In today's electronic world, power converters are needed for everything from medical devices, phone and laptop chargers, to auxiliary power supplies. The constantly shrinking packaging size, thermal management, variable input voltage, and intelligent charging protocols have made the design of power supplies and converters increasingly complex, while also placing higher demands on energy efficiency.
In the past decade, new switch technologies utilizing gallium nitride (GaN) on-chip integrated circuits (ICs) have emerged. The characteristics of gallium nitride circuits vary at the atomic level, so power converter designers face both challenges and solutions.
GaN semiconductors have a wide bandgap; At 3.4 eV, its bandgap is more than three times that of silicon semiconductors. Like other wide bandgap materials, GaN semiconductors are capable of operating at higher voltages and temperatures up to+400 ° C, making them suitable for higher power applications, as well as operating at higher frequencies, making them suitable for radio frequency (RF) and 5G applications.
Compared with silicon ICs, GaN integrated circuits optimize transistor related losses such as series impedance (RDS (ON)) and parallel capacitance (COSS) with smaller external dimensions in power converter applications. Within the same footprint as silicon ICs, GaN ICs can not only handle higher frequencies but also generate less heat. This feature allows designers to shrink or eliminate bulky heat sinks.
However, the control of GaN transistors may be challenging. This type of transistor can withstand high frequencies, which means that the control driver must be physically located close to the transistor to eliminate delay and effectively reduce the switching speed of the transistor, avoiding unnecessary electromagnetic interference (EMI). Designers of power converters using GaN eliminate these challenges by using a single device that combines a high-voltage power switch for the primary side (input) and a control IC and feedback circuit for the secondary side (output).
Detailed characteristics of switch operation
Power Integrations utilizes PowiGaN ™ InnoSwitch 3 technology has developed multiple series of such packaged devices. For example, the InnoSwitch 3-CP series conversion switch IC (Figure 1) uses a quasi resonant (QR) flyback controller to provide constant voltage (CV)/constant current (CC) outputs to achieve a constant power (CP) curve.
The primary and secondary sides of the IC are electrically isolated, but the output voltage and current information are transmitted from the secondary controller to the primary controller through inductive coupling. FluxLink communication technology can quickly provide accurate information to achieve fast load transient response and switch frequencies up to 70 kHz.