MAGNET POWER SUPPLY SYSTEM 7000
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DANFYSIK A/S - DK 4040 JYLLINGE - DENMARK.
inadequate trigger signals in case of power failure.
C430, R455, R445 and R496 perform a 50 mS soft start of the current mode controller.
The two outputs are programmed to have a deed time of app. 1 µS.
4.4.5
FET Gate driver
The FET's gates are driven from two dual gate driver chips. This chip has the following feature.
- High speed
- Capable to drive up 2A gate current.
- Rated for 1200V
- Built in "low supply voltage" detector.
The IR 2213 is an ideal driver when MOS FET’s is driven in an H-bridge configuration.
The 2A-gate drive current is sufficient to drive two or three TO247 housed power MOS FET’s.
The bootjumper capacitor C306 and C307 is charged by D312 and D313, every time the LO output
of the IR2213 is low.
4.4.6
Power output stage
FET's (Field Effect Transistors) are chopped for driving the Power transformer.
Using the new FET’s from International Rectifier with low gate charge, increases the switching
speed and hereby decreases the power switch loss.
The power loss in the FET’s is low due to the very low ON resistance.
Cycle by cycle switch current is measured with a current transformer T302. The output current of
the current transformer is reduced 100 times due to the 1/100 transformer ratio.
The PWM Module for current mode control and overload protection uses the current transformer
signal.
4.4.7
Power Transformer
The ferrite power transformer T301 is wound on an ETD 59 coil form and is designed with
minimum creepage of 6 mm from primary to secondary windings.
Three layer of high temperature isolation material is applied between primary and secondary
windings.
Resistive loses and loses from high frequency skin depth effects are reduced to a minimum by use
of 0.1 mm isolated copper foil in the primary and the secondary windings.
