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Billings, chapters 2.17, “The DC-to-DC Transformer Concept,” and 2.20, “DC-to-DC Switching Regulators” John Griffin EE 136 Project December 2003 Professor Zhou/SJSU. Outline. Chap. 2.17 Obsolete DC-to-DC transformer design Modern transistor-switched DC-to-DC transformerChap. 2.20

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Outline

Billings, chapters2.17, “The DC-to-DC Transformer Concept,”and 2.20,“DC-to-DC Switching Regulators”John GriffinEE 136 ProjectDecember 2003Professor Zhou/SJSU


Outline
Outline

  • Chap. 2.17

    • Obsolete DC-to-DC transformer design

    • Modern transistor-switched DC-to-DC transformerChap. 2.20

  • Chapter 2.20

    • Switch mode families

    • Cuk converter

    • Ripple regulator

  • Relevant URLs


Outline

  • Chap. 2.17

    • Obsolete mechanically switched DC-to-DC transformer design

    • Modern transistor-switched DC-to-DC transformerChap. 2.20



Outline

  • Chap. 2.17

    • Obsolete mechanically switched DC-to-DC transformer design

    • Modern transistor-switched DC-to-DC transformerChap. 2.20


Outline
Modern DC-to-DC transformer: self-oscillating, square wave, push-pull converter with bi-phase rectification

  • Advantages: simplicity, low cost, size

  • Disadvantages: inefficient; frequency varies depending on load & input voltage


Dc transformer
DC transformer push-pull converter with bi-phase rectification

  • Frequency can change with input voltage and load changes, but with screening the electromagnetic interference (EMI) that results can be screened out

  • Circuit does not provide regulation, so normally a regulator circuit is added after this circuit’s output


Square wave transformer circuit analysis half cycle 1
Square wave transformer circuit analysis: half-cycle 1 push-pull converter with bi-phase rectification


Square wave transformer circuit analysis transition
Square wave transformer circuit analysis: transition push-pull converter with bi-phase rectification


Square wave transformer circuit analysis half cycle 2
Square wave transformer circuit analysis: half-cycle 2 push-pull converter with bi-phase rectification


Trying to simulate dc transformer
Trying to simulate DC transformer… push-pull converter with bi-phase rectification

  • Simplest representation works fine…


Trying to simulate dc transformer1
Trying to simulate DC transformer… push-pull converter with bi-phase rectification

…partially built circuit works fine; output voltage trace was like that of simpler version…


But for the full circuit simplorer would not cooperate
…but for the full circuit Simplorer would not cooperate push-pull converter with bi-phase rectification

  • Every try led to error, ‘out of memory’, etc., such as pictured here…


And here
…and here. push-pull converter with bi-phase rectification

  • Varying choices of component sizes could not overcome simulator hanging at its first attempt at transformer polarity change


Outline

  • Chap. 2.20 push-pull converter with bi-phase rectification

    • Switch mode families

    • Cuk converter

    • Ripple regulator


Buck boost b b cuk w current signals
Buck, boost, b-b, Cuk, w / current signals push-pull converter with bi-phase rectification


Which type of regulator to choose
Which type of regulator to choose? push-pull converter with bi-phase rectification

For good performance without needing detailed design: “For most applications, for up to about 100 W, go with the CCM [continuous current] flyback. Over 100 W, line-powered and isolated, use either the isolated Cuk topology or a half-bridge, controlled as a PFC [power factor corrector].”

-- Dennis Feucht, power elect. Designer

(article is in list of URLs)


Outline

  • Chap. 2.20 push-pull converter with bi-phase rectification

    • Switch mode families

    • Cuk converter

    • Ripple regulator


History of cuk converter
History of Cuk converter push-pull converter with bi-phase rectification

  • Further work at Caltech, especially by Cuk in his PhD Thesis, produced a fourth member of the basic dc-to-dc switching regulators which has been described as an optimum topology because of its symmetrical structure and non-pulsating input and output currents. The new optimum topology dc-to-dc switching regulator is now commonly known as the Cuk converter after its inventor.


