Terminal Regulator

Terminal Regulator. As the name suggests three terminal voltage regulators have three terminals namely input which is unregulated (Vin) regulated output (Vo) and common or a ground terminal These regulators do not require any feedback connections Figure shows the basic the 3 terminal voltage regulator What are the three terminals of a fixed voltage regulator? The three terminals of the IC are for apparent reasons designated with the names input common and output.

The LM 317 is a three terminal positive adjustable voltage regulator and can supply 15A of load current over an adjustable output range of 125v to 37v DualTracking Voltage Regulators A dualtracking regulator is used when splitsupply voltages are needed These provide equal positive and negative output voltages.

Electronic Circuits Regulators

The regulator is normally a separate unit or can be built into the vehicle ECU C (Computer Controlled) This terminal is an input signal from the ECU which controls the charge rate This signal will tell the alternator when to stop/start charging.

3 Terminal Fixed Voltage Regulators Working and Application

Block Diagram of 3 Terminal IC based Voltage Regulator Fixed Voltage Regulators These regulators provide a constant output voltage A popular example is the 7805 IC which Adjustable Voltage Regulator An adjustable voltage regulator is a kind of regulator whose regulated output voltage can.

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Types of 78Xx Series RegulatorsMain FeaturesPower DissipationHow to Apply Heatsink to 78Xx IcsApplication CircuitsIncreasing Current CapacityThe most popular and widely used types of fixed voltage monolithic voltage regulators are the 78XX series positive regulators and the 79XX series negative regulators These are found with 3 output current specifications They provide you with 9 positive types and nine 9 negative types of variants as revealed in the chart below These 78XX series of ICs come with additional voltage ratings both in positive and negative forms Standard ranges for these 78XX regulators are 8 V 9 V 10 V 18 V 20 V and 24 V which correspond to ICs 7808 7809 7810 7818 7820 7824 ICs Many of these devices carry suffix characters or figures with their printed number depending on the manufacturer or the brand type However all of them are essentially the same with identical rating Several part dealres will not actually promote these ICs by type number rather just point out their polarity voltage and current specs and occasionally with reference to their package style These ICs feature inbuilt current limiting and short circuit protection for the output load In medium and high power 78XX series of regulators this feature is generally of the foldback type Foldback current limiting is a condition in which an output overload is simply not responded by the output current due to an automatic current limiting When you use these 78XX regulator ICs you must remember that these ICs are rated to handle only a finite amount of power dissipation Hence under highest output load the input voltage should never be allowed to exceed a few volts higher than the maximum tolerable input limit The maximum power dissipation at normal room temperature (25 degrees Celsius) for the low medium and high power 78XX ranges of devices is 07 watts 1 watt and and 2 watts respectively The above limitation could be significantly improved to 17 watts 5 watts and 15 watts respectively if the devices are mounted on a substantially big heatsink The power dissipated in all these regulator devices is proportionate to the difference between the input and output voltages multiplied by the output current In this situation when the device is fully loaded at around 800 mA the dissipation from the device could be as much as 4 watts (08A x 5V = 4W) This appears to be two times more than maximum permisible 2 watts PD for the 7815 device This implies that the extra 2 watts has to be compensated through a heatsink A broad selection of heatsinks are generally available in the market and these are identified with rating of a particular degrees/watt This rating basically indicates the temperature rise that is caused for every single watt of power dissipated via the heatsink This also indicates that for larger heatsink the degrees per watt will proportionately lower The lowest size of heatsinking necessary for a 78xx regulator device could determined in the following way We have to primarily find out the nominal atmospheric temperature where the device is being used Except if the device is likely to be used in an uncommonly warm surroundings a figure of around 30 degrees Centigrad A typical application circuit of a power supply using a fixed voltage 78XX monolithic voltage regulator can be seen below In this design a 7815 IC is used as the regulator IC which provides us with around +15 volts at approximately 800 mA current The transformer used is rated with 18 0 18V for the secondary with a current rating of 1 amp It is connected to a pushpull full wave rectifier which provides an unloaded voltage of about 27 V Dc after being filtered through C1 Capacitors C2 and C3 work like input and output decoupling capacitors which should be attached relatively closer to the body of the IC When the output load is full you will see the applied input voltage to the IC1 attaining a level at 19 to 20 volts allowing approximately 5 volts difference across the input/output of the regulator Another great modification to a 78XX regulator could be implemented for achieving an increased output current higher than the maximum rating of the device One method of doing this is shown below The indicated R1 and R2 configuration ratio assures that for every milliamp current that passes through R1 D1 and the regulator a bit of current in excess of 4 mA is shifted via Tr1 and R2 As a result when the full 1 amp is used through IC1 we have a current of more than 4 amps passing via Tr1 This situation allows the circuit to deliver a optimum output current which is a bit higher than 5 amps Even in an overload conditions the currents through Tr1 and IC1 continue to have a ratio of somewhat higher than 4 1 therefore the current limiting feature of the IC continues to work without issues Circuits of this form have actually proved to be needless nowadays because of the availability of higher power regulators deviceslike the 78H05 781112 etc that come with a maximum current.