[nextpage title=”Introduction”]

The Seasonic S12II Bronze power supply series is comprised of 380 W, 430 W, 520 W, and 620 W models, all with the 80 Plus Bronze certification. Let’s see if the 430 W model is a good pick.

Seasonic S12II Bronze 430 W power supplyFigure 1: Seasonic S12II Bronze 430 W power supply

Seasonic S12II Bronze 430 W power supplyFigure 2: Seasonic S12II Bronze 430 W power supply

The Seasonic S12II Bronze 430 W is 5.5” (140 mm) deep, using a 120 mm ball-bearing fan on its bottom (ADDA AD1212MB-A70GL).

The reviewed power supply doesn’t have a modular cabling system. All cables are protected with nylon sleeves that come from inside the unit. This power supply comes with the following cables:

  • Main motherboard cable with a 20/24-pin connector, 21.3” (54 cm) long
  • One cable with one ATX12V connector, 21.2” (54 cm) long
  • One cable with one EPS12V connector, 21.2” (54 cm) long
  • One cable with one six-pin connector for video cards, 22” (56 cm) long
  • One cable with one six/eight-pin connector for video cards, 22” (56 cm) long
  • Two cables, each with three SATA power connectors, 16.5” (42 cm) to the first connector, 3.9” (10 cm) between connectors
  • Two cables, each with three standard peripheral power connectors, 16.5” (42 cm) to the first connector, 3.9” (10 cm) between connectors

All wires are 18 AWG, which is the minimum recommended gauge. The number of connectors is outstanding for a 430 W power supply, allowing you to install a high-end video card that requires two auxiliary power connectors without the need for adapters.

Seasonic S12II Bronze 430 W power supplyFigure 3: Cables

Let’s now take an in-depth look inside this power supply.

[nextpage title=”A Look Inside the Seasonic S12II Bronze 430 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.

On this page we will have an overall look, and then in the following pages we will discuss in detail the quality and ratings of the components used.

Seasonic S12II Bronze 430 W power supplyFigure 4: Top view

Seasonic S12II Bronze 430 W power supplyFigure 5: Front quarter view

Seasonic S12II Bronze 430 W power supplyFigure 6: Rear quarter view

Seasonic S12II Bronze 430 W power supplyFigure 7: The printed circuit board

[nextpage title=”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 the transient filtering stage, this power supply is flawless, with one X capacitor, four Y capacitors, and one coil more than the minimum required.

Seasonic S12II Bronze 430 W power supplyFigure 8: Transient filtering stage (part 1)

Seasonic S12II Bronze 430 W power supplyFigure 9: Transient filtering stage (part 2)

On the next page, we will have a more detailed discussion about the components used in the Seasonic S12II Bronze 430 W.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of the Seasonic S12II Bronze 430 W. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses one GBU806 rectifying bridge, which is attached to an individual heatsink. This bridge supports up to 8 A at 100° C. So, in theory, you would be able to pull up to 920 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 W without burning itself out. Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply.

Seasonic S12II Bronze 430 W power supplyFigure 10: Rectifying bridge

The active PFC circuit uses two FDP18N50 MOSFETs, each supporting up to 18 A at 25° C or 10.8 A at 100° C in continuous mode (see the difference temperature makes) or 72 A at 25° C in pulse mode. These transistors present a maximum 265 mΩ resistance when turned on, a characteristic called RDS(on). The lower the number the better, meaning that the transistor will
waste less power, and the power supply will have a higher efficiency.

The output of the active PFC circuit is filtered by one 390 µF x 400 V Japanese electrolytic capacitor, from Chemi-Con, labeled at 105° C.

In the switching section, another two FDP18N50 MOSFETs are employed using the traditional two-transistor forward configuration. The specifications for these transistors were already discussed above.

Seasonic S12II Bronze 430 W power supplyFigure 11: One of the switching transistors, the active PFC diode, and the active PFC transistors

The primary is managed by an ICE1CS02 active PFC/PWM combo controller.

Seasonic S12II Bronze 430 W power supplyFigure 12: Active PFC/PWM combo controller

Let’s now take a look at the secondary of this power supply.

[nextpage title=”Secondary Analysis”]

The Seasonic S12II Bronze 430 W uses a regular design in its secondary, with Schottky rectifiers.

