ST AN2321 Application note

AN2321

Application note

Reference design: high performance, L6599-based HB-LLC

adapter with PFC for laptop computers

Introduction

This note describes the performances of a 90 W, wide-range mains, power-factor-corrected
AC-DC adapter reference board. Its electrical specification is tailored on a typical hi-end
portable computer power adapter. The peculiarities of this design are the very low no-load
input consumption (<0.4 W) and the very high global efficiency.

The architecture is based on a two-st age approach: a front -end PFC pre-regulato r based on
the L6563 TM PFC controller and a downstream multi-resonant half-bridge converter that
makes use of the new L6599 resonant controller. The Standby function of the L6599,
pushing the DCDC converter upon recognition of a light load to work in burst mode and the
logic dedicated to stop the PFC stage allows meeting the severe no-load consumption
requirement.

The PFC TM operation and the top-level efficiency performance of the HB-LLC topology
provide also a very good overall efficiency of the circuit.

L6599 & L6563 90W - adapter demo-board (EVAL6599-90W)

May 2007 Rev 2 1/29

www.st.com

Contents AN2321

Contents

1 Main characteristics and circuit description . . . . . . . . . . . . . . . . . . . . . 5

2 Test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1 Efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.2 Resonant stage operating waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.3 Stand-by & no load power consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.4 Short circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.5 Over voltage protections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.6 Start-up sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3 Thermal tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4 Conducted emission pre-compliance test . . . . . . . . . . . . . . . . . . . . . . 17

5 Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

6 PFC coil specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

6.1 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

6.2 Mechanical aspect and pin numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

7 Resonant power transformer specification . . . . . . . . . . . . . . . . . . . . . 25

7.1 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

7.2 Mechanical aspect and Pin numbering . . . . . . . . . . . . . . . . . . . . . . . . . . 26

8 PCB lay-out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2/29

AN2321 List of tables

List of tables

Table 1. Efficiency measurements - Vin=115 Vac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 2. Efficiency measurements - Vin=230 Vac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 3. Stand-by consumption - Vin=115 Vac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 4. Stand-by consumption - Vin=230 Vac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 5. Temperature of measured points @115 Vac - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Table 6. Temperature of measured points @230 Vac - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Table 7. Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Table 8. Winding characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 9. Winding characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 10. Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3/29

List of figures AN2321

List of figures

Figure 1. Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 2. Efficiency vs. Pout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 3. Resonant circuit primary side waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 4. Resonant circuit secondary side waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 5. Input power without load vs. mains voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 6. Waveforms at no-load operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 7. Waveforms at no-load operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 8. Load transition 0 ÷ 100% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 9. Load transition 100% ÷ 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 10. O/P short circuit waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 11. O/P short circuit waveforms (zoomed) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 12. Start-up @115 Vac - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 13. Start-up @115 Vac - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 14. Thermal map @115 Vac - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 15. Thermal map @230 Vac - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 16. CE peak measure at 115 Vac and full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 17. CE peak measure at 230 Vac and full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 18. Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 19. Bottom view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 20. Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 21. Pin lay-out, top view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 22. Thru-hole component placing and top silk screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 23. SMT component placing and bottom silk screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 24. Copper tracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4/29

AN2321 Main characteristics and circuit description

1 Main characteristics and circuit description

The main characteristics of the SMPS are listed here below:

