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voltage regulater
The document discusses various methods for obtaining regulated DC power from AC sources, focusing on the roles of voltage regulators, transformers, and different regulator configurations including linear and switching regulators. It provides a detailed analysis of series and shunt regulators, highlighting their feedback mechanisms for maintaining constant output voltage under varying load conditions. Additionally, it explains the operational principles of switching regulators, emphasizing their efficiency in high-current applications.
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voltage regulater
- 1. UNIT-5 Mohammad Asif Iqbal AssistantProfessor, Deptt of ECE, JETGI, Barabanki
- 2. Have you seenthem ever? In any circuit?
- 3. Introduction • Batteries areoften shown on a schematic diagram as the source of DC voltage but usually the actual DC voltage source is a power supply. • There are many types of power supply. Most are designed to convert high voltage AC mains electricity to a suitable low voltage supply for electronics circuits and other devices. • A more reliable method of obtaining DC power is to transform, rectify, filter and regulate an AC line voltage. • This can be achieved with the help of Voltage Regulators • It converts unregulated power supply into regulated one. • The performance of a voltage regulated circuit is analyzed in terms of its regulation • For better performance of the circuit. % regulation must be as small as possible.
- 4. step-down transformer Rectifier filter Process ofgetting regulated power supply from AC
- 5.
- 6. Series Regulator Circuit(General description) • Control element in series with load between input and output. • Output sample circuit senses a change in output voltage. • Error detector compares sample voltage with reference voltage → causes control element to compensate in order to maintain a constant output voltage.
- 7. Op-Amp Series Regulator Zenerdiode is a constant voltage device or reference voltage R3 is limiting resistance and it will limit the zener current Zener voltage Vz is appearing as voltage at non inverting terminal of op-amp R1 and R2 are potential divider network and 𝑉−= 𝑉0 𝑅2 𝑅1+𝑅2 This voltage 𝑉− is appearing at the inverting input terminal of op-amp. The emitter current 𝐼 𝐸 = 𝑉𝑜 𝑅1+𝑅2 + 𝑉𝑜 𝑅 𝐿 ; if (𝑅1 + 𝑅2)⫺ 𝑅 𝐿 then 𝐼 𝐸 = 𝐼𝐿= 𝑉𝑜 𝑅 𝐿 𝑅 𝐿 Vz 𝑉− 𝑉𝑑= 𝑉𝑧- 𝑉− 𝐼 𝐸 𝑉𝑜1 Control Element Error Detector Sample Circuit
- 8. The difference voltage𝑉𝑑= 𝑉𝑧- 𝑉− appearing at the input terminals of op-amp is very small and it is amplified by the op-amp to get an output voltage 𝑉𝑜1 consideringvirtualshortatop−amp 𝑉+= 𝑉− 𝑉𝑧= 𝑉0 𝑅2 𝑅1+𝑅2 ⇨ 𝑉0= 1 + 𝑅1 𝑅2 𝑉𝑧 𝑅 𝐿 Vz 𝑉− 𝑉𝑑= 𝑉𝑧- 𝑉− 𝑉𝑜1 From this expression it is quite apparent that the output of this circuit doesn't depend on input. It is related with only fixed quantities. That what we were looking for. 𝐼 𝐸= 𝑉𝑜 𝑅 𝐿 Now consider the case, when 𝑉0 tend to increase. 𝑉−= 𝑉0 𝑅2 𝑅1+𝑅2 That will increase 𝑉− That will decrease 𝑉𝑑 And that will decrease 𝑉01 That will decreases 𝐼 𝐸 & hence 𝑉𝑜 will decreases ultimately.
- 9. Shunt Regulator Circuit(General description) • The control element is in parallel with load • The unregulated input voltage provides current to the load. • Some of the current is pulled away by the control element. • If the load voltage tries to change due to a change in the load resistance, the sampling circuit provides a feedback signal to a comparator. • The resulting difference voltage then provides a control signal to vary the amount of the current shunted away from the load to maintain the regulated output voltage across the load.
