ZVS and ZVT converter techniques

Discussion in 'Electronic Design' started by Winfield Hill, Nov 12, 2003.

  1. Would anyone care to elaborate, contrast, compare, and
    expound on the relationship between the ZVS and ZVT
    dc-dc converter concepts, approaches and technologies?
    Etc., etc. [end, boki-style question.]

    Thanks,
    - Win

    whill_at_picovolt-dot-com
    Winfield Hill, Nov 12, 2003
    #1
    1. Advertising

  2. "Winfield Hill" <> wrote in message
    news:...
    > Would anyone care to elaborate, contrast, compare, and
    > expound on the relationship between the ZVS and ZVT
    > dc-dc converter concepts, approaches and technologies?
    > Etc., etc. [end, boki-style question.]
    >
    > Thanks,
    > - Win
    >
    > whill_at_picovolt-dot-com


    Hi Win,
    ZVT is normally a fixed frequency switching PWM, with rise and fall times
    controlled by LC networks to allow the switches to be changed with zero
    volts across them. ZVS is normally variable frequency switching in which
    one state controls input energy charging and the other state controls the
    stored energy discharging to the output.
    In HS physics class they told us that if you try to move energy from a
    charged input cap to an uncharged output cap with a switch you would loose
    half the energy, conserve charge and generate a lot of EMI. If you add an
    inductor in series with the switch and open the switch at zero current, all
    the energy will be transferred to the output cap with no EMI. Now this
    switch is opened and closed at zero current to allow low losses but ZVS
    normally employs ZCS.

    boki style answer
    harry
    Harry Dellamano, Nov 12, 2003
    #2
    1. Advertising

  3. Harry Dellamano wrote...
    >
    > Winfield Hill wrote ...
    >> Would anyone care to elaborate, contrast, compare, and
    >> expound on the relationship between the ZVS and ZVT
    >> dc-dc converter concepts, approaches and technologies?
    >> Etc., etc. [end, boki-style question.]

    >
    > Hi Win,
    > ZVT is normally a fixed frequency switching PWM, with rise and fall times
    > controlled by LC networks to allow the switches to be changed with zero
    > volts across them. ZVS is normally variable frequency switching in which
    > one state controls input energy charging and the other state controls the
    > stored energy discharging to the output.
    > In HS physics class they told us that if you try to move energy from a
    > charged input cap to an uncharged output cap with a switch you would loose
    > half the energy, conserve charge and generate a lot of EMI. If you add an
    > inductor in series with the switch and open the switch at zero current,
    > all the energy will be transferred to the output cap with no EMI. Now this
    > switch is opened and closed at zero current to allow low losses but ZVS
    > normally employs ZCS.
    >
    > boki style answer
    > harry


    Thanks very much Harry, for your boki-style answer! I should have said
    contrast and compare phase-shift ZVS with ZVT; both are fixed-frequency
    approaches. Actually, Unitrode/TI in discussing the UCC3895 phase-shift
    controller IC calls it ZVT switching, whereas LTC with their new LTC3722
    calls it ZVS switching (or say ZCT and ZCS, as appropriate, natch).

    In one IEEE paper* covering both ZVS and ZVT (few articles use both terms),
    there was a distinction made with "soft switching," another widely-used,
    under-defined term. Elsewhere a suggestion was made that FETs associated
    with ZVS can and should have low-gate-current turnon (given that they're
    really in ZCS mode), yet employ high-current hard-switching turnoff (given
    that full current may be flowing at turnoff). Both these sources showed
    capacitors added across the FETs, not as snubbers (no series resistors,
    etc.), but as circuit elements. Are capacitors key soft-switching parts?

    I'm interested in high-frequencies, e.g. 600kHz, and have been using the
    FET's intrinsic Coss capacitance; although nonlinear, it is natural. :>)
    Another issue is that at high currents we're not really talking resonance
    with 1/4-cycle waveforms, but rather dV/dt = I/C, which results in faster
    rail-rail transition times at high currents and pushes one toward adaptive
    turnon delays. (It should be pointed out that in my present project design
    an over 100:1 power-delivery range is involved. Design for full-power soft
    switching and let the chips fall where they may at low power?)

    More about role of soft-switching ... boki-style responses please!

    * Maria D. Bellar, et. al., "A Review of Soft-Switched DC-AC Converters,"
    IEEE Trans on Ind. Apps, 34 - 4, pg 847-860, July 1998.

