Philips TEA1552 User Manual

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TEA1552

GreenChipII SMPS control IC

Product specification
Supersedes data of 2002 Jul 03

2002 Aug 27

Philips Semiconductors Product specification

GreenChipII SMPS control IC TEA1552

FEATURES
Distinctive features

• Universal mains supply operation (70 to 276 V AC)

• High level of integration, giving a very low external

component count.

Green features

• Valley or zero voltage switching for minimum switching
losses

• Efficient quasi-resonant operation at high power levels

• Frequency reductionat low power standby for improved

system efficiency (<3 W)

• Cycle skipping mode at very low loads. Pi< 300 mW at
no-load operation for a typical adapter application

• On-chip start-up current source

• Standby indication pin to indicate low output power

consumption.

Protection features

• Safe restart mode for system fault conditions

• Continuous mode protection by means of

demagnetization detection (zero switch-on current)

• Accurate and adjustable overvoltage protection
(latched)

• Short winding protection

• Undervoltage protection (foldback during overload)

• Overtemperature protection (latched)

• Low and adjustable overcurrent protection trip level

• Soft (re)start

• Mains voltage-dependent operation-enabling level

• General purpose input for lock protection.

APPLICATIONS

Typical application areas are adapters and chargers (e.g.
for laptops, camcorders and printers) and all applications
that demand an efficient and cost-effective solution up to
250 W.

GENERAL DESCRIPTION

The GreenChip

(1)

II is the second generation of green
Switched Mode Power Supply (SMPS) control ICs
operatingdirectly from the rectified universalmains.A high
level of integration leads to a cost effective power supply
with a very low number of external components.

The special built-in green functions allow the efficiency to
be optimum at all power levels. This holds for
quasi-resonant operation at high power levels, as well as
fixed frequency operation with valley switching at medium
power levels. At low power (standby) levels, the system
operates at reduced frequency and with valley detection.

The proprietary high voltage BCD800 process makes
direct start-up possible from the rectified mains voltage in
an effective and green way. A second low voltage
BICMOS IC is used for accurate, high speed protection
functions and control.

Highly efficient, reliable supplies can easily be designed
using the GreenChipII control IC.

(1) GreenChip is a trademark of Koninklijke Philips

Electronics N.V.

2002 Aug 27 2

Philips Semiconductors Product specification

GreenChipII SMPS control IC TEA1552

handbook, full pagewidth

VCOadj

I

sense

STDBY

DRIVER

HVS
HVS

DRAIN

1
2
3
4

TEA1552T

5
6
7

DEM

14

CTRL

13

LOCK

12

V

CC(5V)

11

GND

10

n.c.

9

V

CC

8

MBL498

Fig.1 Basic application.

ORDERING INFORMATION

TYPE

NUMBER

NAME DESCRIPTION VERSION

PACKAGE

TEA1552T SO14 plastic small outline package; 14 leads; body width 3.9 mm SOT108-1

2002 Aug 27 3

Philips Semiconductors Product specification

GreenChipII SMPS control IC TEA1552

BLOCK DIAGRAM

handbook, full pagewidth

V

CC

GND

STDBY

VCOadj

CTRL

LOCK

8

10

3

1

13

12

300 Ω

5.6 V

S1

TEA1552

2.5 V

M-level

lock
detect

FREQUENCY

CONTROL

−1

SUPPLY

MANAGEMENT

internal

supply

VOLTAGE

CONTROLLED

OSCILLATOR

POWER-ON

TEMPERATURE

PROTECTION

UVLO start

RESET

OVER-

V

CC

LOGIC

UVLO

MAXIMUM

ON-TIME

PROTECTION

< 4.5 V

LOGIC

SQ

R

Q

SQ

R

Q

START-UP

CURRENT SOURCE

VALLEY

100 mV

short

winding

OVER-POWER

PROTECTION

OVER-

VOLTAGE

PROTECTION

DRIVER

LEB

blank

OCP

0.88 V

clamp

soft

start

S2

5 V/1 mA

(max)

7

DRAIN

5, 6

HVS

14

DEM

4

DRIVER

I

ss

0.5 V

2

I

sense

11

V

CC(5V)

MBL499

Fig.2 Block diagram.

