Raijintek Ermis 550B PSU Review 3

Raijintek Ermis 550B PSU Review

Voltage Regulation Stability & Ripple »

Component Analysis

Before reading this page, we strongly suggest looking at this article, which will help you better understand the insides of a PSU.

Raijintek Ermis 550B Parts Description
General Data
Manufacturer (OEM)Casecom
PCB TypeDouble-Sided
Primary Side
Transient Filter4x Y caps, 3x X caps, 2x CM chokes, 1x DM choke
Bridge Rectifier(s)1x GBU806 (600 V, 8 A @ 100 °C)
Inrush Current ProtectionNTC Thermistor (MF72-3D13) (3 ohm)
APFC MOSFETs2x First Semiconductor FIR20NS65AFG (650 V, 12.5 A @ 100 °C, Rds (on): 0.19 ohm)
APFC Boost Diode1x WeEn Semiconductor BYC8X-600 (600 V, 8 A)
Bulk Cap(s)2x HCON (400 V, 220 uF each or 440 uF combined, 105 °C, HP)
Main Switchers2x Perfect Intelligent Power Semiconductor PTA20N50A (500 V, 10 A @ 125 °C, Rds (on): 0.3 ohm)
PFC / PWM Combo Controller Champion CM6800UX
TopologyPrimary Side: APFC, double forward
Secondary Side: synchronous rectification & DC-DC converters
Secondary Side
+12 V MOSFETs3x Potens Semiconductor PDD6974A-5 (65 V, 94 A @ 100 °C, Rds (on): 3.3 mOhm)
+5 V & +3.3 VDC-DC Converters
PWM Controller(s): ANPEC APW7159C
Filtering CapacitorsElectrolytic: 11x Asia'x (105 °C, TMX)
Polymer: 3x NJcon
Supervisor ICGrenery GR8313 (OVP, UVP, SCP, PG)
Fan ModelFly-Upwards DF0801512SEHN (80mm, 12V, 0.25A, sleeve bearing fan)
5VSB Circuit
Standby PWM ControllerSC2521Q


The OEM is Casecom. Under proper guidance, this OEM is capable of delivering good high performance per dollar products. The PCB is small since this it is an SFX unit. The heatsinks are not that large, and there is enough clearance between the parts for adequate airflow. The fixed cables don't significantly get in the way of airflow for the filtering caps on the secondary side, which increases their lifetime. The main issue with fixed cables on PSUs is that many wires traverse the secondary side, messing with airflow. This is one of the main reasons I prefer modular PSUs over non-modular ones. Build quality is decent for this price range. The design is a mix of old and new elements. We find an older design with a double-forward topology on the primary side. In contrast, on the secondary side, we have a synchronous design with DC-DC converters to generate the minor rails. Thankfully, Casecom didn't use passive parts for the +12 V rail's rectification, which would lead to increased energy losses.


The transient filter starts on the AC receptacle and continues on the main PCB. There is no MOV to handle voltage surges, which is a big shame.


An NTC thermistor lowers inrush currents. There is no bypass relay to support it. To save money, no such relay is usually installed in Bronze or Silver PSUs.


The single bridge rectifier can handle up to 8 A. For 230 V input, there won't be any problems, but there is not much room left for 100 V input.


The APFC converter uses three First Semiconductor FETs and a strong WeEn Semiconductor boost diode. The bulk caps are by HCON and offer 440 uF combined capacity. They are rated at 105°C, which is the only specification for these I could find. There is no information on the expected lifetime at 105°C.


A blast from the past, the common APFC and PWM controller is a Champion CM6800UX.


The two PTA20N50A primary switching FETs are installed in a double-forward topology.


The main transformer is next to the standby transformer.


Three FETs regulate the +12 V rail.


The electrolytic caps on the secondary side are by Asia'x. There are also three polymer caps.


Two DC-DC converters generate the minor rails. The joint PWM controller is an ANPEC APW7159C.


The standby PWM controller is an SC2521Q.


The supervisor controller is a Grenery GR8313.


Soldering quality is decent.


The cooling fan is from an unknown brand. It measures 80 mm across and uses a sleeve bearing.
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