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AN1114 PDF даташит

Спецификация AN1114 изготовлена ​​​​«ST Microelectronics» и имеет функцию, называемую «BURST MODE TRIAC CONTROL».

Детали детали

Номер произв AN1114
Описание BURST MODE TRIAC CONTROL
Производители ST Microelectronics
логотип ST Microelectronics логотип 

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AN1114 Даташит, Описание, Даташиты
AN1114
® APPLICATION NOTE
BURST MODE TRIAC CONTROL BY USING ST52x301
Authors: A. Cucuccio, M. Lo Presti
1. INTRODUCTION
The aim of this application note is to provide a complete hardware schematic and the software routines
for a system using a Triac in Burst mode driven by the peripherals included in the ST52x301 DuaLogic
microcontroller.
www.DataSThheiest4sUy.scotemm is suitable for thermal regulation in home appliance (i.e. heating system) or in industrial ther-
mal controls. In particular, all the parts useful to develop the above-mentioned application are described
hereafter:
a) 1 power supply for ST52x301, from the mains voltage, in order to drive a triac in quadrant 2 and 3;
b) 1 circuit to detect the pre zero-crossing and post zero-crossing of the triac current;
c) 1 general purpose ST52x301 software to manage the application by using FUZZYSTUDIO3.0
software tool.
Note: The load has been supposed as purely ohmic: in this case it is possible to directly check the
main voltage to detect the zero crossing triac current.
Figure 1 . Triac PinOut Notation
L
G
Load
Il
A2
A1
N
January 1999
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AN1114 Даташит, Описание, Даташиты
AN1114 - APPLICATION NOTE
2. SYMMETRICAL BURST MODE CONTROL
By contrast with phase control, based upon power control on the basis of every half-wave, the periodic
pulse-train control system cyclically supplies a certain number of pulses (one period=positive and negati-
ve half-wave) to the load (see following figure).
Figure 2. Periodic Pulse Train
Ton
Tb
1,5
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1
Power 0,5
Line 0
-0,5
-1
-1,5
Triac
Pulses1,5
1
0,5
Load
Power 0
-0,5
-1
Toff
The number of periodic pulse trains can be controlled within a given cycle time, thus determining the sup-
plied power.
A periodic pulse train control system is used whenever the load specific time constant increases about
300 ms (heating systems with a power delay or inertia). This system is not appropriate for motor control
or lighting control systems. This triac control method does not produce interferences. This means that no
interference suppression measures is required.
In order to implement this working mode, a flexible peripheral has been included in ST52x301 (please re-
fer to ST52x301 Data Sheet, pages 44/51). When configured for Burst mode triac control, a square
wave, Tb, (Fig. 2) is generated with a duty cycle proportional to the power the user intend to transfer on
the load. A pulse is generated for each zero crossing of the main voltage included in the Ton of the fixed
period.
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AN1114 Даташит, Описание, Даташиты
BURST MODE TRIAC CONTROL BY USING ST52x301
3. POWER SUPPLY
This section, although developed as a result of a typical triac application, can be used as general purpo-
se AC/DC Converter in any application requiring ST52x301. To fire the triac in quadrant 2 and 3, a nega-
tive polarity of G with respect to A1 is required, then a possible solution would be to keep A1 terminal to
Vdd and control the gate pin with negative pulse (Vdd to Gnd transition).
The proposed system allows to obtain two outputs, -1.2V and +5V, by using above all a 6.2V Zener dio-
de and a Darlington transistor. Using the negative output, the use of rail to rail operational amplifiers in si-
gnal conditioning circuit for the analog inputs of ST52x301 will be avoided (working range: 0V to 2.47V)
thus optimizing the overall cost of the application. The described circuit is able to supply up to 50 mA with
the main voltage in the range 180 - 240 Vrms. Figure 3 displays the circuit:
Figure 3. Power Supply Circuit
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2.2uF
C1
400VDC
D1
56
R1
D2
220Volt
2
1
-1.2V
120
R2
Q1
BDX54S
GND
25V
470uF
C4
C2
220uF
16V
6.2V
D3
16V
220uF
C3
The mains voltage drops principally across C1 then we chose a capacitor with a high working voltage
and a small impedence (i.e. big capacity) in order to have enough current to supply the board consump-
tion and to hold the zener over the knee of the voltage-current characteristic. The bigger the capacitor
value is, the higher the current possible to supply will be.
The zener diode provides -6.2V (as regards to the cathode of D3) to the base terminal of the darlington
transistor BDX54S that is used like a voltage stabilizer. Supposing the transistor Q1 is in saturation, the
emitter voltage will be 1.2V (2*Vbe=2*0.6V=1.2V) higher than the base voltage. With this configuration, it
is possible to choose the emitter of Q1 for the GND, the cathode of D3 for the +5V (Vdd) voltage and the
base pin of Q1 for the -1.2V voltage.
An alternative solution (but it does not provide -1.2V supply) is to use a negative voltage regulator as
shown in fig. 4.
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