EVL6566B-65W - STMicroelectronics

August 2005 1/11

Figure 1: EVL6566B-65W Adapter demo-board

A

PPLICATION NOTE

12V-65W WIDE-RANGE INPUT MAINS ADAPTER USING THE L6566B

®

Introduction

This note describes the characteristics and the features of a 65 W reference board, wide-range

input mains, AC-DC adapter using the L6566B controller. The peculiarities of this design are the

low standby input consumption (<200mW@265Vinac), low cost and small size.

APPLICATION NOTE

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Main characteristics and circuit description

• UNIVERSAL INPUT MAINS RANGE: 90÷264Vac - Frequency 45 ÷ 65Hz

• OUTPUT VOLTAGE: 12V@5.42A continuous operation

• MAINS HARMONICS: Acc. to EN61000-3-2 Class-D

• ST-BY MAINS CONSUMPTION: TYP. 0.2 W @265Vac

• OVERALL EF FICIENCY: TYP. 83 % @ 230Vac

• EMI: According to EN55022-Class-B

• SAFETY: According to EN60950

• DIMENSIONS: 51 x 109.5mm - 25mm maximum height

• PCB: Double layer

mixed PTH/SMD technology

Circuit description

The topology of this converter is the classical Flyback working in continuous and discontinuous

conduction mode at fixed frequency.

The controller, the new L6566B, is an extremely versatile current mode primary controller ICs. The

nominal switching frequency, 80 KHz, has been chosen to get a compromise between the

transformer size and the converter efficiency. The input EMI filter is a classical Pi-filter, 2-cells for

differential and common mode noise filtering. A NTC limits the inrush current produced by the

capacitor charging at plug-in. The MOSFET is a standard and inexpensive 600V-0.75Ωmax, TO-

220FP, needing a heat sink. The transformer is a layer type, using a standard ferrite type EER28L.

The reflected voltage is 90 V, providing enough room for the leakage inductance voltage spike with

still margin for reliability of the MOSFET. The network D3, R11A, R11B, R11C and C11 clamps the

peak of the leakage inductance voltage spike.

At power on, the L6566B has an internal high-voltage current source sourcing a current from the

DC bus and charging the capacitors C2 and C3 connected to the Vcc pin. Once the turn-on

threshold is reached, the HV current source is turned-off. This allows saving power dissipation

during normal operation and provides very good circuit efficiency during standby. The divider R4,

R10, R45 and R46 senses the input voltage and it is dedicated to the Brownout and Voltage feed-

forward pins. The AC_OK pin (#16) is dedicated to the brownout protection. When the voltage on

this pin is below the internal threshold (0.45V typ.) the IC is disabled. The VFF pin (pin#15), is

dedicated to limit the maximum power deliverable according to the input voltage of the converter.

As previously mentioned, the control system is Current Mode, so the current flowing in the

transformer primary winding is sensed by R7B, R7C and R7D then it is fed into the CS (pin #7).

For over voltage protection (OVP), the transformer auxiliary winding is connected to ZCD (pin #11)

via the R3 and R9 divider. In case of feedback network failures or open loop operation, if the

voltage on ZCD pin rises over its threshold the L6566B is latched. After OVP detection and the

following latch, the controller operation can be resumed by disconnecting the mains plug.

The switching frequency is programmed by OSC (pin #13) connected to the resistor R18.

Furthermore the L6566B has the Soft Start (pin #14), Disable (pin #8) and 5 Volt Reference

voltage VREF (pin #10) available.

The output rectifier is a dual common-cathode Schottky diode, Q201. A snubber, made up of

R19A, R19B and C12, damps the oscillation produced by the diode Q201. A small LC filter has

been added on the output in order to reduce the high frequency ripple.

The output regulation makes use of a dedicated control IC, the TSM1014, embedding a refernce

and an error ampliifer. The output signal of the error amplifier drives the optocoupler OPTO4

transferring the information to primary side with the required insulation of the secondary side.

