Power Tips: Power Supplies for Car Audio


When I was in high school, I worked at a local fast food restaurant.  Rather than save the money I earned for college, or something else more practical, I invested in something else - car audio. 

I had a Toyota Corolla with a hatchback. It was a junker (a perfect first car).  Over the course of a couple of years, I saved and upgraded and eventually had a stereo system in my car that was worth more than the car itself.  It was an impressive system and LOUD!  I drove that car all through college and for the first two years I worked at TI.  Eventually, I out grew the car and stereo system, but I still have a place in my heart high performance car audio.

Aftermarket Car Audio system (not mine, but similar!)

The main power source in a car system is the car battery and alternator. It is a 12V system with an alternator that runs at approximately 14.4V. The sound system environment is also pretty nasty in terms of voltage transients.  In order to make the windows shake, you will need a lot of power. 

There are many components to a car audio system: head units, amplifiers, equalizers, etc.  All of these components require power.  For the sake of this blog, we are going to focus on the highest power devices, the amplifiers. The newest amplifiers use class D power stages, which means, the sound system requires a voltage that is higher than the battery or alternator voltage in the car. In this case, a boost power supply makes the most sense. It is not uncommon for a power amplifier to be capable of 500 to 1000W of output power. Operating from a 12V input, the input current for the boost converter with 1000W of output power is close to 100A!

A boost converter with 100A of input current is no simple task.  To make this task easier, you can use one of a number of PowerLab designs and ICs. In order to handle the amount of power, a multiphase approach is necessary.  I wrote a previous blog covering the advantages of a multiphase approach see it here. Based on the high output voltage and power levels, a non-synchronous approach can be used and still achieve efficiencies over 90%. The TPS4009x family of controllers can be used in a 2, 3 or 4 phase boost design. In some cases, a synchronous approach can provide better efficiency with slightly more complexity. The LM5122 is a synchronous boost controller that is capable of multiphase operation.

High power trunk amplifier for automotive block diagram with four phase design.

The block diagram shows a four phase design with 4 x LM5122 devices plus 8 x CSD18501 MOSFETs.  This design is perfect for a high efficiency car audio application. You can find this design in PowerLab along with several others for car audio amplifiers:

PMP2445: TPS40090 + 2x UCC27324 – This design generates 24V at 13A from 8 to 18.5V input.  This is a four phase non synchronous boost design.

PMP4538: TPS40090 + 4x UCC27201 – This design generates 28V at 20A from 11 to 18V input2.  This is a four phase non synchronous boost design.

PMP7837: 4x LM5122 + 8x CSD18501 – This design generates 24V at 450W from 6 to 17V input.  This is a four phase synchronous boost design.  The synchronous operation allows for up 96% efficiency.

Do you ever build your own car audio systems? What has your experience been? What do you think of these designs? 


See all PowerLab Notes here.

  • I have a design which is used in a chemical reaction chamber, and requires 0-36 VDC @ 40 Amps.  The power will be PWM into the Reactor, from 0-100% at a rate of 15KHZ.  Could one of the automotive Boost designs be used to accomplish these design requirements?

    If it can would you recommend the design changes to make this work.

    I have a working PWM control circuit already working.

    I appreciate your assistance in this matter.

  • Hi Jim,

    Thanks for reading the post and the comments.  I think it will be difficult to use the boost in this application.  The boost converter always has to have an output voltage that is higher than the input voltage.  In your requirements you need to go all the way to 0V.  What is the range for the input voltage?

    Thanks,

    Robert

  • Hello Robert,

    This is an excellent post that shows how TI offers full automotive solutions to its customers, including devices for power, computing and signal chain.

    I would like to add that TI's portfolio of Automotive Class-D Audio Amplifiers offer several features including: top of the line power efficiency, Load-Dump Protection (up to 50 V), complete automotive diagnostics suite and compliance to the tough EMC standards of the automotive industry (including CISPR-25).

    Notable new releases, for the automotive infotainment market, include TI's: Single-Ended-input/Quad-channel/25-W Class-D Amplifier TAS5414C-Q1 (www.ti.com/.../tas5414c-q1); Differential-input/Quad-channel/25-W Class-D Amplifier TAS5424C-Q1 (www.ti.com/.../tas5424c-q1) and Stereo/50-W Class-D Amplifier TPA3116D2 (www.ti.com/.../tpa3116d2).