IRPLLNR2E Datasheet IRPLLNR2E, IRPLLNR2U | P10-P12

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Figure 7: Typical lamp voltage at startup;

Startup

= f

P reheat

Figure 8: Improved lamp voltage at startup;

Startup

> f

P reheat

The duration of the Preheat mode as well as which mode of operation the ballast is operating in is

determined by the voltage on the CPH pin of IC2. At the completion of the UVLO mode, Preheat

mode is entered and an internal current source is activated at the CPH pin of IC2 which begins to

charge up capacitor CPH. The ballast remains in the Preheat mode until the voltage on the CPH

pin of IC2 exceeds the Ignition Ramp mode threshold (4V).

Ignition Ramp Mode

At the completion of the Preheat mode (4V < CPH

pin < 5.1V) the ballast switches to the Ignition Ramp

mode and the frequency ramps down to the ignition

frequency. The frequency ramping is accomplished

by turning off the internal open drain MOSFET on

the RPH pin of IC2 (see Figure 1, IR21571 block

diagram). Resistor RPH is no longer connected di-

rectly in parallel with resistor RT. The shift in frequency

does not occur in a step function but rather with an

exponential decay because of capacitor CRAMP in

series with resistor RPH to ground. The duration of

this frequency ramp is determined by the time con-

stant of the RC combination of capacitor CRAMP

and resistor RPH. The minimum frequency of oscil-

lation occurs at the end of this ramp and is deter-

mined by resistor RT and capacitor CT. During this

ramping downward of the frequency, the voltage

across the lamp increases in magnitude as the

frequency approaches the resonant frequency of

the LC load circuit until the lamp ignition voltage

Figure 9: Upper trace: voltage on capacitor

CRAMP during Ignition Ramp mode

Lower trace: Lamp voltage during Ignition

Ramp mode.

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is exceeded and the lamp ignites. Figure 9 shows the ramping of voltage appearing across the lamp

and also the voltage on capacitor CRAMP. Note that the sudden drop in lamp voltage indicates that

the lamp has ignited. Also note that the voltage on capacitor C12 is still increasing at the point when

the lamp has already ignited meaning the frequency is still ramping down to the final minimum

ignition frequency. This minimum frequency corresponds to the absolute maximum ignition voltage

required by the lamp under all conditions.

During the Ignition Ramp mode the voltage on the CPH pin of IC2 continues to ramp up until the

voltage at the CPH pin of IC2 exceeds the Run mode threshold (5.1V). Over-current sensing is also

enabled at the beginning of the Ignition Ramp mode. A full explanation of the functionality of the

over-current sensing is in the section on Fault Mode.

Run Mode

At the end of the Ignition Ramp mode (CPH pin

> 5.1V) the ballast switches to the Run mode at

which point the frequency is shifted to the run

frequency. The run frequency is determined by

the parallel combination of resistors RT and

RRUN and capacitor CT. Resistor RRUN is

connected in parallel by turning on the internal

open drain MOSFET connected to the RUN pin

of IC2 (see Figure 1, IR21571 block diagram).

The sensing of under-current conditions is also

enabled at the beginning of the Run mode. The

full explanation of the functionality of the under-

current sensing is in the section on Fault Mode.

Figure 10 shows the functionality of the CPH,

RPH and RUN pins of IC2 during Startup, Pre-

heat, Ignition Ramp and Run modes.

The Run mode frequency is that at which the lamp is driven to the lamp manufacturer’s recom-

mended lamp power rating. The running frequency of the lamp resonant output stage for selected

component values is defined as,

Figure 10: Top trace: CPH pin IC2

Middle trace: RPH pine IC2

Bottom trace: RUN pin IC2

LCCV

Lamp

DCbus

Lamp

run













−

























−+













−=

(3)

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C = Lamp resonant circuit capacitor (C14) (F)

Lamp

= Lamp running power (W)

Lamp

= Lamp running voltage amplitude (V)

= Lamp resonant circuit inductor (L3) (H)

where,

Figure 11 shows the voltage appearing across the lamp while Figure 12 shows the current flowing

through the lamp during Startup, Preheat, Ignition Ramp and Run modes.

Figure 11: Lamp voltage during Startup, Preheat,

Ignition Ramp and Run

Figure 12: Lamp current during Startup, Preheat,

Ignition Ramp and Run (100mA/div.)

Normal Powerdown

A Normal Powerdown occurs when the AC line voltage is disconnected from the ballast. When this

occurs the voltage on the VDC pin of IC2 drops below the line fault threshold (3V) and IC2 shuts

down in a controlled fashion. The oscillator is stopped, the half-bridge driver outputs (LO and HO)

are turned off and capacitors CPH, CRAMP, CSTART and CT are discharged. IC2 also goes into its

UVLO/micro-power mode and the bus voltage begins to collapse.

Fault Mode

Fault mode is when the ballast driver is shutdown due to the detection of a lamp fault. Note that when

the ballast is in this Fault mode the power factor correction section of the ballast is also shutdown

and the bus voltage will drop to the non-boosted/unregulated level. There are several lamp fault

conditions which can put the ballast into the Fault mode. The lamp fault conditions detected include:

near/below resonance (under-current) detection, hard-switching detection and over-current detec-

tion. Resistor RCS in the source lead of the low side MOSFET (M3) serves as the current sensing

point for the half-bridge which is used to detect these lamp fault conditions. In operation when the

half-bridge is oscillating, a voltage appears across RCS whenever the low side MOSFET, M3, is

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IRPLLNR2E

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KIT BALLAST LINEAR INT 230VAC

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IRPLLNR2E

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