ML4835 查看數據表（PDF） - Micro Linear Corporation

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ML4835

Compact Fluorescent Electronic Dimming Ballast Controller

Micro Linear Corporation 

FUNCTIONAL DESCRIPTION (Continued)

The ML4835 implements a triple frequency operation

scheme: programmable three-frequency sequence for pre-

heat, ignition, and dimming, that extends lamp life,

simplifies lamp network design, and starts lamps at any

dimming level without flashing. This addresses the need

for a high-Q network for starting sequence and low-Q

network for operation, minimizing parasitic losses and

improving overall power efficiency. The values for the

pre-heat, start, operation, and restart can be programmed

or selected (Figure 2).

ML4835

POWER FACTOR SECTION

The ML4835 power factor section is a peak or average

current sensing boost mode PFC control circuit in which

only voltage loop compensation is needed. It is simpler

than a conventional average current control method. It

consists of a voltage error amplifier, a current sense

amplifier (no compensation is needed), an integrator, a

comparator, and a logic control block. In the boost

topology, power factor correction is achieved by sensing

the output voltage and the current flowing through the

current sense resistor. Duty cycle control is achieved by

comparing the integrated voltage signal of the error

amplifier and the voltage across RSENSE. The duty cycle

control timing is shown in Figure 3.

SET TIME VALUES

FOR PREHEAT,

START AND OPERATION,

AND RESTART

ML4835

HIGH Q

PREHEAT

f1

f2

START

LOW Q

f3

OPERATION

Figure 2. Three Frequency Design Model

EMI

FILTER

L

RSENSE

SW2

SW1

VOUT

RA

INVERTER

RB

LAMP

NETWORK

3

PIFB

4

PIFBO

–A

18

PFC OUT

+

–

PIFBO

RAMP

OSC

V TO I

CLK

PFC OUT

CRAMP

13

CRAMP

RQ

S

CLK

PEAO –

+

VREF1

PEAO

2

R1

C2

C1

1

PVFB/OVP

LAMP

LAMP

Figure 3. ML4835 PFC Controller Section

7

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