PIN CONFIGURATION

Pin

Number

Description

1

Regulating voltage : information input concerning secondary voltage.

By comparing the regulating voltage obtained from the regulating winding of the transformer with the

internal reference voltage, the output pulse width on Pin 5 is adapted to the load of the secondary side

(normal, overload, short circuit, no load)

2

Primary current simulation : information input regarding the primary current. The primary current rise in the

primary winding is simulated at Pin 2 as a voltage rise by means of external RC element. When a value is

reached that is derived from the regulating voltage at Pin 1, the output pulse at Pin 5 is terminated. The

RC element serves to set the maximum power at the overload point.

3

Primary voltage detector : input for primary voltage monitoring. When the line voltage is too low the IC is

compensation.

4

Ground

5

Output : push-pull output for charge and discharge of the gate capacitance of the power MOS transistor.

6

7

Soft-start : input for soft-start and integration network. Start-up will begin with short pulses by connecting a

capacitor between Pin 7 to ground. This capacitor together with a resistor connected between Pin 7 and

error amplifier output also as acts an integrator network for regulation.

8

Zero detector : Input for the oscillator feedback. After starting oscillator, every zero transit of the feedback

voltage (falling edge) triggers an output pulse at Pin 5. The trigger threshold is at typically - 50mV

1

2

3

4

5

6

78

V

6min

V

6ma x

V

6E

V

6A

V

2B

V

R

V

u

V

REF

Re fere nce

Volta ge

(typ. 3V)

S upply

Voltage

Monitor

Prima ry

Current

Recopy

Output S ta ge

and

Current Limit

Logic

S ta rting

Impulse

G enera tor

Regulating

& Ove rload

Amplifier

Current

S ource

Ove rloa d

Point

Corre ction

Low Volta ge

P rote ction

Monitoring

Stop

Comp.

Zero

Crossing

De te ctor

TDA4605

BLOCK DIAGRAM

TDA4605

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