    Thanks,
    - Win

    whill_at_picovolt-dot-com
    Winfield Hill, Nov 12, 2003
    #3
  4. Winfield Hill

    Joe Legris Guest

    Winfield Hill wrote:
    > More about role of soft-switching ... boki-style responses please!
    >
    > * Maria D. Bellar, et. al., "A Review of Soft-Switched DC-AC Converters,"
    > IEEE Trans on Ind. Apps, 34 - 4, pg 847-860, July 1998.
    >
    > Thanks,
    > - Win
    >
    > whill_at_picovolt-dot-com
    >


    What is this thing boki-style?

    --
    Joe Legris
    Joe Legris, Nov 12, 2003
    #4
  5. "Winfield Hill" <> wrote in message
    news:...
    > Harry Dellamano wrote...
    > >
    > > Winfield Hill wrote ...
    > >> Would anyone care to elaborate, contrast, compare, and
    > >> expound on the relationship between the ZVS and ZVT
    > >> dc-dc converter concepts, approaches and technologies?
    > >> Etc., etc. [end, boki-style question.]

    > >
    > > Hi Win,
    > > ZVT is normally a fixed frequency switching PWM, with rise and fall

    times
    > > controlled by LC networks to allow the switches to be changed with zero
    > > volts across them. ZVS is normally variable frequency switching in

    which
    > > one state controls input energy charging and the other state controls

    the
    > > stored energy discharging to the output.
    > > In HS physics class they told us that if you try to move energy from a
    > > charged input cap to an uncharged output cap with a switch you would

    loose
    > > half the energy, conserve charge and generate a lot of EMI. If you add

    an
    > > inductor in series with the switch and open the switch at zero current,
    > > all the energy will be transferred to the output cap with no EMI. Now

    this
    > > switch is opened and closed at zero current to allow low losses but ZVS
    > > normally employs ZCS.
    > >
    > > boki style answer
    > > harry

    >
    > Thanks very much Harry, for your boki-style answer! I should have said
    > contrast and compare phase-shift ZVS with ZVT; both are fixed-frequency
    > approaches. Actually, Unitrode/TI in discussing the UCC3895 phase-shift
    > controller IC calls it ZVT switching, whereas LTC with their new LTC3722
    > calls it ZVS switching (or say ZCT and ZCS, as appropriate, natch).
    >
    > In one IEEE paper* covering both ZVS and ZVT (few articles use both

    terms),
    > there was a distinction made with "soft switching," another widely-used,
    > under-defined term. Elsewhere a suggestion was made that FETs associated
    > with ZVS can and should have low-gate-current turnon (given that they're
    > really in ZCS mode), yet employ high-current hard-switching turnoff

    (given
    > that full current may be flowing at turnoff). Both these sources showed
    > capacitors added across the FETs, not as snubbers (no series resistors,
    > etc.), but as circuit elements. Are capacitors key soft-switching parts?
    >
    > I'm interested in high-frequencies, e.g. 600kHz, and have been using the
    > FET's intrinsic Coss capacitance; although nonlinear, it is natural. :>)
    > Another issue is that at high currents we're not really talking resonance
    > with 1/4-cycle waveforms, but rather dV/dt = I/C, which results in faster
    > rail-rail transition times at high currents and pushes one toward

    adaptive
    > turnon delays. (It should be pointed out that in my present project

    design
    > an over 100:1 power-delivery range is involved. Design for full-power

    soft
    > switching and let the chips fall where they may at low power?)
    >
    > More about role of soft-switching ... boki-style responses please!
    >
    > * Maria D. Bellar, et. al., "A Review of Soft-Switched DC-AC Converters,"
    > IEEE Trans on Ind. Apps, 34 - 4, pg 847-860, July 1998.
    >
    > Thanks,
    > - Win


    I'm sticking with ZVS uses frequency modulation for power control and ZVT
    uses fixed frequency PWM but maybe Maria knows best, but only boki knows.
    Look at adding Cds and increasing the circulating current to force this
    added capacity to the other rail thus increasing rise and fall times,
    putting less stress on your driver and generating less EMI. This will
    greatly reduce your FET's turn-off loses with some added conductive losses.
    Since the newer FET's lower Rds_on, the overall efficiency will be improved.
    Nothing like those controlled rise and fall times and the room radio coming
    in crystal clear.
    regards
    harry
    Harry Dellamano, Nov 12, 2003
    #5
  6. Winfield Hill