APPLICATION NOTE

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Figure 2: Electrical diagram

APPLICATION NOTE

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Test Results

Efficiency measurements at full load

In table 1 the converter overall efficiency measurement at nominal load (5.42 A) and different input

voltage are reported. In table 2 the efficiency measurements according to the Energy Star

regulation are taken. The average values at both the nominal input mains voltages are reported

too, in bold. In all conditions the efficiency measurements are compliant with the current energy

saving rules.

Table 1: Efficiency measurements at full load

(*) Compliant to CEC, EU-COC, regulation

Table 2: Energy star

ENERGY STAR EFFICIENCY

Vinac 1.35 A

(25%) 2.7 A

(50%) 4.1 A

(75%) 5.42 A

(100%) Average

115 [V] 84.24% 84.46% 83.53% 82.52% 83.69%

230 [V] 82.77% 83.92% 84.34% 83.91% 83.74%

Vinac EFFICIENCY

90 [V] 80.47 %

115 [V ] 82.52 % (*)

230 [V ] 83.91 % (*)

265 [V ] 83.64 %

APPLICATION NOTE

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Functional Check

Full load operation

In figure 3 and 4 some waveforms during steady state operation are reported. It is possible also

to note which the working switching frequency is 79 kHz.

Stand by and No-load operation

In figures 5 and 6, some waveforms during no-load condition are captured. As visible, the L6566B

works in burst mode achieving the best efficiency. In the pictures even the Vcc value is captured. It

is shown that even in worst condition, at maximum input voltage (265Vac), the L6566B is powered

correctly with good margin with respect to its maximum turn-off threshold (8 V). This prevents from

spurious turn off that could affect the output voltage stability.

Figure 3: EVL6566B-65W

Waveforms @115V-60Hz – Full load Figure 4: EVL6566B-65W

Waveforms @230V-50Hz – Full load

CH1: Q101 Drain voltage CH1: Q7 Drain voltage

CH2: Q101 Gate voltage CH2: Q7 Gate voltage

CH3: VCC CH3: VCC

Figure 5: EVL6566B-65W

Burst mode @90V-60Hz – No load operation Figure 6: EVL6566B-65W

Burst mode @265V-60Hz – No load operation

CH1: Q101 Drain voltage CH1: Q101 Drain voltage

CH2: L6566B Vcc (pin #5) CH2: L6566B Vcc (pin #5)

APPLICATION NOTE

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In Table 3, the input power consumption at no load is reported: as visible, thanks to the L6566B

stand-by functions, the input power remains always below 200mW.

Table 3: Input power at no load vs. mains voltage

(*) Compliant to CEC, EU-COC, Energy Star

Over Current and Short Circuit Protection (OCP)

In figure 7 and 8 it is shown the circuit behaviour in case of an output short circuit: as visible the

L6566B stops switching and the Vcc voltage drops till the UVLO threshold. The controller reduces

its consumption so increasing the duration of the Off-time and avoiding high dissipation on the

secondary side in short conditions. The restart tentative is repeated indefinitely, until the short is

removed.

Vin [Vrms] Input power [W]

90 0.066

115 0.077 (*)

230 0.162 (*)

265 0.200

Figure 7: EVAL6566B-65W

Short circuit at 230Vac-50Hz – Full lo ad Figure 8: EVAL6566B-65W

Sho r t ci rcui t at 23 0Vac- 5 0 Hz – No l o ad

CH1: Q101 Drain voltage CH1: Q101 Drain voltage

CH2: L6566B Vcc (pin #5) CH2: L6566B Vcc (pin #5)

APPLICATION NOTE

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Open Loop Protection (OVP)

In figure 9 and 10 it is shown the circuit behaviour simulating an open loop condition by opening

R17. Once the voltage on ZCD pin connected to the transformer auxiliary winding by a divider rises

over its threshold, the L6566B stops switching. To prevent from unlatching the circuit by the Vcc

drop, the internal HV current source of the L6566B is periodically reactivated to keep the Vcc

voltage above the turn-off threshold. The IC consumption is reduced too. To resume the normal

operation the input mains has to be re-cycled.