The maximum theoretical current each line can deliver is given by the formula I / (1 – D) where D is the duty cycle used and I is the maximum current supported by the rectifying diode. As an exercise, we can assume a duty cycle of 30 percent.

The +12 V output uses two SBR30A50CT Schottky rectifiers (30 A, 15 A per internal diode at 110° C, 0.55 V maximum voltage drop), giving us a maximum theoretical current of 43 A or 514 W for the +12 V output.

The +5 V output uses one MBR30H30CTG Schottky rectifier (30 A, 15 A per internal diode at 138° C, 0.55 V maximum voltage drop). This gives us a maximum theoretical current of 21 A or 107 W for the +5 V output.

The +3.3 V output uses another MBR30H30CTG Schottky rectifier. This gives us a maximum theoretical current of 21 A or 71 W for the +3.3 V output.

Seasonic S12II Bronze 430 W power supplyFigure 13: The +12 V, +5 V, and +3.3 V rectifiers

This power supply uses an HY510N monitoring integrated circuit, which only supports over voltage (OVP) and under voltage (UVP) protections.

Seasonic S12II Bronze 430 W power supplyFigure 14: Monitoring circuit

The electrolytic capacitors that filter the outputs are also Japanese, from Chemi-Con, and labeled at 105° C, as usual.

[nextpage title=”Power Distribution”]

In Figure 15, you can see the power supply label containing all the power specs.

Seasonic S12II Bronze 430 W power supplyFigure 15: Power supply label

According to the power supply label, this unit has two +12 V rails. However, this information is incorrect. Inside the unit, all yellow (+12 V) wires are connected to the same point, and the power supply doesn’t implement over current protection (OCP), which is required to create individual +12 V virtual rails. Curiously, on the product box and on the manufacturer’s website, this unit is correctly listed as having a single +12 V rail. Therefore, it is clear that the label was printed incorrectly.

How much power can this unit really deliver? Let’s find out.

[nextpage title=”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 powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (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. During this test, both inputs were connected to the power supply’s single +12 V rail. (The power supply’s EPS12V connector was installed on the +12VB input of the load tester.)

Input Test 1 Test 2 Test 3 Test 4 Test 5
+12VA 3 A (36 W) 6 A (72 W) 9 A (108 W) 12 A (144 W) 14.5 A (174 W)
+12VB 3 A (36 W) 6 A (72 W) 9 A (108 W) 12 A (144 W) 14.25 A (171 W)
+5 V 1 A (5 W) 2 A (10 W) 4 A (20 W) 6 A (30 W) 8 A (40 W)
+3.3 V 1 A (3.3 W) 2 A (6.6 W) 4 A (13.2 W) 6 A (19.8 W) 8 A (26.4 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 92.6 W 174.1 W 264.8 W 347.1 W 431.4 W
% Max Load 21.5% 40.5% 61.6% 80.7% 100.3%
Room Temp. 45.2° C 46.4° C 46.3° C 46.9° C 48.9° C
PSU Temp. 45.3° C 48.1° C 48.3° C 48.7° C 50.2° C
Voltage Regulation Pass Pass Pass Pass Pass
Ripple and Noise Pass Pass Pass Pass Pass
AC Power 110.1 W 202.1 W 306.9 W 407.6 W 518.2 W
Efficiency 84.1% 86.1% 86.3% 85.2% 83.2%
AC Voltage 113.5 V 112.9 V 112.4 V 110.9 V 109.1 V
Power Factor 0.994 0.994 0.996 0.996 0.996
Final Result Pass Pass Pass Pass Pass

The Seasonic S12II Bronze 430 W graduated from our tests with the highest honors. It presented efficiency between 83.2% and 86.3%, which is outstanding for an entry-level unit with the 80 Plus Bronze certification. This certification promises efficiency between 82% and 85%; however, time and time again we see units with this certification not being able to present at least 82% efficiency when delivering their labeled wattage.

All voltages were closer to their nominal values during all tests (3% voltage regulation), making the S12II Bronze 420 W a “flawless” power supply. The ATX12V specification states that positive voltages must be within 5% of their nominal values, and negative voltages must be within 10% of their nominal values.

Let’s discuss the ripple and noise levels on the next page.

