirements of IEC62979).

Economic Benefit Analysis

In photovoltaic power stations, the ideal bypass diode can save up to 7GWh of electrical energy loss within 20 years. Calculated at a price of $0.07 per kWh (which varies depending on the country), its value can reach $500,000. When the shading time increases to 5%, the saved electrical energy loss can be as high as 12.2GWh, with a value of $860,000.

Conclusion

In summary, compared with the traditional three-piece junction box, the ideal diode exhibits excellent performance in terms of forward voltage drop, heat generation, and reverse leakage current. It can more easily pass the 30A thermal runaway test and junction temperature test. It not only improves the overall efficiency and safety of the photovoltaic system but also brings significant economic benefits.