In pictures 9 and 10 the output voltage during Open loop operation has been captured. As visible

comparing the two pictures, thanks to the L6566B internal circuitry, the output voltage value in this

condition is almost independent by the load.

Start up behaviour

In the pictures below, the start up behaviour is shown in two different load conditions. The output

voltage rising is monotonic and doesn’t show any overshoot

Figure 9: EVAL6566B-65W

Open loop at 230Vac-50Hz – Full load Figure 10: EVAL6566B-65W

Open loop at 230Vac-50Hz – No load

CH1: Q101 Drain voltage CH2: L6566B Vcc (pin #5)

CH2: L6566B Vcc (pin #5) CH3: VOUT

CH3: VOUT

Figure 11: EVAL6566B-65W Start up behaviour

at 230Vac-50Hz – Fu l l l o ad Figure 12: EVAL6566B-65W Start up behaviour

at 230Vac-50Hz – No l o ad

CH1: L6566B Soft Start (pin#14) CH1: L6566B Soft Start (pin#14)

CH2: L6566B Vcc (pin #5) CH2: L6566B Vcc (pin #5)

CH3: VOUT CH3: VOUT

APPLICATION NOTE

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Bill of material

Table 4: EVAL6566B-65W: Bill of Material

Reference Part name Description

BR1 DB 4A 600 V SINGLE PHASE BRIDGE RECTIFIER

C2 100uF - 25 V 25V - ALUMINIUM ELCAP - 105°C

C3 100nF 50V CERCAP - GENERAL PURPOSE 0805

C4 470u - 25 V 25V - ALUMINIUM ELCAP - 105°C

C5 470u - 25 V 25V - ALUMINIUM ELCAP - 105°C

C7 470u - 16 V 16V - ALUMINIUM ELCAP - 105°C

C8 2.2nF 50V CERCAP - GENERAL PURPOSE 0805

C9 100nF 50V CERCAP - GENERAL PURPOSE 0805

C10 100nF 50V CERCAP - GENERAL PURPOSE 0805

C11 3nF - 1kV

C12 470pF 100V CERCAP - GENERAL PURPOSE 1206

C13 0R0 SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

C16 1nF 50V CERCAP - GENERAL PURPOSE 0805

C18 100nF 50V CERCAP - GENERAL PURPOSE 0805

C19 120u - 400V 400V - ALUMINI UM ELCAP - 85°C

C214 330nF 50V CERCAP - GENERAL PURPOSE 0805

CN1 CON2-IN TWO WIRES CONNECTOR

CX1 100nF X2 - FLM CAP - 250V

CX2 100nF X2 - FLM CAP - 250V

CY3 3.3nF Y1 - SAFETY CAP. - 250V

D1 LL4148 FAST SWITCHING DIODE SOD-80

D2 STTH108 HIGH VOLTAGE ULTRAFAST RECTIFIER DO41

D3 STTH108 HIGH VOLTAGE ULTRAFAST RECTIFIER DO41

D105 LL4148 FAST SWITCHING DIODE SOD-80

F1 FUSE 2A FUSE T2A

HS1 HEAT-SINK HEAT-SINK

HS2 HEAT-SINK HEAT-SINK

L1 2.2uH 2u2 - RADIAL INDUCTOR - 6A

LF1 CHOKE-D15x10 INPUT EMI FILTER

LF2 CHOKE-D15x10 INPUT EMI FILTER

OPTO4 SFH617A-4_0 OPTOCOUPLER

Q101 STP10NK60ZFP N-CHANNEL POWER MOSFET TO-220FP

Q201 STPS20H100FP COMMON CATHODE SCHOTKY DIODE TO-220FP

R1 33R SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R1A 510K SMD FILM RES - 1/4W - 5% - 250ppm/°C 1206

R1B 510K SMD FILM RES - 1/4W - 5% - 250ppm/°C 1206

R2 200K SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R3 10K SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R4 12K SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R6 100K SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R7 15K SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R7B 1R2 SMD FILM RES - 1/4W - 1% - 100ppm/°C 1206

