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Ballast Demonstrator User Guide

7629A–AVR–04/06

source due to the voltage drop across the source resistor. Enough energy is available

from the current source circuit during the conduction angles to keep the IXI859 (U1) pin

1 greater than 14VDC as required to enable the Under Voltage Lock Out (UVLO) cir-

cuitry in the IXI859.

3.1.9

IXYS IXD611 Half

bridge MOSFET

driver

The IXD611 half bridge driver includes two independent high speed drivers capable of

600mA drive current at a supply voltage of 15V. The isolated high side driver can with-

stand up to 650V on its output while maintaining its supply voltage through a bootstrap

diode configuration. In this ballast application, the IXD611 is used in a half-bridge

inverter circuit driving two IXYS IXTP3N50P power MOSFETs. The inverter load con-

sists of a series resonant inductor and capacitor to power the lamps. Filament power is

also provided by the load circuit and is wound on the same core as the resonant induc-

tor. Pulse width modulation (PWM) is not used in this application, instead the power is

controlled through frequency variation. It is important to note that pulse overlap, which

could lead to the destruction of the two MOSFETs due to current shoot through, is pre-

vented via the input drive signals through the microcontroller. This parameter, also

known as dead time, is not available on this particular driver. However, a dead time

option is built in on other driver models within the IXYS bridge driver family.

Other features of the IXD611 driver include:

– Wide supply voltage operation 10-35V

– Matched propagation delay for both drivers

– Undervoltage lockout protection

– Latch up protected over entire operating range

• +/- 50V/ns dV/dt immunity

3.1.10

IXYS IXTP3N50P

PolarHV N-Channel

Power MOSFET

The IXTP3N50P is a 3A 500V general purpose power MOSFET that comes from the

family of IXYS PolarHV MOSFETs. When comparing equivalent die sizes, PolarHT

results in 50% lower R DS(ON), 40% lower R THJC (thermal resistance, junction to

case), and 30% lower Qg (gate charge) enabling a 30% - 40% die shrink, with the same

Within the ballast demonstrator itself the IXTP3N50 serves two functions. The first of

which is the power switching pair of devices in the half-bridge circuit that drives the

lamps. While a third device serves duty in the main PFC circuit as the power switch that

drives the PFC inductor.