CRD-060DD17P-2: Auxiliary Power Supply evaluation board for C2M1000170J SiC MOSFET Board Summary The CRD-060DD17P-2 is a demonstration board for a single-end Flyback converter design with a commercially available 1700V Silicon Carbide (SiC) MOSFET. The design utilizes Crees 1700V SiC MOSFET in a new 7LD2PAK surface mount package which combines a small footprint with a wide creepage distance: 7mm between drain and source. By moving to the new surface mount package, design engineers can achieve economical thermal designs without the need for heat sink on the MOSFET. The demonstration board is not designed to be a product and is to be only used as a tool to evaluate the performance of Cree switching devices. INTRODUCTION Three-phase applications, such as motor drive, UPS and PV inverter, have a front end AC/DC or DC/DC converter to boost the DC link voltage up to 600Vdc to 800Vdc. Factoring in a design margin, the maximum DC link voltage is up to 1000V. To support such systems in practice, an auxiliary power supply is used to generate power for cooling fans, displays, control logic and system protection functions with the DC link voltage as its input. For such low power applications, Flyback topology is the most common type in the industry however, the conventional single end Flyback topology has difficulty in meeting high input voltage. The first difficulty is caused by the high input voltage (1000Vdc) the single-end Flyback topology would require high blocking voltage switching devices. Currently, the Silicon MOSFET only has 1500V blocking voltage, which has low voltage stress design margin and thus affects the reliability of the power supply. The second challenge is that most of the 1500V Si MOSFETs have very large on-state resistance, and this will lead to higher losses, higher thermal and lower efficiency, especially when the whole three-phase system is operating at light output load and auxiliary power losses occupy most of total system losses. Lastly, to support a wide input voltage range, a pure resistance start up circuit is normally used. However, the start-up resistance will lead to losses at high input voltage. Larger start-up resistance will have less losses but lead to long start-up time at low input voltage. In order to overcome these auxiliary power supply design challenges to supply high input voltage, two-switch Flyback converter was proposed to use high side and low side 800V Si MOSFETs as shown in Fig.1, but it has the additional isolation gate drive circuit which increases component counts and complicates the design. This application note proposes a single-end Flyback converter to replace complicated two-switch Flyback converter by using 1700V SiC MOSFET. An active start-up circuit is also introduced to achieve less start-up losses with faster start up time. The 60W experimental reference design demonstrates that the 1700V SiC MOSFET can reduce total cost and simplify the design of auxiliary power supply. Subject to change without notice. 1 www.cree.com CPWR-AN15, Rev -, 03-2016 Auxiliary Power Supply board for 7LD2PAK600V to 1000V DC line Gate driver 800V Si transformer MOSFET Main transformer 800V Si MOSFET Figure 1: A conventional two-switch Flyback converter with 800V Si MOSFET User Guide Desription: A wide input, dual output, fly-back evaluation board designed to showcase the performance of a 1700V, 1 ohm SiC Wolfspeed MOSFET in a surface mount package (C2M1000170J). Warning This Cree designed evaluation hardware for Cree components is meant to be used as an evaluation tool in a lab setting and to be handled and operated by highly qualified technicians or engineers. The hardware is not designed to meet any particular safety standards and the tool is not a production qualified assembly. Specifications: Vin: 300 1000 VDC Vout A: 12V 4A Vout B: 12V 0.1A Controller: TI UCC2844D Cooling: Using two sided non-isolated copper pads Pout Max.: 48W Size: 120(l)x70(w)x35(h) mm Figure 1 Basic circuit diagram. Weight: 125 g This document is provided for informational purposes only and is not a warranty or a specification. For product CPWR-AN15, Rev -, 03-2016 specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Auxiliary Power Supply board for 7LD2PAK Cree Sales at PowerSales cree.com. 2