[nextpage title=”Ripple and Noise Tests”]

Voltages at the power supply outputs must be as “clean” as possible, with no noise or oscillation (also known as “ripple”). The maximum ripple and noise levels allowed are 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V, +3.3 V and +5VSB outputs. All values are peak-to-peak figures. We consider a power supply as being top-notch if it can produce half or less of the maximum allowed ripple and noise levels.

The Seasonic S12II Bronze 430 W provided extremely low ripple and noise levels, making it a “flawless” unit here as well.

Input Test 1 Test 2 Test 3 Test 4 Test 5
+12VA 12.2 mV 13.4 mV 15.6 mV 17.8 mV 20.2 mV
+12VB 11.4 mV 12.2 mV 14.4 mV 16.4 mV 18.6 mV
+5 V 8.2 mV 8.2 mV 7.8 mV 8.2 mV 9.2 mV
+3.3 V 8.4 mV 8.2 mV 8.8 mV 10.6 mV 12.2 mV
+5VSB 10.2 mV 10.8 mV 10.2 mV 13.4 mV 15.0 mV
-12 V 8.2 mV 8.4 mV 9.6 mV 11.8 mV 13.8 mV

Below you can see the waveforms of the outputs during test five.

Seasonic S12II Bronze 430 W power supplyFigure 16: +12VA input from load tester during test five at 431.4 W (20.2 mV)

Seasonic S12II Bronze 430 W power supplyFigure 17: +12VB input from load tester during test five at 431.4 W (18.6 mV)

Seasonic S12II Bronze 430 W power supplyFigure 18: +5 V rail during test five at 431.4 W (9.2 mV)

Seasonic S12II Bronze 430 W power supplyFigure 19: +3.3 V rail during test five at 431.4 W (12.2 mV)

[nextpage title=”Overload Tests”]

Below you can see the maximum we could pull from this power supply. The objective of this test is to see if the power supply has its protection circuits working properly. This unit passed this test, as it shut down when we tried to pull more than listed in the table below. Noise and ripple levels were still extremely low and voltages were still within 3% of their labeled values.

Input Overload Test
+12VA 18 A (216 W)
+12VB 18 A (216 W)
+5 V 6 A (30 W)
+3.3 V 8 A (26.4 W)
+5VSB 3 A (15 W)
-12 V 0.5 A (6 W)
Total 500.4 W
% Max Load 116.4%
Room Temp. 49.5° C
PSU Temp. 52.9° C
AC Power 605.0 W
Efficiency 82.7%
AC Voltage 108.2 V
Power Factor 0.996

[nextpage title=”Main Specifications”]

The main specifications for the Seasonic S12II Bronze 430 W power supply include:

  • Standards: NA
  • Nominal labeled power: 430 W
  • Measured maximum power: 500.4 W at 49.5° C
  • Labeled efficiency: Up to 87%, 80 Plus Bronze certification
  • Measured efficiency: Between 83.2% and 86.3%, at 115 V (nominal, see complete results for actual voltage)
  • Active PFC: Yes
  • Modular Cabling System: No
  • Motherboard Power Connectors: One 20/24-pin connector, one ATX12V connector, and one EPS12V connector
  • Video Card Power Connectors: One six-pin connector and one six/eight-pin connector on separate cables
  • SATA Power Connectors: Six on two cables
  • Peripheral Power Connectors: Six on two cables
  • Floppy Disk Drive Power Connectors: None
  • Protections (as listed by the manufacturer): Over voltage (OVP), over power (OPP), and short-circuit (SCP)
  • Are the above protections really available? Yes. The unit also has under voltage protection (UVP).
  • Warranty: Five years
  • More Information: https://www.seasonicusa.com
  • Average Price in the U.S.*: USD 60.00

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

[nextpage title=”Conclusions”]

The Seasonic S12II Bronze 430 W is a flawless power supply. It has superb voltage regulation, with all its voltages within 3% of their nominal values, extremely low noise and ripple levels, and efficiency between 83.2% and 86.3%, which is outstanding for an entry-level power supply. It is also worth mentioning the outstanding cable configuration for a 430 W unit, with two connectors for video cards and six SATA power connectors. And, to top it off, the price is more than right for all the features this power supply brings. In summary, you can buy this power supply with your eyes closed. You won’t regret it.