Thermaltake Purepower 430W NP Power Supply Review

Secondary Analysis

This power supply uses a mix between new and obsolete designs, showing us that the manufacturer instead of creating a new design from scratch adapted an old design.

The main difference between this power supply and newer (and better) models is how power is distributed. This power supply was projected when most of the power drawn by the computer was concentrated on the +5 V line and not on the +12 V line like it is today. We can say this because it uses a rectifier with lower specs for the +12 V line and the rectifier with higher specs for the +5 V line.

The +12 V rectifier is connected like in old power supplies (half-bridge design). The maximum theoretical current under this design is a simple addition of the maximum current each diode can deliver. Since the +12 V output is produced by one MBR20100CT Schottky rectifier, which can deliver up to 20 A (10 A per internal diode, measured at 133° C), the maximum theoretical power the +12 V output can deliver is of 240 W. The maximum current this line can really deliver will depend on other components. As mentioned, this output supports less current/power than required by today’s standards.

The +5 V output is produced by one MBR4045PT Schottky rectifier, which support up to 40 A (20 A per internal diode, measured at 125° C). The maximum theoretical current the +5 V output can deliver depends on the duty cycle used. If this power supplies uses a 30% duty cycle (which is a typical value), the maximum current would be 29 A [20 A/(1 – 0.30)], with a maximum power of 143 W. Of course the maximum current (and thus power) this line can really deliver will depend on the other components.

Then it comes how +3.3 V is produced. It has a separated rectifier like all current power supplies, but the output of this rectifier is +5 V, so it uses a voltage regulator to decrease this +5 V to +3.3 V. This is a mix between old and new designs. Old ATX power supplies generated their +3.3 V output by using a voltage regulator connected to the +5 V output. New power supplies have a completely separated rectifier. So this power supply uses a mix of these two approaches.

The +3.3 V output is produced by one MBR3045PT Schottky rectifier, which supports up to 30 A (15 A per diode, measured at 105° C). Using the same math presented above, this rectifier could in theory deliver up to 21 A or 71 W. Like we explained, the output of this rectifier is connected to a +3.3 V voltage regulator, controlled by an IPP09N03LA power MOSFET transistor, which is capable of handling up to 50 A at 25° C or 46 A at 100° C. Since in configurations like this the component with the lower current limit is the one that limits the circuit, in theory the +3.3 V output from this power supply can deliver up to 21 A or 71 W (if the duty cycle from the waveform applied on the rectifying diode is really 30%). As we explained the real limit depends on other factors.

Figure 13: +12 V, +5 V and +3.3 V rectifiers.

Figure 14: Power MOSFET transistor used on the +3.3 V regulator circuit.

As you can see in Figure 14 this power supply has a thermal
sensor attached to its secondary heatsink. This sensor is used to control the fan speed according to the power supply internal temperature.

On this power supply the big electrolytic capacitors from the voltage doubler are from Teapo (a Taiwanese company) and rated at 85° C, while the electrolytic capacitors from the secondary are from Teapo and Su’scon (another Taiwanese company) and rated at 105° C.