Delta DPS-250AB-81 E 300W NAS Server PSU Teardown: 1U Hot-Swap Module, Active PFC + Forward, 12V 24.2A
2026-10-08 · Compiled by Best IT Parts from public industry reporting
A teardown of the Delta DPS-250AB-81 E examines a 300W modular power supply built for NAS and rack storage systems, where 7x24h operation, complete protection and hot-swap presence detection are required. The unit uses a 1U long-form brick enclosure with a wide-range AC input. The nameplate rates 100-240V AC at 5A-2.5A, 50-60Hz, with a +12V main output at 24.2A and +5VSB standby at 2A, for 300W maximum output, and certification covers CCC, CE and EAC. Measured dimensions are 194.05mm long, 71.73mm wide and 38.58mm thick, at about 740g.
Inside, the design pairs active PFC with a forward converter in a classic isolated switching topology. A Champion CM6802BHG ZVS-like PFC/PWM combo controller in SOP-16 handles both stages. The PFC stage uses an STMicroelectronics STP26NM60N MOSFET rated 600V and 165 mOhm in TO-220, with an STTH5R06B 5A/600V boost rectifier; an ON Semiconductor MURS360T3G bypass diode protects the PFC inductor from inrush. The forward switch is an STF21NM60ND rated 650V and 0.22 Ohm in TO-220FP, driven through an isolation transformer. Secondary 12V rectification uses two STPS30H100CT 100V/30A common-cathode dual diodes.
Output filtering combines Nippon Chemi-Con KZE 2200uF/16V and TAICON 1500uF/16V electrolytics, while the standby rail uses an ON Semiconductor FQPF3N80C 800V switch and an STPS10150CT 150V/10A rectifier. A Delta FFB0412VHN 40x40x28mm 12V/0.24A ball-bearing fan provides cooling, and a dedicated microswitch handles presence detection.
For B2B buyers, the teardown shows how a 300W storage-class supply spreads protection across discrete analog parts, including Diodes AS393M-E1 and STMicro LM339 comparators, an STMicro TSM102 analog array and LM324A op-amps, rather than concentrating everything in the controller. The DPS-250AB-81 E remains relevant for NAS repair and replacement demand.
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Technical details are reproduced as reported. Verify specifications against the original source before design or procurement decisions.