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MT7930

Single Stage, High PFC, AC-DC LED Driver

Unspecified 

Maximizing IC Performance

BLOCK DIAGRAM

MT7930

Single Stage, High PFC, AC-DC LED Driver

APPLICATION INFORMATION

MT7930 is a primary-side controller for AC-DC

LED driver. The LED current can be accurately

regulated through sensing the primary side

information to realize real current control.

MT7930 integrates power factor correction

function to eliminate pollution to the AC line and

works in DCM and constant OFF time mode.

Real Current Control

With MAXIC proprietary technique, MT7930

accurately regulate LED current through sensing

the primary side information. The LED current

can be easily set as following (refer to the

application circuit in page 1):

I LED

 0.94 1  NP

2 NS

VFB

RS

Where NP is primary winding, NS is secondary

winding; VFB (=400mV) is the internal voltage

reference and RS is an external current sensing

resistor (Rs is R4 in page1 application circuit).

Start Up

During start-up process, VDD is charged through

a start-up resistor. As VDD reaches 18.5V, the

control logic starts to work, and the gate drive

begins to switch. A soft-start function is

implemented to prevent the transformer from

entering into CCM (continuous current mode) as

show in Fig.1.

The power supply is taken over by the auxiliary

winding once the voltage of this winding is high

enough.

After MT7930 control logic starts to work, STP

pin is clamped to lower than VDD voltage about

0.2V.

MT7930 will shut down if VDD goes below 7.2V

(UVLO threshold voltage).

MT7930 Rev. 1.30

www.maxictech.com

Copyright © 2011 Maxic Technology Corporation

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