Lab Variable Symmetric Power Supply circuit 2x30V 3.5A

The diodes around the LM317 & LM337 are used to protect them from accidental short circuits at the output of the power supply or by discharging their electrolytic media, which could damage them.

The positive voltage setting is done with the potentiometer R3, while the negative voltage, which is an LM301. This is connected to the non-inverting input, via a voltage divider, consisting of R4, R5 & R6, to the positive and negative supply voltage.

The inverting input is connected to the earth via a resistor of R9. If for any reason the positive voltage changes, then the LM301 causes exactly equal variation in the negative supply voltage.

The capacitor connected to the legs 1 and 8 prevents the power amplifier from being immobilized. The basic resistors present at the output serve as a load for the operation of the circuit and for discharging the capacitors after the power supply is switched off. The capacitors in the positive and negative output lines, as well as the coils, act as frequency and noise cut-off filters from the devices we feed.

The RF Ripple Factor is calculated by:

RF = VAC / VDC * 100%

Where V_AC or AC voltage component (V_pp / 2) at the specified DC voltage V_DC.

Where V_pp = 2.24 mV thus Vp = 1.12mV or VAC = 1.12mV

And V_DC = 10V

RF = (Ripple Factor) = 1.12 * 10-3 V / 10V * 100%

= 1.12 * 10-4 * 100% = 0.000112%

TABLE OF COMPONENTS