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TEA2018A
CURRENT MODE SWITCHING POWER SUPPLY CONTROL CIRCUIT
. . . . . . . . . . .
DIRECT DRIVE OF THE EXTERNAL SWITCHING TRANSISTOR POSITIVE AND NEGATIVE OUTPUT CURRENTS UP TO 0.5 A CURRENT LIMITATION TRANSFORMER DEMAGNETIZATION SENSING FULL OVERLOAD AND SHORT-CIRCUIT PROTECTION PROPORTIONAL BASE CURRENT DRIVING LOW STANDBY CURRENT BEFORE STARTING (< 1.6 mA) THERMAL PROTECTION
DESCRIPTION The TEA2018A is an 8-pin DIP low-cost integrated circuit designed for the control of switch mode power supplies. Due to its current mode regulation, the TEA2018A facilitates design of power supplies with following features : High stability regulation loop Automatic input voltage feed-forward in discontinuous mode fly-back Automatic pulse-by-pulse current limitation Typical applications : Video Display Units, TV sets, typewriters, microcomputers and industrialapplications Where synchronization is required, use the TEA2019. For more details, see application note AN406/0591 PIN CONNECTIONS
DIP8 (Plastic Package) ORDER CODE : TEA2018A
OSCILLATOR GROUND COLLECTOR CURRENT SENSING NEGATIVE SUPPLY VOLTAGE
1 2 3 4
8 7 6 5
ERROR AMPLIFIER NON-INVERTING INPUT DEMAGNETIZATION SENSING POSITIVE SUPPLY VOLTAGE
2018A-01.EPS
OUTPUT
May 1993
1/7
TEA2018A
BLOCK DIAGRAM
VCC 6
TEA2018A
IS 7 DEMAGNETIZATION SENSING
V CC INTERNAL BIAS MONITORING
V REF 2.4V
0.1V
VCC "Good"
Undervoltage
Rt
Ct 1
OSCILLATOR
& FLIP-FLOP
Ic RECOPY 5 OUTPUT DELAY 500ns 1
MAXIMUM DUTY CYCLE 70%
& 1
COMPARATOR 8 G 50 2.4V
-1V VOLTAGE LIMITATION
2018A-02.EPS
THERMAL SHUTDOWN
3 I SENSE
2 GROUND
4 V CC
ABSOLUTE MAXIMUM RATINGS
Symbol VCC+ VCCIO(peak) II Tj Toper Tstg Parameter Positive Supply Voltage Negative Supply Voltage Peak Output Current (duty cycle < 5%) Input Current (Pin 3) Junction Temperature Operating Ambient Temperature Range Storage Temperature Range Value 15 -5 1 5 +150 -20, +70 -40, +150 Unit V V A mA o C o C o C
Symbol Rth (j-a)
Parameter Junction-ambient Thermal Resistance
Value 80
Unit
o
C/W
ELECTRICAL OPERATING CHARACTERISTICS Tamb = 25oC, potentials referenced to ground (unless otherwise specified) (see test circuit)
Symbol VCC+ VCCVCC(start) VCC(stop) Parameter Positive Supply Voltage Negative Supply Voltage Minimum Positive Supply Voltage required for starting (VCC+ rising) Minimum Positive Voltage below wich device stops operating (VCC+ falling) Min. 6.6 -1 4.2 Typ. 8 -3 6 4.9 Max. 15 -5 6.6 5.6 Unit V V V V
2/7
2018A-03.TBL
2018A-02.TBL
THERMAL DATA
2018A-01.TBL
TEA2018A
ELECTRICAL OPERATING CHARACTERISTICS Tamb = 25oC, potentials referenced to ground (unless otherwise specified) (see test circuit)
Symbol VCC+ ICC(sb) Vth(IC) R (IC) V7(th) IS max AV II+ VREF VREF T tOSC fOSC T fOSC VCC ton(min) Parameter Hysteresis on VCC+ Threshold Stand-by Supply Current before starting (VCC+ < VCC(start)) Current Limitation Threshold Voltage (Pin 3) Collector Current Sensing Input Resistance Demagnetization Sensing Threshold Demagnetization Sensing Input Current (Pin 7 = 0V) Maximum Duty Cycle Error Amplifier Gain Error Amplifier Input Current (non-inverting input) Internal Reference Voltage Reference Voltage Temperature Drift Oscillator Free-running Period ( R = 59k, C = 1.2nF) Oscillator Frequency Drift with Temperature (VCC+ = +8V) Oscillator Frequency Drift with VCC+ (+8V < VCC+ < +14V) Minimum Conducting Time (Ct = 1nF) 44 Typ. Max. 1.1 1.6 1 1.6 -1100 -1000 -880 1000 75 100 125 1 60 70 50 2 2.3 2.4 2.5 10-4 48 0.05 0.5 2 52 Min. 0.7 Unit V mA mV mV A % A V V/oC s %/ C %/V s
2018A-04.TBL 2018A-03.EPS 2018A-05.TBL
o
RECOMMENDED OPERATING CONDITIONS
Symbol VCC+ VCCIO foper Parameter Positive Supply Voltage Negative Supply Voltage Output Current Operating Frequency Min. Typ. 8 -3 30 Max. Unit V V A kHz
0.5
TEST CIRCUIT
V8 V7 V6
22nF
470
10
22nF 8 7 6 5
TEA2018A
59k 1% 1 2 3 4 22nF 470nF
1.2nF 1%
4.7nF
100
V1
V3
V4
3/7
TEA2018A
GENERAL DESCRIPTION (see application note AN-086) Operating Principles (Figure 1) On every period, the beginning of the conduction time of the transistor is triggered by the fall of the oscillator sawtooth which acts as clock signal. The period Tosc is given by : Tosc 0.66 Ct (Rt + 200) (Tosc in seconds, Ct in Farad, Rt in ) The end of the conduction time is determined by a signal issued from comparing the following signals : a) the sawtooth waveform representing the collector current of the switching transistor, sampled across the emitter shunt resistor, b) the output of the error amplifier. Base Drive - Fast turn-on : On each period, a current pulse ensures fast transistor switch-on. This pulse performs also the ton(min) function at the beginning of the conduction. - Proportional base drive : In order to save power, the positive base current after the starting pulse becomes an image of the collector current. IC The ratio is programmed as follows Figure 2) : IB TEST CIRCUIT
