ST AN2961 Application note

AN2961

Application note

STEVAL-ILL026V1 non-isolated 3 W offline

LED driver based on the VIPER22A-E

Introduction

This application note describes the functioning of the STEVAL-ILL026V1 non-isolated 3 W offline LED driver power supply designed using the VIPER22A-E low power offline SMPS primary switcher from STMicroelectronics. The circuit regulates the load current to 350 mA and generates about 10 V. The load is composed of three high-brightness (HB) LEDs, connected in series.

The project does not provide safety isolation between the input and output.

This document provides the power supply specification, circuit diagrams, the complete bill of materials, and reports the results of circuit testing.

Figure 1. STEVAL-ILL026V1 board photographs

!-V

November 2009

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Contents	AN2961

Contents

1	Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 4
2	Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
3	Electrical schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
4	Circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7
5	Test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	8
6	Conducted emission tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	11
7	Adapting the board for a 230 V input mains range . . . . . . . . . . . . . . .	12
8	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	13

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AN2961	List of figures

List of figures

Figure 1. STEVAL-ILL026V1 board photographs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Figure 2. STEVAL-ILL026V1 schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Figure 3. VIPER22A-E startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure 4. 110 V steady state operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure 5. LED current regulation vs. input voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Figure 6. Board efficiency vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Figure 7. Conducted emissions at 230 VAC 50 Hz - line 1 peak detector . . . . . . . . . . . . . . . . . . . . . 11 Figure 8. Conducted emissions at 230 VAC 50 Hz - line 2 peak detector . . . . . . . . . . . . . . . . . . . . . 11

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Specification	AN2961

1 Specification

The electronic lamp ballast electrical specifications are given in the table below.

Table 1.	Specification
		Input parameters
	VIN	Input voltage range		90 to 265 VRMS
	fline	Line frequency		50/60 Hz
		HB LEDs
	Number		3
	Power / current		3 W / 350 mA

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AN2961	Bill of material

2 Bill of material

	Table 2.	STEVAL-ILL026V1 bill of material
	Type	Name	Value	Rated	Description
	C	C1	22 µF	50 V	Electrolytic
	C	C3	2.2 µF	450 V	Electrolytic
	C	C4	470 nF	50 V	Ceramic
	C	C5	22 µF	50 V	Electrolytic
	C	C6	470 nF	50 V	Ceramic
	C	C7	470 nF	400 VDC	Polyester EPCOS
					B32561J6474K
	C	C8	Do not fit	Do not fit	Do not fit
	D	D1	39 V		Zener diode
	D	D2	STTH1R06A	600 V	STMicroelectronics
	D	D3	Bridge	600 V 500 mA	Rectifier bridge
	D	D4	STTH1R06A	600 V	STMicroelectronics
	L	L1	1 mH		EPCOS B7818S1105J000
	L	L2	1 mH		Coilcraft MSS1260-105KLB
	Q	Q1	BC557B		PNP transistor
	Q	Q2	BC547B		NPN transistor
	R	R1	4.7 kΩ		SMD resistor 0805
	R	R2	4.7 kΩ		SMD resistor 0805
	R	R3	10 kΩ		SMD resistor 0805
	R	R4	10 kΩ		SMD resistor 0805
	R	R5	1.3 Ω		SMD resistor 1206
	R	R6	6.8 kΩ		SMD resistor 0805
	R	R7	10 Ω	1/2 W	Through hole resistor
	U	IC1	VIPER22A-E		STMicroelectronics

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