    Yzordderex Guest

    I've been playing with the older UC3875 part. My plan is to use it to
    modulate a class E resonant ZVS AM transmitter. I have similar
    problem - Have to go from zero current to about 3 amps at 5-10 kHz on
    the output. I'm also playing with the adaptive delay time. I now
    have current sources on the delay set pins which are slaved to the
    input voltage command - messy. I spoke to Unitrode and they agreed
    that this may be one of the applications where curent mode control
    isn't the better way to go. I think the newer 3895 part looks like it
    has an enhanced adaptive delay scheme which should get you down to low
    current switching. I think it looks at peak current and adjust delay.
    The idea of a small capacitor sounds counter productive, but my gut
    is agreeing with you. I'll have to mull that one over.

    regards,
    Bob


    "Harry Dellamano" <> wrote in message news:<kHzsb.35913$>...
    > "Winfield Hill" <> wrote in message
    > news:...
    > > Harry Dellamano wrote...
    > > >
    > > > Winfield Hill wrote ...
    > > >> Would anyone care to elaborate, contrast, compare, and
    > > >> expound on the relationship between the ZVS and ZVT
    > > >> dc-dc converter concepts, approaches and technologies?
    > > >> Etc., etc. [end, boki-style question.]
    > > >
    > > > Hi Win,
    > > > ZVT is normally a fixed frequency switching PWM, with rise and fall

    > times
    > > > controlled by LC networks to allow the switches to be changed with zero
    > > > volts across them. ZVS is normally variable frequency switching in

    > which
    > > > one state controls input energy charging and the other state controls

    > the
    > > > stored energy discharging to the output.
    > > > In HS physics class they told us that if you try to move energy from a
    > > > charged input cap to an uncharged output cap with a switch you would

    > loose
    > > > half the energy, conserve charge and generate a lot of EMI. If you add

    > an
    > > > inductor in series with the switch and open the switch at zero current,
    > > > all the energy will be transferred to the output cap with no EMI. Now

    > this
    > > > switch is opened and closed at zero current to allow low losses but ZVS
    > > > normally employs ZCS.
    > > >
    > > > boki style answer
    > > > harry

    > >
    > > Thanks very much Harry, for your boki-style answer! I should have said
    > > contrast and compare phase-shift ZVS with ZVT; both are fixed-frequency
    > > approaches. Actually, Unitrode/TI in discussing the UCC3895 phase-shift
    > > controller IC calls it ZVT switching, whereas LTC with their new LTC3722
    > > calls it ZVS switching (or say ZCT and ZCS, as appropriate, natch).
    > >
    > > In one IEEE paper* covering both ZVS and ZVT (few articles use both

    > terms),
    > > there was a distinction made with "soft switching," another widely-used,
    > > under-defined term. Elsewhere a suggestion was made that FETs associated
    > > with ZVS can and should have low-gate-current turnon (given that they're
    > > really in ZCS mode), yet employ high-current hard-switching turnoff

    > (given
    > > that full current may be flowing at turnoff). Both these sources showed
    > > capacitors added across the FETs, not as snubbers (no series resistors,
    > > etc.), but as circuit elements. Are capacitors key soft-switching parts?
    > >
    > > I'm interested in high-frequencies, e.g. 600kHz, and have been using the
    > > FET's intrinsic Coss capacitance; although nonlinear, it is natural. :>)
    > > Another issue is that at high currents we're not really talking resonance
    > > with 1/4-cycle waveforms, but rather dV/dt = I/C, which results in faster
    > > rail-rail transition times at high currents and pushes one toward

    > adaptive
    > > turnon delays. (It should be pointed out that in my present project

    > design
    > > an over 100:1 power-delivery range is involved. Design for full-power

    > soft
    > > switching and let the chips fall where they may at low power?)
    > >
    > > More about role of soft-switching ... boki-style responses please!
    > >
    > > * Maria D. Bellar, et. al., "A Review of Soft-Switched DC-AC Converters,"
    > > IEEE Trans on Ind. Apps, 34 - 4, pg 847-860, July 1998.
    > >
    > > Thanks,
    > > - Win

