3

Application Examples

DC and AC Overvoltage

Suppression

The regulator can be used as a

voltage surge suppressor. The device

is again connected in series with the

lead (Fig. 5) and would normally

operate at a current level lower than

the plateau (Fig. 6a). Any incoming

voltage surge (Fig. 6b) less than the

breakdown voltage of the regulator will

be clamped by the IXCP regulator to

voltage less than the plateau current

times the effective resistance of the

load.

Testing & Handling

Recommendations

For initial assessment of the parts

where the customer may test the

device characteristics in free air

without heat sinking, the continuous

power dissipation should be kept

(R

R

Normal electrostatic handling

precautions for MOS devices

should be adhered to.

Fig. 5. DC surge suppression

Soft Start-Up Circuits

Here the regulator characteristic will

clamp initial current surges which can

occur when power is initially applied

to a load. The device, with its 450 V

capability could, for example, be used

with a DC power supply or with AC

mains to limit the initial high inrush of

current into lamp filaments, thereby

increasing the filament life several

times. It could, therefore, be used

effectively in lighting displays and in

the transportation lighting industries.

Highly Stable Voltage Sources

Another obvious application would be

to use the current regulator as a

Fig. 9. Normal fusing links in

series with each board

Fig.8. Low cost current regulators

instead of fuses

Fig. 6b. Incoming surge/output surge

across load

Fig. 6a. DC surge suppression

source of a highly stable current to

produce a usable voltage reference

(Fig. 7). This would be effectively

independent of temperature and a low

cost approach. A high voltage

reference is also possible, thanks to

their high breakdown voltages.

Instantaneous "Fuse"

Another application would be

protection against sudden voltage

droops on voltage supply lines to logic

cards in computing systems, resulting

from one component suddenly

shorting to ground. Normal fusing

networks will draw considerable

current during the time it takes for the

fuse to clear. This could cause a

sufficient dip in power rail voltage to

cause malfunctions of the other logic

cards, even with fast-blow fuses (Fig.

8). The current regulator in series with

the logic card restricts the current to

its own operating level (Fig. 9).

Therefore the voltage supply does not

become overloaded and the regulator

remains intact.

The current regulator thus provides an

"instantaneous fusing" function. When

the logic component is replaced, the

regulator resumes its normal

functioning mode.

The obvious advantages to having this

regulator as fuse substitute are:

Prevents a "dip" in the power

supply during a fault condition

Regulator remains intact

Can be easily tied in with logic to

indicate a "down state" board

R = 100

Ω V

R = 50

Ω

V

R = 25

Ω

V

Fig. 7. Simple voltage source with

high stability

IXC Series

IXYS MOSFETs and IGBTs are covered by 4,835,592

4,931,844

5,049,961

5,237,481

6,162,665

6,404,065 B1

6,683,344

6,727,585

one or moreof the following U.S. patents:

4,850,072

5,017,508

5,063,307

5,381,025

6,259,123 B1

6,534,343

6,710,405B2

6,759,692

4,881,106

5,034,796

5,187,117

5,486,715

6,306,728 B1

6,583,505

6,710,463