12V/5A AC Adapter Demoboard

L6565 – Quasi-Resonant Controller

Demoboard Performance

L6565 – Features Overview

L6565 – Block Diagram

Zero Current Detection

Once detect the negative going edge demag signal, it triggers the MO

SFET turn-on.

Output Drive Capability 400mApk

Error Amplifier feedback input, FB regulate at

2.5V

Current sense input, signal exceeds 2V

will make the controller running into hiccup mode.

Input of the comparator, the outcoming signal depending on the comp and the VFF pin

UVLO, Vcc turn-on 13.5V and turn-off 9.5V

Output of the current compara

tor block,

It will be active when the current signal excee

ds 2V

L6565 – Internal Supply Block

Once the Vcc reaches the startup voltage, the controller b

egins to operate

L6565 – Zero Current Detection

Once the demag pin goes down below 1.6V, the EXT MOSFET will be switched on.To ensure high noise immunity, the triggering block must be armed first: prior to falling below 1.6V, the voltage on pin 5 must experience a positive-going edge exceeding 2.1 V.

Zero Current Detect Operation

Major Parasitic Elements in Flyback Converter

whereCd is the total capacitance of the drain nodeLlk is the leakage inductance of the transformerLm is the magnetizing inductance of the transformer

VDS Waveform

The first valley occurs at T = Tv, where Tv will be as the following

For zero voltage condition, it implies that

where

QR Timing and Power Relationship

MOSFET ON time:

MOSFET OFF time:

Switching Frequency:

Input Power:

The switching frequency related to input power:

where

L6565 – Power Compensation, high line and low line

Switching Frequency vs. Operating Condition

In order to deliver the full loading power at minimum input voltage, the inductance should not exceed the following value:

Switching Frequency Foldback

The Tblank function is the function of the Vcomp output

L6565 – Syn-Rect Demoboard Circuit

QR mode is the perfect topology for syn-rect because secondary current

flow stops before primary MOSFET switches on!

Low Startup Circuit

This part is for startup purpose use. The power loss dissipation is much reduced compared with the traditional lossy R-C startup circuit.The charge current pump into the Vcc capacitor at a rate of .

ac

acstart

f

VC

2

2

Isolation Gate Drive Transformer

• L202 – isolated gate drive transformer

• The gate drive voltage is converted from the

secondary current.

• When the secondary current is large

enough, it turns on the Q203, then an output

voltage is directly going into the totem pole

input and drive the secondary MOSFET.

• When the secondary current drops to zero,

there will be no driving voltage from the

isolated gate drive transformer, and Q203

turn-off and the MOSFET will not turn on.

Isolated gate drive transformer

Secondary current

Make use of syn-rect approach, efficiency improves significantly!

Operating Waveforms

Primary current

Vdrain

Vin = 100Vac, Vo=12.3V and Io=5A

Primary current

Vdrain

Vin = 240Vac, Vo=12.3V and Io=5A

Operating Waveforms

Vin = 240Vac, Output Short Circuit

Primary current

Vdrain

Vin = 100Vac, Vo=12.3V and Io=5A

Primary current

Vdrain

Transformer Design (I)

in

pkpon V

ILT

voffon TTTfsw

1

R

pkpoff V

ILT

dpv CLT

2

minmax

minmax

max

112

1

dswRin

swin

p

CfVV

fP

L

Calculation Worksheet -- Primary InductanceParameters Value Lp 4.59E-04 Ipk 2.469034416

Pin 70

Fsw 50000 where Lp is the primary inductance

Vin 100 Fsw is the Switching Frequency

Vr 142 Vin is the minimum input voltage

Cd 1.00E-10 Cd is the equivalent output drain to source capacitance

Transformer Design (II)

ep

p

AN

ILB

Calculation Worksheet - Magnetic Flux DensityParameters Value

ΔB 0.25 ΔB is the magnetic flux density

Δ I 2.34 Δ I is the change of current

Np 3.43E+01 Np is the primary inductance

Ae 1.42E-04 Ae is the effective area of the magnetics

Lp 5.20E-04 Lp is the primary inductance

In Quasi-Resonant mode control, the current always starting from zero of every switching cycle.

pkII

Syn-Rect Demoboard Transformer

Np: 520uH

Syn-Rect DemoboardFull Load Efficiency

Efficiency

0. 00

10. 00

20. 00

30. 00

40. 00

50. 00

60. 00

70. 00

80. 00

90. 00

100. 00

Input Voltage（V）

Eff

icie

ncy

%

No Load Input Power

No Load Power Loss

0. 00

100. 00

200. 00

300. 00

400. 00

500. 00

600. 00

700. 00

800. 00

900. 00

1000. 00

100

110

120

130

140

150

160

170

180

190

200

210

220

230

240

Input Voltage（V）

No

Lo

ad

Po

wer

Lo

ss（

mW）

Demoboard BOM

Item Reference Part Description

1 　 　 Assembly Dwg.

2 　 　 Schemaitc

3 　 PC Board PC Board,1-Layers,60mm x118mm

4 F101 3A/250V fuse

5 RT 9D-207 　

6 RV G471 varistor

7 R101 15ohm resistor

8 R102 100K 3W resistor

9 R104 10ohm resistor

10 R105 15ohm resistor

11 R106 3M resistor

12 R107 16K resistor

13 R108A,R108B 510K resistor

14 R110 47K resistor

15 R201,R203 1K resistor

16 R202 100ohm resistor

17 R204 470ohm resistor

Demoboard BOM

18 R207 5.1K resistor

19 R208 20K resistor

20 RS101 0.33ohm 3W resistor

21 CX101 0.22UF/275V X2 cap

22 C101 1nF/1KV capacitor

23 C102 150U/400V Ecap

24 C103 220U/25V capacitor

25 C104 10nF/50V capacitor

26 C105,C205 1nF/50V capacitor

27 C106 56nF/400V capacitor

28 C201,C202,C203 1000uF/25V Ecap

29 C204 470U/25V Ecap

30 C206 6.8nF/63V capacitor

31 C207 100nF/50V capacitor

32 CY 222U/275V Y1 cap

33 BR101 KBU406 bridge rectifier

34 D101,D102,D201 1N4148 diode

Demoboard BOM

35 D103 clamper diode diode

36 D104 FR107 diode

37 Q101 STP10NK60Z MOSFET

38 Q201 STP1806 MOSFET

39 Q202,Q203 2N3904 transistor

40 Q204 2N3906 transistor

41 Q205 TL431 voltage reference

42 L101 共模 common mode choke

43 L102 共模 common mode choke

44 L201 差模 differential mode choke

45 L202 感应磁环 gate drive transformer

46 OPT K817P6 opto-coupler

47 IC101 L6565 SO8

48 TR1 Transformer transformer