2002 Aug 27 4

Philips Semiconductors Product specification

GreenChipII SMPS control IC TEA1552

PINNING FUNCTIONAL DESCRIPTION

SYMBOL PIN DESCRIPTION

VCOadj 1 VCO adjustment input
I

sense

2 programmable current sense input
STDBY 3 standby indication or control output
DRIVER 4 gate driver output
HVS 5 high voltage safety spacer, not

connected

HVS 6 high voltage safety spacer, not

connected

DRAIN 7 drain of external MOS switch, input for

start-up current and valley sensing

V

CC

8 supply voltage
n.c. 9 not connected
GND 10 ground
V

CC(5V)

11 5 V output
LOCK 12 lock input
CTRL 13 control input
DEM 14 input from auxiliary winding for

demagnetization timing, OVP and OPP

The TEA1552 is the controller of a compact flyback
converter, with the IC situated at the primary side.
An auxiliary winding of the transformer provides
demagnetization detection and powers the IC after
start-up.

The TEA1552 operates in multi modes (see Fig.4).
The next converter stroke is started only after

demagnetization of the transformer current (zero current
switching), while the drain voltage has reached the lowest
voltage to prevent switching losses (green function). The
primary resonant circuit of primary inductance and drain
capacitor ensures this quasi-resonant operation. The
design can be optimized in such a way that zero voltage
switching can be reached over almost the complete
universal mains range.

To prevent very high frequency operation at lower loads,
the quasi-resonant operation changes smoothly in fixed
frequency PWM control.

At very low power (standby) levels, the frequency is
controlled down, via the VCO, to a minimum frequency of
approximately 25 kHz.

Start-up, mains enabling operation level and
undervoltage lock-out (see Figs 11 and 12)

handbook, halfpage

VCOadj

STDBY

DRIVER

I

sense

HVS
HVS

DRAIN

1
2
3
4

TEA1552T

5
6
7

Fig.3 Pin configuration.

MBL497

Initially, the IC is self supplying from the rectified mains
voltage via pin DRAIN. Supply capacitor C

is charged

VCC

by the internal start-up current source to a level of
approximately 4 V or higher, depending on the drain

DEM

14
13

CTRL

12

LOCK

11

V

CC(5V)

GND

10

n.c.

9

V

8

CC

voltage. Once the drain voltage exceeds the M-level
(mains-dependent operation-enabling level), the start-up
current source will continue charging capacitor C

VCC

(switch S1 will be opened); see Fig.2. The IC will activate
the power converter as soon as the voltage on pin V
passes the level V

. The IC supply is taken over by

CC(start)

CC

the auxiliary winding as soon as the output voltage
reaches its intended level and the IC supply from the
mains voltage is subsequently stopped for high efficiency
operation (green function).

The moment the voltage on pin VCC drops below the
undervoltage lock-out level V

, the IC stops switching

UVLO

and enters a safe restart from the rectified mains voltage.
Inhibiting the auxiliary supply by external means causes
the converter to operate in a stable, well defined burst
mode.

Supply management

All (internal) reference voltages are derived from a
temperature compensated, on-chip band gap circuit.

2002 Aug 27 5

Philips Semiconductors Product specification

GreenChipII SMPS control IC TEA1552

The maximum fixed frequency of the oscillator isset by an
internal current source and capacitor. The maximum
frequency is reduced once the control voltage enters the
VCO control window. Then, the maximum frequency
changeslinearly with thecontrol voltage untilthe minimum
frequency is reached (see Figs 5 and 6).

handbook, halfpage

(kHz)

f

VCO fixed quasi resonant

125

MBL500

25

P (W)

Fig.4 Multi mode operation.

Current mode control

Current mode control is used for its good line regulation
behaviour.

The ‘on-time’ iscontrolled by theinternally inverted control
pin voltage, which is compared with the primary current
information. The primary current is sensed across an
external resistor. The driver output is latched in the logic,
preventing multiple switch-on.

The internal control voltage is inverselyproportional to the
external control pin voltage, with an offset of 1.5 V. This
means that a voltage range from 1 to 1.5 V on pin CTRL
will result in an internal control voltage range from

0.5 to 0 V (a high external control voltage results in a low
duty cycle).

Oscillator

V

handbook, halfpage

sense(max)

0.52 V

MGU233

handbook, halfpage

f

(kHz)

125

25

VCO

VCO

level

1

2

level

Fig.6 VCO frequency as a function of V

MBL501

125 kHz

V

sense(max) (V)

sense(max)

.

VCO adjustment

The VCOadj pin can be used to set the VCO operation
point. As soon as the peak voltageon thesense resistoris
controlledbelow half thevoltage on the VCOadjpin (VCO
level), frequency reduction will start. The actual peak
voltageonsense will be somewhat higherduetoswitch-off
delay (see Fig.7). The frequency reduction will stop
approximately 25 mV lower (VCO2 level), when the
minimum frequency is reached.

Cycle skipping

At very low power levels, a cycle skipping mode will be
activated. A high control voltage will reduce the switching
frequency to a minimum of 25 kHz. If the voltage on the
controlpin has raisedeven more, switch-onof the external
power MOSFET will be inhibited until the voltage on the
control pin has dropped to a lower value again (see Fig.7).

