Contents
- 1Introducing the Zalman ZM750-EBT
- 1.1Packaging and accessories
- 2Connectors & cabling
- 2.1Casing & cooling
- 3Input filtering
- 4Primary side
- 4.1+5 V stand-by rail
- 5Secondary side
- 5.1Build quality
- 6Load testing
- 6.1Loading +5 V SB
- 6.2Voltage hold-up time
- 6.3Combined loading
- 6.4Combined loading ripple
- 6.5Crossloading, overloading
- 6.6Crossloading, overloading ripple
- 6.7Fan speed, temperatures and noise
- 7Conclusion and evaluation
- 7.1Thanks
- 7.2Discussion
- 8Important addendum
Primary side
This time the unit uses an ordinary layout, and actually one we’re already familiar with from some previously-reviewed Sirtec-made units. The bridge rectifier in use is the Hy Electronics GBU1506F, which provides a maximum current of 15 A continuously at 600 V and 100 °C (or 240 A peak for 8.3 ms). Its voltage drop (which counts for losses) is 0.95 V per diode at 7.5 A. That is with it heatsinked and this one does indeed have a small black heatsink mounted to it. There are two transistors in the boost-type PFC circuit, and both are the Infineon IPA50R140CP (23/56 A at 25 °C and 550 V, RDS(On) is 0.14 Ω at 14 A and 25 °C or 0.32 Ω at 150 °C) in TO-220F package. The diode is a Cree C3D08060 (23/220 A at 25 °C and 600 V, drop of 1.8 V at 25 °C or 2.4 V at 175 °C) in TO-220-2. The PFC coil is somewhat small for my tastes (for a 750 W unit, that is), it is similarly sized to the one inside the ZM600-GVM, but this particular unit is rated for a higher efficiency, so we shall see.
As for the bulk cap charged from the PFC, there is a Rubycon MXG 470 μF/400 V (measures at 443 μF). This series is rated for 3000 hours at maximum temperature (105 °C) and ripple. We can observe that the cap sits very close to the heatsink, and indeed the overall primary side is quite crowded. I believe a slightly larger board would have been better suited for a 750 W unit, and I have some concern about the cooling here. The switching transistors are Infineon IPA50R190CE (18.5/63 A at 25 °C and 500 V, RDS(On) 0.19 Ω or 0.45 Ω at 150 °C) in a TO-220F package again. As usually, all the primary power silicon is mounted to a common, black heatsink. The main transformer is larger than before, in order to accommodate the higher power rating, and it uses a 40mm wide core.
This platform also uses controller ICs from Infineon, the ICE3PCS01G for PFC and the ICE2HCS01G as resonant LLC switching controller. It controls transistors in a half-bridge configuration and is located on a daughterboard, physically situated between the main transformer and secondary heatsink. No longer are there any quality capacitors to be seen here in this area, there are only some Teapo SC series parts filtering the feedback and the power for the ICs.
+5 V stand-by rail
Here we meet the good (?) ol’ SanKen STR-A6069H current-mode PWM controller with integrated power MOSFET. Its switching frequency is 100 kHz and the transistor has a drain-source resistance of 6 Ω. This IC is rated for 10W devices but is has previously shown it can deliver up to 15 W (with slightly raised no-load voltage). More Teapo capacitors around here.
Next we jump over the 20mm transformer to the secondary side where we can see what is most likely a 5A Schottky rectifier diode in a DO package. Its output is then filtered by two more Teapo SCs, both 1000/10. A very poor choice here of capacitor for a high-end unit, I would have at least expected that the stand-by rail have quality caps…
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