TEST REPORT
Multiple Output Isolated SiC Driver Bias Supply Reference Design for Onboard Charger Applications
Description
This reference design is an open-loop LLC converter, which provides four 18 V and 2.5 V outputs, up to 2.4 W for onboard charger applications. The UCC25800-Q1 device is used here as the controller. The LLC topology allows the transformer to have significant leakage inductance, but a much smaller primary-secondary capacitance, which significantly reduces common-mode current injection through the bias transformer.
Features
- Small size, open-loop LLC
- Reinforced insulation
- Compact PCB size (55 mm × 45 mm)
Applications
- On-board (OBC) and wireless charger
- IGBT and SiC gate transformer driver bias supply
Top of Board
Block Diagram
Bottom of Board1 Test Prerequisites
1.1 Voltage and Current Requirements
Table 1-1 Voltage and Current
Requirements
| Parameter | Specifications |
|---|---|
| Input voltage range | 12 V |
| Output voltage and current | 4 × (18 V and –2.5 V, 30 mA), 2.4 W maximum |
| Nominal switching frequency | 400 kHz |
| Isolation | Yes, 3000 VAC, 1 min |
| Topology | Open-loop LLC |
1.2 Required Equipment
- Multimeter (voltage): Fluke 287C
- Multimeter (current): Fluke 287C
- DC Source: Chroma 62012P-100-50
- E-Load: Chroma 63110 module
- Oscilloscope: Tektronix DPO3054
- Electrical Thermography: Fluke TiS65
1.3 Dimensions
The board dimensions are 55 mm (length) × 45 mm (width) × 25 mm (height).
Figure 1-1 Dimensions2 Testing and Results
2.1 Efficiency Graphs
Efficiency is shown in the following figure.
Figure 2-1 Efficiency Graph