The launch of 5G, the next generation cellular networ, promises a trio of capabilities that will change the way we approach wireless applications. Many applications will finally be able to ditch the wire thanks to massive connectivity, tremendous throughput, and ultra-low latency.
While businesses and consumers wait for 5G to be available in their regions, network operators must carefully consider how to install the necessary hardware. Today’s equipment frequently makes use of rented sites and properties that have strict floor area, volume, and allowable weight limits.
Furthermore, 5G employs more equipment than 4G, such as active antenna systems (AAS) and micro base transceiver stations (BTS), to provide the coverage required for massive connectivity.
Figure 1. Diagram Massive connectivity necessitates the use of small cell BTS and active antenna systems, all of which have high power demands. Bodo’s Power Systems supplied the image.
Available power at such locations may also be limited, limiting what can be installed. Because rental costs account for roughly one-third of operating expense (OPEX), 5G systems must do more than the 4G systems they replace while being the same or lighter in weight and volume.
Switching Power from Silicon to Gan
Wide-bandgap gallium nitride (GaN) transistors are already contributing to the radio-side of 5G, but they are also being considered for power supplies.
Its superior performance when compared to silicon MOSFETs translates to higher efficiency, which leads to lower heat dissipation, smaller, more compact designs, and improved robustness. Telecom operators benefit from lower energy consumption and fewer on-site visits to service and repair equipment.
GaN high-electron-mobility transistors (HEMT) are well-suited to both power factor correction (PFC) and DC-DC converter stages due to their relatively temperature-independent RDS(ON) and almost no reverse recovery charge (Qrr). Smaller passives can also be used due to the higher switching frequencies supported, resulting in designs that are both compact and lighter in weight than silicon-based alternatives. A switch to natural convection instead of forced-air cooling is frequently considered.
At full load, conduction losses are the most significant contributor, so the switch to gallium nitride makes sense has little effect on efficiency at maximum current consumption
Figure 2. Comparison of the efficiency of a 1 kW fixed-frequency 48 V to 12 V 14 brick DC-DC LLC using silicon MOSFETs and CoolGaNTM. Bodo’s Power Systems supplied the image.
Even when the PFC is already GaN-based, replacing silicon MOSFETs with CoolGaNTM in a 3.6 kW, 385 V to 52 V DC-DC LLC results in even greater improvements. Heat dissipation was reduced by approximately 15% by switching the two synchronous rectifier stages to gallium nitride (GaN).
Despite similar RDS(ON) values in both devices, the supply achieved a peak efficiency of 97.83% in this 160 W/inch3 design (Figure 3). When the impact of the housekeeping supply and cooling fan is taken into account, the peak efficiency approaches 98.5%.
Packaging and Gate Drivers
With an optimized gate driver IC, the advantages of switching from silicon to gallium nitride (GaN) can be enhanced even further. Today’s isolated gate driver enables designers to achieve the lowest switching loss and fastest switching transitions for CoolGaNTM Schottky Gate HEMTs while avoiding excessive ringing or spurious switching.
Today’s isolated gate driver comes witj active Miller clamp and optional negative charge pump to avoid Miller-induced turn-on events, bootstrap voltage clamping, and truly differential input with high common-mode transient immunity are key features. There are available in different driving strengths, allowing designers to optimize the switching speed for each GaN SG HEMT without the need for gate resistors.
Figure 3. CoolGaNTM versus silicon MOSFETs efficiency comparison in a 3.6 kW DC-DC LLC. Bodo’s Power Systems supplied the image.
New power supply housings, as well as heat extraction innovation, are required to reduce equipment weight and provide aesthetically pleasing alternative installation approaches, such as in street lighting. CoolGaNTM‘s low inductance, low-profile PG-VSON surface mount packaging makes this possible.
With a width of only 5 3 1.075 mm, it not only aids passive heat dissipation approaches in narrow, low-profile, and rack-mounted designs, but it also aids in keeping traces short and inductance low.
Figure 4. With its low inductance leakage, the PG-VSON surface mount package of the medium voltage CoolGaNTM device* is ideal for high-frequency switching applications. Bodo’s Power Systems provided the image.
Gans’s Greater Influence On 5g
Gallium Nitride (GaN) is frequently associated with the implementation of 5G RF transceivers due to its performance at high frequencies. However, because of the constraints on equipment volume and weight imposed by the cost of site rental and physical constraints, it is especially relevant for base station power supplies.