    >
    > I'm sticking with ZVS uses frequency modulation for power control and ZVT
    > uses fixed frequency PWM but maybe Maria knows best, but only boki knows.
    > Look at adding Cds and increasing the circulating current to force this
    > added capacity to the other rail thus increasing rise and fall times,
    > putting less stress on your driver and generating less EMI. This will
    > greatly reduce your FET's turn-off loses with some added conductive losses.
    > Since the newer FET's lower Rds_on, the overall efficiency will be improved.
    > Nothing like those controlled rise and fall times and the room radio coming
    > in crystal clear.
    > regards
    > harry
    Yzordderex, Nov 13, 2003
    #6
  7. Joe:

    [snip]
    > What is this thing boki-style?
    >
    > --
    > Joe Legris

    [snip]

    "boki" is a "well known" USENET poster.

    If you hang on USENET engough and the boki posts you will have your answer.

    --
    Peter
    Consultant
    Indialantic By-the-Sea, FL
    Peter O. Brackett, Nov 13, 2003
    #7
  8. Winfield Hill

    Fred Bloggs Guest

    Winfield Hill wrote:
    > Would anyone care to elaborate, contrast, compare, and
    > expound on the relationship between the ZVS and ZVT
    > dc-dc converter concepts, approaches and technologies?
    > Etc., etc. [end, boki-style question.]
    >
    > Thanks,
    > - Win
    >
    > whill_at_picovolt-dot-com
    >


    See Robert W. Erickson's FoPE- I know you own it-)
    Fred Bloggs, Nov 13, 2003
    #8
  9. Winfield Hill

    Genome Guest

    "Winfield Hill" <> wrote in message
    news:...
    > Would anyone care to elaborate, contrast, compare, and
    > expound on the relationship between the ZVS and ZVT
    > dc-dc converter concepts, approaches and technologies?
    > Etc., etc. [end, boki-style question.]
    >
    > Thanks,
    > - Win
    >
    > whill_at_picovolt-dot-com
    >


    You are looking for Definitions of Acronyms.

    ZVS sounds like zero voltage switching
    ZVT sounds like zero voltage transistions

    Here's another one

    MVS, minimum voltage switching.

    And you might try

    AMVS, adaptive minimum voltage switching.
    Also known as AdMVS.

    While I'm being marketing man I'll also include AdZVS... It just rolls of
    the tongue.

    Just made them up and they are now copyright and trademark me. Genome in
    conjunction with the sign off DNA are also copyright and trademark me, as is
    anything that me does.

    OK

    ZVT is a guess as to when things might give you ZVS. That's your phase
    modulated bridge thing. That's why your latest version of the IC tries to
    cope with some idea of the available energy that is used to stick the switch
    voltage at nuffink.

    It's a bloody hard subject.

    ZVS uses something to look at when the switch has nuffink volts across it
    and turn it on.

    AdZVS knows it can't catch the sweet spot and adjusts itself accordingly.

    PredZVS predicts it on the basis of something else.

    MVS deals with converters that can't reach zero volts on the switch but
    tries to minimise the voltage across the switch when it turns on.

    AdMVS adapts the turn on time to coincide with its idea of when it should
    happen.

    PredMVS adapts the turn on time according to other parameters.

    Lovely, all makes sense now.

    Blarg Blarg, Off to buy some spudsz.

    DNA
    Genome, Nov 13, 2003
    #9
  10. Winfield Hill

    R.Legg Guest

    > In one IEEE paper* covering both ZVS and ZVT (few articles use both terms),
    > there was a distinction made with "soft switching," another widely-used,
    > under-defined term.


    This must have been an interesting exercise in semantics, but the
    terms are used interchangeably, depending mostly on the power level,
    application and school.

    > Elsewhere a suggestion was made that FETs associated
    > with ZVS can and should have low-gate-current turnon (given that they're
    > really in ZCS mode), yet employ high-current hard-switching turnoff (given
    > that full current may be flowing at turnoff). Both these sources showed
    > capacitors added across the FETs, not as snubbers (no series resistors,
    > etc.), but as circuit elements. Are capacitors key soft-switching parts?


    The unavoidable existence of the capacitance makes ZV turn-on a
    desirable feature at higher frequency. When this capacitance becomes a
    required feature for predictable operation, however, it tends to be
    desirable to swamp the strays with known, controlled quantities.