● Universal inpu t mains range: 90÷264 Vac - frequency 45 to 65 Hz

● Output v oltage: 19 V@4.7 A continuous operation

● Mains harmonics: Compliance with EN61000-3-2 specifications

● Standby mains consumption: Typ. 0.4 W @230 Vac; Max 0.5 W @265 Vac

● Overall efficiency: better than 90%

● EMI: Compliance with EN55022-class B specifications

● Safety: Compliance with EN60950 specifications

● Low profile design: 25 mm maximum height

● PCB single layer: 78x174 mm, mixed PTH/SMT technologies

The circuit consists of two stages: a front - end PF C imp l eme nt ing the L65 63 and a r eson ant
DC/DC converter based on the new resonant controller, the L6599. The Power Factor
Corrected (PFC) stage delivers a stable 400 VDC and provides for the reduction of the
mains harmonic, allowing to meet European standard EN61000-3-2. The controller is the
L6563 (U1), working in transition mode and integrating all functions needed to control the
PFC and interface the downstream resonant converter. The power stage of the PFC is a
conventional boost converter, connected to the output of the rectifier bridge. It includes coil
L2, diode D4 and capacitor C9. The boost s witch is re presented by the po w er MOSFET Q1.
The L2 secondary winding (pins 8-10) is dedicated to provide to the L6563 the information
about the PFC coil core demagnetization, necessary to the controller for the TM operation.
The divider R1, R2 and R14 provides to the L6563 the information of the instantaneous
voltage that is used to modulate the boost current, and to derive some further information
like the average value of the AC line, used by the V
function keeps the ou tput voltage almost independent of the mains on e . The divide r R7, R8 ,
R9, R10 detects the output voltage . The second divider R11, R12, R13 and R28 protects the
circuit in case of voltage loop fail. The second stage is a resonant converter, half bridge
topology, working in ZVS. The controller is the new L6599, incorporating the necessary
functions to drive properly the Half-bridge by a 50 percent fixed duty cycle with dead-time,
working with variable frequency.

(voltage feed-forward) function. This

FF

The main features of the L6599 are a non-linear soft-start, a new current protection pin
(ISEN, pin 6) that programs the hiccup mode timing, a dedicat ed pin for sequencing or
brown-out (LINE) and a stand-by pin (STBY) for burst mode operation at light load. The
transformer uses the integrated magnetic approach, incorporating the resonant series
inductance. Thus, no any external additional coil is needed for the resonance. The
transformer configuration chosen for the secondary winding is centre tap, using two
Schottky rectifiers, type STPS10L60FP. The feedback loop is implemented by means of a
typical circuit using a TL431 modifying the current in t he optocoupler diode . The optocoupler
transistor modulates the current from pin 4, so the frequency will change accordingly, thus
achieving the output voltage regulation. Resistor R34 sets the maximum operating
frequency and the load at which the controller starts to work in Burst mod e. In case of a
short circuit, the current into the primary winding is detected by the lossless circuit R41,
C27, D11, D10, R39, and C25 and it is fed into the pin 6. In case of o v erload, th e v oltage on
pin #6 will overpass an internal threshold that will trigger a protection sequence via pin #2,
keeping the current flo wing in the circuit at a safe lev el. In case of output v oltage loo p f ailure,
the intervention of the zener diode connected to pin #8 (DIS) will activate the latched
protection of the L6599. The DIS pin can be also activated by the L6563 via the
PWM_LATCH pin in case of PFC loop failure.