R7C 1R2 SMD FILM RES - 1/4W - 1% - 100ppm/°C 1206

R7D 1R2 SMD FILM RES - 1/4W - 1% - 100ppm/°C 1206

R8 470R SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R9 36K SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R10 62K SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

APPLICATION NOTE

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R11A 300K SMD FILM RES - 1/4W - 5% - 250ppm/°C 1206

R11B 300K SMD FILM RES - 1/4W - 5% - 250ppm/°C 1206

R11C 300K SMD FILM RES - 1/4W - 5% - 250ppm/°C 1206

R14 10R SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R15 12K SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R17 23K4 SMD FILM RES - 1/8W - 1% - 100ppm/°C 0805

R18 27K SMD FILM RES - 1/8W - 1% - 100ppm/°C 0805

R19 6K2 SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R19A 100R SMD FILM RES - 1/4W - 5% - 250ppm/°C 1206

R19B 100R SMD FILM RES - 1/4W - 5% - 250ppm/°C 1206

R22 2K7 SMD FILM RES - 1/8W - 1% - 100ppm/°C 0805

R23 22K SMD FILM RES - 1/8W - 5% - 250ppm/°C 0805

R45 3M SMD FILM RES - 1/4W - 5% - 250ppm/°C 1206

R46 3M SMD FILM RES - 1/4W - 5% - 250ppm/°C 1206

T1 ERL28-12PIN POWER TRANSFORMER

TH1 NTC 10R NTC RESISTOR

U1 TSM1014AIDT LOW CONSUMPTION CC/CV CONTROLLER MINI SO-8

U5 L6566B ADVANCED PWM CONTROLLER SO-16

U4 TS2431ILT VOLTAGE REFERENCE SOT-23

APPLICATION NOTE

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TRANSFORMER specification

PIN DISTANCE: 5.08 mm

PIN ROW DISTANCE: 30.5 mm

PINS #7, 8, 12 are removed – Pin 3, 9 are for insertion polarity key.

MECHANICAL ASPECT AND PIN NUMBERING

1

2

3

4

5

6

12

11

10

9

8

7

37.5 mm

28.5 mm

30.5 mm

5.08 mm

TOP VIEW

Transformer specification

General description and characteristics

• APPLICATION TYPE: Consumer, Home Appliance

• TRANSFORMER TYPE: Open

• WINDING TYPE Layer

• COIL FORMER: Horizontal type, 6+6 pins

• MAX. TEMP. RISE: 45

°

C

• MAX. OPERATING AMBIENT

TEMP.: 60

°

C

Electrical characteristics

• CONVERTER TOPOLOGY: Flyback, CCM/DCM Mode

• CORE TYPE: EER28L – PC40

• MIN. OPERATING FREQUENCY: -

• TYPICAL OPERATING FREQ: 80 KHz

• PRIMARY INDUCTANCE: 480

µ

H

±

5% @1KHz – 0.25V [1]

• LEAKAGE INDUCTANCE: 5.12

µ

H @ 100KHz – 0.25V [1]-[2]

[1]: Measured between pins 4-6

[2]: Measured between pins 4-6 with all secondary windings shorted

APPLICATION NOTE

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Electrical diagram and winding characteristics

PINS: WINDING

NUMBER

OF TURNS WIRE TYPE

6-2 PRIMARY - B 28 G2– 2 x φ 0.45 mm

21mm x 0.1mm Copper Shielding connected to pin 5

10-11 12V 8

G2 – 4 x φ 0.4 mm

21mm x 0.1mm Copper Shielding connected to pin 5

2-4 PRIMARY - A 28 G2 – 2 x φ 0.45 mm

1-5 AUX 12

G2 – φ 0.3 mm

AUX

PRIMARY B

12 V

PRIMARY A

SHIELDING

NOTE: PRIMARIES A & B ARE IN SERIES

COIL FORMER