Siemens TDA 4601 Technical data

TDA4601

Control ICs for Switched-Mode Power Supplies

TDA 4601

Bipolar IC

Features

●Direct control of the switching transistor

●Low start-up current

●Reversing linear overload characteristic

● Base current drive proportional to collector current ● Protective circuit in case of disturbance

P-SIP-9-1

Type	Ordering Code	Package
TDA 4601	Q67000-A2379	P-SIP-9-1

The integrated circuit TDA 4601/D is designed for driving, controlling and protecting the switching transistor in self-oscillating flyback converter power supplies as well as for protecting the overall power supply unit. In case of disturbance, the rise of the secondary voltage is prevented. In addition to the ICs application range including TV-receivers video tape recorders, hifi devices and active loudspeakers, it can also be used in power supply units for professional applications due to its wide control range and high voltage stability during increased load changes.

Semiconductor Group

7

06.94

TDA 4601

Pin Definitions and Functions

Pin No.																						Function
1																						VREF output
2																						Zero passage identification
3																						Input control amplifier, overload amplifier
4																						Collector current simulation
5																						Connection for additional protective circuit
6																						Ground (rigidly connected to substrate mounting plate)
7																						DC-output for charging coupling capacitor
8																						Pulse output - driving of switching transistor
9																						Supply voltage

Block Diagram

Semiconductor Group

8

TDA 4601

Circuit Description

The TDA 4601 is designed for driving, controlling and protecting the switching transistor in flyback converter power supplies during start-up, normal and overload operations as well as during disturbed operation. In case of disturbance the drive of the switching transistor is inhibited and a secondary voltage rise is prevented.

Start-Up

The start-up procedures (on-mode) include three consecutive operating phases as follows:

1.Build-Up of Internal Reference Voltage

The internal reference voltage supplies the voltage regulator and effects charging of the coupling electrolytic capacitor connected to the switching transistor. Current consumption will remain at I9 < 3.2 mA with a supply voltage up to V9 approx. 12 V.

2.Enabling of Internal Voltage - Reference Voltage V1 = 4 V

Simultaneously with V9 reaching approx. 12 V, an internal voltage becomes available, providing all component elements, with the exception of the control logic, with a thermally stable and overload-resistant current supply.

3.Enabling of Control Logic

In conjunction with the generation of the reference voltage, the current supply for the control logic is activated by means of an additional stabilization circuit. The integrated circuit is then ready for operation.

The start-up phase above described are necessary for ensuring the charging of the coupling electrolytic capacitor, which in turn supplies the switching transistor. Only then is it possible to ensure that the transistor switches accurately.

Normal Operating Mode / Control Operating Mode

At the input of pin 2 the zero passages of the frequency provided by the feedback coil are registered and forwarded to the control logic. Pin 3 (control input, overload and standby identification) receives the rectified amplitude fluctuations of the feedback coil. The control amplifier operates with an input voltage of approx. 2 V and a current of approx. 1.4 mA. Depending on the internal voltage reference, the overload identification limits inconjunction with collector current simulator pin 4 the operating range of the control amplifier. The collector current is simulated by an external RC-combination present at pin 4 and internally set threshold voltages. The largest possible collector current applicable to the switching transistor (point of return) increases in proportion to the increased capacitance (10 nF). Thus the required operating range of the control amplifier is established. The range of control lies between a DC-voltage clamped at 2 V and a sawtooth - shaped rising ACvoltage, which can vary up to a max. amplitude of 4 V (reference voltage). During secondary load reduction to approx. 20 W, the switching frequency is increased (approx. 50 kHz) at an almost constant pulse duty factor (1:3). During additional secondary load decreases to approx. 1 W, the switching frequency increases to approx. 70 kHz and pulse duty factor to approx. 1:11. At the same time collector peak current is reduced to < 1 A.

Semiconductor Group

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TDA 4601

The output levels of the control amplifier as well as those of the overload identification and collector current simulator are compared in the trigger and forwarded to the control logic. Via pin 5 it is possible to externally inhibit the operations of the IC. The output at pin

pin 8 will be inhibited when voltages of £	VREF	– 0.1 are present at pin 5.
	-----------
	2

Flipflops for controlling the base current amplifier and the base current shut-down are set in the control logic depending on the start-up circuit, the zero passage identification as well as on the enabling by the trigger. The base current amplifier forwards the sawtoothspahed V4 voltage to the output of pin 8. A current feedback with an external resistor (R = 0.68 W) is present between pin 8 and pin 7. The applied value of the resistor determines the max. amplitude of the base driving current for the switching transistor.

Protective Operating Mode

The base current shut-down activated by the control logic clamps the output of pin 7 to 1.6 V. As a result, the drive of the switching transistor is inhibited. This protective measure is enabled if the supply voltage at pin 9 reaches a value £ 6.7 V or if voltages of

£ VREF

----------- – 0.1 are present at pin 5. 2

In case of short-circuits occurring in the secondary windings of the switched-mode power supply, the integrated circuit continuously monitors the fault conditions. During secondary, completely loadfree operation only a small pulse duty factor is set. As a result the total power consumption of the power supply is held at N = 6 ... 10 W during both operating modes. After the output has been inhibited for a voltage supply of £ 6.7 V, the reference voltage (4 V) is switched off if the voltage supply is further reduced by DV9 = 0.6 V.

