Power supply with smooth voltage inversion. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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To set up radio-electronic equipment, power reversible electric motors, electromagnets, power supplies with voltage inversion are required. The figure shows a diagram of a simple power supply that allows you to smoothly change the voltage at the load from +Uout to -Uout.
The power supply is based on two adjustable voltage stabilizers DA1, DA2 type mA7805 (LM7805) or their analogue - KR142EN5A(V). Adjusting the output voltage of the stabilizers is interdependent and is carried out by the potentiometer R2. So, when the value of R2 changes, the voltage across the resistor R4 changes from 5 to 10 V; at the same time, the voltage across the resistor R5 changes from 10 to 5 V. Thus, the output voltage at the terminals AB is smoothly regulated from +5 to -5 V.
Adjustment of the device consists in the selection of resistors R1 (P3) until it is obtained on resistors R4 and R5 when adjusting R2 (with the voltage turned off to the required limits of voltage change relative to the common bus - 5 ... 10 V and 10 ... 5 V, respectively.
The minimum value of the load resistance is determined by the ratio Rload 4 Ohm (R5=R10=1 Ohm), resistor dissipation power is 1,5 W, and the maximum load current is 4 mA (when Rload>5 Ohm, the maximum load current is limited to 10 mA).
When Rload drops below the minimum value (up to a short circuit), Uout decreases. There is no damage to integrated circuits.
The circuit can be easily converted to a higher output voltage using the mA7806, mA7809, etc. series of integrated circuits. or their counterparts of the KR142EN5, 8, 9 series. When the potentiometer R2 is made on an annular closed core with diametrically connected contacts and connected to the potentiometer axis through a motor reducer, a slowly changing voltage of a sinusoidal or other form can be obtained at the output of the device.
Author: M. Shustov, Tomsk; Publication: N. Bolshakov, rf.atnn.ru
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