ZXGD3101 Diodes, Inc., ZXGD3101 Datasheet - Page 5

• Manufacturer Part Number: ZXGD3101
• Description: Synchronous Rectifier Controller For Flyback Converters.
• Manufacturer: Diodes, Inc.

Operation
Normal Operation
The operation of the device is described step-by-step with reference to the timing diagram below.
1. The detector monitors the MOSFET Drain-Source voltage.
2. When, due to transformer action, the MOSFET body diode is forced to conduct there is
3. The detector outputs a positive voltage with respect to ground, this voltage is then fed to the
4. The current out of the GATEH pin is sourced into the synchronous MOSFET Gate to turn the
5. The GATEH output voltage is now proportional to the Drain-Source voltage drop across the
6. MOSFET conduction continues until the drain current reaches zero.
7. At zero current the detector output voltage is zero and the synchronous MOSFET Gate voltage
Issue 4 - January 2009
© Diodes Incorporated 2009
approximately -0.6V on the Drain pin.
MOSFET driver stage and current is sourced out of the GATEH pin.
device on.
MOSFET due to the current flowing through the MOSFET.
is pulled low by the GATEL, turning the device off.
D rain Voltage
M OSF ET
Gate Voltage
Gate C urrent
M OSF ET
M OSF ET
1
3
2
4
Body D iode
C onduction
5
current
D rain
zero
5
6
7
ZXGD3101T8
www.diodes.com
www.zetex.com