ST AN1246 Application note

AN1246

Application note

VIPower: auxiliary BIAS power supply using VIPer20A-E

Introduction

This application note describes a bias power supply to meet the needs of powering up Power MOSFETs as well as providing standby power when the main unit is off.

The VIPer20ADIP-E, a part of STMicroelectronics proprietary VIPower (Vertical Intelligent Power), is a current mode PWM with a 700 V avalanche rugged Power MOSFET. It uses a fabrication process which allows the integration of analog control circuits with a vertical power device on the same chip. It can provide an output of 10 W power capability for wide range input, or 20 W for single input voltage range.

October 2007

Rev 4

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Contents	AN1246

Contents

1	Key features of the VIPer20ADIP-E . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	3
2	General circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	3
3	Connecting the demoboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
4	Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
5	Burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
6	Performance and cost consideration . . . . . . . . . . . . . . . . . . . . . . . . . . .	7
7	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7

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AN1246	Key features of the VIPer20ADIP-E

1Key features of the VIPer20ADIP-E

■Adjustable switching frequency up to 200 kHz

■Current mode control

■Burst mode operation in standby mode, meets “Blue Angel” standards

■Undervoltage lock-out with hysteresis

■Integrated start-up supply

■Avalanche rugged

■Overtemperature protection

■Primary or secondary regulation general circuit description

2General circuit description

This demo board (see schematic in Figure 1) is a 110 to 375 VDC input discontinuous flyback, working at 100 kHz. The output can deliver 12 V at 0.5 A continuous. This circuit can be powered from the main bulk capacitors of an off-line power supply, power factor correction output stage, or the AC line with the addition of a low current bridge rectifier. It benefits from the EMI filter present in a typical power supply. The output uses a Schottky diode for better efficiency. C7 is a low ESR capacitor which manages the ripple current. IC2 provides the reference and the feedback to tightly regulate the output. CS5, CS6, and RS3 form the feedback loop compensation to optimize stability during transients. The demoboard can be tested with convection air. Depending on the final application, air flow might be needed to keep the VIPer20ADIP-E under the thermal shutdown limit.

Figure 1.		Schematic
J1		R9
	F1
2		3.9
1	0.5 A Pico Fuse			D1				T1
CON				BYT11-600				Cramer Coil CSM 1608-027
		C12						4	6
		220pF
				RS14	C10
		1KV
				82K	220pF			128T
					1KV
									16T
								3
								2
				RS4		DS3		14T
				1.6		LL4148			7
								1
		C2
		4.7uF
		400V
								c9
								2.2n
								Y cap
			C3
			120uF				RS2
			16V				4.99K
			8	IC1		1
		RS10		drain	osc
		nu	7	drain	vdd	2
			6	drain	source	3
			5	drain	comp	4
				VIPer20ADIP-E
								CS5	CS6
							CS4	33n	.47u
							3.9nF
						D4
						NU			RS3
									5.1k

DS2

STPS1H100A

C7

680uF

16V

		R6	R8
		150	1.2k
4	1
		IC3
		H11A817A
3	2
	C	IC2	CS11
		TL431
		R	47n

A

	L2
	10uH		J2
			1
			2
	C8	R11	CON
	330uF	2.7k
	16V

R7

5.23k

RS5

1.37k

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