Primary Analysis

We were very curious to check what components were chosen for the power section of this power supply and also how they were set together, i.e. the design used. We were willing to see if the components could really deliver the power announced by Zalman.

From all the specs provided on the databook of each component, we are more interested on the maximum continuous current parameter, given in ampères or amps for short. To find the maximum theoretical power capacity of the component in watts we need just to use the formula P = V x I, where P is power in watts, V is the voltage in volts and I is the current in ampères.

We also need to know under which temperature the component manufacturer measured the component maximum current (this piece of information is also found on the component databook). The higher the temperature, the lower current semiconductors can deliver. Currents given at temperatures lower than 50º C are no good, as temperatures below that don’t reflect the power supply real working conditions.

Keep in mind that this doesn’t mean that the power supply will deliver the maximum current rated for each component as the maximum power the power supply can deliver depends on other components used – like the transformer, coils, capacitors, the PCB layout, the wire gauge and even the width of the printed circuit board traces – not only on the specs of the main components we are going to analyze.

For a better understanding of what we are talking here, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU606 rectifying bridge on its primary stage, which can deliver up to 6 A (rated at 100º C). This bridge is attached to the same heatsink where the switching transistors are located.

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Figure 11: Rectifying bridge.

On the active PFC circuit two STP14NK50ZFP power MOSFET transistors are used, each one capable of handling up to 14 A at 25º C or 7.6 A at 100º C in continuous mode or up to 48 A at 25º C in pulse mode. These transistors are located on a separated heatsink, together with the active PFC diode.

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Figure 12: Active PFC transistors and diode.

On the switching section this power supply uses two FQPF9N50C power MOSFET transistors in two-transistor forward configuration. Each one of these transistors can deliver up to 9 A at 25º C or 5.4 A at 100º C in continuous mode or up to 36 A at 25º C in pulse mode, which is the mode used. As mentioned, these transistors are located on the same heatsink as the rectifying bridge.

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Figure 13: Switching transistors.

The primary section is controlled by a CM6800 integrated circuit, which is a very popular active PFC and PWM controller combo. It is located on a small printed circuit board attached to the main board.

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Figure 14: PFC and PWM controller combo.

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