AN2042 datasheet(3/30 Pages) STMICROELECTRONICS

3 / 30 page

AN2042

List of figures

3/30

List of figures

Figure 1.

Light emitting diode structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 2.

The electromagnetic spectrum and visible region of light . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 3.

Human relative vision curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 4.

C.I.E. chromaticity diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 5.

Forward current vs. forward voltage in a typical commercial LEDs . . . . . . . . . . . . . . . . . . . 8

Figure 6.

PWM technique for dimming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 7.

Brightness variation versus duty cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 8.

Dimming technique using series switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 9.

Dimming technique using the new methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 10.

New dimming technique: typical waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 11.

Converter schematic for European input voltage range . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 12.

Transformer features: (a) schematic, (b) mechanical characteristics and (c) pinout . . . . . 17

Figure 13.

VDS and ID at 230 VAC: 1 LED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 14.

VDS and ID at 230 VAC: 8 LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 15.

Typical waveforms: drain voltage and output current ripple at 230 VAC . . . . . . . . . . . . . . . 19

Figure 16.

Typical waveforms: startup at 265 VAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 17.

Drain voltage VDS and output current IOUT: 1 LED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 18.

Drain voltage VDS and output current IOUT: 8 LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 19.

Drain voltage VDS and output current IOUT at 50% dimming: 1 LED . . . . . . . . . . . . . . . . . 20

Figure 20.

Drain voltage VDS and output current IOUT at 50% dimming: 8 LEDs . . . . . . . . . . . . . . . . 20

Figure 21.

Drain voltage VDS and output current IOUT at 10% dimming: 1 LED . . . . . . . . . . . . . . . . . 20

Figure 22.

Drain voltage VDS and output current IOUT at 10% dimming: 8 LEDs . . . . . . . . . . . . . . . . 20

Figure 23.

Control signals at 230 VAC: 1 LED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 24.

Control signals at 230 VAC: 8 LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 25.

Control stage at 230 VAC: 1 LED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 26.

Control stage at 230 VAC: 8 LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 27.

Open load condition at 230 VAC: no dimming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 28.

Open load condition at 230 VAC: minimum dimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 29.

Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 30.

PCB layout (not in scale) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 31.

Conducted emissions at full load: line 1 emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 32.

Conducted emissions at full load: line 2 emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 33.

Non dimmable solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 34.

Application circuit for U.S. input voltage range: changes on the input section . . . . . . . . . . 26

Figure 35.

STEVAL-ILL001V1 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

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