ml4827cs-2 Fairchild Semiconductor, ml4827cs-2 Datasheet

ml4827cs-2

Manufacturer Part Number

ml4827cs-2

Description

Fault-protected Pfc And Pwm Controller Combo

Manufacturer

Fairchild Semiconductor

Datasheet

1.ML4827CS-2.pdf (16 pages)

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Features

• Pin-compatible with industry-standard ML4824-1

• TriFault Detect™ to conform to UL1950™ requirements

• Available in 50% or 74% max duty cycle versions

• Low total harmonic distortion

• Reduces ripple current in the storage capacitor between

• Average current, continuous boost leading edge PFC

• High efﬁciency trailing-edge PWM can be conﬁgured for

• Average line voltage compensation with brown-out

• PFC overvoltage comparator eliminates output

• Current fed gain modulator for improved noise immunity

• Overvoltage protection, UVLO, and soft start

General Description

The ML4827 is a controller for power factor corrected,

switched mode power supplies, that includes circuitry

Block Diagram

ML4827

Fault-Protected PFC and PWM Controller Combo

the PFC and PWM sections

current mode or voltage mode operation

control

“runaway” due to load removal

I AC

V FB

V RMS

I SENSE

RAMP 1

RAMP 2

V DC

DC I LIMIT

2.5V

V CC

50µA

–

VEA

VEAO

MODULATOR

1.25V

GAIN

3.5kΩ

–

IEA

IEAO

–

POWER FACTOR CORRECTOR

OSCILLATOR

0.5V

–

2.5V

V FB

PULSE WIDTH MODULATOR

–

BROKEN WIRE

COMPARATOR

V IN OK

DUTY CYCLE

necessary for conformance to the safety requirements of

UL1950. A direct descendent of the industry-standard

ML4824-1, the ML4827 adds a TriFault Detect™ function to

guarantee that no unsafe conditions may result from single

component failure in the PFC. Power Factor Correction

(PFC) allows the use of smaller, lower cost bulk capacitors,

reduces power line loading and stress on the switching FETs,

and results in a power supply that fully complies with

IEC1000-3-2 speciﬁcation. The ML4827 includes circuits

for the implementation of a leading edge, average current,

“boost” type power factor correction and a trailing edge,

pulse width modulator (PWM). The device is available in

two versions; the ML4827-1 (Duty Cycle

the ML4827-2 (Duty Cycle

maximum duty cycle of the -2 allows enhanced utilization of

a given transformer core’s power handling capacity. An over-

voltage comparator shuts down the PFC section in the event

of a sudden decrease in load. The PFC section also includes

peak current limiting and input voltage brown-out

protection. The PWM section can be operated in current or

voltage mode, and includes a duty cycle limit to prevent

transformer saturation.

LIMIT

2.7V

–1V

PFC I LIMIT

–

OVP

DC I LIMIT

V CCZ

2µA

V REF

MAX

www.fairchildsemi.com

V CCZ

UVLO

13.5V

= 74%). The higher

V CC

MAX

REFERENCE

REV. 1.0.1 6/27/01

7.5V

= 50%) and

PWM OUT

PFC OUT

V REF

GND

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