四月 07, 2017
This post was written by EDN senior technical editor, Steve Taranovich for the Power-management Design Center , How To Article section on APEC 2017. Originally published on April 03, 2017.
While visiting Efficient Power Conversion’s booth at APEC 2017, I became keenly aware of what CEO and co-Founder, Alex Lidow has been leading up to when he hired an immensely talented technical team initially in 2007 and added more talent along the journey to 2017 which would lead GaN power element development toward a process perfection effort and on through to the creation of a growing set of high profile industry applications to performance heights that the power industry has never seen.
Some key members of the EPC team at APEC 2017 including (left-to-right) Joe Engle, Director of Marcom; Alex Lidow, PhD, CEO and co-Founder; Dr. Yuanzhe Zhang, Director, Applications Engineering; and Michael de Rooij, PhD, Vice President, Applications Engineering posed with with EDN/Planet Analog editor Steve T.
LIDAR: Seeing the light to automotive safety with eGaN
John Glaser, PhD was instrumental in developing the eGaN-enhanced LIDAR system which led EPC to designs in most every automotive LIDAR application in the industry today. Glaser told me that he learned much about the intricacies of LIDAR design to successfully and reliably perform for the safety needs of the demanding automotive sector.
In this video, John Glaser, PH.D, discusses EPC’s LiDAR design using pulsed lasers which quickly create a three-dimensional image/map of any surrounding area with the need for speed and accuracy of the laser and the capability of eGaN FETs to enable ultra-short transition times of < 1ns. This technology provides increased accuracy in applications such as autonomous vehicles and augmented reality systems.
Glaser explained to me that the EPC9126 demo board was the culmination of his development efforts to create the best LASER driver system for the automotive industry as well as for other LASER applications.
The EPC9126, a 100V, high current, pulsed LASER diode driver demo board highlighting the EPC2016C
eGaN power FET capable of 75A pulses with a total pulse-width of 5 ns (10% of peak). The eGaN FET is driven by a Texas Instruments UCC27611 gate driver. This board has multiple options for mounting laser diodes and can drive these via a discharging capacitor (as shipped) or directly from a power bus.
The EPC9126 demo board was designed to operate as a capacitive discharge laser diode driver and comes with the EPC2016C eGaN FET and a commercially available gate driver, the Texas Instruments UCC27611, although it can accommodate the much larger EPC2001C, a 100-V, 7-mΩ FET with a 150-A pulse current rating
Glaser commented on the two different techniques for driving Laser diodes1. In a LIDAR application, the primary factor is device speed, which is determined by gate resistance, gate charge, and gate and source inductance.
Glaser told me about the two most common laser diode driver circuits for pulsed LIDAR applications: (a) A capacitive discharge driver and (b) an FET-controlled driver. (Image courtesy of Reference 1)
Simplicity and the ability to accept stray inductance make the Capacitive Discharge approach popular.
In the FET-controlled driver approach, the circuit must switch slowly enough that stray parasitic inductance does not significantly degrade the waveforms. Considering parasitic inductance, this means rise and fall times as much as an order of magnitude slower than the capacitive discharge approach. This will not work well in a LIDAR system.
Glaser chose the Capacitive discharge driver technique in EPC’s demo.
So what does eGaN do for LIDAR?:
- Faster Switching for more accurate and smaller pulses
- Higher Efficiency using a higher pulse repetition rate
- Smaller Footprint which enables higher power density, lower inductance, integration with Laser Diode
The LIDAR pulse can be seen here in the demo booth. Fast edge rates in the sub-nanosecond region in LIDAR translate to more accurate measurements of the surrounding area and how close objects are to the vehicle.
Automotive LED headlamps
Gallium Nitride (GaN) FETs have a decided advantage over Silicon FETs because they much higher conductivity and smaller size/capacitance which enable a more efficient power conversion at high switching frequency (fSW). Some issues must be resolved before using GaN in automotive applications. GaN’s high fSW incurs larger di/dt and dv/dt transitions which inject high frequency electromagnetic interference (EMI) noise into the input bus. This unwanted noise can create a malfunction in a safety-critical system. The implementation of a large input filter can reduce this EMI, but will increase the size and cost of the solution---not a good thing in automobiles.
There are various techniques that may be employed to alleviate this problem. GaN’s higher switching frequency ensures operation well above the AM radio band. Soft switching architectures may be employed to remedy this problem as well.
EPC’s eGaN power drive circuitry demo for automotive LED Headlamps at APEC 2017
This Phoenix Aerial Systems aerial drone using 40A, 5ns-wide pulses can be used for high-definition aerial mapping via a drone.
Wireless Power Transfer: “Cut the cord”
Alex Lidow explaining the exciting aspects of ‘cutting the cord’ with wireless power
For more, see my EDN book review of Michael de Rooij’s Wireless Power Handbook.
Wireless Power Table top
EPC’s team, led by Michael de Rooij, Ph.D., created this embedded wireless power demo at APEC 2017. An innovative new antenna design was developed by Dr. de Rooij and embedded into this table with excellent power transfer distance capability as well as capability to power all of the devices you see on this table with no need to position the devices accurately over any antennas.
Wireless power wall-mounted flat-screen TV
The wireless power electronics that enable a large flat-screen TV to be mounted to a wall without power wiring. The design bypasses the AC circuitry inside the TV and directly powers the electronics with wireless DC power.
Be ready for more big announcements by the Efficient Power Conversion team as we progress further into 2017. I will be covering these announcements in technical detail.
- How GaN Power transistors Drive High-Performance LIDAR, John Glaser, Efficient Power Conversion, IEEE Power Electronics Magazine, March 2017