In today's electronic world, power converters are needed from medical devices, cell phone and laptop chargers to auxiliary power supplies. Shrinking package sizes, heat management, variable input voltages, and smart charging protocols all complicate power and converter designs and require higher energy efficiency.
In the last decade, new switching technologies using gallium nitride (GaN) on-chip integrated circuits (IC) have emerged. Gallium nitride circuits differ in atomic level characteristics, so power converter designers face both challenges and solutions.
GaN semiconductor has very wide bandgap; At 3.4 eV, the bandgap is more than three times that of a silicon semiconductor. Like other wide band gap materials, GaN semiconductors can operate at higher voltages and temperatures up to+400 ° C, making them suitable for higher power applications, at higher frequencies, and in radio frequency (RF) and 5G applications.
In power converter applications, the GaN IC optimizes transistor-related losses such as series impedance (RDS (ON) and parallel capacitance (COSS) in a smaller overall dimension than silicon IC. Within the same footprint as the silicon IC, the GaN IC can handle not only higher frequencies but also less heat. This feature allows designers to shrink or eliminate bulky radiators.
However, control of GaN transistors can be cumbersome. The ability of this type of transistor to withstand high frequencies means that the control driver must be physically close to this transistor in order to eliminate delays and effectively reduce the switching speed of this transistor to avoid unnecessary electromagnetic interference (EMI). Power converter designers using GaN eliminate these challenges by using a single device that combines a high voltage power switch for the primary side (input) with a control IC for the secondary side (output) and a feedback circuit.
Detailed characteristics of switch operation
Power Integrations uses its PopwiGaN ™ Technical InnoSwitch3 products have developed multiple series of such packaging devices. For example, InnoSwitch3-CP series transfer switch IC (Figure 1) uses a quasi-resonant (QR) anti-excitation controller to provide a constant voltage (CV)/constant current (CC) output to achieve a constant power (CP) curve.
The primary and secondary sides of this IC are electrically isolated, but the output voltage and current information is transmitted from the secondary controller to the primary controller via inductive coupling. FluxLink communication technology provides fast, accurate information for fast load transient response and switching frequencies up to 70 kHz.
Power Innovations InnoSwitch3-CP Series Change-over Switch IC
Figure 1: The primary and secondary controllers of InnoSwitch3-CP series transfer switch IC are electrically isolated, but feedback can be shared via a flux link (dashed line). Image source: Power Innovations)
InnoSwitch3-CP series integrated circuits handle power from 50 W to 100 W without the need for a heat sink, reducing the total volume of the power supply. These components have a rated continuous operating voltage of 650 V but can withstand surges up to 750 V.
For power supplies using InnoSwitch3-CP series IC, 94% energy efficiency is achieved within the allowable load range, while silicon-based switches are approximately 90% energy efficient. InnoSwitch3-CP series is not only energy efficient but also extremely low in power consumption (less than 30 mW), which helps meet global energy efficiency regulations.
To ensure safety and extend component life, InnoSwitch3-CP Series IC provides enhanced 4000 VAC galvanic isolation between the primary and secondary sides, complies with Underwriters Laboratories (UL) 1577, and each unit passes HIPOT testing. Other safety functions include detection and response to synchronous rectifier field-effect transistors (SR FET) gate open circuit, input line undervoltage or overvoltage, and output overvoltage. The IC controller also limits overcurrent and shuts off before overheating occurs.
InnoSwitch3-EP series IC (Figure 2) is similar to InnoSwitch3-CP series IC. These IC's are not optimized for a single constant power output, but use weighted secondary side regulation (SSR) technology to average the output voltages of multiple channels into control signals.