Vi
IC RB = IB Re - Efficient and fast switch-off : When the positive base drive is removed, 1ms (typically) will elapse before the application of negative current therefore allowing a safe and rapid collector current fall. Safety Functions - Overload & short-circuit protection : When the voltage applied to pin 3 exceeds the current limitation threshold voltage [Vth(Ic)], the output flip-flop is reset and the transistor is turned off. The shunt resistor Re must be calculated so as to obtain the current limitation threshold on pin 3 at the maximum allowable collector current. - Demagnetization sensing : This function disables any new conductioncycle of the transistor as long as the core is not completely demagnetized. When not used, pin 7 must be grounded. - ton(max) : Outside the regulation area and in the absence of current limitation, the maximum conduction time is set at about 70 % of the period. - ton(min) : A minimum conducting time is ensured during each period (see Figure 2) - Supply voltage monitoring : The TEA2018A will stop operating if VCC+ on pin 6 falls below the threshold level VCC(stop)
FLIP-FLOP OSCILLATOR ERROR AMPLIFIER VREF ERROR SIGNAL R COMPARATO R Re I C SENSE S IC Q
OUTPUT FILTER
LOAD
OSCILLATOR SAW-TOOTH
t
Error signal
I C (sample)
2018A-04.EPS - 2018A-05.EPS
t
FLIP-FLOP OUTPUT
t
4/7
TEA2018A
Figure 2
IC
COLLECTOR CURRENT I C 0 IC RB TEA2018A 5 IB 3 Re 0 IB IB t on(min) BIAS CURRENT RB Re t IC
2018A-06.EPS
t
SCHEMATICS OF INPUTS AND OUTPUTS
E +
Is
V CC+ Vd + 0.1V
Vo
50A
V CC
7.5k
7.5k
1k
V ref V CC V H = 0.66 V CC th
V L = 0.33 V th
CC 1k
2k
15k
15k
1k
DISCH.
OSC.
GND
Ic
V CC -
5/7
2018A-07.EPS
TEA2018A
Starting Process (Figure 3) Prior to starting, a low current is drawn from the high voltage source through a high value resistor. This current charges the power supply voltage capacitor of the device. No output pulses are available before the voltage on pin 6 has reached the threshold level [VCC(start), Figure 3 : Normal Start-up Sequence
+ V CC
VCC rising]. During this time the TEA2018A draws only 1mA (typically). When the voltage on pin 6 reaches this threshold, base drive pulses appear. The energy drawn by these pulses tends to discharge the power supply storage capacitor. However a hysteresis of about 1.1V (typically) ( VCC) is implemented to avoid the device from stopping. Figure 4 : tON (min.) versus Ct
t
on (min.) (s)
V CC (start)
12
10
6V 4.9V
+ V CC
8 6
V CC (stop)
4
2018A-08.EPS
t
2
C t (nF)
1
2
3
4
5
6
7
8
9
10
TYPICAL APPLICATION
4 x 1N4007 47F 385V 1N41 48 68 BYW98-50 +12V 100 0 F 15 4.7k 0.1F 4.7F 220F 16V 1N414 8
BYW98-50 +5V 470 0 F
RF Filter 2 x 12mH 1k 8 0.1F 47k 0.5A 1 220 V C A 1.2nF 100 2 3 3.9V 4 22k 4.7k 7 6 5
BA 15 9 RB 8.2 BUV 46 A BA 159
2.2k 3W
TEA2018A
10F 150 1nF 1kV
47F Re 1
2018A-10.EPS
Maximum Power 30W Operating Frequency 30kHz
1k 3W
Primary Ground Second ary Ground
6/7
2018A-09.EPS
TEA2018A
PACKAGE MECHANICAL DATA 8 PINS - PLASTIC DIP
e4
A a1
L
I
b1
B B1 b e3 e Z E
Z
D
8
5
F
1
4
Dimensions A a1 B b b1 D E e e3 e4 F i L Z
Min. 0.51 1.15 0.356 0.204 7.95
Millimeters Typ. 3.32
Max.
Min. 0.020 0.045 0.014 0.008 0.313
Inches Typ. 0.131
Max.
1.65 0.55 0.304 10.92 9.75 2.54 7.62 7.62 6.6 5.08 3.81 1.52
0.065 0.022 0.012 0.430 0.384 0.100 0.300 0.300 0260 0.200 0.150 0.060
Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics 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 licence is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of SGS-THOMSON Microelectronics. (c) 1994 SGS-THOMSON Microelectronics - All Rights Reserved Purchase of I2C Components of SGS-THOMSON Microelectronics, conveys a license under the Philips I2C Patent. Rights to use these components in a I2C system, is granted provided that the system conforms to the I2C Standard Specifications as defined by Philips. SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - China - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco The Netherlands - Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A.
7/7
DIP8.TBL
3.18
0.125
PM-DIP8.EPS

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