Power regulators for active load. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Regulators of current, voltage, power
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When operating a mains soldering iron, lighting lamp, electric heaters and a number of other energy consumers, it is convenient to be able to control the power supplied to them. For such devices, as a rule, it is not required to have an adjustment of the supplied voltage from zero. After all, it is impossible to solder with a cold soldering iron, and a flickering effect is clearly visible at a lighting lamp at low voltage, which tires the eyesight.
On fig. 1 shows a diagram of a simple electronic regulator operating on one half-wave of mains voltage. Due to this, it provides voltage regulation in the range of 110 ... 215 V.
Fig.1 (click to enlarge)
If the thyristor VS1 is completely closed, only one half-cycle of the mains voltage will pass through the diode VD1. To open the thyristor, short pulses are applied to its control electrode. They are generated by an oscillator assembled on a unijunction transistor VT1. The pulse frequency of such a generator is synchronized with the mains frequency due to the pulsating supply voltage at VT1. And the pulses themselves have a phase shift relative to the time of the transition of the mains voltage through "0". The shift value depends on the values of the capacitor C1 and resistors R5-R6. By adjusting R6, you can change the opening moment of the thyristor, and hence the effective output voltage in the load (the voltage shape for the active load does not matter).
When setting up the circuit, it may be necessary to select the resistor R5 so that when the resistance R6 is zero, the maximum voltage is supplied to the load.
The following details are used in the circuit: resistors of the MLT type or similar (their power is indicated in the diagram); capacitor C1 type K10-17.
Diode VD1 is replaced by any one with a current of at least 3 ... 5 A, for example KD257B; VD2 - for current up to 100 mA. Thyristor VS1 can be used T122-25-6 or T112-10-6, T112-16-6.
The maximum power of the connected load to the regulator is determined by the allowable current through the VD1 diode and the VS1 thyristor (it is better to choose them with a double current margin). For a circuit with the elements indicated on it, the load power Rload = 500 W (in this case, a heat sink for the power switch VS1 is not needed). When the diode is set to a higher current, the load power can be increased up to 2 kW.
For the installation of circuit elements, the topology of the printed circuit board is shown, fig. 2.
Ris.2
The scheme shown in fig. 3, works similarly to that described above, but when turned on, when the regulator R5 is set to the maximum output voltage, due to the use of additional elements VT2, VT3 and C2, it provides a stepwise increase in brightness within 1 ... 2 s.
Fig.3 (click to enlarge)
The process of warming up the filament of the lamp is inertial and an increase in its time reduces the impulse overload.
See other articles Section Regulators of current, voltage, power.
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