Enermax Digifanless 550W Power Supply Review

A Look Inside And Component Analysis

Our main tools for disassembling PSUs are a Thermaltronics soldering and rework station and a Hakko 808 desoldering gun.

Parts Description

It is nice to see Enermax release a fresh semi-digital platform. We describe it as semi-digital because the digital circuit controls only the +12V rail. The other sections of this unit (APFC, main switchers, 5VSB circuit and the minor rails) are controlled by classic analog components. We would like to see the digital circuit controlling more sections; however, we suspect that Enermax wanted to mix the already tested and reliable analog technology with the digital in order to minimize problems in the long run. On the primary side of the EDF550AWN, we find an LLC resonant converter, while on the secondary side two DC-DC converters generate the minor rails. The +12V rail is generated by a series of MOSFETs, which are handled by a Microchip 32-bit RISC CPU.

A small PCB holds the AC receptacle and the on/off switch along with one X and two Y caps. The EMI filter continues on the mainboard with two CM chokes and an MOV (metal-oxide varistor). Normally, this filter should have an additional X cap and another pair of Y caps. For protection against large inrush currents, Enermax used an NTC thermistor along with an electromagnetic relay, which allows it to cool down and at the same time provides a small efficiency boost.

A pair of bridge rectifiers are provided by Shindengen (model number LL25XB60); both are bolted on the heat sinks and they are very strong for this unit’s capacity.

In the APFC converter, we find not one, but two PFC input capacitors, which filter the high-frequency ripple of the fully rectified AC signal. Two MOSFETs (2x Toshiba K20J60U) along with a single CREE C3D08060A boost diode shape the current's waveform in the APFC. A single Chemi-Con (400V, 470uF, 105-degree Celsius, KMQ) is used as a smoothing/reservoir cap; its capacity is adequate for the needs of this PSU.

The APFC converter controls include a Champion CM6502TX and a CM03X Green PFC controller, used to further decrease energy loss. Both of the controllers are installed on a small daughterboard.

The main switchers are a couple of Toshiba K20J60U MOSFETs, the same that the APFC converter uses. In the control section of the LLC resonant converter, there is a Champion CM6901TX IC, which is installed on the solder side of the main PCB.

On the secondary side, we had to remove the modular board, which attaches to the main PCB through four small screws, in order to get a clear view of the components. The +12V rail includes several MOSFETs that are installed on a vertical PCB. The vertical PCB is cooled by a mix of large heat sinks, which compensate for the lack of active cooling (a fan). We didn't want to dismantle the PSU further, so we stopped at the heat sinks. All capacitors in this section of the PCB are electrolytics provided by Chemi-Con, so they are of high quality. In a passive PSU with increased internal temperatures, Japanese electrolytic caps are the only way to go; lower-quality caps would compromise the unit's reliability and decrease its lifetime.

Both DC-DC converters are installed directly on the modular PCB in an effort to decrease energy loss. Two Anpec APW7073 controllers handle eight Sinopower SM3116NA MOSFETs, which deliver the minor rails. We also found a SITI PS113 IC on the solder side of the modular board, which is a secondary monitoring IC, offering some of the PSU's protection features (like over-voltage and under-voltage protection). 

On the front side of the modular PCB, several polymer caps from Enesol and Duratech filter the rails. These caps, although not Japanese, are still of high quality.

The standby off-line switcher that generates the 5VSB rail is a Power Integrations TOP265EG model. It incorporates a MOSFET along with other components to deliver up to 26W of power, even with 50 degrees C ambient. With 230VAC input, this IC can deliver up to 40W.

The solder quality is good, and at the level expected from a high-end PSU. If you look closely at the photos above, you'll notice that the name of the worker who inspected the PCB is printed on it. Enermax does this on all of its PSUs, possibly to identify the right person in case something goes wrong. In any case, we think it's pretty cool.

The digital controller is a 32-bit RISC CPU clocked at 40MHz, provided by Microchip (model number PIC32MX230F064D, supported by 24LC02B EEPROM) and installed on a modular board located on the PSU's secondary side.

Zero Delay Power Monitoring System

Since this PSU utilizes a digital interface, it is able to connect to the system's mainboard through a USB interface in order to transmit data and receive commands. Enermax's ZDPMS software allows users to monitor the PSU's operation and customize some important functions, including switching between multi or single +12V rail mode, fine-tuning +12V output voltage levels and setting the OCP/OVP trigger points. You can download the software from the product's webpage.

The first thing you will see once you start the ZDPMS program is its welcome screen, which stays on for about five seconds but can be disabled by clicking the Don't Remind Me option. Once you enter the main program, you see an intuitive and easy-to-follow interface. The software's manual provides a nice screenshot of the program's main control window, explaining the interface.

In the Additional Information tab, you will find the Usage button, which allows the tracking of the operation time from the moment the ZDPMS software is started. By entering what your local utility charges, you can estimate the PSU's electricity cost. In addition to usage information, the control/monitor program will show a warning if something goes wrong. The most important one to watch out for is the Over Temperature message, which pops up once the PSU's internal temperature exceeds 80 degrees C. According to Enermax, once it hits roughly 90 to 120 degrees C, the over-temperature protection kicks in and shuts the PSU down to save it from breaking. The other two warning messages have to do with over-current and over-voltage protection, and they pop up if the output current/voltage readings reach the preset warning points.

Another interesting feature of the ZDPMS software is Simple Mode, which can be enabled by clicking the middle button on the Window Control tab. This mode provides only the essential information like total output, efficiency and temperature data. To return to the normal window, just click the Simple Mode window twice.

The ZDPMS may lack a fancy interface, but it is easy to follow and it won't confuse anyone (even inexperienced users). It provides all the necessary functionality, and throughout our long test sessions, we found it to be reliable. Communication with the program was lost only when we removed the AC input from the PSU, which was expected; once we restored power, the communication link was up again and the program worked perfectly without needing to restart.