Control Ics For Switched-Mode Power Supplies Tda 4601: Bipolar Ic
Control Ics For Switched-Mode Power Supplies Tda 4601: Bipolar Ic
Control Ics For Switched-Mode Power Supplies Tda 4601: Bipolar Ic
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
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.
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.
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.
Semiconductor Group 9
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
V REF
pin 8 will be inhibited when voltages of ≤ ------------ – 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 Ω) 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.
V REF
≤ ------------ – 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 load-
free 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 ∆V9 = 0.6 V.
Semiconductor Group 10
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
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 Rth SA 60 K/W
system-case 2) TDA 4601-D Rth SA1 44 K/W
Semiconductor Group 12
TDA 4601
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
Semiconductor Group 13
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
Vcont = 0 V V4*) 1.8 2.2 2.5 V
Vcont = 0 V/– 10 V ∆V4 *) 0.3 0.4 0.5 V
Clamping voltage V5 6.0 7.0 8.0 V
Output voltages
Vcont = 0 V VQ7 *) 2.7 3.3 4.0 V
Vcont = 0 V VQ8 *) 2.7 3.4 4.0 V
Vcont = 0 V/– 10 V ∆VQ8 1.6 2.0 2.4 V
Feedback voltage V2 *) 0.2 V
*) DC-component only
Semiconductor Group 14
TDA 4601
Protective Operation
V9 = 10 V; Vcont = – 10 V; Vclock = 0.5 V; f = 20 kHz;
duty cycle 1:2
Parameter Symbol Limit Values Unit
min. typ. max.
Current consumption
V5 < 1.9 V I9 14 22 28 mA
Switch-off voltage
V5 < 1.9 V VQ 7 1.3 1.5 1.8 V
Switch-off voltage
V5 < 1.9 V V4 1.8 2.1 2.5 V
Blocking input
V1 V
Blocking voltage ------ – 0.1 -----1-
Vcont = 0 V V5 2 2 V
Supply voltage blocked for V8 V4 6.7 7.4 7.8 V
Vcont = 0 V
V1 off (with further reduction of V9) ∆V9 0.3 0.6 1.0 V
Characteristics
TA = 25 ˚C; according to measurement circuit 2
Parameter Symbol Limit Values Unit
min. typ. max.
Switching time (secondary voltage) tON 350 450 ms
Voltage variation S3 = closed
∆N3 = 20 W ∆V2 sec 100 500 mV
Voltage variation S2 = closed
∆N3 = 15 W ∆V2 sec 500 1000 mV
Standby operation S1 = open
secondary useful load = 3 W ∆V2 sec 20 30 V
f 70 75 – kHz
Semiconductor Group 15
TDA 4601
Circuit Diagram
Semiconductor Group 16
TDA 4601
Semiconductor Group 17
TDA 4601
Application Circuit 2
Semiconductor Group 18
TDA 4601
Semiconductor Group 19
TDA 4601
Semiconductor Group 20
TDA 4601
Semiconductor Group 21
TDA 4601
Further Applications
Application Circuit 3
Semiconductor Group 22
TDA 4601
Technical Data
Parameter Symbol Limit Values Unit
Breakdown voltage at TA = 60 ˚C VBD rms 350 V
Resistance at TA = 25 ˚C R 25 5 kΩ
Resistance tolerance ∆R 25 25 %
Trip current (typ.) IK 20 mA
Residual current at VA max IR 2 mA
Max. application voltage Vop max rms 265 V
Reference temperature (typ.) TREF 190 ˚C
Temperature coefficient (typ.) TC 26 %/K
Max. operating current I max 0.1 A
Storage temperature range Tstg – 25 to 125 ˚C
Semiconductor Group 23
TDA 4601
Application Circuit 4
Semiconductor Group 24
TDA 4601
f = -----------------
1
≈ 500 kHz
2π LC
Semiconductor Group 25
TDA 4601
Application Circuit 5
Semiconductor Group 26
TDA 4601
Semiconductor Group 27
TDA 4601
Application Circuit 6
Semiconductor Group 28
TDA 4601
Semiconductor Group 29
TDA 4601
Application Circuit 7
Semiconductor Group 30
TDA 4601
Wide Range SMPS with Reducing Peak Collector Current IC BU 208 for Rising Line Voltage
(variable point of return)
Wide range SMPS have to be dimensioned at line voltages of 90 to 260 Vac. The difference
between the maximum collector current I C BU 208 max and the largest possible limit current
IC BU 208 limit which causes magnetic saturation of the flyback transformer and flows through the
primary inductance winding 5/7 is to be determined at Vacmin (IC BU 208 limit ≥ 1.2 x IC BU 208 max).
Then, the transmissible power of the flyback transformer and its value at Vacmax is to be determined.
In the standard circuit the collector current IC BU 208 max is almost constant at the point of return
independent of the line voltage. The transmissible power on the secondary side, however,
increases at the point of return in proportion to the rising rectified line voltage applied (figures 1 and
2).
In the wide range SMPS a line voltage ratio of 270/90 = 3/1 is obtained, causing doubling of the
transmissible power on the secondary side, i.e. in the wide range SMPS a far too large flyback
transformer had to be implemented.
The point of return protecting the SMPS against overloads or short circuits, is derived from the time
constant at pin 4 t 4 = 270 kΩ x 4.7 nF. Thus, the largest possible pulse width is determined.
With the introduction of the 33-kΩ resistor this time constant is reduced as a function of the control
voltage applied to winding 13/15, rectified by diode BY 360 and filtered by the 1-µF capacitance,
which means that the pulse time becomes shorter. By means of the Z-diode C18 the line voltage
level can be defined at which the influence of the time constant correction becomes noticeable. The
change in the rectified voltage of winding 13/15 is proportional to the change in the rectified line
voltage.
At the point of return IC BU 208 the peak collector current has been reduced with the aid of the given
values from 5.2 A at 90 Vac to 3.3 A at 270 Vac. The transmissible power at the point of return
remains stable between 125 and 270 Vac due to the set activation point of the point of return
correction (unbroken curve in figure 2).
Semiconductor Group 31
TDA 4601
Load Characteristics
Figure 1
Figure 2
Semiconductor Group 32