Introduction

Costing only USD 100, the Rosewill Libertas 800 W (LIB800) is a power supply that comes with a full modular cabling system, synchronous design, and DC-DC conversion for the +5 V and +3.3 V outputs. The manufacturer promises it can deliver 800 W at 50º C, peaking 900 W for up to 12 seconds. One curious thing about this unit is that it is officially an 80 Plus Gold power supply, but Rosewill decided to downgrade it to an 80 Plus Bronze.

We couldn’t discover the real manufacturer of this power supply (it looks like it is ATNG, but we couldn’t confirm this).

click to enlarge
Figure 1: Rosewill Libertas 800 W power supply

click to enlarge
Figure 2: Rosewill Libertas 800 W power supply

The Rosewill Libertas 800 W is 6.5” (165 mm) deep, using a 135 mm ball-bearing fan on its bottom, that is manufactured by Globe Fan (model RL4ZB1352512HH), even though the brand, “Rosewill,” is printed on it.

This unit features active PFC, of course.

It comes with a full modular cabling system, meaning that even the main motherboard cable is attached to this system. This system has 12 connectors, four red ones for the video card cables, five six-pin black ones for SATA and peripheral cables, two eight-pin black ones for the CPU cables (ATX12V and EPS12V), and one 24-pin black one for the main motherboard cable. The cables included are the following:

• Main motherboard cable with a 20/24-pin connector, 19.7” (50 cm) long
• One cable with two ATX12V connectors that together form an EPS12V connector, 19.7” (50 cm) long
• One cable with one EPS12V connector, 19.7” (50 cm) long
• Four cables, each with one six/eight-pin connector for video cards, 20” (51 cm) long
• One cable with four SATA power connectors, 19.7” (50 cm) to the first connector, 5.9” (15 cm) between connectors
• Two cables, each with three SATA power connectors, 20” (51 cm) to the first connector, 5.9” (15 cm) between connectors
• Two cables, each with three standard peripheral power connectors and one floppy disk drive power connector, 20” (51 cm) to the first connector, 5.9” (15 cm) between connectors

All wires are 18 AWG.

The cable configuration is satisfactory for an 800 W product, allowing you to have up to two video cards that require two power connectors each without needing to use adapters.

click to enlarge
Figure 3: Cables

Now let’s take an in-depth look inside this power supply.

A Look Inside The Rosewill Libertas 800 W

We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.

This page will be an overview, while in the following pages we will discuss the quality and ratings of the components used in detail.

click to enlarge
Figure 4: Top view

click to enlarge
Figure 5: Front quarter view

click to enlarge
Figure 6: Rear quarter view

click to enlarge
Figure 7: Printed circuit board

Transient Filtering Stage

As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil. 

In this power supply, this stage is flawless. It has three X capacitors and two Y capacitors more than the minimum required, plus one X capacitor and two Y capacitors after the rectifying bridges.

click to enlarge
Figure 8: Transient filtering stage (part 1)

click to enlarge
Figure 9: Transient filtering stage (part 2)

In the next page we will have a more detailed discussion of the components used in the Rosewill Libertas 800 W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Rosewill Libertas 800 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU1006 rectifying bridges connected in parallel, both attached to the same heatsink used by the active PFC transistors and the switching transistors. Each bridge supports up to 10 A at 100º C if a heatsink is used, so in theory, you would be able to pull up to 2,300 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,840 W without burning themselves. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply.

click to enlarge
Figure 10: Rectifying bridges

The active PFC circuit uses two IXTQ26N50P MOSFETs, each one capable of delivering up to 26 A at 25º C or up to 17 A at 100º C in continuous mode (note the difference temperature makes), or up to 78 A in pulse mode at 25º C. These transistors present a 230 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will have a higher efficiency.

click to enlarge
Figure 11: Active PFC transistors

This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two capacitors with the same total capacitance are physically smaller than a single capacitor with equivalent capacitance. The Rosewill Libertas 800 W uses two 220 µF x 400 V capacitors connected in parallel, the equivalent of one 440 µF x 400 V capacitor. They are manufactured by Teapo and labeled at 85º C.

