The Growing Ecosystem for GaN Power Conversion
Mar 21, 2018
There are many reasons to increase frequency of power conversion. Fundamentally, these reasons boil down to size/weight reduction, and cost reduction. There are several components in the design of a power system that must perform efficiently at the targeted increased switching frequencies. These include power switches, power switch drivers, controllers, magnetics, and capacitors. Taken collectively, these components represent the high frequency power conversion ecosystem. Without any of these elements, the benefits of increased frequency cannot be fully realized.
Let’s take a look at the progress in the development of each type of component:
Power Switches – GaN’s ability to conduct electrons more than 1000 times more efficiently than silicon, while being able to be manufactured at a lower cost than silicon has now been well established. But, the superior switching performance of eGaN® technology alone (greater than 10 MHZ in some cases) cannot drive down overall system cost.
- EPC introduced eGaN® FETs in 2010. Since then, gallium nitride power transistors have seen a remarkable pace of progress, and have been demonstrated to be efficient at very high frequencies. EPC recently released the EPC9204, 20 VIN, 20 MHz POL, 1.2 cm2, and EPC9205, 1,400 W/in3 80 V non-isolated intermediate bus converter reference designs. These development boards utilize the latest in eGaN FET technology with the EPC9204 using the EPC2111, 30 V monolithic half-bridge IC and the EPC9205 using the EPC2045, 100 V FET.
Gate Drivers – For high frequency power control, gate drivers require high dv/dt capability, fast rise and fall times, matched propagation delays, and low deadtime capability.
- Texas Instruments introduced the LM5113, 100 V half-bridge driver and LM5114 and UCC27611 single gate drivers several years ago. TI recently introduced three new gate drivers to increase high frequency performance. The LMG1205 is 100 V and is pin compatible to the LM5113. This new gate driver offers increased frequency capability with 35 ns propagation delay and 1.5 ns propagation delay matching. Also recently introduced, the LMG1020 is an extremely fast single driver with 60 MHz and 1 ns minimum pulse width capability and the LMG1210 is a 200 V half-bridge driver with 1.5 ns propagation delay. These two components have matching, adjustable dead time control, and 1 pF of high side to low side capacitance.
- UPI Semiconductor this month announced the uP1966A, half-bridge driver, which is pin compatible with Texas Instruments’ LM5113 and LMG1205. The uP1966A has 0.7 Ω pull up and 0.4 Ω pull down resistances for high current designs. UPI Semiconductor also recently introduced the uP1964 single gate driver with low propagation delay and fast rise and fall times. This uP1966A driver is used on the EPC9205 demo.
- pSemi (formerly Peregrine Semiconductor) has, this year, introduced the PE29102 half-bridge driver, which has sub-nanosecond rise and fall times along with adjustable dead time. The PE29102 is used on the EPC9204 demo.
- Silicon Labs has digital isolators for high voltage designs. Silicon Labs has the Si8610BC with 50 V/ns capability and 1.5 ns pulse width distortion.
Magnetics – With the advancement of metal alloy materials, the frequency capability of magnetic cores has also advanced in recent years. Low core loss at high magnetic flux density is the key to size reduction in the magnetics.
- Vishay has made excellent progress with their IPLP series of inductors. IHLP1616ABERR10M01 is the 4.06 mm x 4.06 mm x 1.2 mm that is used on the 15 A, 10 MHz EPC9204 POL demo. IHLP4040DZER2R2M01 is the 10.16 mm x 10.80 x 4.0 mm used on the 10 A, 1 MHz EPC9205, intermediate bus converter demo.
- Murata has also made excellent progress in metal alloy cores with the Toko TB-P material.
Controllers – For frequencies up to around 1 MHz, digital controllers are an outstanding solution to power control, as they can not only control multiple phases of PWM, but critical parameters such as dead time and over-current and over-temperature protection can be programmed. Recent advances in controllers have reduced quiescent current. For the ultra-high frequencies, such as used in the EPC9204, analog controllers are still the answer with high frequency improvements as well.
- Texas Instruments has TPS and TMS series of digital controllers and Microchip has their dsPIC33 series of controllers. EPC9130, 48 V to 12 V, 60 A regulated 5 phase intermediate bus converter utilizes the DSPIC33EPXXGS504.
- On semiconductor has the NCP81111-D three-phase controller for ultra-high frequency control,.
- Analog Devices has also introduced several controller/drivers, such as the LTC7800 and LTC7801, with reduced dead time for higher frequency capability.
Capacitors – Ceramic capacitors with high frequency capability have been around for quite some time. For ultra-high frequency capability, look for capacitors with low ESL.
High frequency power conversion reduces size and weight of power conversion systems, thus lowering overall cost. GaN transistors have been available since 2010 with integrated circuits appearing in 2014. The ecosystem of complementary components to support the implementation of GaN devices has increased with the introduction of GaN-optimized gate drivers, magnetics, controllers, and capacitors. With these supporting components the adoption of GaN-based power solutions is accelerating and permiting power systems designers to take full advantage of GaN’s high frequency, small footprint, superior efficiency, and low cost.