Cuk converter operation
Cuk converter operation push-pull converter with bi-phase rectification

"The Cuk converter is obtained by using the duality principle on the circuit of a buck – boost converter. Similar to the buck – boost, the Cuk provides a negative-polarity regulated output voltage with respect to the common terminal of the input voltage. The most important feature of this topology is the fact that a capacitor, instead of an inductor, is used as the primary means of storing and transferring energy from input to the output. This causes energy transfer to occur during both ON and OFF gated switch intervals. Operation is performed at almost zero ripple current at both the input and output of the circuit. These characteristics make the Cuk converter the closest to an ideal DC power supply of any topology.”

-- "2001 Future Energy Challenge Final Report“, on

inverter design project at UTEP (article in URL list)


Some cuk converter applications
Some Cuk converter applications push-pull converter with bi-phase rectification

  • Magnetic Recording Head Bias

  • Digital camera CCD bias

  • LCD bias

  • GaAs FET bias

  • Positive to negative conversion

    (Source: National Semiconductor LM2611A/B 1.4MHz Cuk Converter data sheet)


Outline

  • Chap. 2.20 push-pull converter with bi-phase rectification

    • Switch mode families

    • Cuk converter

    • Ripple regulator


Ripple regulator purpose action
Ripple regulator purpose, action push-pull converter with bi-phase rectification

  • Strictly limits output voltage ripple to “hysteresis” of op amp comparator

  • Tends to be used with buck converter more than with other types

  • Hysteresis ramp-up and ramp-down voltage are defined by inductor, output capacitor, supply voltage, load current



Outline
Ripple regulator output voltage: magnitude and frequency can be varied by choice of components. Often around 40 mV peak-to-peak.


Hysteretic control of ripple by regulator
Hysteretic control of ripple by regulator be varied by choice of components. Often around 40 mV peak-to-peak.

  • From Texas Instruments design guide for synchronous buck converters: “Although some may see the variable switching frequency of hysteretic control as a drawback, it is usually not a problem. Input voltage, output capacitor ESR, capacitor ESL, and output inductance have the most influence on switching frequency. If the input voltage is regulated within a relatively narrow range, and stable filter components are used, the frequency variation is small. Also, since the output voltage ripple is well controlled, this variation is rarely a problem for overall system operation. In addition to excellent output-voltage regulation and user-adjustable output-voltage ripple, the controller also provides user-adjustable soft-start and overload protection, fixed overvoltage protection, and a logic level enable input.”


Ripple regulator simulation
Ripple regulator simulation be varied by choice of components. Often around 40 mV peak-to-peak.


Ideal and simulated ripple reg output voltage
Ideal and simulated ripple reg. output voltage be varied by choice of components. Often around 40 mV peak-to-peak.

  • Ideal:

  • Simulated: as component values vary, ripple size varies; flat peaks of wave indicate saturation of ripple regulator op amp


Relevant urls billings 2 17 2 20
Relevant URLs / Billings 2.17 & 2.20 be varied by choice of components. Often around 40 mV peak-to-peak.

  • Ripple regulator application (re. 2.17)

    • http://focus.ti.com/lit/ug/slvu007/slvu007.pdf

  • Case study of using a DC-to-DC transformer (re. 2.17)

    • http://www.reed-electronics.com/ednmag/archives/1995/031695/06df4.htm

  • Choosing the right power converter article (re. 2.20)

    • http://www.analogzone.com/col_0106.htm

  • History of swtiched-mode power supplies (re. 2.20)

    • http://www.steve-w.dircon.co.uk/fleadh/mphil/history.htm

  • Lots of Cuk information (re. 2.20)

    • http://www.energychallenge.org/2001Reports/UTEP.pdf

  • Cuk converter applet (re. 2.20)

    • http://www.ece.umr.edu/links/power_electronics/CukConverter.html

  • LM 2611 datasheet (Cuk converter IC) (re. 2.20)

    • http://www.national.com/pf/LM/LM2611.html