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IRS2980SPBF

LED DRIVER CONTROL IC

International Rectifier 

IRS2980S

Operating frequency and duty cycle will vary when

there is ripple in the DC bus voltage. For example

where a passive valley fill circuit is used for power

factor correction (PFC) the LED current will be

regulated dynamically by constantly changing

frequency and duty cycle to maintain a constant

average.

Current Sense Filter Selection

The recommended values for RF and CF are

100Ohms and 1nF. This is sufficient to prevent

instability due to switching noise appearing at the

current sense input. These values have negligible

effect on the frequency and ripple. In a test

application using a 3.3mH inductor to drive a

17.5V LED panel, the output current varied from

338mA to 347mA (2.7%) over a DC voltage input

range of 40V to 200V.

A resistor (RG) between the gate driver output

and the gate of the power MOSFETs is also

recommended to reduce switching transients by

reducing dv/dt. A value of 10Ohms is

recommended, however this can be increased to

reduce noise if required.

Filter values may be increased in order to lower

the running frequency without increasing inductor

size. This results in higher current ripple and

higher current change over input voltage

variations. This may be an acceptable

compromise depending on the application

specification.

pin of the IRS2980S is rated up to 450V, the

actual maximum voltage that can be applied is

limited by the by the power dissipation of the IC.

The internal VCC regulator is recommended for

use up to 200VDC or with a passive valley fill PFC

circuit operating from up to 250VAC input. It can

be operated at higher voltages only with sufficient

heat sinking.

Figure 2: Passive valley fill PFC circuit

Frequency Limiter

The switching frequency of the IRS2980S is

internally limited to approximately 150 kHz (fMAX).

The IRS2980S is designed for use below this

frequency in order to limit current consumption in

the VCC and floating high side bias supplies. This

is necessary because the IRS2980S uses internal

regulators to supply these voltages, which can

supply only a limited current. This restriction is

acceptable in most LED driver applications.

Where higher frequency operation is needed the

IRS25401/11 is recommended.

Figure 3: Passive valley fill PFC bus voltage (blue)

and line input current (red) waveforms.

The VCC current (ICC) drawn by the IRS2980S

can be estimated from the following formula:

ICC ≈ 1mA + QG ⋅ f SW

High Voltage Regulator

The IRS2980S includes a high voltage regulator

to supply VCC from the DC input bus voltage.

This eliminates the need for external VCC supply

circuitry. A VCC capacitor of 1uF is recommended

for reliable startup and smooth operation. The

IRS2980S may shut down if CVCC is not present

or too small.

If necessary the internal regulator may also be

bypassed by supplying an external DC supply

from 14V to 15V to the VCC pin. Although the HV

Therefore power dissipation due to the high

voltage regulator can be calculated as:

PREG = VBUS _ DC _ AV ⋅ I CC

Floating Differential Current Sense

The floating high side current sense incorporated

in the IRS2980S is able to operate up to 450V and

withstand voltage surges up to 600V. An internal

bias supply is derived between the HV and VS

www.irf.com

© 2011 International Rectifier

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