■ The VGS threshold range and the RDS(on) difference between transistors are important.

Another consideration when devices are operating in parallel is the effect of parasitic inductance and capacitance on the PCB (layout, traces, layer arrangement) along with component selection.

When it comes to CoolGaN™ HEMTs , the VGS threshold range and the RDS(on) difference between transistors are important considerations.br />
To verify this, we performed simulations using transistor models in SIMetrix with threshold voltages ranging from 0.9 V to 1.6 V and RDS(on) values ranging from 55 mΩ to 70 mΩ. We also modeled the effects of trace inductance and layer capacitance.

The results of this analysis show that the static imbalance due to current sharing is entirely related to the difference in RDS(on) between the transistors. This can be resolved by device matching.

Also, as mentioned above, continuous and destructive oscillations can be eliminated by using CM inductors. It is also important to follow good layout practices.

The power loop and gate drive loop should be as small and symmetrical as possible, and the switch node parasitic capacitance should also be as low as possible.

■ Infineon provides parallel half-bridge evaluation board with four 70mΩ IGOT60R070D1 GaN power transistors

The best way to understand the problem and its solution is to try it out in the lab. For this purpose, Infineon offers a parallel half-bridge evaluation board featuring four 70 mΩ IGOT60R070D1 GaN power transistors .

This evaluation board has been designed following the aforementioned design guidelines, making evaluation and development tasks easy and fast.

It also provides multiple test points to allow for comprehensive analysis.
However, some measurement points require the use of high-bandwidth isolated differential probes, which must be deskewed prior to use to achieve accurate channel timing.
When used with an external inductor, this board can be used for things like buck or boost mode testing, double pulse testing, and PWM operation testing.

Additionally, the board is suitable for both hard and soft switching at power levels in the kW range and frequencies up to 1MHz.

A removable terminal block simplifies test setup configuration and provides connectors for adding capacitance in addition to the onboard 100 μF 450 V bulk capacitor.

This onboard capacitor is rated at 450V along with two additional high frequency bypass capacitors.Sets the output or bus voltage limits.
This evaluation board can operate with up to 28A continuous current and 70A peak current with hard switching or soft switching.

However, suitable heatsinks, thermal interface materials, and airflow must be used.

It also includes a potentiometer as a dead-time circuit, implementing delayed turn-on via an RC network and non-delayed turn-off via a diode.
■ Be aware of differences in gate drive when using GaN power transistors

Silicon MOSFETs have been widely used in parallel configurations in power converters, but GaN power transistors have attracted many design engineers.It's completely low.

The first thing to know when using GaN power transistors is that the gate drive is different.

Using it in a parallel configuration is then relatively straightforward, but there are a few considerations to keep in mind.

Especially during design, attention must be paid to current balancing between devices and PCB layout under static conditions.

Destructive oscillations can be prevented by using appropriately sized CM inductors in the gate and Kelvin source paths. - Check the GaN HEMT evaluation board
ransistor/?utm_source=ed4s&utm_medium=referral&utm_campaign=202104_ap_en_pss_+pss.pphv_gan.2021-kr&utm_content=paralleling+gan+article#!applications" target="_blank">- SMPS application examples for servers and communications
- Case study of ultra-fast wireless charging application
- Class D Audio Amplifier Application Case
.2021-kr&utm_content=paralleling+gan+article#!documents" target="_blank">- Check the GaN HEMT Datasheet
- Watch CoolGaN Transistor Video Lecture