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Pro Class G audio amplifier power supply

gary davies
Prodigy 110 points
Other Parts Discussed in Thread: TAS5631, TAS5630, UCC28950, TPA3255

I need suggested parts to make:

 

Pro Class G audio amplifier power supply

Class G with modulated power rails, 15 volts absolute beyond channel output

 

Outer rails +/- 100 Volts, 20% ripple with full load

Inner rails +/- 50 Volts, 20% ripple with full load

 

When normalized loudspeaker peak power is 5000 Watts, average power would be about 250 Watts over 8 music bar-beats. I was after both positive and negative power factor controller IC’s to make the above power supply. I also want to control the initial switch on in-rush current to the capacitor banks, three seconds to charge up capacitors in the power supply.

I was considering using 2 x 50Hz 500 Watt isolation toroidal transformers to make the power rails.

I don't want to use any electro-mechanical relay's if possible.

  • 0
    Prodigy 5 points
    Hello Gary,
    I don't know of an exact match of a TI reference design to what you are looking for.

    We have this 600W reference design;
    www.ti.com/.../ucc25600evm-644
    Users Guide www.ti.com/.../slou293
    A 600-W, Isolated PFC Power Supply for AVR Amplifiers Based on the TAS5630 and TAS5631

    Does it have the basic elements that you are looking for?
    The output of the supply is not Class G, though it may be a good starting point for a design.
  • 0 in reply to Ed Walker
    Prodigy 110 points

    Hello Ed walker,

     

    Thank you for your suggestion, it is however a long way away from my goal.

     

    I don’t think I am going to get a SMPS with PFC at the power levels I am trying to achieve, 5000 Watts peak power, 250 Watts average power.

     

    I was looking at using two toriodal transformers to make my power rails; I need from Texas Instruments a solution for either design strategy below:

     

    Solution A - preferred

    Capacitor in-rush limiter that uses TRIACS to switch both the 500VA transformers ON, charging the capacitors slowly to avoid in-rush currents over a three-second period.

     

    Solution B

    SMPS with PFC to charge the capacitors up slowly when the amplifier is initially switched ON with the capacitors charged below 100%. Then a TRIAC switches ON the 500VA transformers. The mentioned SMPS with PFC then runs all of the time at upto a hundred watts or so mainly before and sometimes after the main rectifying diodes are conducting to improve power factor.

     

    I have uploaded a schematic that shows transformers, rectifier, and massive capacitors.

    Regards

    Gary Davies

    H5_TRA_TI_0.pdf

  • 0 in reply to gary davies
    Prodigy 5 points

    Well Gary, TI doesn't make Triacs nor the discretes or IC's to control them.

    For Solution A we don't have an example of driving Triacs.
    I suppose it would be possible to have a linear circuit, driving an opto triac (MOC3012) which then controls the Triac phase turn on.
    Again I have no examples of that because it would probably be done with some discretes.

    For Solution B, a PFC will not turn on slowly.
    It is a boost circuit so even without the IC turned on, the rectified AC will be passed directly to the capacitors through the boost diode.
    But you need isolation anyway, PFC does not provide isolation.
    Many PFC's do have inrush limiting on their front end.
    See this Blog for an idea:
    e2e.ti.com/.../powertips-how-to-limit-inrush-current-in-an-ac-dc-power-supply

    A typical TI solution would consist of:
    PFC front end, non isolated boost of course.
    5KW Interleaved CCM Power Factor Correction Converter, 180-264VAC, 400Vout 12 Amps
    http://www.ti.com/tool/PMP4311


    Follow this with a Phase Shifted Full Bridge or other isolated DCDC converter.
    UCC28950 would be the IC used for controlling this. There are a few other similar IC's for Phase Shift Full Bridge.
    The PSFB is a forward converter, and could make all the rails you need.
    And this would be what brings up the output caps on the rails.
    PFSB soft start would be able to slowly charge up those capacitors.

    For high power audio TI has this landing page:
    www.ti.com/.../high-power-audio-amplifiers-greater-than-50W-product.page

    Our Class D TPA3255 is the highest power 600W mono amp we have presently.

  • 0 in reply to Ed Walker
    Prodigy 110 points

    Thankyou Ed Walker,

    I will investigate your recommended products and then procure the parts to build the amplifier, hopefully as eval kits to start.

    I am looking at poly-rail class G amplifiers to take on class-D amplifiers for sound quality.

    Attached is a schematic I am using to show the basic concept.

    Gary0_PolyRail linear PSU_0.pdf

  • 0 in reply to gary davies
    Prodigy 5 points
    Thanks Gary,
    It is an art, designing with discretes, and you circuit looks great.
    I can see current mirrors and how you are controlling the fets.
    Very clever.

    I will close this now, and please use the forum again for discussion.