Wide bandgap technology to maximize efficiency and power density in high-voltage LED lighting
easy. It is clear that GaN switch implementation using CCM is a great combination for high- voltage LED lighting applications, as well as many others. The basic scheme of an Inverse Buck topology is shown in Figure 2 along with an implementation that uses the MASTERGAN4 . MASTERGAN4 embeds two 225 mΩ (typical at 25°C) 650 V GaN transistors in Half-Bridge configuration, a dedicated Half-Bridge gate driver and the bootstrap diode. This high level of integration simplifies the design and minimizes PCB area in a small 9x9 mm QFN package. The evaluation board that is shown in Figure 3, was designed with the MASTERGAN4 in an inverse
buck topology has the following specifications: it accepts up to 450 V input, the output voltage of the LED string can be set between 100 V and 370 V; it operates in Fixed Off Time (FOT) CCM with a switching frequency of 70 kHz; the max output current is 1 A. The controller in this solution, the HVLED002 , is used to generate a single PWM control signal. An external circuit based on simple Schmitt Triggers is then used to generate two complementary signals to drive the low side and high side GaN transistors with a suitable dead time. Two linear regulators are also included to generate the supply voltages needed by the MASTERGAN4. The inverse buck topology
Figure 3: Example of Inverse Buck Demo with MASTERGaN4. (Image source: STMicroelectronics)
Figure 4: Efficiency vs. LED voltage for MasterGaN and Silicon MOSFET. (Image source: STMicroelectronics)
16
Powered by FlippingBook