IR2520 Ver la hoja de datos (PDF) - International Rectifier

Número de pieza

componentes Descripción

Fabricante

IR2520

ADAPTIVE BALLAST CONTROL IC

International Rectifier 

IR2520D(S)& (PbF)

VVCO

6V

4.8V

0.85V

Freq

fmax

Frequency Sweep Mode

Run Mode

fmin

Fig. 3 IR2520D Frequency sweep mode timing

diagram.

Vout

Vin

High -Q

Ignition

Run Mode

The IR2520D enters RUN mode when the voltage on pin

VCO exceeds 4.8V (VVCO_RUN). The lamp has ignited and

the ballast output stage becomes a low-Q, series-L, paral-

lel-RC circuit. Also, the VS sensing and fault logic blocks

(Figure 5) both become enabled for protection against non-

ZVS and over-current fault conditions. The voltage on the

VCO pin continues to increase and the frequency deceases

further until the VCO pin voltage limits at 6V (VVCO_MAX)

and the minimum frequency is reached. The resonant in-

ductor, resonant capacitor, DC bus voltage and minimum

frequency determine the running lamp power. The IC stays

at this minimum frequency unless non-ZVS occurs at the

VS pin, a crest factor over-current condition is detected at

the VS pin, or VCC decreases below the UVLO- threshold

(see State Diagram).

DCBUS(+)

RSUPPLY

DCP2

CVCC

VCC

1

COM

2

FMIN

3

RFMIN

VCO

4

CVCO

Bootstrap

FET

Driver

15.6V

CLAMP

VCO

High-

and

Low-

side

Driver

Fault

Logic

VS

Sense

VB

8

HO

7

VS

6

LO

5

MHS

CBS

MLS

CSNUB

TO LOAD

DCP1

Run

Low -Q

Start

fmin

fmax

Frequency

Fig. 4 Resonant tank Bode plot with lamp operating

points.

DCBUS(-)

Fig. 5 IR2520D Run mode circuitry.

LOAD RETURN

Non Zero-Voltage Switching (ZVS) Protection

During run mode, if the voltage at the VS pin has not slewed

entirely to COM during the dead-time such that there is

voltage between the drain and source of the external low-

side half-bridge MOSFET when LO turns-on, then the system

is operating too close to, or, on the capacitive side of,

resonance. The result is non-ZVS capacitive-mode

switching that causes high peak currents to flow in the

half-bridge MOSFETs that can damage or destroy them

(Figure 6). This can occur due to a lamp filament failure(s),

8

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