IR2161 datasheet(12/20 Pages) IRF

12 / 20 page

IR2161(S)&(PbF)

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Figure 10, Overload Output Current.

In figures 9 and 10, trace (1) shows the half bridge

oscillations during both types of fault mode and trace (2)

shows the charging and discharging of the CSD capacitor.

The IR2161 can also be externally shut off by applying a

voltage above 9V (VCSLATCH) to the CS pin. This will

cause the system to go directly to a latched fault mode,

after a delay of approximately 1uS to avoid the possibility of

false tripping caused by transients. To restart the system, it

is necessary to cycle Vcc off and on.

In addition, any time Vcs exceeds VCSLATCH

(approximately half Vcc), this latching shutdown function

will be triggered and the system will remain in FAULT mode

until VCC is re-cycled.

The IR2161 also includes over temperature shutdown, which

latches the convertor off when the die temperature of the

IC exceeds 130-135

°C. Experimental measurements reveal

that the die temperature will be no more than 20

°C above

the ambient temperature at all operating frequencies inside

the convertor.

Calculating Rcs

The value of the current sense resistor Rcs is critical to

achieve correct operation in the IR2161 based Halogen

convertor.

Figure 11, Calculating RCS

Ignoring the output transformer we can assume for this

calculation that the load is connected from the half bridge to

the mid point of the two output capacitors and that the

voltage at this point will be half the DC bus voltage. The

RMS voltage of the DC bus is the same as that of the AC line

so we can see that the RMS voltage across the load shown

in Figure 8, will be half the RMS voltage of the line. The load

is the maximum rated load of the convertor. The current in

Rcs will be half the load current given by :

LOAD

RCS

VCS

DC Bus

Voltage

1/2 DC Bus

Voltage

VCSpk

Figure 9, Short Circuit Output Current.

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