Protective Operating Mode at Pin 5 in Case of Disturbance

The protection against disturbances such as primary undervoltages and/or secondary overvoltages (e.g. by changes in the component parameters for the switched-mode power supply) is realized as follows:

Protective Operating Mode with Continuous Fault Condition Monitoring

In case of disturbance the output pulses at pin 8 are inhibited by falling below the protective threshold V5 , with a typical value of V1/2. As a result current consumption is reduced (I9 ³ 14 mA at V9 = 10 V).

With a corresponding high-impedance start-up resistor *), supply voltage V9 will fall below the minimum shut-down threshold (5.7 V) for reference voltage V1 . V1 will be switched off and current consumption is further reduced to I9 £ 3.2 mA at V9 £ 10 V.

Because of these reductions in current consumption, the supply voltage can rise again to reach the switch-on threshold of V9 ³ 12.3 V. The protective threshold at pin 5 is released and the power supply is again ready for operation.

Semiconductor Group

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TDA 4601

In case of continuing problems of disturbance (V5 ≤ V1/2 – 0.1 V) the switch-on mode is interrupted by the periodic protective operating mode described above, i.e. pin 8 is inhibited and V9 is falling, etc.

Switch-On in the Wide Range Power Supply (90 Vac to 270 Vac)

(application circuit 2)

Self-oscillating flyback-converters designed as wide range power supplies require a power source independent of the rectified line voltage for TDA 4601. Therefore the winding polarity of winding 11/13 corresponds to the secondary side of the flyback converter transformer. Start-up is not as smooth as with an immediately available supply voltage, because TDA 4601 has to be supplied by the start-up circuit until the entire secondary load has been charged. This leads to long switch-on times, especially if low line voltages are applied.

However, the switch-on time can be shortened by applying the special start-up circuit (dotted line). The uncontrolled phase of feedback control winding 15/9 is used for activating purposes. Subsequent to activation, the transistor T1 begins to block when winding 11/13 generates the current supply for TDA 4601. Therefore, the control circuit cannot be influenced during operation.

Semiconductor Group

11

TDA 4601

Absolute Maximum Ratings

Parameter		Symbol	Limit Values		Unit
			min.	max.
Supply voltage		V9	0	20	V
Voltages
Reference output		V1	0	6	V
Zero passage identification		V2	– 0.6	0.6	V
Control amplifier		V3	0	3	V
Collector current simulation		V4	0	8	V
Blocking input		V5	0	8	V
Base current cut-off point		V7	0	V9	V
Base current amplifier output		V8	0	V9	V
Currents
Zero passage identification		Il i2	–5	5	mA
Control amplifier		Il 3	– 3	3	mA
Collector current simulation		Il 4	0	5	mA
Blocking input		Il 5	0	5	mA
Base current cut-off point		IQ 7	– 1	1.5	A
Base current amplifier output		IQ 8	– 1.5	0	A
Junction temperature		Tj		125	˚C
Storage temperature range		Tstg	– 40	125	˚C
Thermal resistances:
system-air	TDA 4601	Rth SA		70	K/W
system-case	TDA 4601	Rth SC		15	K/W
system-air 1)	TDA 4601-D	R		60	K/W
system-case 2)		th SA
	TDA 4601-D	R		44	K/W
		th SA1

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TDA 4601

Absolute Maximum Ratings (cont’d)

Parameter		Symbol	Limit Values		Unit
			min.	max.
Operating Range
Supply voltage		V9	7.8	18	V
Case temperature	TDA 4601	TC	0	85	˚C
Ambient temperature range 3)	TDA 4601-D	TA	0	70	˚C

1)Case soldered on PC-board without cooling surface

2)Case soldered on PC-board with copper-clad 35 μm layer, cooling surface 25 cm2

3)Rth SA1 = 44 K/W and PV = 1 W

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TDA 4601

Characteristics

TA = 25 ˚C

according to measurement circuit 1 and diagram

Parameter		Symbol		Limit Values		Unit
			min.	typ.	max.
Start Operation
Current consumption (V1 not yet
switched on)
V9	= 2 V	I9			0.5	mA
V9	= 5 V	I9		1.5	2.0	mA
V9	= 10 V	I9		2.4	3.2	mA
Switching point for V1		V9	11.0	11.8	12.3	V

Normal Operation

V9 = 10 V; Vcont = – 10 V; Vclock = ± 0.5 V; f = 20 kHz duty cycle 1:2 after switch-on

Current consumtion
Vcont = –			10 V	I9			110	135	160	mA
Vcont = 0 V				I9			50	75	100	mA
Reference voltage
I1 < 0.1 mA				V1			4.0	4.2	4.5	V
I1 < 5 mA				V1			4.0	4.2	4.5	V
Temperature coeffiecient of				TC1			–	10– 3		1/K
reference voltage
Control voltage Vcont = 0 V				V3			2.3	2.6	2.9	V
Collector current simulation voltage
V	cont	= 0	V	V *)			1.8	2.2	2.5	V
				4
V	cont	= 0	V/– 10 V	V	4	*)	0.3	0.4	0.5	V
Clamping voltage				V5			6.0	7.0	8.0	V
Output voltages
V	cont	= 0	V	V		*)	2.7	3.3	4.0	V
				Q7
V	cont	= 0	V	V		*)	2.7	3.4	4.0	V
				Q8
Vcont = 0			V/– 10 V	VQ8			1.6	2.0	2.4	V
Feedback voltage				V *)				0.2		V
				2
*)	DC-component only

Semiconductor Group

14