One standard method of configuring the backlight is to use two discrete devices: a 100V MOSFET in a DPAK package and a 100V Schottky diode in the same DPAK package. In LED backlight units, the high leakage current of Schottky diodes can cause problems, especially at higher temperatures. Some customers have experienced problems with leaking Schottky diodes during mass production. One way to improve leakage faults is to increase the Schottky diode's voltage rating from 100V to 120V, but leakage current is still a problem when the system temperature is high.
Fairchild's design team developed an alternative approach to adopting the 100V BoostPak solution. The BoostPak series (Figure 1) integrates two devices in a single package: a 100V MOSFET and a 150VNP diode.
Figure 1. BoostPak integrates 100V MOSFET and 150VNP diode in a single package
The BoostPak series is available in a 5-pin DPAK single package. N-Channel MOSFETs are designed to minimize on-resistance and maintain excellent switching performance. The NP diode is an ultra-fast rectifier with low forward voltage drop and excellent switching performance. It has much lower leakage current than Schottky diodes and provides higher system reliability in high temperature applications.
Compared to the dual discrete device solution, the BoostPak solution is smaller in size and saves up to 20mm2 of PCB space. Using a single package instead of two packages also means easier assembly and lower system cost.
The BoostPak series is available in two versions, one with a rated output power of 25W and the other with a rating of 40W. Table 1 lists the details.
Table 1. BoostPak Assembly Specifications
Better performance at higher temperatures
We want to know how low the leakage current of the NP diode is, so we did some testing. The test results are shown in Figure 2.
Figure 2: Comparison of diode leakage current
Compared to 100V, 5A Schottky diodes, the 150V, 5ABoostPak series of NP diodes have much lower rated leakage currents under all conditions, but the two are very different at high temperatures. As the temperature rises, the leakage current of the Schottky diode increases at a very fast rate, while the leakage current of the NP diode is still lower.
The BoostPak series of NP diodes are fabricated using an excellent lifecycle control process for extremely fast reverse recovery times and reasonable forward voltage drop (VF (typ): 0.9V, condition IF = 5A, TJ = 100 degree)
Figure 3: Comparing reverse recovery times
Shenzhen GEME electronics Co,.Ltd , https://www.gemeelectparts.com