MV1012SC

2

Contents

1. Overview........................................................................................................................................................................ 4

1.1 Features................................................................................................................................................................... 4

1.2 Block diagram .......................................................................................................................................................... 4

1.3 Pin assignment ........................................................................................................................................................ 5

1.4 Pin functions ............................................................................................................................................................ 5

2. Explanation of basic operations..................................................................................................................................... 6

2.1 Starting sequence .................................................................................................................................................... 7

3. Component selection procedure and calculation method .............................................................................................. 8

3.1 Basic circuit configuration ........................................................................................................................................ 8

3.2 Component selection ............................................................................................................................................... 9

3.2.1

MOSFET (Q1) ................................................................................................................................................. 9

3.2.2

Fly-wheel diode (D1) ..................................................................................................................................... 10

3.2.3

Current detection resistor (R1 and R2).......................................................................................................... 10

3.2.4

Inductor (L1) .................................................................................................................................................. 11

3.2.5

Gate drive circuit (R4, R9, and D2)................................................................................................................ 11

3.2.6

Resistors for Svin and Svout pins(R5, R6, R7 and R8) ................................................................................. 12

3.2.7

CS pin filter (R3 and C4) ............................................................................................................................... 12

3.2.8

Vcc pin smoothing capacitor (C3).................................................................................................................. 13

3.2.9

REF pin capacitor (C5) .................................................................................................................................. 13

3.2.10 Svin pin capacitor (C9) .................................................................................................................................. 13

3.2.11 Resonant capacitor (Cr) ................................................................................................................................ 13

3.2.12 Input capacitor (C1) and Output capacitor (C2)............................................................................................. 13

3.2.13 Svout pin capacitor (C8) ...........................................................................................................................13-14

3.3 Winding voltage supply .......................................................................................................................................... 15

3.3.1

Configuration of a winding voltage supply ..................................................................................................... 15

3.3.2

Selecting the auxiliary winding (Nc)............................................................................................................... 15

3.3.3

Selecting the auxiliary winding rectifier diode (D3) ........................................................................................ 15

3.3.4

LED open-circuit protection using auxiliary winding....................................................................................... 16

4. Cautions on pattern designing..................................................................................................................................... 17

4.1 Cautions................................................................................................................................................................. 17

4.2 PCB pattern example............................................................................................................................................. 18

CAT.No.1A0602-1E