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3-Terminal Positive Regulators

3-Terminal Positive Regulators.

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3-Terminal Positive Regulators

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  1. 3-Terminal PositiveRegulators The LM140/LM340A/LM340/LM78XXC monolithic 3-terminal positive voltage regulators employ internal current-limiting, thermal shutdown and safe-area compensation,making them essentially indestructible. If adequate heatsinking is provided, they can deliver over 1.0A output current.They are intended as fixed voltage regulators in a widerange of applications including local (on-card) regulation forelimination of noise and distribution problems associatedwith single-point regulation. In addition to use as fixed voltageregulators, these devices can be used with externalcomponents to obtain adjustable output voltages and currents. Considerable effort was expended to make the entire seriesof regulators easy to use and minimize the number of externalcomponents. It is not necessary to bypass the output,although this does improve transient response. Input bypassingis needed only if the regulator is located far from thefilter capacitor of the power supply.

  2. There are common configurations for 78xx ICs, including 7805 (5 volt), 7806 (6 volt), 7808 (8 volt), 7809 (9 volt), 7810 (10 volt), 7812 (12 volt), 7815 (15 volt), 7818 (18 volt), and 7824 (24 volt) versions. The 7805 is common, as its regulated 5 volt supply provides a convenient power source for most TTL components.

  3. Complete specifications at 1A load • Output voltage tolerances of ±2% at Tj = 25°C and ±4%over the temperature range (LM340A) • Line regulation of 0.01% of VOUT/V of ΔVIN at 1A load • Internal thermal overload protection • Internalshort-circuitcurrent limit • Output transistor safe area protection

  4. Transformer: isolation and voltage conversion • Diode:rectification • Input capacitor(electrolytic): Filter • Input capacitor(AC): AC Filter • 7815: regulator, a constant voltage • Resistance: capacitors to discharge • Output capacitor(electrolytic): to meet high load current

  5. The maximum value of the output voltage of the rectifier • The amount of ripple voltage at the capacitor is, • The minimum value of the output voltage of the rectifier Vdcgmin= Vdcgmax - V • To avoid deterioration of the output voltage VdcgminVdcç + 1 V V = Içmax .Ty / Cg

  6. VF : AC rmsvalue • VAK :Voltagedrop of diode • Vdcg :Inputvoltage at theregulator (DC) • Vdcç:Inputvoltage at theregulator (DC) • Iç : DC outputcurrent • a :Transformerturnratio • V :The amount of ripple voltage at the capacitor • Ty :Halfperiod of the AC main (10 ms) • Cg :Inputcapacitor

  7. Torealize 12 V DC powersupply, a singlephasetransformerwhich is 220/2*12 is usedtoinsulation. Thevoltagedropvalue of thediode is 0,6 V andtheinputcapacitorvalues is 470 F. Theoutputcurrent is 100 mA, • V • Minandmaxvalue of the DC voltage

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