5/29

Main characteristics and circuit description AN2321

Figure 1. Electrical diagram

+19V

RTN

J2

1

2

C32

100N

C31

L3

2u2

100uF-35V YXF

C21

C20

2N2 - Y1

R11

3M0

R12

3M0

R13

5K1

R28

27K

R7

1M0

R8

1M0

R10

15K

R9

82K

C9

R6

NTC_1 0R S23 6

47uF-450V

D4

STTH2L06

D3

1N4005

2-35

L2

86A-5158C

810

R3

2M4

D1

GBU4J

C5

470N-400V

R69

4K7

D20

BZV55- B15

Q9

BC847C

D7

LL4148

R70

100K

R71

Q10

R4

2M4

Q8

6K8

BC847C

D16

D17

BZV55 -B1 2

LL4148

STQ1HNK60R

R20

10K

2N2 - Y1

C18

2u2-6.3V

R44

2K7

R101

R19

56K

C39

100N

R66

2K2

Q6

BC847C

Q5

BC847C

R65

+19V@4.7A

D18

U2

*

39R

47K

D15

BZV5 5-C18

R56

1K8

R62

4K7

470uF-35V YXF

C30

470uF-35V YXF

C29

STPS10L60FP

D12

13

14

2

Q3

STP9NK50Z

LL4148

C19

100N

16

VBOOT

L6599D

CSS

1

Q1

4

C26

R58

100K

10uF-50V

R25

56R

13

14

15

NC

OUT

HVG

CF

DELAY

3

2

4

C45

220NF

C17

470PF

R24

1M0

R31

R30

STP12 NM50 FP

R46

100K

R27

470R

R21

39R

D13

STPS10L60FP

11

12

5

C28

22N

R59

100K

Q4

STP9N K50Z

R38

56R

C40

100N

D19

11

10

12

VCC

LVG

GND

LINE

STBY5RFmin

ISEN

7

6

R34

3K3

15K

10R

R23

R22

C43

0R47

0R47

C16

2N2

R49

39K

R43

51R

C36

1uF-50V

R42

5K6

T1

86A-5166A

6

R41

100R

C27

220PF

D10

LL4148

LL4148

4N7

D11

LL4148

9

R39

130R

PFC_STOP

C25

DIS

8

100N

C44

3N9

R32

47R

D8

BZV55 -B2 4

R29

1K0

R47

1K0

12

43

R60

10K

C23

10N

Q2

BC847C

R51

120K

R50

6K2

R48

47K

C34

220N

U4

TL431AIZ

U3

SFH617A-2

R40

6R8

D9

LL4148

220uF-35V

C24

R35

0R0

R37

100K

R52

6K8

C15

C4

470N-X2

L1

86A-5163

C3

C2

2N2

F1

FUSE 4A

1

J1

INPUT CONN.

2N2

C1

470N-X2

2

3

R1

1M0R21M2

90-264Vr ms

10uF-50V

U1

L6563

C14

100N

6/29

14

VCC

INV

1

C13

1uF

11

13

12

GD

ZCD

RUN

GND

MULT

COMP

3

2

R18

56K

PWM_STOP

PWM_LATCH

C10

PFC_OK

VFF5CS

TBO

4

C11

R14

18K

7

6

C12

470N

10N

150K

R15

22N

C22

220PF

R26

240K

*: R101 MOUNTED BY REWORKING

8

10

9

AN2321 Test results

2 Test results

2.1 Efficiency measurements

Table 1 and Table 2 show the output voltage measurements at nominal mains with different

load conditions. Efficiency is then calcu lated . For all measurements, both at full load and no
load operation, the input pow er has been mea sured b y a digita l po wer meter, Yokogawa WT-

210. Particular attention has to be paid when measuring input power at full load in order to
avoid measurem ent errors due to the voltage drop on cables and connections. Therefore
please connect the WT210 voltmeter termination to the board inpu t connector . F or the same
reason please measure the output voltage at the output connector or use th e r emot e d etect
option of your active load for a correct voltage measurement.

Table 1. Efficiency measurements -

Vout [V] Iout [A] Pout [W] Pin [W] Efficiency (%)

18.95 4.71 89.25 99.13 90.04

18.95 3.72 70.49 78.00 90.38

18.97 2.7 51.22 56.55 90.57

18.98 1.71 32.46 36.00 90.16

18.99 1.0 18.99 21.70 87.51

18.99 0.5 9.50 11.30 84.03

Vin=115 Vac

19.00 0.25 4.75 5.86 81.06

Table 2. Efficiency measurements - Vin=230 Vac

Vout [V] Iout [A] Pout [W] Pin [W] Efficiency (%)

18.95 4.71 89.25 97.23 91.80

18.96 3.72 70.53 76.74 91.91

18.97 2.7 51.22 55.85 91.71

18.98 1.71 32.46 35.57 91.24

18.99 1.0 18.99 21.30 89.15

19.00 0.5 9.50 10.87 87.40

19.00 0.25 4.75 5.77 82.32

In Table 1, Table 2 and Figure 2, the overall circuit efficiency is measured at different loads,
powering the board at the tw o nominal input mains v oltages. The measures hav e been do ne
after 30 minutes of warm-up at maximum load. The high efficiency of the PFC working in
transition mode and the very high efficiency of the resonant stage w orking in ZVS , provides
for an overall efficiency better than 90%. This is a significant high number for a two-stage
converter delivering an output current of 4.7 amps, especially at low input mains voltage
where the PFC conduction losses increase. Even at lower loads, the efficiency remains still
high.

