TDA4605 CONTROL CIRCUIT FOR SWITCH MODE POWER SUPPLIES USING MOS TRANSISTORS ■ ■ ■ ■ ■ ■ ■ ■ ■ Fold-Back Characteristic provides Overload Protection for External Diodes Burst Operation under Short-Circuit and no Load Conditions Loop Error Protection Switch-off in case of too low Line Voltage (Under Voltage Switch-off) Line Voltage Compensation of Overload Point Soft-Start for smooth Start-up Chip Over-Temperature Protection (Thermal Shutdown) On-Chip Parasitic Transformer Oscillation Suppression Circuitry Decrease of Regulated Voltage for low Power Consumption DIP28 (Plastic Package) ORDER CODE: TDA4605 DESCRIPTION The IC TDA4605 controls the MOS Power Transistor and performs all necessary regulation and monitoring functions in free running flyback converters. Since good load regulation over a wide load range is attained, this IC is particularly suitable for Consumer as well as Industrial Power Supplies. Alternative source of the TDA4605 is also available from SIEMENS Semiconductors Consumer Electronics A.G. SO8 (Plastic Micropackage) ORDER CODE: TDA4605D Figure 1. Pin Connections 1 8 ZERO CROSSING DETECTOR INPUT PRIMARY CURRENT SIMULATION 2 7 SOFT-START PRIMARY VOLTAGE MONITORING 3 6 SUPPLY VOLTAGE GROUND 4 5 OUTPUT 4605-01.eps REGULATION INPUT September 2003 1/7 1 TDA4605 PIN CONFIGURATION Pin Number 1 2 3 4 5 6 7 8 Description 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) 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. Primary voltage detector : input for primary voltage monitoring. When the line voltage is too low the IC is switched-off by comparing V3 with an internal reference. Voltage at Pin 3 is used for overload point compensation. Ground Output : push-pull output for charge and discharge of the gate capacitance of the power MOS transistor. Supply voltage : Supply voltage input. From it are derived a stable internal reference voltage (VREF) and the switching threshold V6A, V6E, V6 max and V6 min for the supply voltage detector. if V6 > V6E the VREF is switched on and switched off when V6 < V6A. In addition the logic is only enable for V6 min < V6 < V6 max. 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. 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 Figure 2. Block Diagram 6 Reference Voltage (typ. 3V) V REF 4 Current Source Overload Point Correction 2/7 1 V 2B Primary Current Recopy Output Stage and Current Limit V 6min V 6A V 6E V 6max V st Starting Impulse Generator Logic Regulating & Overload Amplifier Vu Low Voltage Protection Monitoring 3 5 Supply Voltage Monitor VR 1 2 Stop Comp. Zero Crossing Detector 7 8 4605-02.eps TDA4605 TDA4605 ABSOLUTE MAXIMUM RATINGS Symbol V1 V2 V3 V4 V6 V7 I1 I2 I3 I4 I5 I6 I7 I8 Tj Tstg Parameter Pin 1 2 3 4 6 7 1 2 3 4 5 6 7 8 Supply Voltage Supply Current tp ≤ 50µs, V ≤ 0.1 tp ≤ 50µs, V ≤ 0.1 tp ≤ 50µs, V ≤ 0.1 Junction Temperature (autom. thermal disjunction) Storage Temperature Value -0.3, +3 -0.3 -0.3 -0.3 -0.3, +20 -0.3 3 3 3 - 1.5 -0.5, +1.5 0.5 3 -3, +3 +125 -40, +125 Unit V V V V V V mA mA mA A A A mA mA oC oC THERMAL DATA Symbol Rth(j-a) Rth(j-c) Tamb Parameter Junction-ambient Thermal Resistance Junction-case Thermal Resistance Ambient Temperature Value 80 45 -20, +85 Unit C/W o C/W oC o ELECTRICAL CHARACTERISTICS (VCC = 10V, Tamb = 25oC, unless otherwise specified) Symbol Parameter START-UP HYSTERESIS Start-up Current Drain I6E0 Switch-on Voltage V6E Switch-off Voltage V6A Switch-on Current I6E1 Switch-off Current I6A1 VOLTAGE CLAMP (V6 = 10V, IC Switched off) V2(Max.) At Pin 2 (V6 < V6E) V3(Max.) At Pin 3 (V6 < V6E) CONTROL RANGE Control Input Voltage V1R -VR Voltage Gain of the Control Circuit in the Control Range PRIMARY CURRENT SIMULATION VOLTAGE Basic Value V2B OVERLOAD RANGE AND SHORT CIRCUIT OPERATION Peak Value in the Range of Secondary Overload V2O Maximum Ramp Amplitude DV2 Peak Value in the Range of Secondary Short V2S Circuit Operation FOLDBACK POINT CORRECTION Foldback Point Correction Current -I2 Test Conditions Min. Typ. Max. Unit V6 = V6E 11 4.5 V6 = V6 = V6E V6A I2 = 1mA I3 = 1mA 5.6 5.6 0.6 12 5 11 10 0.8 13 5.5 mA V V mA mA 6.6 6.6 9 9 V V 400 410 420 mV VR = d(V2S - V2B)/dV1 f = 1kHz 43 dB 0.955 1.00 1.03 V V1 = V1R - 10mV V2O - V2B 2.8 2.95 3.1 1.82 1.95 2.08 V V V1 = 0 2.3 V V3 = 3.7V 300 500 650 2.5 2.7 µA 3/7 1 TDA4605 ELECTRICAL CHARACTERISTICS (VCC = 10V, Tamb = 25oC, unless otherwise specified) - Continued Symbol Parameter GENERALLY VALID DATA (V6 = 10V) VOLTAGE OF THE ZERO Transition DETECTOR Positive Clamping Voltage V8P Negative Clamping Voltage V8N Threshold Value V8S TUL Suppression of Transformer Ringing Input Current -I8 PUSH-PULL OUTPUT STAGE SATURATION VOLTAGES Pin 5 Sourcing VSatU Pin 5 Sinking VSatU Pin 5 Sinking VSatU OUTPUT SLOW RATE Rising Edge dV5/dt Falling Edge -dV5/dt REDUCTION OF CONTROL VOLTAGE Current to reduce the Control Voltage -I1 PROTECTION CIRCUIT Undervoltage Protection for V6 : V6(Min.) Voltage at Pin 5 = V5(Min.) if V6 < V6(Min.) Overvoltage Protection for V6 : V6(Max.) Voltage at Pin 5 = V5(Min.) if V6 > V6(Max.) Undervoltage Protection for VAC : V3A Voltage at Pin 5 = V5(Min.) if V3 < V3A Over Temperature : at the given chip temperature the Oj IC will switch V5 to V5(Min.) Voltage at Pin 3 if one of the protection functions was V3Sat triggered ; (V3 will be clamped until V6 < V6A) I6 Current Drain during Burst Operation 4/7 1 Test Conditions Min. Typ. Max. Unit I8 = 1mA I8 = -1mA V8 = 0 40 3 0 I5 = -0.1A I5 = 0.1A I5 = 0.5A 1.5 1.0 1.4 V7 = 1V V2 = 0V 0.75 -0.2 50 3.8 4.5 4 V V mV µs µV 2.0 1.2 1.8 V V V 70 100 V/µs V/µs 50 µA 7.0 7.25 7.5 V 15 16 16.5 V 970 1005 1040 mV o C 150 I3 = 750µA V3 = V2 = 0V 0.4 8 0.8 V mA TDA4605 FUNCTIONAL DESCRIPTION In free running fly-back converters, the TDA4605 assumes control of a MOS power transistor and all necessary regulation and monitoring functions. The serial circuit of power transistor and primary winding of the flyback transformer is connected to the input voltage. During the switch-on period of the transistor, energy is stored in the transformer and during the switch-off period it is fed to the load via the secondary winding. By varying the switchon time of the power transistor, the IC controls each portion of energy transferred to the secondary side such that the output voltage remains nearly independent of load variations. The required control information is taken from the input voltage during the switch-on period and from a regulation winding during the switch-off period. A new cycle begins as soon as the energy stored in the transformer has been totally delivered to the secondary side. In different load ranges, the SMPS will behave as follows: – No-Load Operation: The power supply unit oscillates in non continuous mode at a typical frequency of 20 to 40kHz. Depending upon the transformer winding and the regulated voltage divider, the output voltage can be slightly above the nominal value. – Normal Operation: Starting from typ. 200kHz, the switching frequency falls with increasing load and decreasing AC voltage. The duty cycle depends primarily on the AC voltage. The output voltage is only slightly load-dependent. – Overload Point: Maximum output power is available at this point of the output characteristics – Overload: The energy transferred per operation cycle is limited at the top. Therefore, the output voltage will fall with secondary overloading. 5/7 1 TDA4605 PACKAGE MECHANICAL DATA 8-PINS - PLASTIC DIP Figure 3. 8-Pin Package 8-PINS - PLASTIC SO Figure 4. 8-Pin Plastic Micropackage 6/7 1 TDA4605 Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without the express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics 2003 STMicroelectronics - All Rights Reserved. Purchase of I2C Components by STMicroelectronics conveys a license under the Philips I2C Patent. Rights to use these components in an I2C system is granted provided that the system conforms to the I2C Standard Specification as defined by Philips. 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