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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Discrete phase power controller. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Regulators of current, voltage, power Quite a few schemes have been created to change the power at the load, however, radio amateurs continue to experiment. Although the existing schemes for phase power control, although they attract with their ease of manufacture, they have one significant drawback: with the departure of the voltage amplitude, it is necessary to re-select the triac control elements. In addition, it is not so convenient to regulate the power with a potentiometer; if you need to return to the previously set mode, then you need to connect a voltmeter. Existing discrete control circuits are based on the principle of frequency division, and it is not possible to use such a regulator for incandescent lamps. They are mainly used to control the power of heating elements. The proposed scheme (Fig. 1) is based on the principle of phase power control at the load in a discrete way.
Consider the operation of the circuit with the switch set to position 10. The sinusoidal mains voltage (Fig. 2, a) 50 Hz is current-limited by the resistor R1 and rectified by the diode bridge VD1-VD4 (Fig. 2, b), the pulse frequency doubles, the amplitude at the output of the bridge is approximately 1,4 more than the stabilization voltage of the zener diode VD10 , and hence the supply voltage of the microcircuits.
Sync pulses, limited by resistors R4, R5, are supplied to 1 pin D1.1. At the initial time, pin 1 of the D1.1 chip is a logical zero, as a result, pin 3 of the D1.1 RS flip-flop is a logical unit (Fig. 2, c), which will start the generator on the elements D1.3, D1.4. The generator is tuned to a frequency of 1000 Hz. At the time of connection to the network, 100 Hz pulses, passing through the VD9 diode, will be filtered by the capacitance C2 and stabilized by VD10, the capacitance C3 will start charging, and the counter D2 will be reset. Pulses from the generator will begin to fill the counter D2, after the 10th pulse (Fig. 2, d) a log "11" will appear at pin 2 D1, which will open the transistor VT8 through the resistor R1, as a result of which the optodistor VS1 will be opened and through the diode bridge VD5-VD8 - triac VS2. The power on the load will be minimal due to the opening of the triac at the end of the period (Fig. 2, e). Simultaneously with the opening of the transistor VT1, the RS-trigger D1, D1.1 will be reset through the capacitor C1.2, and the counter D9 will be reset through the resistor R2. The duration of the reset pulse, as well as the opening of the triac, depend on the ratings of R9, R11, C3. If the switch SA1 is set to position 1, then the counter will be reset at the first incoming pulse (Fig. 2, f). In this case, the load power will be maximum. This circuit is shown with one switch and one counter, so the power switching resolution is approximately 10%. For a smoother change in power, it is necessary to install additional meters and switches. All reset inputs are combined, from the output of the first switch, the signal is sent to input "C" of the second counter, etc., from the output of the last switch to resistors R8, R9. It is also necessary to increase the filling frequency of the counters 2, 3, 4 kHz, etc. It is possible to use this circuit to operate at a low voltage of 12 ... 36 V, you only need to change the value of the resistor R1. The power setting accuracy depends mainly on the frequency drift of the generator. If greater accuracy is needed, then a crystal oscillator circuit can be recommended (Fig. 3), unless, of course, the instability of the mains voltage in both voltage and frequency is taken into account.
The device is assembled on a printed circuit board (Fig. 4) with dimensions of 55x80 mm from one-sided foil fiberglass. All parts, except for the switch, are located on the printed circuit board. SA1 is mounted on the front panel of the device.
The cable connecting the switch to the board must be no longer than 25 cm. Details. Any triac in this device can be used, since it depends only on the required regulated power. The design was tested using TO125-12,5 optothyristors. To do this, the LEDs of the optothyristors were connected in series, and the output thyristors were connected in antiparallel, the resistor R6 was replaced by a 220 Ohm resistor. Any VD10 zener diode for a stabilization voltage of 9 ... 15 V. It is possible to replace the 561 series microcircuits with 176 series microcircuits, you just need to set the zener diode to a stabilization voltage of 9 V. It is desirable to use C4 with the least temperature drift. VT1 any of the KT315, KT3102 series. Diodes VD1-VD4, VD9 for voltage 50...300 V and current 100...300 mA. Diodes VD5-VD8 for a voltage of at least 300 V. SA1 of any 1 group with 10 positions. Author: S.M. Abramov
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