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The high voltage MOSFET technology derives from the well-established high voltage SuperMESH series with a new carrier lifetime control technique. The technology, called SuperFREDmesh, is the perfect match for HID lamps, high-end ballasts and switch-mode power supplies that use zero-voltage resonant switching. |
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| The challenge of modern power supplies is to achieve ever-increasing efficiency at higher frequencies.
A special technique, developed for this purpose, utilizes zero-voltage transition to minimize switching losses. The phase-shifted ZVS (zero voltage switching) mode of operation, associated with bridge circuits, is achieved by imposing a resonance in the switching transistor circuit that causes the voltage across it to decrease to almost zero before the switching on of the device; as a result, switching losses are greatly minimized. A possible failure mode occurs at low or no load when the ON-MOSFET is turned-off at hard-switching conditions. Such an occurrence causes a Cdv/dt shoot-through current to create a voltage spike at the gate of the OFF-MOSFET on the same bridge leg causing a false turn-on and leading to the premature failure of the device. To increase dv/dt capability a right value of VGSth has been defined; a gate drive circuit with very low impedence should be used.
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In topologies such as bridge converters, it is required that the MOSFETs have a fast body drain diode. In fact, if the reverse recovery charge has not been removed, the body diode is not able to block the reverse voltage. Therefore, if the remaining charges are still in the junction during the turning-on of the other MOSFET of the same leg of the bridge, its body diode may be subjected to dv/dt stress. The higher dv/dt values are able to generate a sufficiently high impulse of currect Ic = cdv/dt that joined with the reverse current flowing through the junction becomes the breakdown current through the drain-body junction that turns on the parasitic BJT bearing a destructive avalanche effect.
MOSFETs developed utilizing this high-voltage advanced process show high dv/dt immunity, along with optimized body diode reverse-recovery time (trr) and very soft recovery. A lower Irrm and trr means lower Qrr and minimized switching losses.
These benefits are coupled to a low on-resistance, optimal dynamic performance and cost competitiveness characterizing the whole SuperMESH family.
The STW29NK50ZD is a 500V device suitable for high power ZVS bridge SMPS.
The STP4NK50ZD, a 500V 2.7Ohm device, and STD5NK52ZD, a 520V 1.2Ohm device, have an improved dv/dt immunity up to 15V/ns and are suitable for lighting applications.
STP9NK60ZD now presents an improved trr of 130ns. It handles 600V and is available in TO-220, TO-220FP and D2PAK. Its typical application is for notebook adapters in half-bridge configuration. The STE45NK80ZD and the STE40NK90ZD handle 800V and 900V respectively, and are suitable for welding and very high power ZVS SMPS topologies. |
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