7/29

Test results AN2321

Figure 2. Efficiency vs. Pout

Effi ci en cy v s P out

Eff. @115Vac
Eff. @230Vac

O/P P o wer

Efficiency

94.00

92.00

90.00

88.00

86.00

84.00

82.00

80.00

78.00

76.00

74.00
89 71 51 32 19 10 5

The global efficiency at full load has been measured with good results even at the limits of
the input voltage range :

Vin = 90Vac - full load
Pin = 100.5 W
Efficiency = 88.9%

Vin = 264 Vac - Full load
Pin = 96.3 W
Efficiency = 92.6%

2.2 Resonant stage operating waveforms

Figure 3. Resonant circuit primary side waveforms

CH1: L6599 - V
CH2: L6599 - V

(HB voltage)

PIN14

(CF)

PIN3

CH3: +400 V PFC Output voltage
CH4: T1 primary winding current

In Figure 3 are reported some waveforms during steady state operation of the circuit at full
load. The CH2 waveform is the oscillator signal at pin #3 of the L6599, while the CH3
waveform is the PFC output voltage , po wering th e resonant stage . The CH1 tra ce is the ha lf
bridge waveform, driving the resonant circuit. In the picture it is not obvious, but the
switching frequency is normally slightly modulated following the PFC 100 Hz ripple that is
rejected by the resonant control circuitry. The switching frequency has been chosen around
90 kHz, in order to have a good trade off between transformer losses and its dimensions.

8/29

AN2321 Test results

The transformer primary current wave shape is the CH4 trace. As shown, it is almost
sinusoidal, because the operating frequency is slightly above the resonance of the leakage
inductance and the resonant capacitor (C28).

In this condition, the circuit has a good margin for ZVS operations providing good efficiency
and the almost sinusoidal wave shape provides for an extremely low EMI generation.

Figure 4. Resonant circuit secondary side waveforms

CH2: +19V Output voltage ripple and noise
CH3: D12 rectifiers anode voltage
CH4: D12 rectifiers current

In Figure 4 are represented some waveforms relevant to the secondary side: the rectifiers
reverse voltage is measured by CH3 and the peak to peak value is indicated on the right of
the picture. It is a bit higher than the theoretical value that would be 2(V
about 40 V. It is possible to observe a small ringing on the bottom side of the waveform,
responsible for this difference. The channel CH4 (green in the picture) shows the current in
the diode D12, equal to that one flowing in D13. Even this current shape is almost a sine
wave, its average value is half of the output current. The ripple and noise on the output
voltage is measured by CH2.

Thanks to the advantages of the resonant converter, the high frequency ripple and noise of
the output voltage is o nly 100mV (0.52%) including spik es, whi le the resi dual ripple at mains
frequency is 130 mV at maximum load and any line condition.

2.3 Stand-by & no load power consumption

The board is specifically designed for li ght load and zero load operation, like during
operation with load disconnected. The result s are reported in the diagram of Figure 5, he re
following. As high lighted in the diagram of Figure 4, the input power at no load is always
below 0.4 W for any input mains voltage. Thanks to the L6599 stand-by function, at light load
conditions both the resonant converter and the PFC work skipping switching cycles,
according to the load. In fact, the L6599 via the PFC_ST OP pin (#9) stops the operation of
the L6563 during the burst mode off-time.

OUT+VF

), hence

9/29