IR2161 datasheet(13/20 Pages) IRF

13 / 20 page

IR2161(S)&(PbF)

www.irf.com

Since the load is resistive the current waveform will have a

sinusoidal envelope and so the peak can be easily deter-

mined taking into account that the current has a high fre-

quency component with an approximate 50% duty cycle:

Therefore:

For correct operation at maximum load the peak voltage

should be 0.4V.

The calculation can be simplified by combining the formulae,

Which can be simplified to:

Example

For a 100W convertor working from a 230VAC supply the

current sense resistor would need to be :

The nearest preferred value to this would be 0.33 Ohms.

The power dissipation in Rcs should also be considered

and is given by :

In this case :

It is important to bear in mind that the resistor must be rated

to handle this current in a high ambient temperature.

IMPORTANT NOTE

The filter resistor RL should be 1K, which is needed to

protect the CS input from negative going transients. CCS

should be 1nF and is also necessary to filter out switching

transients that can impair the operation of the shutdown

circuit.

Adaptive Dead Time

Because of the fact that the DC bus voltage varies during

the mains half cycle, the dead time may need to vary in

order to achieve soft switching. The IR2161 has an adap-

tive dead time circuit (ADT) that detects the point at which

the voltage at the half bridge slews to 0V (COM) and sets

the LO output high at this point. There is an internal sample

and hold system that allows approximately the same delay

to be used to set HO high after LO has gone low. This

reacts on a cycle-by-cycle basis of the oscillator and there-

fore will adjust the dead time as necessary regardless of

external conditions.

Figure 12, ADT when VS slews from VBUS to COM

LOAD

RMS

)

(

)

(

)

(

RMS

)

(

)

(

062

230

100

⎟

⎠

⎞

⎜

⎝

⎛

LOAD

⋅

LOAD

⋅

= 141

324

100

230

141

LOAD

⎟

⎠

⎞

⎜

⎝

⎛

IR2161 Datasheet(PDF) 13 Page - International Rectifier

IR2161 Datasheet(HTML) 13 Page - International Rectifier

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Datasheet Download

Link URL