HR2000 — FLUORESCENT LAMP HB DRIVER WITH PFC

HR2000 Rev. 1.0

www.MonolithicPower.com

18

2/20/2013

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© 2013 MPS. All Rights Reserved.

CP

REF

preheat

C

R

T

600

(ms)

100nF

51k

=

×

×

Ω

CP

REF

ignition

C

R

T

562

(ms)

100nF

51k

=

×

×

Ω

Setting the Preheat Current Limitation

In the preheat stage, the CS pin limits the

preheat current through the filament of the FL.

The preheat current is limited by setting the

sense resistor on CS pin (R202 in figure 1)

through:

CS(pre)

preheat _ pk

CS

V

I

R

=

Where the

voltage of CS pin to limit the preheat current.

If using the filament transformer for preheating,

this CS pin function will limit the resonant current

in the preheat stage.

The over current limitation function on CS pin

limits the ignition voltage or ignition current in the

ignition

state

and

any

exceeded

output

current/power condition. Add a diode (D203 in

figure 1) like 1N4148 in parallel with the sense

resistor and a 1k resistor (R203 in figure 1)

between the CS pin and the current sense

resistor to limit the negative voltage on CS pin.

Design the PFC Inductor

The HR2000 operates the PFC in boundary

conduction mode (BCM) with on-time (Ton)

control. The frequency of the PFC stage is

variable. The design of the PFC inductor relates

to the output power, the range of the input AC

voltage and the desired minimum operating

frequency. It is also limited by the maximum turn

on time of HR2000. The maximum peak current

through this inductor is:

o _ max

L _ pk _ max

in _ min_ RMS

2 2P

I

V

=

η ×

Where ηis the efficiency of the PFC stage,

usually in range of 0.95 to 0.98.

The maximum turn on time of the PFC MOSFET

occurs at the minimum AC input voltage:

L _ pk _ max

o _ max

on _ max

2

in _ min_ RMS

in _ min_ RMS

L I

L 2P

T

V

2V

×

×

=

=

η ×

Then the inductor is restricted by the maximum

on time limit of IC:

2

in _ min_ RMS

on _ limit

o _ max

V

T

L

2P

η ×

×

≤

time, design its value with 20µs.

The minimum operating frequency occurs at the

minimum AC input voltage or the maximum AC

input voltage.

in _ min_ RMS

o

in _ min_ RMS

in _ max_ RMS

o

in _ max_ RMS

min

o

L _ pk _ max

o

L _ pk _ max

2V

(V

2V

)

2V

(V

2V

)

f

min(

,

)

L V

I

L V

I

×

−

×

−

=

×

×

×

×

For most of the specifications, such as the

universal input (85VAC to 265VAC) and 400V

PFC output, the minimum frequency occurs at

the maximum AC input voltage.

Design the inductor value with the desired

minimum operating frequency, and it should be in

the restricted range by the IC’s limit of the

maximum on time.

Application Example

This application example introduces the design of

a 16W FL based on HR2000. It requires the PF

(power factor) over 0.9. The boost PFC stage

and resonant half bridge power structure is used

for this FL driver. The integrated PFC control and

half bridge driver of HR2000 fits for this type of

application well.