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Sub Woofer amplifier solutions

Sub Woofer amplifier solutions. An introduction. Objectives. Focussed market Quality solution for quality prospects Specific application: Subwoofers Added value for customers Flexible reference designs Ease of design Maintain value Competitive BOM cost.

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Sub Woofer amplifier solutions

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  1. Sub Woofer amplifier solutions An introduction

  2. Objectives • Focussed market • Quality solution for quality prospects • Specific application: Subwoofers • Added value for customers • Flexible reference designs • Ease of design • Maintain value • Competitive BOM cost

  3. Zetex audio product strengths • Audio quality • Value what it sounds like • Value specifications • Power & efficiency in a small space • ‘Mid up’ power (50W to 500W) • Smaller amplifiers & speakers • Smaller PSUs • Less heat • Ease of implementation • Integrated features • Good support • Reference designs

  4. Zetex audio market focus • End product focus • AVR (multi-channel) • Stereo • Subwoofer • High end home theatre • Powered speakers • Distributed audio • Pro-audio • Non focus markets • Very low power: mobile phone, MP3 player • Mid power integrated: flat panel TV, theatre in a box, boom box, PC audio

  5. Zetex subwoofer customer profile • End product brand • Recognised quality product • Sound commercial & technical opportunity • Market influencer • OEM/ODM • Visible good link to end brand • Already building subwoofer • Electronic design capability • Fit • Audio: value performance • Commercial: channel cost, volume match • Technical: specifications, reference designs • Support requirements • Priority vs. capacity (time & effort) • Use of reference designs & demo boards Key point: Try to link these together

  6. Switching amplifier theory • A general recap on Class D • Modulate an input signal with a clock to generate a PWM output • Amplify the PWM signal with an H bridge and filter to recover the analogue power signal • The advantages are: • 90% efficiency (Class AB at 50%) • Less heat dissipation • Smaller PSU • Cost effective solution But it still has to sound good: Zetex does!

  7. Power supply 1000W Audio input 500W 500W Class AB Amplifier Power supply 550W Audio input 50W 500W Class D Amplifier Switching amplifier theory • Class AB • 50% efficiency • For 500W out, need 1kW in • Class D • 90% efficiency • For 500W out, need 550W in Actually in practice PSU can be smaller still. Typical audio content is 1/8 full power (but still must be able to supply short term full power)

  8. Switching amplifier products • All Zetex switching amplifiers are Class D. Two types: • Analogue input • ZXCD Series based • Focus on subwoofer applications • Can still support mid power full band applications • Digital input • DDFATM is the focus (Class Z) • Not ready yet for general release

  9. Analogue input products • Part numbers • ZXCD1000/1010 Focus on: • ZXCD1210 (New for subwoofers) • Reference designs • ZXCD50STEVAL: 50W 4Ω stereo • ZXCD100MOEVAL: 100W 4Ω mono • ZXCDSUBEV series: 150W to 500W 4Ω mono: (New for subwoofers)

  10. Why Class D for subwoofers? • Subs reproduce deep bass in movie soundtracks • Sound you can feel (Explosions, rumbles etc) • Requirement for higher power • The ear is less sensitive to low frequencies • The trend to smaller cabinets and a requirement to reach a high sound pressure level (SPL) • Sealed cabinets offer no resonant assistance at low frequencies • Competition with other speakers (fronts, centre and surrounds) • Subwoofer solution • A separate channel for low frequencies: Front end EQ • A higher power amplifier: Needs class D for efficiency • A self contained amplifier & speaker unit: Includes its own PSU

  11. Subwoofer supply • Home theatre in a box • DVD receiver and speakers together • More likely to be passive subs • Home theatre speaker sets • Higher quality systems • Powered or passive subs • Subwoofer separates (most likely target) • Powered subs • Higher quality systems • Higher power • Custom install

  12. AMP AMP AMP AMP AMP AMP AMP AMP Subwoofer variants • Downward firing drive unit • Front firing drive unit • Sealed or ported • Passive radiator design • Second diaphragm on the back face of the sub • Twin drive unit • Two drivers, possibly each with its own amp • Twin voice coil unit • Single driver, twin coils, twin amps

