ST AN3360 Application note

AN3360

Application note

3.2 W LED power supply based on HVLED805

Introduction

This application note describes the demonstration board of the all-primary sensing switching regulator HVLED805 and presents the results of its bench evaluation. The board implements a 3.2 W (16 V / 0.2 A) wide range mains LED power supply with constant current.

HVLED805 combines a high-performance low-voltage PWM controller chip and an 800 V avalanche rugged power MOSFET in the same package. The PWM chip is a quasi-resonant (QR) current mode controller IC specifically designed for QR ZVS (zero voltage switching at switch turn-on) flyback converters. The device provides constant output current (CC) regulation using primary sensing feedback. This eliminates the need for the optocoupler, the secondary voltage reference, and also the current sensor, while still maintaining quite accurate regulation. The device can provide a constant output voltage regulation (CV). This makes the application able to work safely when the LED string opens due to a failure.

However, an auxiliary winding is required in the transformer to correctly perform CV/CC regulation, the chip is able to power itself directly from the rectified mains. This is useful during CC regulation, where the flyback voltage generated by the winding drops.

Figure 1. STEVAL-ILL037V1 demonstration board image

July 2011

Doc ID 018586 Rev 2

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Contents	AN3360

Contents

1	Test board design and evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 4
2	Transformer specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 8
3	Efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	9
4	Typical board waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	10
5	Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	13
6	References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	14
7	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	15

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AN3360	List of figures

List of figures

Figure 1. STEVAL-ILL037V1 demonstration board image. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Figure 2. For E26/E27 application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Figure 3. Electrical schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 4. PCB top side and through hole components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 5. PCB bottom side and SMD components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 6. EEE13-11 vertical type for under 10 W . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure 7. Output characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 8. Normal operation at full load - at 115 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Figure 9. Normal operation at full load - at 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Figure 10. Normal operation at no load - at 115 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 11. Normal operation at no load - at 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 12. Short-circuit at 115 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 13. Short-circuit at 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 14. Startup at full load at 115 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Figure 15. Startup at full load at 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Doc ID 018586 Rev 2

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Test board design and evaluation	AN3360

1 Test board design and evaluation

As a reference design, a 3.2 W LED power supply based on HVLED805 is presented.

●Table 1 summarizes the electrical specifications of the application

●Table 2 provides the bill of material

●Table 4 lists transformer specifications

The electrical schematic is shown in Figure 3 and the PCB layout in Figure 4. and 5.

Table 1.	STEVAL-ILL037V1 demonstration board: electrical specifications
	Parameter	Value
	Input voltage range (VIN)	90 - 265 VAC
	Mains frequency (fL)	50 - 60 Hz
	Output power consumption	3.2 W
	Output voltage	16 VDC (3~5 LEDs)
	Output current	200 mA
	Target average efficiency	>70%

Figure 2. For E26/E27 application

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