A Look Inside And Component Analysis
Before proceeding with this page, we strongly encourage you to a look at our PSUs 101 article, which provides valuable information about PSUs and their operation, allowing you to better understand the components we're about to discuss. Our main tools for disassembling PSUs are a Thermaltronics soldering and rework station, and a Hakko FR-300 desoldering gun.
|Transient Filter||6x Y caps, 3x X caps, 2x CM chokes, 1x MOV|
|Inrush Protection||NTC Thermistor & Relay|
|Bridge Rectifier(s)||2x Vishay LVB2560 (600 V, 25 A @ 105 °C)|
|APFC MOSFETs||2x Infineon IPP50R140CP (550 V, 15 A @ 100 °C, 0.14 Ω)|
|APFC Boost Diode||1x SCS110AG (600 V, 10 A @ 117 °C)|
|Hold-up Cap(s)||2x United Chemi-Con (400 V, 450 uF each or 900 uF combined, 105 °C, CST)|
|Main Switchers||4x Infineon IPP50R199CP (550 V, 11 A @ 100 °C, 0.199 Ω)|
|Drivers For Main Switchers||2x Silicon Labs Si8230BD|
|APFC Controller||ON Semiconductor NPC1654|
|Switching Controller||Champion CM6901|
|Topology||Primary side: Full-Bridge & LLC Resonant Converter Secondary side: Synchronous Rectification & DC-DC converters|
|+12V MOSFETs||4x Fairchild FDMS015N04B (40 V, 100 A @ 25 °C, 1.5 mΩ)|
|5V & 3.3V||DC-DC Converters: 6x Infineon BSC0906NS (30 V, 40 A @ 100 °C, 4.5 mΩ) PWM Controller: APW7159|
|Filtering Capacitors||Electrolytics: Nippon Chemi-Con (105 °C, KZE, KZH) 1x Rubycon (5VSB circuit, 105 °C, YXD) Polymers: FPCAP, Nippon Chemi-Con|
|Supervisor IC||Weltrend WT7527V (OVP, UVP, OCP, SCP, PG )|
|Fan Model||Hong Hua HA13525M12F-Z (135 mm, 12 V, 0.36 A, 1800 RPM, Fluid Dynamic Bearing)|
|PWM Controller||Leadtrend LD7750R|
|MOSFET||STU6N65K3 (650V, 3A @ 100 °C, 1.3 Ω)|
This is a new platform from Seasonic, featuring a cleaner design than the previous XP2S, KM3S, and XP3 high-end configurations. No power cables are used internally, since the modular panel is connected to the main PCB through copper plates offering less resistance. So, less energy is lost on them, especially at higher loads. Moreover, Seasonic finally decided to use a >120 mm fan, so we expect the noise output to be much lower compared to its previous high-end offerings. The 135 mm fluid dynamic bearing (FDB) fan is provided by Hong Hua.
Briefly, as the shaft rotates in an FDB fan, lubrication oil drifts along the grooves of the bearing sleeve under high pressure, creating a thin layer between the bearing and shaft. This greatly reduces friction. As the rotational speed increases, the oil's pressure goes up as well, preventing the shaft from coming in contact with the bearing. An FDB fan's only weakness is during the start-up phase, when the speed of the shaft is low, resulting in low oil pressure that can allow for friction between the shaft and bearing. This might be a reason to avoid FDB fans in PSUs featuring a semi-passive mode, causing the fan to start and stop frequently. A long-lasting passive mode can address this by mitigating the constant start/stop cycle.
Seasonic doesn't use a bridgeless APFC design like Flextronics and Super Flower to achieve high efficiency levels. Instead, it chose to push the boundaries of analog circuits with a simpler design featuring standard bridge rectifiers. Apparently, Seasonic's engineers believe that bridge rectifiers aren't responsible for high energy losses, and that there are other ways to increase efficiency besides using more FETs in the APFC converter. The final result definitely proves their point, since the SSR-650TD is among the most efficient PSUs that we have ever measured.
The first part of the transient filtering stage is hosted on a small PCB that's properly shielded against EMI. It consists of two X and two Y caps. As usual, the transient filter continues on the main PCB with four more Y caps, an additional X cap, two CM chokes, and an MOV. All in all, this filter is complete; it is equipped with more components than it requires.