  13. Power supply Amplifier Front end Audio input Peripherals HP filter (e.g. 10Hz) LP filter (e.g. 250Hz) Mix & volume Phase (e.g. 0 to 180) What’s in a powered sub? • Amplifier • High power & efficiency, cool running: Class D • Good performance: Damping factor, THD+N, DNR • Power supply • Linear vs. switching • Regulated vs. unregulated • Front end processing • Analogue audio input • Volume, phase, LP/HP filter • Peripherals • Short, thermal, DC protection

  14. Left Right Centre Left sur HPF HPF HPF HPF HPF Right sur LFE +10dB LPF Decoded AV source Bass Management LFE Bass M’gement Main channels Frequency Subwoofer bandwidth Where does the signal come from? • LFE signal • Low frequency effects channel • Level preset at +10dB • Bass management signal • Mix of low frequency information filtered from other channels

  15. Subwoofer design issues • Damping factor • Mass of drive unit and coil back EMF makes it difficult to control • Low amplifier output impedance helps significantly • Closed loop designs reduce output impedance • Ratio of load to amplifier output impedance is the damping factor • Power supply • With unregulated supplies, amplifier must accommodate off load voltages and deal with supply dips • Means more headroom in the amp (higher power) and closed loop amp design (PSRR) • Thermal • Subwoofer enclosure plus high power amplifier means lots of heat • High efficiency Class D is essential

  16. Zetex sub reference designs Architecture: • ZXCDSUBEV series (New) • ZXCD1210 based (New) • Opportunity for Zetex FETs • ZXMN10A09L3 in 150W design (New) • Other Zetex FETs in development • Closed loop • BTL (B) and SE (S) designs • All N channel output • Split power supply rail • Optional additional circuits

  17. New modulator: ZXCD1210 New device specification: QFN16 4x4 • ZXCD1210JB16 (New) • Developed for ZXCDSUBEV series of reference designs • Performance matched for ZXCDSUBEV reference designs • QFN SM package • Smaller space (4mm x 4mm) • Thermally efficient (thermal pad) Bottom view

  18. New FETs: ZXMN10A09 New device specification: • ZXMN10A09L3 (New) • Developed for ZXCDSUBEV150S reference design • FETs for the rest of the reference designs under consideration • TO220 package

  19. Solution value Note: guide prices only. Always refer back to your local Zetex office • ZXCDSUBEV BOM cost is approximately $20 in volume • This is low compared to many competitive solutions • Must maintain the value in Zetex BOM content • ZXCD1210 $2 • ZXMN10A09 $0.25 (ea)

  20. ZXCDSUBEV Series Why closed loop: • AC feedback • Reduces THD+N • Increases supply rejection • DC servo • Ensures no DC offset • Feedback after inductor • Increased damping factor for tighter bass

  21. ZXCDSUBEV Series Performance: • Power options: • ZXCDSUBEV500B: 500W into 4 • ZXCDSUBEV250B: 250W into 4 • ZXCDSUBEV150S: 150W into 4 • THD+N @ 1W to 400W 0.05%, • Dynamic range 98dB • Noise floor -135dB • Damping factor >285 • >90% efficiency • Frequency response flat 10Hz to 250Hz (-3dB @ 5kHz)

  22. ZXCDSUBEV150S Single ended (SE) ZXCD1210 ZXMN10A09 ZXCDSUBEV250B Bridge tied load (BTL) ZXCD1210 ZXCDSUBEV500B Bridge tied load (BTL) ZXCD1210 Supply voltage (±V) 40 35 25 75 150 250 500 Output power (W) ZXCDSUBEV Series Power options:

  23. ZXCDSUBEV Series Architecture:

  24. ZXCDSUBEV Series Performance: • THD+N <0.05% @ 1W to 400W

  25. ZXCDSUBEV Series Performance: • Frequency response flat 10Hz to 250Hz

  26. ZXCDSUBEV Series Design flexibility: • Supports PSU options • Unregulated linear: simplest to • Regulated switcher: most efficient • Single platform • One design supports BTL and SE • One design supports power options • Other features added easily • Front end: Volume, phase, high/low pass filters • Protection: Short circuit, thermal, DC

  27. ZXCDSUBEV Series Design flexibility:

  28. Zetex subwoofer platform advantage • High performance solution • Sound quality advantage • High efficiency, cool running • Small size • Cost effective • Single adaptable platform • Flexible power range • System power supply options • Easy addition of value added features

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