In the switching section, two SPW24N60C3 MOSFET transistors are used, connected in the traditional two-transistor forward configuration. Each switching transistor is capable of delivering up to 24.3 A at 25º C or 15.4 A at 100º C in continuous mode (see the difference temperature makes), or 72.9 A in pulse mode at 25º C, with an RDS(on) of 160 mΩ.

click to enlarge
Figure 12: +5VSB switching transistor, active PFC diode, and the two switching transistors

Unfortunately the manufacturer covered the active PFC/PWM circuit with a black material that was impossible to remove, making it impossible for us to identify the integrated circuit used in this stage.

click to enlarge
Figure 13: Active PFC/PWM combo controller

Now let’s take a look at the secondary of this power supply.

Secondary Analysis

This power supply uses a synchronous design on its secondary, meaning that the Schottky rectifiers were replaced by MOSFET transistors in order to increase efficiency. On top of that, this unit uses a DC-DC design, meaning that this unit is basically a +12 V power supply, with the +5 V and +3.3 V outputs being generated by two small power supplies attached to the +12 V output.

The +12 V output is generated by four IXTP230N075T2 MOSFETs, each one capable of handling up to 75 A at 100º C in continuous mode, with an RDS(on) of only 4.2 mΩ. Two of these transistors are in charge of the direct rectification, while the other two are in charge of the “freewheeling” part of the rectification. A DSB60C45HB Schottky rectifier is used to complement the “freewheeling” part of the rectification.

click to enlarge
Figure 14: +12 V transistors

The +5 V and the +3.3 V outputs are generated by two small power supplies found on small daughter boards attached to the +12 V rail. Each of these power supplies is comprised of four ME90N03 MOSFETs (47 A at 70º C, 4.8 mΩ resistance) and one PWM controller (we couldn’t identify as the manufacturer covered this integrated circuit with a black material that was impossible to remove).

click to enlarge
Figure 15: The +5 V DC-DC converter

click to enlarge
Figure 16: The +5 V DC-DC converter

This power supply uses a PS232S monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP), and over current (OCP) protections. The over current protection circuit available in this integrated circuit has six channels, one for +3.3 V, one for +5 V, and four for +12 V, but the manufacturer decided to configure this power supply as a single-rail unit.

click to enlarge
Figure 17: Monitoring circuit

Electrolytic capacitors in the secondary are from Teapo, labeled at 105º C. Some solid capacitors from CapXon are found as well. The capacitors used on the DC-DC boards are solid, as you can see in Figure 16.

Power Distribution

In Figure 18, you can see the power supply label containing all the power specs.

click to enlarge
Figure 18: Power supply label

This power supply has only one +12 V rail (even though internally the circuit can support up to four +12 V rails), so there is not much to talk about here.

Now let’s see if this power supply can really deliver 800 W.

Load Tests

We conducted several tests with this power supply, as described in the article, Hardware Secrets Power Supply Test Methodology.  

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching the behavior of the reviewed unit under each load. In the table below, we list the load patterns we used and the results for each load.

If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at 5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester, which during our test were connected to the power supply single +12 V rail.

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	5.5 A (66 W)	12 A (144 W)	18.5 A (222 W)	23 A (276 W)	29 A (348 W)
+12VB	5.5 A (66 W)	11 A (132 W)	16 A (192 W)	23 A (276 W)	29 A (348 W)
+5V	2 A (10 W)	4 A (20 W)	6 A (30 W)	8 A (40 W)	10 A (50 W)
+3.3 V	2 A (6.6 W)	4 A (13.2 W)	6 A (19.8 W)	8 A (26.4 W)	10 A (33 W)
+5VSB	1 A (5 W)	1.5 A (7.5 W)	2 A (10 W)	2.5 A (12.5 W)	3 A (15 W)
-12 V	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)
Total	161.5 W	325.9 W	483.3 W	637.1 W	799.4 W
% Max Load	20.2%	40.7%	60.4%	79.6%	99.9%
Room Temp.	46.4º C	45.2º C	44.4º C	45.2º C	49.5º C
PSU Temp.	45.9º C	46.3º C	46.5º C	47.9º C	51.4º C
Voltage Stability	Pass	Pass	Pass	Failed on +5 V	Failed on +5 V
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	186.9 W	370.9 W	558.0 W	755.0 W	974.0 W
Efficiency	86.4%	87.9%	86.6%	84.4%	82.1%
AC Voltage	108.3 V	106.4 V	104.1 V	102.2 V	99.6 V
Power Factor	0.993	0.996	0.996	0.996	0.996
Final Result	Pass	Pass	Pass	Fail	Fail

The Rosewill Libertas 800 W can really deliver its labeled wattage at high temperatures.