- 10. Op-Amp Shunt Regulator Thatwill increase 𝑉+ That will increase 𝑉𝑑 And that will increase 𝑉01 Now consider the case, when 𝑉0 tend to increase. Vz 𝑉+ 𝑉𝑑= 𝑉+ − 𝑉𝑧 𝑉𝑜1 𝑉+= 𝑉0 𝑅2 𝑅1+𝑅2 And that will increase 𝐼SH Now, since 𝐼SH+ 𝐼L is constant, this increment in 𝐼SH will ultimately decrease the 𝐼𝐿 and that will decrease 𝑉𝑜
- 11. Switching Regulator Circuit(General description) • The switching regulator is more efficient than the linear series or shunt type. • This type regulator is ideal for high current applications since less power is dissipated. • Basically, a switching regulator passes voltage to the load pulses, which are then filtered to provide a smooth dc voltage. • With switching regulators 90% efficiencies can be achieved.
- 12. Step-Down Configuration Switch Filter Thepulse width oscillation control the operation of switch Q1 as on or off depending on the load requirement Equiva lent Load Switch
- 13. Now consider thecase, when this switch is on Charging Now consider the case, when this switch is off discharging NB 1.The charging and discharging time of capacitor depends on the time, for which transistor is on or off 2. And that time is dependent on the error signal. More the error signal, more the charging. Less the error signal, more discharging..
- 14. Now, lets analyzethe circuit in the case when Vout try to decrease That will decrease 𝑉− It means that the transistor will be on for higher amount of time And that will increase 𝑉01 It will increase the charging time and decrease the discharging time & hence the output voltage Now, lets analyze the circuit in the case when Vout try to increase That will increase 𝑉− And that will decrease 𝑉01 It means that the transistor will be on for smaller amount of time It will decrease the charging time and increase the discharging time & hence the output voltage Another important discussion 𝑑𝑢𝑡𝑦 𝑐𝑦𝑐𝑙𝑒 𝛿 = 𝑡 𝑜𝑛 𝑡 𝑜𝑛 + 𝑡 𝑜𝑓𝑓
- 15. Step-up Configuration 1- whenQ1 is ON 𝑉𝐿 = 𝑉𝑖𝑛-𝑉𝐶𝐸 𝑉𝐶𝐸 Andasthe 𝑉𝐶𝐸 willincrease, 𝑉𝐿 will decrease.Hencelongertheontime ofQ,thesmallerwillbethevoltage acrossL. 2- when Q1 is OFF 𝑉𝐶𝐸=0 Thusvoltage acrosscapacitor =𝑉𝑖𝑛 +𝑉𝐿. Notethis output voltageisgreater thaninput,thatis whythis configurationis knownasstep-up configuration + − +− This polarity will change because Inductor tries to maintain constant current across its terminal, and oppose changes in its current.
- 16. Now, lets analyzethe circuit in the case when Vout try to decrease That will also decrease That will reduce the op-amp output It means that the transistor will be on for smaller amount of time Remember 𝑉𝐿was decreasing with the increase in 𝑉𝐶𝐸. As Q is on for smaller time so the decrease in 𝑉𝐿 will be low, and when transistor will get off this 𝑉𝐿 will be added in 𝑉𝑖𝑛and compensate the decrease in output voltage. Now, lets analyze the circuit in the case when Vout try to increase That will also increase That will increase the op- amp output It means that the transistor will be on for higher amount of time Againrememberthat 𝑉𝐿wasdecreasingwith theincreasein 𝑉𝐶𝐸.AsQ isonforhigheramount oftimesothedecrease in 𝑉𝐿 willbehigh,and whentransistorwillget offthisreduced 𝑉𝐿 will beaddedin 𝑉𝑖𝑛,hence reducingtheoutput voltage.
- 17.