1

V

CTRL

CTRL

.

Fig.5 V

1 V

(typ)

sense(max)

1.5 V
(typ)

as a function of V

2002 Aug 27 6

For system accuracy, it is not the absolute voltage on the
control pin that will trigger the cycle skipping mode, but a
signal derived from the internal VCO will be used.

Remark: If the no-load requirement of the system is such
that the output voltage can be regulated to its intended
level at a switching frequency of 25 kHz or above, the
cycle skipping mode will not be activated.

Philips Semiconductors Product specification

GreenChipII SMPS control IC TEA1552

handbook, full pagewidth

1.5 V − V

CTRL

CTRL

V

CC(5V)

VCOadj

The voltage levels dV1,dV2,dV3and dV4are fixed in the IC to typically 50 mV, 18 mV, 40 mV and 15 mV respectively.
The level at which VCO mode of operation starts or ends can be externally controlled with the VCOadj pin.

X2

5 V

V

x

current

comparator

V

I

DRIVER

OSCILLATOR

DRIVER

I

sense

MBL502

f

osc

f

max

f

min

V

STDBY

(V)

5

0

cycle

skipping

1

0

dV

2

dV

dV

1

4

VCO

Vx (mV)

adj

Vx (mV)

Vx (mV)

3

dV

Fig.7 A functional implementation of the standby and cycle skipping circuitry.

Standby output

TheSTDBY output pin (V

= 5 V)can be used to drive

STDBY

an external NPN transistor or FET in order to e.g.
switch-off a PFCcircuit. The STDBY output is activated by
the internal VCO: as soon as the VCO has reduced the
switching frequency to (almost) the minimum frequency of
25 kHz, the STDBY output will be activated (see Fig.7).
The STDBY output will go low again as soon as the VCO
allows a switching frequency close to the maximum
frequency of 125 kHz.

Demagnetization

The system will be in discontinuous conduction mode all
the time. The oscillator will not start a new primary stroke
until the secondary stroke has ended.

Demagnetization features a cycle-by-cycle output
short-circuit protection by immediately lowering the
frequency (longer off-time), thereby reducing the power
level.

Demagnetizationrecognition is suppressedduringthe first
time (t

). This suppression may be necessary in

suppr

applications where the transformer has a large leakage
inductance and at low output voltages/start-up.

OverVoltage Protection (OVP)

An OVP mode is implemented in the GreenChip series.
For the TEA1552, this works by sensing the auxiliary
voltage via the current flowing into pin DEM during the
secondary stroke. The auxiliary winding voltage is a
well-defined replica of the output voltage. Any voltage
spikes are averaged by an internal filter.

If the output voltage exceeds the OVP trip level, the OVP
circuit switches off the power MOSFET. The controller
then waits until the UVLO level is reached on pin VCC.
When VCC drops to UVLO, capacitor C
recharged to the V

level, however the IC will not start

start

VCC

will be

switching again. Subsequently, VCC will drop again to the
UVLO level, etc.

2002 Aug 27 7

Philips Semiconductors Product specification

GreenChipII SMPS control IC TEA1552

Operation only recommenceswhen the VCCvoltage drops
below a level of approximately 4.5 V (practically when the
V

has been disconnected for a short period).

mains

The output voltage (V
can be set by the demagnetization resistor R

N

V

OVP

where N

s

-----------­N

is the number of secondary turnsand N

s

I

aux

) at which the OVP function trips,

OVP

R

OVP DEM()

+×[]×=

DEMVclamp DEM()pos()

DEM

:

aux

is the

number of auxiliary turns of the transformer.
Current I

OVP(DEM)

The value of the demagnetization resistor (R

is internally trimmed.

DEM

) can be
adjusted to the turns ratio of the transformer, thus making
an accurate OVP possible.

handbook, full pagewidth

primary

stroke

secondary

stroke

Valley switching (see Fig.8)
A new cycle starts when the power switch is switched on.

After the ‘on-time’ (which is determined by the ‘sense’
voltage and the internal control voltage), the switch is
opened and the secondary stroke starts.

After the secondary stroke, the drain voltage shows an
oscillation with a frequency of approximately

---------------------------------------------------­2π×L

where L

1

C

×()×()

p

d

is the primary self inductance of the transformer

p

and Cd is the capacitance on the drain node.

secondary

ringing

drain

valley

secondary

stroke

oscillator

A: Start of new cycle at lowest drain voltage.
B: Start of new cycle in a classical PWM system at high drain voltage.

Fig.8 Signals for valley switching.

BA

MGU235

2002 Aug 27 8