SGS Thomson Microelectronics TDA4605 Datasheet
TDA4605
CONTROLCIRCUIT FOR SWITCH MODE POWER SUPPLIES
USING MOS TRANSISTORS
.
FOLD-BACK CHARACTERISTIC PROVIDES
OVERLOAD PROTECTION FOR EXTERNAL
DIODES
.
BURST OPERATION UNDER SHORT-CIRCUIT AND NO LOADCONDITIONS
.
LOOP ERRORPROTECTION
.
SWITCH-OFF IN CASE OF TOO LOW LINE
VOLTAGE(under voltage switch-off)
.
LINE VOLTAGE COMPENSATION OF OVERLOADPOINT
.
SOFT-STARTFOR SMOOTH START-UP
.
CHIP OVER-TEMPERATURE PROTECTION
(thermalshutdown)
.
ON-CHIP PARASITIC TRANSFORMER OSCILLATIONSUPPRESSIONCIRCUITRY
.
DECREASE OF REGULATED VOLTAGE FOR
LOW POWERCONSUMPTION
ORDER CODE : TDA4605
DIP8
(Plastic Package)
DESCRIPTION
The ICTDA4605controlstheMOSPowerTransistor and performs all necessary regulation and
monitoring functions in free running flyback converters. Since good load regulation over a wide
load rangeisattained,thisICis particularlysuitable
for ConsumeraswellasIndustrialPowerSupplies.
Alternative source of the TDA4605 is also available from SIEMENS Semiconductors Consumer
ElectronicsA.G.
PINCONNECTIONS
REGULATION INPUT
PRIMARY CURRENT SIMULATION
PRIMARY VOLTAGE MONITORING
GROUND OUTPUT
1
2
3
4
SO8
(Plastic Micropackage)
ORDER CODE : TDA4605D
8
7
6
5
ZERO CROSSING DETECTOR INPUT
SOFT-START
SUPPLY VOLTAGE
April 1996
4605-01.EPS
1/6
TDA4605
PIN CONFIGURATION
Pin
Number
1 Regulating voltage : informationinput concerning secondary voltage.
By comparingthe regulating voltage obtainedfrom the regulating winding of the transformer with the
internal reference voltage, the output pulse width on Pin 5 is adaptedto the load of the secondary side
(normal, overload, short circuit, no load)
2 Primary currentsimulation : information input regarding the primary current. The primary current rise in the
primary winding is simulated at Pin 2 as a voltage riseby means of external RC element. When a value is
reached that is derived from the regulating voltage at Pin 1, the output pulse atPin 5 is terminated.The
RC element serves to set the maximum power at the overload point.
3 Primary voltagedetector : input for primary voltage monitoring.When the line voltage is too low the IC is
switched-off by comparing V
compensation.
with an internal reference. Voltage at Pin 3 is used for overload point
3
4 Ground
5 Output : push-pull output for charge and discharge of the gate capacitance of the power MOS transistor.
6 Supply voltage : Supply voltageinput. From it are derived a stable internal reference voltage (V
the switching threshold V
6>V6E
the V
REF
if V
V
6 min<V6<V6 max
6A,V6E,V6 max
isswitched on andswitched offwhen V6<V6A. In addition the logic is only enablefor
.
7 Soft-start : input forsoft-start and integration network. Start-up willbegin with short pulses by connecting a
capacitor between Pin 7 to ground. This capacitor together with a resistor connected between Pin 7and
error amplifier output also as acts an integrator network for regulation.
8 Zero detector : Input for theoscillator feedback. After starting oscillator, every zero transit of the feedback
voltage (falling edge) triggersan output pulse at Pin 5.The trigger threshold is at typically - 50mV
and V
Description
for thesupply voltage detector.
6 min
REF
) and
4605-01.TBL
BLOCK DIAGRAM
TDA4605
Reference
Volta ge
(typ. 3V)
4
Current
S ourc e
1
Overload
Point
Correction
2
S upply
Voltage
V
2B
Monitor
V
REF
V
V
6min
V
V
6ma x
6E
6A
V
st
Primary
Current
Re copy
Sta rting
Impulse
Generator
R
Regulating
&Overload
Amplifier
Stop
Comp.
V
56
Output Sta ge
and
Current Limit
Logic
Zero
u
Low Voltage
Protection
V
Crossing
Detector
Monitoring
3
78
4605-02.EPS
2/6
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