Efficiency was high, peaking 88% during test two (320 W). At full load the reviewed power supply achieved 82.1% efficiency, and Rosewill did a really good thing in downgrading this unit from 80 Plus Gold to 80 Plus Bronze. In a world full of companies trying to deceive consumers, it is always nice to see a company being honest.

The problem with the Libertas 800 W is that the +5 V output presented a voltage below the minimum allowed (4.75 V) during tests four (4.67 V) and five (4.61 V), a problem that can make your computer unstable.

Noise and ripple levels were always low. Below you can see the results for the power supply outputs during test number five. The maximum allowed is 120 mV for +12 V and -12 V, and 50 mV for +5 V and +3.3 V. All values are peak-to-peak figures.

click to enlarge
Figure 19: +12VA input from load tester during test five at 799.4 W (39.8 mV)

click to enlarge
Figure 20: +12VB input from load tester during test five at 799.4 W (39.8 mV)

click to enlarge
Figure 21: +5V rail during test five at 799.4 W (26.2 mV)

click to enlarge
Figure 22: +3.3 V rail during test five at 799.4 W (22.6 mV)

Let’s see if we can pull even more from the Rosewill Libertas 800 W.

Overload Tests

Below you can see the maximum we could pull from this power supply. Here we were limited by our equipment, that can only pull up to 1,000 W. However, during this test, noise levels were way above the maximum allowed (678.4 mV at +12VA, 717.8 mV at +12VB, and 708.4 mV at -12 V), and voltages were outside specs (+4.57 V at +5V, and +3.06 V at +3.3 V), which means the unit was not working correctly anymore.

Input	Overload Test
+12VA	32.5 A (390 W)
+12VB	32.5 A (390 W)
+5V	24 A (120 W)
+3.3 V	24 A (79.2 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	989.4 W
% Max Load	123.7%
Room Temp.	39.4º C
PSU Temp.	45.1º C
AC Power	1,283 W
Efficiency	77.1%
AC Voltage	99.4 V
Power Factor	0.993

Main Specifications

The specs of the Rosewill Libertas 800 W include:

• Standards: ATX12V 2.3 and EPS12V 2.92
• Nominal labeled power: 800 W continuous at 50º C, 900 W peak
• Measured maximum power: 989.4 W at 39.4º C ambient
• Labeled efficiency: Between 80% and 85%, 80 Plus Gold certification (downgraded to 80 Plus Bronze by the manufacturer)
• Measured efficiency: Between 82.1% and 87.9% at 115 V (nominal, see complete results for actual voltage)
• Active PFC: Yes
• Modular Cabling System: Yes, total
• Motherboard Power Connectors: One 20/24-pin connector, two ATX12V connectors that together form an EPS12V connector, and one EPS12V connector
• Video Card Power Connectors: Four cables with one six/eight-pin connector each
• SATA Power Connectors: 10 on three cables
• Peripheral Power Connectors: Six on two cables
• Floppy Disk Drive Power Connectors: Two on two cables
• Protections: Over voltage (OVP) and over power (OPP) protections –although not listed by the manufacturer, this unit has under voltage (UVP), over current (OCP), and short-circuit (SCP) protections
• Warranty: Three years
• Real Manufacturer: Information not available
• More Information: http://www.rosewill.com
• Average price in the US*: USD 100.00

* Researched at Newegg.com on the day we published this review.

Conclusions

Rosewill is a brand targeted at the mainstream market, offering products at an affordable cost for the Average Joe.

The Libertas 800 W could be an excellent power supply and deserve our recommendation if it hadn't failed the voltage regulation test at +5 V when we pulled 640 W and above from it.

On the good side we have very low noise and ripple levels, a full modular cabling system, and an outstanding price for a power supply with this feature set and design.

Another interesting thing is that this unit was officially certified as 80 Plus Gold, but the manufacturer decided to downgrade it to 80 Plus Bronze, since it can’t maintain efficiency above 87% at full load at high temperatures. In a world full of companies trying to deceive users, this is good news.