Buck Boost Circuit Using IC 555

Buck Boost Circuit Using IC 555  The post explains explains an universal IC 555 based based buck-boost circuit circuit which can be used for various dierent applications involving ecient power processing requirements

 This highl! ecient and eective eective buck-boost circuit circuit using the work horse horse IC 555 would allow !ou to convert an input source source voltage to an! an! required required degree" either bucked or boosted" as desired #e have alread! learned the concept comprehensivel! through one of m! previous articles where articles where we discussed the versatilit! of this buckboost t!pe of topolog! $s shown in the circuit diagram below %click to enlarge& the con'guration is basicall! a combination of two distinct stages" vi( the upper buck-boost converter stage and the lower IC 555 )#* controller stage  The buck-boost stage stage consists of a mosfet mosfet which acts like like a switch" the inductor which is the main power converting component" the diode which  +ust like the mosfet forms forms a complementar! complementar! switch" and the capacitor capacitor quite like the inductor forms a complementar! power converter device  The mosfet needs to operate through through pulsed triggering triggering so that it alternatel! switches the input voltage , and ,.. across the inductor in response to its gate voltage  Therefore the gate voltage should also  Therefore also be in a pulsed form which is accomplished through a IC555 )#* generator stage  The associated IC555 )#* )#* generator is integrated integrated to the mosfet mosfet for accomplishing the above discussed operation /uring the , time of the mosfet" the input voltage is allowed to pass through the mosfet and is applied right across the inductor  The inductor owing to to its inherent propert! propert! tries to counter counter this sudden in0iction of current b! absorbing and storing the power in it /uring the subsequent ,.. period of the mosfet" the input voltage is shut o b! the mosfet" the inductor now experiences a sudden change in current curr ent from peak to (ero In response" the inductor counters this b! reversing its stored power across the output terminals via the diode which

now acts in the forward biased condition  The above power from the inductor appears with opposite polarit! across the output where the intended load is connected  The capacitor is positioned to store a portion of the power in it" so that it can be used b! the load during the , time of the mosfet when the diode is reverse biased and power cut o across the load  This heps to maintain a stead! and stable voltage across the load during both , and ,.. c!cles of the mosfet  The level of voltage" whether it1s a boosted voltage or bucked voltage depends upon how the mosfet is controlled b! the )#* generator If the mosfet is optimi(ed with higher , time than the ,.. time then the output would generate boosted voltage and vice versa 2owever there ma! be a limit to this" care must be taken not to exceed the , time be!ond the full saturation time of the inductor" and the ,.. time must not be below the minimum saturation time of the inductor .or instance suppose it takes 3ms for the inductor to become full! saturated" the , time in this case can be set within 4 - 3ms" and not be!ond that" This will result in a boost from minimum to maximum depending upon the value of the chosen inductor  The associated pot wit the IC555 )#* generator can be eectivel! tweaked for acquiring an! desired buck-boost voltage at the output  The inductor value is a matter of trial and error" tr! to incorporate as man! winding as possible for acquiring better and ecient results and diverse range

 The above design can be suitabl! upgraded for implementing an automatic output voltage correction with the help of the following medications

 The 67 preset ma! be appropriatel! set initiall! for determining the desired control point