The main power cables are connected to the main PCB through spade terminals. This means less trouble for us, since we don't have to desolder thick wires.
The bridge rectifiers are a couple of Vishay LVB2560s that can handle up to 50 A of current. Obviously, they are overkill for a 650 W PSU. Seasonic could use smaller rectifiers and save some money.
This is the NTC thermistor that provides protection against large inrush currents. It is accompanied by a bypass relay, which allows it to cool down faster and helps minimize energy losses, since it isolates the thermistor from the circuit once the start-up phase finishes.
The APFC converter is reviewer-friendly: all of its parts are exposed except the PFC controller. In this circuit, two Infineon IPP50R140CP (550 V, 15 A @ 100 °C, 0.14 Ω) FETs are used along with a single SCS110AG (600 V, 10 A @ 117 °C) boost diode. The bulk caps are provided by United Chemi-Con (400 V, 450 uF each or 900 uF combined, 105 °C, CST) and their combined capacity is very large for a mid-capacity PSU. Seasonic speaks of a greater than 30 ms hold-up time, while the ATX spec only requires 17 ms. We wonder why Seasonic's engineers wanted to achieve such a long hold-up time, since this can affect efficiency as more energy is lost on the large bulk caps. Finally, the PFC controller is installed on a small PCB that's covered by tape. It is provided by ON Semiconductor, and its model number is NPC1654.
The primary switchers are four Infineon IPP50R199CP (550 V, 11 A @ 100 °C, 0.199 Ω) FETs configured into a full-bridge topology. All primary FETs are bolted on a dedicated heat sink, while an LLC resonant converter is used to provide a significant efficiency boost. Finally, the driver ICs that handle the main FETs are two Silicon Labs Si8230BD ICs; they're installed on the solder side of the main PCB.
On the secondary side there is a small heat sink, empty of components, which actually consists of two parts bolted together with screws. Seasonic uses thermal conductive grease between those parts to increase the heat sink's efficiency. Underneath it, a series of polymer caps (provided by FPCAP) filter the +12V rail along with several Chemi-Con electrolytic caps. As you'd expect in this price range, the capacitor choice is top-notch. FPCAP now belongs to Nichicon, and it is well known for its high-quality products.
The +12V rail is regulated by four Fairchild FDMS015N04B (40 V, 100 A @ 25 °C, 1.5 mΩ) FETs. In addition to the heat sink described above, they're also cooled down by the chassis.
We had to fight with the board that holds the DC-DC converters in order to remove it and identify all relevant components. This board houses six Infineon BSC0906NS (30 V, 40 A @ 100 °C, 4.5 mΩ) FETs, and the common PWM controller is a Anpec APW7159 IC.
There's an APW9010 IC on the fan control board. The PCB right beside the fan control board houses the LLC resonant controller, a Champion CM6901.
Another board on the secondary side has a Lite-On LSP5523 buck converter installed, which most likely handles the -12V rail. The 5VSB rail uses a Leadtrend LD7750R PWM controller, which is installed on the solder side of the main PCB. The same rail also uses a STU6N65K3 FET, provided by STMicroelectronics, while a single Rubycon cap is used for the its filtering.
A daughterboard on the secondary side hosts the supervisor IC, a Weltrend WT7527V (OVP, UVP, OCP, SCP, PG), along with an AS393 dual-voltage comparator. The WT7257V supports OCP for up to two +12V virtual rails, through the SSR-650TD only has one. Between the WT7527V and the AS393, four optocouplers are installed for isolation purposes.
A number of FPCAP and Chemi-Con polymer caps, along with two electrolytic caps, filter the rails on the front of the modular board.
The soldering quality is good, although not the best we have seen from Seasonic.
The cooling fan is provided by Seasonic's new favorite manufacturer, Hong Hua. Its model number is HA13525M12F-Z, and as we already explained, it uses a fluid dynamic bearing for increased lifetime. Seasonic speaks of 40,000 hours at 40 °C, so it should last a long time, especially if you consider the PSU's aggressively-enforced passive mode. At high speeds, this fan is loud. However, its profile is so loose that you will barely hear any noise coming from the fan, even if you deactivate the semi-passive mode.