HR2000 — FLUORESCENT LAMP HB DRIVER WITH PFC

HR2000 Rev. 1.0

www.MonolithicPower.com

17

2/20/2013

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2013 MPS. All Rights Reserved.

APPLICATION INFORMATION

PFC Part

Setting the PFC Output Voltage

The Vo pin is used to set the PFC output voltage.

Connect a resistor (R105, R106, R107 in figure 1)

between the PFC output and Vo pin, its value is

set by:

O _ PFC

PFC _ OUT

VO(REF)

V

2V

R

I

−

=

through Vo pin.

Connect a capacitor in range of 0.47µF to 10µF

(C103 in figure 1) or a R-C-C network from Vo

pin to GND to compensate the PFC regulation

loop.

Setting the Over Voltage and Over Current

Protection

The OVC pin is used for the over voltage and

over current protection for the PFC stage.

Connect this pin to the voltage divider (R108,

R109, R110 and R102 in figure 1) of the PFC

output to set the over voltage protection point.

OV _ H

o _ PFC _ pro

OV _ L

OVC(ref )

R

V

R

V

=

low side resistor of the voltage divider.

The over current protection senses the peak

current through the PFC MOSFET. the sensing

resistor (R101 in figure 1) is set by:

OVC(ref )

f _ diode

oc

oc

V

V

R

I

+

=

current protection point.

Setting the ZCD Detection

An auxiliary winding of the PFC inductor is used

to sense the voltage across the inductor to

indicate the zero inductor current condition. Set

the turn ratio of the auxiliary winding large

enough to make sure the reflected voltage across

the auxiliary winding is higher than the ZCD

reference voltage Vzcdref. Usually, setting the

reflected ZCD voltage at around 5V at maximum

input voltage is recommended.

A zener diode is integrated on ZCD pin. Add a

resistor in 10k

to 100k

range between the

auxiliary winding and the ZCD pin to limit the

current sunk into ZCD pin, according to the input

voltage range.

Half Bridge Part

Setting the Oscillator of Half Bridge

The capacitor on CT pin (C201 in figure 1) and

the resistor on REF pin (R201 in figure 1)

determine the bottom operating frequency. The

resistor on REF pin also determines the non-

overlap time of the half bridge.

Estimate the frequency set resistor on REF pin

with the desired non-overlap time:

REF

no

R

T

0.15 1.127

( s)

51k

=

+

×

µ

Ω

range in the limiting values.

Choose a proper capacitor on CT pin to set the

bottom operating frequency.

B

REF

int

T

par

0.5

f

2(R

R ) * (C

C

) 300ns

=

+

+

+

is the internal parasitic resistance on REF pin

on CT pin. Choose a proper capacitor on CT pin

and then redesign the resistor on REF pin to

make sure the bottom operating frequency is

accurate.

The start up frequency is:

ST

T

par

REF

int

0.5

f

2.5V (C

C

)

300ns

2.5V

35 A

2(R

R )

=

×

+

+

+

µ

+

Setting the Preheat time and Ignition Time

The capacitor on CP/EOL pin (C203) and the

resistor on REF pin determine the preheat time

and ignition time.