    Current need not be low at the node being switched - in resonant
    converters it may even be at a maximum in the reverse direction, when
    fet gate bias is applied . If reverse transfer capacitance is not
    discharged by the driver, then drive power is reduced. If low dV/dT
    gate drive waveforms are acceptible then resonant gate drive may be
    acceptible - with drive energy being recovered in each cycle.

    >
    > I'm interested in high-frequencies, e.g. 600kHz, and have been using the
    > FET's intrinsic Coss capacitance; although nonlinear, it is natural. :>)
    > Another issue is that at high currents we're not really talking resonance
    > with 1/4-cycle waveforms, but rather dV/dt = I/C, which results in faster
    > rail-rail transition times at high currents and pushes one toward adaptive
    > turnon delays. (It should be pointed out that in my present project design
    > an over 100:1 power-delivery range is involved. Design for full-power soft
    > switching and let the chips fall where they may at low power?)


    Very few practical loads exhibit an operating consumption range that
    approaches 100:1. In critical applications, eating 5% of the rating at
    lighter loads will not affect the thermal profile of the total
    package. Choosing unrealistic or unnecessary goals can be a major
    stumbling block in getting anything constructive done.

    The whole idea behind the design of application-specific power sources
    is to address the application's needs only, realizing a pre-calculated
    commercial benefit.

    RL
    R.Legg, Nov 16, 2003
    #10
  11. Genome wrote ...
    > Winfield wrote ...
    >> Would anyone care to elaborate, contrast, compare, and
    >> expound on the relationship between the ZVS and ZVT
    >> dc-dc converter concepts, approaches and technologies?
    >> Etc., etc. [end, boki-style question.]

    >
    > You are looking for Definitions of Acronyms.
    >
    > ZVS sounds like zero voltage switching
    > ZVT sounds like zero voltage transistions
    >
    > Here's another one
    >
    > MVS, minimum voltage switching.
    >
    > And you might try
    >
    > AMVS, adaptive minimum voltage switching.
    > Also known as AdMVS.
    >
    > While I'm being marketing man I'll also include AdZVS... It just rolls of
    > the tongue.
    >
    > Just made them up and they are now copyright and trademark me. Genome in
    > conjunction with the sign off DNA are also copyright and trademark me, as is
    > anything that me does.
    >
    > OK
    >
    > ZVT is a guess as to when things might give you ZVS. That's your phase
    > modulated bridge thing. That's why your latest version of the IC tries to
    > cope with some idea of the available energy that is used to stick the switch
    > voltage at nuffink.
    >
    > It's a bloody hard subject.
    >
    > ZVS uses something to look at when the switch has nuffink volts across it
    > and turn it on.
    >
    > AdZVS knows it can't catch the sweet spot and adjusts itself accordingly.
    >
    > PredZVS predicts it on the basis of something else.
    >
    > MVS deals with converters that can't reach zero volts on the switch but
    > tries to minimise the voltage across the switch when it turns on.
    >
    > AdMVS adapts the turn on time to coincide with its idea of when it should
    > happen.
    >
    > PredMVS adapts the turn on time according to other parameters.
    >
    > Lovely, all makes sense now.
    >
    > Blarg Blarg, Off to buy some spudsz.
    >
    > DNA


    Thanks DNA, there's gold in that answer, someplace. :>)

    - Win
    Winfield Hill, Nov 16, 2003
    #11
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Vicky
    Replies:
    11
    Views:
    2,547
    ddwyer
    Oct 19, 2003
  2. Lino
    Replies:
    3
    Views:
    562
    DHarper
    Aug 6, 2003
  3. z.s.tar.gz

    Current and Voltage Sensing - Parts/Techniques?

    z.s.tar.gz, Jan 18, 2010, in forum: Datasheets, Schematics, Manuals and Parts
    Replies:
    5
    Views:
    1,551
    (*steve*)
    Jan 24, 2010
  4. abhimanyu671

    9V to 5V converter and 5V to 9V converter

    abhimanyu671, Jun 17, 2010, in forum: Datasheets, Schematics, Manuals and Parts
    Replies:
    1
    Views:
    3,095
    (*steve*)
    Jun 17, 2010
  5. dark night

    Closed loop boost converter using ZVS

    dark night, Nov 19, 2012, in forum: General Electronics Chat
    Replies:
    0
    Views:
    232
    dark night
    Nov 19, 2012
Loading...

Share This Page