Philips TEA1620 Service Manual

INTEGRATED CIRCUITS

DATA SH EET

TEA1620P

STARplug

Preliminary speciﬁcation File under Integrated Circuits, IC11

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Philips Semiconductors Preliminary speciﬁcation

STARplug

FEATURES

• Designed for general purpose supplies up to 50 W

• Integrated power switch: – TEA1620: 48 Ω; 650 V

• Operates from universal AC mains supplies

(80 to 276 V)

• Adjustable frequency for flexible design

• RC oscillator for load insensitive regulation loop

constant

• Valley switching for minimum switch-on loss

• Frequency reduction at low power output makes low

standby power possible (<100 mW)

• Adjustable overcurrent protection

• Under voltage protection

• Temperature protection

• Short circuit winding protection

• Simple application with both primary and secondary

(opto) feedback

• Available in 8-pin DIP package.

TEA1620P

Initsmostbasic version of application, the TEA1620P acts as a voltage source. Here, no additional secondary electronics are required. A combined voltage and current source can be realized with minimum costs for external components.ImplementationoftheTEA1620Prenders an efficient and low cost power supply system.

APPLICATIONS

Typical application areas for the STARplugTM are:

• Chargers

• Adapters

• STB (Set Top Box)

• DVD

• CD(R)

• TV/monitor standby supplies

• PC peripherals

• PC Silverbox standby SMPS

• Microcontroller supplies in home applications and small

portable equipment, etc.

GENERAL DESCRIPTION

The TEA1620P is a Switched Mode Power Supply (SMPS) controller IC that operates directly from the rectified universal mains.Itis implemented in the high voltage EZ-HV SOI process, combined with a low voltage BICMOS process. The device includes a high voltage power switch and a circuit for start-up directly from the rectified mains voltage.

A dedicated circuit for valley switching is built in, which makes a very efficient slim-line electronic powerplug concept possible.

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Philips Semiconductors Preliminary speciﬁcation

STARplug

TEA1620P

QUICK REFERENCE DATA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

drain(max)

maximum voltage at the DRAIN

Tj>0°C −−650 V

DS(on)

CC(max)

osc

drain

drain-source on-state resistance of TEA1620

Tj=25°C; I Tj= 100 °C; I

= −0.06 A − 48 55.2 Ω

source

= −0.06 A − 68 78.2 Ω

source

maximum supply voltage −−40 V frequency range of oscillator 10 − 200 kHz supply current drawn from DRAIN

no auxiliary supply − 0.5 − mA

amb

ambient temperature −20 − +85 °C

ORDERING INFORMATION

TYPE

NUMBER

NAME DESCRIPTION VERSION

PACKAGE

TEA1620P DIP8 plastic dual in-line package; 8 leads (300 mil) SOT97-1

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Philips Semiconductors Preliminary speciﬁcation

STARplug

BLOCK DIAGRAM

handbook, full pagewidth

GND

TEA152x

TEA1620P

SUPPLY

LOGIC

VALLEY

100 mV

TEA1620P

DRAIN

n.c.

REG

stop

OSCILLATOR

low freq

1.8 U

2.5 V 10x

PWM

THERMAL

SHUTDOWN

POWER-UP

RESET

PROTECTION

LOGIC

overcurrent

short circuit winding

blank

0.5 V

0.75 V

MGT419

SOURCE

AUX

Fig.1 Block diagram.

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Philips Semiconductors Preliminary speciﬁcation

STARplug

PINNING

SYMBOL

DESCRIPTION

TEA1620P

1 supply voltage GND 2 ground RC 3 frequency setting REG 4 regulation input AUX

input for voltage from auxiliary winding for timing

(demagnetization) SOURCE 6 source of internal MOS switch n.c. 7 not connected DRAIN

drain of internal MOS switch; input for start-up current

and valley sensing

TEA1620P

handbook, halfpage

Fig.2 Pin configuration of TEA1620P.

