HV9801A 데이터 시트보기 (PDF) - Supertex Inc

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HV9801A

Switch Dimmable LED Driver

Supertex Inc 

Functional Block Diagram

VIN

VDD

CS

VDD Regulator

Leading

Edge

Blanking

250mV

440mV

GND

Average

Current

Regulator

OR

Hiccup

RT

Current Mirror from VDD Rail

HV9801A

OTP

UVLO

AND

GATE

SQ

RQ

OFF

Time

Generator

HV9801A

Application Information

Current Control

Continuous Conduction Mode

The HV9801A is designed for control of a buck converter

operating in continuous conduction mode.

CCM operation is characterized by converter operation with

non-zero inductor current throughout the switching cycle.

Such operation can be achieved by selection of the induc-

tance.

LED Current

The HV9801A regulates the LED current with an accuracy

far superior to that of competing peak current mode control-

lers.

Average LED current is set by the current sense resistor

RCS and the current regulator reference voltage :

V = (I) • (R)

Current Control Performance

The control method of the HV9801A virtually eliminates the

regulation errors associated with peak current mode control-

lers, such as errors caused by: inductor tolerance; propa-

gation delay of the current sense comparator; tolerance in

the oscillator frequency or off-timer; and changes in line and

load voltage.

Fig. 1 compares the load regulation of the HV9801A and that

of a device with peak current control. The difference in load

regulation between the HV9801A and the HV9910B, a peak

current regulator, is clearly visible.

Output Characteristics

0.60

0.55

HV9801A

0.50

VIN = 170VDC

0.45

0.40

HV9910B

250mV = (ILED ) • (RRCS )

0.35

0.30

For example, a 2Ω resistor correponds to a 125mA (aver-

age) LED current.

0.25

0

10

20

30

40

50

60

Output Voltage, V

Fig.1. Typical output characteristic of the HV9801A LED

driver.

Doc.# DSFP-HV9801A

B051412

4

Supertex inc.

www.supertex.com

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