I am interested in thoughts on appropriate topologies for a challenging power supply project. Requirements:
- Wide Input voltage range (8.5-65 VDC)
- Mulitple outputs (3.3V, 5, +/-12 and 40+)
- Primary/Secondary isolation
- Good cross-regulation amongst outputs
- Low power: 2.5 watts typical, 8 watts max
- High efficiency - 90% for 10-35 VIN, 85% elsewhere
- Minimal conducted emissions (e.g. DO-160)
- Minimal physical size/volume
- 50+ millisecond hold-up time at max load
Coupled inductor SEPIC feeding isolation transformer comes close, but secondary voltage/current stress is extreme at limits of VIN range.
Would prefer symmetric excitation of isolation transformer to reduce stresses in secondary (and transformer volume), but conventional, voltage fed topologies (push-pull, bridge, half-bridge) have significant input ripple that would require significant filtering.
Two stage approaches (e.g. boost to a high voltage storage cap followed by push-pull) would seem to have difficulties meeting the efficiency requirements (especially with sagging in the push-pull during hold-up time).
Seems like the converter will need to run in both DCM and CCM, calling into question most of the conventional current-fed, full-bridge converter topologies.
Can anyone suggest a symmetric, current-fed topology that can handle the wide DC input voltage range ?
Thanks !
- Wide Input voltage range (8.5-65 VDC)
- Mulitple outputs (3.3V, 5, +/-12 and 40+)
- Primary/Secondary isolation
- Good cross-regulation amongst outputs
- Low power: 2.5 watts typical, 8 watts max
- High efficiency - 90% for 10-35 VIN, 85% elsewhere
- Minimal conducted emissions (e.g. DO-160)
- Minimal physical size/volume
- 50+ millisecond hold-up time at max load
Coupled inductor SEPIC feeding isolation transformer comes close, but secondary voltage/current stress is extreme at limits of VIN range.
Would prefer symmetric excitation of isolation transformer to reduce stresses in secondary (and transformer volume), but conventional, voltage fed topologies (push-pull, bridge, half-bridge) have significant input ripple that would require significant filtering.
Two stage approaches (e.g. boost to a high voltage storage cap followed by push-pull) would seem to have difficulties meeting the efficiency requirements (especially with sagging in the push-pull during hold-up time).
Seems like the converter will need to run in both DCM and CCM, calling into question most of the conventional current-fed, full-bridge converter topologies.
Can anyone suggest a symmetric, current-fed topology that can handle the wide DC input voltage range ?
Thanks !