High-Voltage, 800-W SEPIC Converter Reference Design for Server Battery Backup Charging
1 Description
This Discontinuous Conduction Mode (DCM), non-isolated, 800-W SEPIC converter battery charger provides an adjustable output voltage and current. The output voltage can be adjusted from 282 V to 400 V by setting an external DC voltage between 0 V to 3 V. The output charging current can be adjusted between 0 A to 2 A by adjusting the duty cycle of a PWM input. It operates over an input voltage range of 340 Vdc–420 Vdc. Independent voltage and current feedback loops are used to maintain regulation.
Figure 1-1 Top Photo
Figure 1-2 Bottom Photo2 Test Prerequisites
2.1 Voltage and Current Requirements
| Parameter | Specifications |
|---|---|
| Input voltage range | 340 V–420 V, after > 335-V startup |
| Output voltage | 282 V–400 V, (CHG VSET DAC = 0 Vdc–3 Vdc) |
| Output current | 0 A–2 A, (CHG ISET DAC = 0% to 100%, 100 kHz, 2.5 V) |
| Switching frequency | 100 kHz |
| Isolation | No |
2.2 Required Equipment
- Li-Ion batteries or load (active or resistive), 400 V, 2 A, 800 W minimum
- Input source power supply, adjustable, 0 V–500 V, 1000 W, 3 A minimum
- Oscilloscope and high-voltage probes
- Digital multimeters
- 12-V bias supplies, 100 mA minimum
- Function generator, adjustable frequency, amplitude and duty cycle