12V/5A AC Adapter Demoboard L6565 – Quasi-Resonant Controller Demoboard Performance

L6565 – Features Overview

L6565 – Block Diagram Input of the comparator, the outcoming signal depending on the comp and the VFF pin Current sense input, signal exceeds 2V will make the controller running into hiccup mode. Error Amplifier feedback input, FB regulate at 2.5V Output Drive Capability 400mApk UVLO, Vcc turn-on 13.5V and turn-off 9.5V Output of the current comparator block, It will be active when the current signal exceeds 2V Zero Current Detection Once detect the negative going edge demag signal, it triggers the MOSFET turn-on.

L6565 – Internal Supply Block Once the Vcc reaches the startup voltage, the controller begins 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 where Cd is the total capacitance of the drain node Llk is the leakage inductance of the transformer Lm is the magnetizing inductance of the transformer

VDS Waveform where The first valley occurs at T = Tv, where Tv will be as the following For zero voltage condition, it implies that

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 .

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. Secondary current Isolated gate drive transformer Make use of syn-rect approach, efficiency improves significantly!

Operating Waveforms Vin = 240Vac, Vo=12.3V and Io=5A 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 = 100Vac, Vo=12.3V and Io=5A Primary current Primary current Vdrain Vdrain Vin = 100Vac, Vo=12.3V and Io=5A Vin = 240Vac, Output Short Circuit

Transformer Design (I)

Transformer Design (II) In Quasi-Resonant mode control, the current always starting from zero of every switching cycle. 

Syn-Rect Demoboard Transformer Np: 520uH

Syn-Rect Demoboard Full Load Efficiency

No Load Input Power

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 10 R105 11 R106 3M 12 R107 16K 13 R108A,R108B 510K 14 R110 47K 15 R201,R203 1K 16 R202 100ohm 17 R204 470ohm

Demoboard BOM 18 R207 5.1K resistor 19 R208 20K 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 25 C104 10nF/50V 26 C105,C205 1nF/50V 27 C106 56nF/400V 28 C201,C202,C203 1000uF/25V 29 C204 470U/25V 30 C206 6.8nF/63V 31 C207 100nF/50V 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 37 Q101 STP10NK60Z MOSFET 38 Q201 STP1806 39 Q202,Q203 2N3904 transistor 40 Q204 2N3906 41 Q205 TL431 voltage reference 42 L101 共模 common mode choke 43 L102 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