DOC PREVIEW
SJSU EE 136 - Converters

This preview shows page 1-2-22-23 out of 23 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 23 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 23 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 23 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 23 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 23 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

Direct-Off-Line Single-Ended Forward Converters and The Right-Half-Plane ZeroDirect-Off-Line Single-Ended Forward ConverterForward converter with energy recovery windingOperating PrinciplesSlide 5Slide 6Slide 7Slide 8Output VoltageSlide 10Circuit SimulationThe Right-Half-Plane ZeroCauses of the RHP ZeroThe RHP Zero A simplified ExplanationEffects of Increasing Duty RatioSlide 16Duty Raito Control EquationsSlide 18Slide 19Current-Mode Control EquationsSlide 21Slide 22Slide 2312/06/200312/06/2003 11Direct-Off-Line Single-Ended Direct-Off-Line Single-Ended Forward ConvertersForward ConvertersandandThe Right-Half-Plane ZeroThe Right-Half-Plane ZeroPresented by:Presented by:Geetpal KaurGeetpal KaurEE136 StudentEE136 Student12/06/200312/06/2003 22Direct-Off-Line Single-Ended Direct-Off-Line Single-Ended Forward ConverterForward ConverterThe power stage of a typical The power stage of a typical single-ended forward convertersingle-ended forward converterLs carries a large DC current Ls carries a large DC current componentcomponentThe term “Choke” is used to The term “Choke” is used to describe this componentdescribe this componentThe general appearance of the The general appearance of the power stage is similar to the power stage is similar to the flyback unitflyback unit12/06/200312/06/2003 33Forward converter with energy Forward converter with energy recovery windingrecovery winding12/06/200312/06/2003 44Operating PrinciplesOperating PrinciplesWhen transistor Q1 turns onWhen transistor Q1 turns onSupply voltage Vcc is applied to Supply voltage Vcc is applied to the primary winding P1the primary winding P1As a result a secondary voltage As a result a secondary voltage Vs is developed and applied to Vs is developed and applied to output rectifier D1 and choke Lsoutput rectifier D1 and choke Ls12/06/200312/06/2003 55Operating PrinciplesOperating PrinciplesThe voltage across the choke Ls The voltage across the choke Ls will be Vs less the output voltage will be Vs less the output voltage VoutVoutThe current in Ls will increase The current in Ls will increase linearly linearly di / dt = (Vs – Vout) / Lsdi / dt = (Vs – Vout) / Ls12/06/200312/06/2003 66Operating PrinciplesOperating PrinciplesAt the end of an on periodAt the end of an on periodQ1 will turn ofQ1 will turn ofSecondary voltages will reverseSecondary voltages will reverseChoke current IChoke current ILL will continue to will continue to flow in the forward directionflow in the forward direction12/06/200312/06/2003 77Operating PrinciplesOperating PrinciplesAs a result diode D2 will turn onAs a result diode D2 will turn onD2 allows the current to D2 allows the current to continue circulating in the loop continue circulating in the loop D2, Ls, Co, and loadD2, Ls, Co, and loadThe voltage across the choke Ls The voltage across the choke Ls will reversewill reverse12/06/200312/06/2003 88Operating PrinciplesOperating PrinciplesThe current in Ls will decreseThe current in Ls will decrese-di / dt = Vout / Ls-di / dt = Vout / Ls12/06/200312/06/2003 99Output VoltageOutput VoltageVVoutout = (V = (Vss * t * tonon) / (t) / (tonon + t + tofof))Vs = secondary voltage, peak VVs = secondary voltage, peak Vton = time that Q1 is conduction, ton = time that Q1 is conduction, µsµs12/06/200312/06/2003 1010Output VoltageOutput Voltagetof = time that Q1 is of, µstof = time that Q1 is of, µsthe ratio:the ratio: ton / (ton + tof)ton / (ton + tof) is called the duty ratiois called the duty ratio12/06/200312/06/2003 1111Circuit SimulationCircuit Simulation12/06/200312/06/2003 1212The Right-Half-Plane ZeroThe Right-Half-Plane ZeroThe difficulty of obtaining a The difficulty of obtaining a good stability margin and good stability margin and high-frequency transient high-frequency transient performance from the performance from the continuous-inductor-mode continuous-inductor-mode flyback and boost convertersflyback and boost converters12/06/200312/06/2003 1313Causes of the RHP ZeroCauses of the RHP ZeroA negative zero in the small-A negative zero in the small-signal duty cycle control to signal duty cycle control to output transfer functionoutput transfer functionThe negative sign locates this The negative sign locates this zero in the right half of the zero in the right half of the complex frequency planecomplex frequency plane12/06/200312/06/2003 1414The RHP ZeroThe RHP ZeroA simplified ExplanationA simplified ExplanationThe right-half-plane (RHP) zero The right-half-plane (RHP) zero has the same 20dB/decade rising has the same 20dB/decade rising gain magnitude as a gain magnitude as a conventional zero, but with 90º conventional zero, but with 90º phase lag instead of lead phase lag instead of lead12/06/200312/06/2003 1515Effects of Increasing Duty RatioEffects of Increasing Duty RatioThe peak inductor current The peak inductor current increases in each switching cycleincreases in each switching cycleThe diode conduction time The diode conduction time decreasesdecreasesThis is the circuit efect which is This is the circuit efect which is mathematically the RHP Zeromathematically the RHP Zero12/06/200312/06/2003 1616The RHP ZeroThe RHP ZeroA simplified ExplanationA simplified Explanation12/06/200312/06/2003 1717Duty Raito Control EquationsDuty Raito Control EquationsThe equations for the flyback The equations for the flyback circuit are developed starting circuit are developed starting with the voltage VL across the with the voltage VL across the inductor:inductor:VVLL = V = ViiD–VD–Vo o (1-D) = (V(1-D) = (Vii+V+Vaa)D – V)D – Voo12/06/200312/06/2003 1818Duty Raito Control EquationsDuty Raito Control EquationsModulating the duty ratio D by a Modulating the duty ratio D by a small AC signal d whose small AC signal d whose frequency is much smaller than frequency is much smaller than the switching frequency the switching frequency generated an ac inductor voltage generated an ac inductor voltage ννLL::ννLL = (Vi + Va)d – = (Vi + Va)d – ννo(1-D) =o(1-D) = (Vi + Vo)d (Vi + Vo)d12/06/200312/06/2003 1919Duty Raito Control EquationsDuty Raito Control EquationsRHP zero frequency:RHP zero frequency: ωωz z = Vi / L IL= Vi / L IL12/06/200312/06/2003 2020Current-Mode Control EquationsCurrent-Mode Control EquationsIo = iL (1-D) – (j Io = iL (1-D) – (j ωω L IL iL) / (Vi + L IL iL) / (Vi + Vo) = Vi iL / (Vi + Vo) -


View Full Document
Download Converters
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Converters and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Converters 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?