REG

1 2

TEA152xP

TEA1620P

3 4

MGT420

DRAIN

n.c.GND

SOURCE

AUX

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Philips Semiconductors Preliminary speciﬁcation

STARplug

FUNCTIONAL DESCRIPTION

The TEA1620P is the heart of a compact flyback converter, with the IC placed at the primary side. The auxiliary winding of the transformer can be used for indirect feedback to control the isolated output. This additional winding also powers the IC. A more accurate control of the output voltage and/or current can be implemented with an additional secondary sensing circuit and optocoupler feedback.

The TEA1620P uses voltage modecontrol. The frequency isdeterminedbythemaximum transformer demagnetizing time and the time of the oscillator. In the first case, the converter operates in the Self Oscillating Power Supply (SOPS) mode. In the latter case, it operates at a constant frequency, which can be adjusted with external components RRC and CRC. This mode is called Pulse WidthModulation(PWM).Furthermore,aprimarystrokeis startedonlyinavalleyofthesecondary ringing. This valley switching principle minimizes capacitive switch-on losses.

Start-up and under voltage lock-out

Initially, the IC is self supplying from the rectified mains voltage. The IC starts switching as soon as the voltage on pin VCC passes the V

level. The supply is taken

CC(start)

over by the auxiliary winding of the transformer as soon as VCCis high enough and the supply from the line is stopped for high efficiency operation.

As soon as the voltage on pin VCC drops below the V

CC(stop)

level, the IC stops switching and restarts from the

rectified mains voltage.

Oscillator

The frequency of the oscillator is set by the external resistor and capacitor on pin RC. The external capacitor is charged rapidly to the V new primary stroke, it discharges to the V

level and, starting from a

RC(max)

RC(min)

level. Because the discharge is exponential, the relative sensitivity of the duty factor to the regulationvoltage at low duty factor is almost equal to the sensitivity at high duty factors. This results in a more constant gain over the duty factor range compared to PWM systems with a linear sawtooth oscillator. Stable operation at low duty factors is easily realized. For high efficiency, the frequency is reduced as soon as the duty factor drops below a certain value. This is accomplished by increasing the oscillator charge time.

TEA1620P

regulation voltage is equal to the external regulation voltage (minus 2.5 V) multiplied by the gain of the error amplifier (typical 20 dB (10 ×)).

Valley switching

A new cycle is started when the primary switch is switched on (see Fig.3). After a certain time (determined by the oscillator voltage RC and the internal regulation level), the switch is turned off and the secondary stroke starts. The internal regulation level is determined by the voltage on pin REG. After the secondary stroke, the drain voltage shows an oscillation with a frequency of approximately

---------------------------------------------------2 π× LpCp×()×()

where L parasitic capacitance on the drain node.

As soon as the oscillator voltage is high again and the secondary stroke has ended, the circuit waits for a low drain voltage before starting a new primary stroke. Figure 3 shows the drain voltage together with the valley signal, the signal indicating the secondary stroke and the RC voltage.

The primary stroke starts some time before the actual valley at low ringing frequencies, and some time after the actual valley at high ringing frequencies. Figure 4 shows a typical curve for a reflected output voltage N × V This voltage is the output voltage Vo (see Fig.5) transferred to the primary side of the transformer with the factor N (determined by the turns ratio of the transformer). Figure 4 shows that the system switches exactly at minimum drain voltage for ringing frequencies of 480 kHz, thus reducing the switch-on losses to a minimum. At 200 kHz,the next primary stroke is started at 33°before the valley. The switch-on losses are still reduced significantly.

Demagnetization

Thesystemoperatesindiscontinuousconductionmodeall the time. As long as the secondary stroke has not ended, the oscillator will not start a new primarystroke. During the first t suppressed. This suppression may be necessary in applications where the transformer has a large leakage inductance and at low output voltages.

is the primary self inductance and Cp is the

seconds, demagnetization recognition is

suppr

of 80 V.

Duty factor control

The duty factor is controlled by the internal regulation voltage and the oscillator signal on pin RC. The internal

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