EPC’s 1kW, 48VDC/12VDC Converter Offers a Power Density of 1226 W/in3
The 1/8th brick sized demonstration board uses eGaN FETs switching at 1 MHz to deliver its best in class power density
The EPC9149 from Efficient Power Conversions (EPC) is sized at 2.3 x 0.9 inches, about half the size of devices employing increasingly outdated silicon semiconductors
The EPC9149. Image courtesy of EPC
The converter is intended for evaluation purposes only and can’t be used as part of OEM products. However, to simplify the task of replicating the design in actual products, EPC provides schematics, BOMs, and Gerber files on their website.
EPC2218 and EPC2024 eGaN FETs
The EPC9149 is an LLC converter employing four 100 volt EPC2218 eGaN FETs for the primary rectification, and for the secondary synchronous rectification eight 40 volt rated EPC2024 eGaN FETs are employed. These fast-switching devices, while only 1/3 the size of silicon MOSFETs with similar RDS(ON)s, make it possible for the converter to operate at 1 MHz, with a corresponding decrease in the size and weight of filtering components.
In addition to the eGaN FETs, the other star of the show is the Microchip dsPIC33CKMP102T-I/M6. This 16-bit digital controller, measuring 4 x 4 mm, allows for programmability, communications and configuration flexibility.
The EPC9149 delivers up to 83.4 amps at 12 volts at full load, and operates from an input voltage range of 36 to 60 VDC. Peak efficiency is 98%, and only drops down to 97% at full load. Using the available heatsink, airflow of 400 LFM is required for the full 83 amp output. Without the heatsink, 1700 LFM is required.
The EPC9149 employs a soft startup to limit the input current drawn while powering up and while the output voltage is low or zero. To achieve this, both the four EPC2218s in the primary circuit (Q1 … Q4) and the eight EPC2024s (SR1 … SR8) are, at first, commanded with a minimum pulse width.
Simplified schematic for the EPC9149 LLC Module. Modified image courtesy of Quick Start Guide
As output voltage quickly reaches 12 volts, the duty cycle increases. In this manner, excessive currents and voltage stresses can be avoided.
The EPC9149 Operates in an Open Loop
The consequence of open loop design is that the output voltage can droop downwards with a higher load. With a 48 volt input and a full 83 amp output, the output drops to ≈11.8 volts
The Microchip dsPIC33CK32MP102 Digital Signal Controller (DSC)
This DSP is an100 MHz single core unit equipped with dedicated peripheral modules for switched Mode Power Supply (SMPS) applications. These include:
- Digital Signal Processing (DSP) core
- A 4-channel (8x output)
- 250 ps resolution PWM logic
- Three 3.5 Msps ADCs
- Three 15 ns propagation delay analog comparators, including DACs, to support ramp signal generation
- Three Op Amps
The DSC can be readily reprogrammed.
EPC’s Commitment to Higher Power and Smaller Size
As per Alex Lidow, CEO of EPC, “eGaN FETs and integrated circuits increase power density for 48 V to 12 V converters and address data center application demands for higher power in a small size.” He goes on to state that, “The use of a Microchip digital controller allows flexibility for programming and configuration of the EPC9149 demonstration board.”
Designs derived from the EPC9149 demo board include power for:
- Data Centers
- Server racks
Getting to Market Faster
EPC also provides a motherboard on which to mount the EPC9149, greatly facilitating testing and evaluation.