MC33368

http://onsemi.com

13

Figure 17. Power Factor Test Setup

10

AC Power

Analyzer

PM 1000

A

V

Voltech

EMI Filter

T

2X Step–up

Isolation

Transformer

Autoformer

115 Vrms

Input

Line

Neutral

0 to 270 Vac

Output to

Power Factor

Correction

Circuit

HI

HI

L.O.

L.O.

0.1

1.0

WVA

PF Vrms Arms

VD Acf Ainst Freq HARM

An RFI filter is required for best performance when connecting the preconverter directly to the ac line. The filter attenuates the level of high frequency switching that

appears on the ac line current waveform. Figures 15 and 16 work well with commercially available two stage filters such as the Delta Electronics 03DPCG6. Shown

above is a single stage test filter that can easily be constructed with four ac line rated capacitors and a common–mode transformer. Coilcraft CMT3–28–2 was used

to test Figures 15 and 16. It has a minimum inductance of 28 mH and a maximum current rating of 2.0 A. Coilcraft CMT4–17–9 was used to test Figure 19. It has a

minimum inductance of 17 mH and a maximum current rating of 9.0 A. Circuit conversion efficiency

η (%) was calculated without the power loss of the RFI filter.

Figure 18. On/Off Control

Multiplier

8

C1

22

Frequency

Clamp

R

S

Q

R

S

S

Timer

R

Vref

Leading Edge

Blanking

Low

Load Detect

Comp

FB

6

LEB

13

PGnd

Gate

ZCD

VCC

Line

RD

AGnd

MC33368

16

12

7

11

10

FC

9

3

1

4

Quickstart

Overvoltage

Comparator

Set Dominant

1.5 V

15 V

Q

5.0 V

Reference

DC

Out

D5

C3

330

MTW14N50E

Q1

D6

C4

100

T

R4

22 k

EMI

Filter

92 to

270 Vrms

R7

0.1

C5

1.0

R5

1.3 M

R3

10 k

C2

0.01

R1

10 k

R2

820 k

R8

10 k

C9

330

µF

D1

D3

D2

D4

R11

10

15 V

C6

0.1

13/8.0

UVLO

1.2/1.0

R13

51

D8

RS Latch

Vref

Vref

Vref

CS

2

5

Mult

VCC

6.9 V

1.0 k

10 k

1.0 k

2N3904

1N4148

On/Off

Input

Zero

Current

Detect

1.08 x Vref

5.0 V

Off

0 V

On