A simple power regulator on trinistors. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Regulators of current, voltage, power
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The main advantage of power regulators, in which the switching of trinistors occurs at the moment the mains voltage passes through zero, is a low level of interference. To simplify the circuit, these regulators use stepwise regulation of the output power.
In the device described below, a variable resistor is used as a control element. The number of control steps can be changed from four to sixteen with a resolution of 25 to 6,25%, respectively. The minimum of switching interference in the entire range of power regulation ensures the inclusion of the trinistor at an instantaneous mains voltage of about 5 V.
A schematic diagram of an eight-stage power controller (i.e., with a resolution of 12,5%) is shown in fig. 1, timing diagrams - in fig. 2 Pulses with a repetition rate of 100 Hz form a diode bridge VD5 ... VD8, a circuit R4VD3R3 and an element DD2.1 from the mains voltage, and the frequency divider DD1 lowers it to 12,5 Hz. To change the discreteness of regulation, it is necessary to increase (or decrease) the division factor of the divider and by the same number of times, respectively, change the value of the capacitance C1.
Rice. 1. Schematic diagram of the power regulator
Rice. 2. Timing charts
Pulses from the divider switch the RS flip-flop on the elements DD2.2, DD2.3. The voltage at pin 6 of the DD2.3 element will increase exponentially. When a single signal appears on this pin, the trigger will be set to zero (on pin 4 of the DD2.3 element - signal 0). At pin 10 of element DD2.4 there will be a high level signal that will open transistor VT1 and trinistor VS1. The switching of the RS flip-flop to the zero state will occur at the moment when the mains voltage passes through zero. When a single voltage appears at pin 5 of the DD1 counter, capacitor C1 starts charging through the R2VD2R1 circuit. When a low level signal appears at the output of the counter DD1, the capacitor C1 starts to discharge through the circuit R2-VD1-R1. The voltage at the input of the element DD2.3 decreases, and when it becomes less than the threshold, the trigger will stop switching. Thus, by adjusting the ratio of the charging and discharging rate of the capacitor C2 with resistor R1, they change the number of pulses arriving at the base of the transistor VT1, thereby adjusting the power in the load from zero (the engine of the resistor R2 in the upper position according to the circuit) to 100% (the engine in the lower position).
On the decline of the pulse at pin 6 of the DD2.3 element, the RS flip-flop returns to its original state, and the transistor VT1 closes. The trinistor VS1 will close when the load current becomes less than the holding current of the trinistor, i.e. at a moment close to the transition of the mains voltage through zero.
The device used resistors MLT-0,125, R2 - SP-1. Resistor R4 is made up of four MLT-2 resistors connected in parallel. Capacitor C1 - KM-5b, C2 - K50-16. Diodes VD5 ... VD8 - silicon with a reverse voltage of at least 300 V and an average forward current of 10 A. The printed circuit board of the device is shown in fig. 3.
Rice. 3. Regulator printed circuit board
The tuning process can be controlled by an incandescent lamp connected to the output of the device. However, it should be taken into account that for 4-, 8- and 16-step regulators, the current switching frequency in the load will be 25, 12.5, 6.25 Hz, respectively, therefore, only devices with close thermal inertia (soldering irons, electric stoves, etc.) can be used as a load. .).
Author: S. Zolotarev, Dobrush; Publication: cxem.net
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