Convert Car Charger to USB

Crack Open a USB Car Charger to make it a Variable DC-DC Converter

[Boolean90] hacked a cheap USB car charger into a variable power supply. His proof of concept is to use this as a variable-speed motor controller. The best part is that nothing is being abused, the regulator inside is still running within manufacturer’s spec.

While we’ve seen similar hacks before, [Boolean90]s video is pretty cool and provides a nice insight into the components used in these cheap devices. Rather than a linear regulator, which would dissipate too much heat the device uses a common jelybean MC34063A (PDF) switching DC-DC converter which costs about 10 cents on eBay (about two dollars for twenty, shipped). Here it’s used to step the car batteries 12 volts down to 5, but can also be used in step-up and inverting configurations.

Like all switching buck converters the MC34063A uses a PWM (pulse width modulated) signal to drive an inductor and capacitor, which effectively form an LC filter. By controlling the pulse width, the output voltage can be regulated. [Afrotechmods] has a great tutorial on the basic principle. The regulation is controlled by feedback resistors. [Boolean90] simply added a variable resistor to allow the output voltage to be controlled.

BESTEK 2-Socket Cigarette Lighter Power Adapter DC Outlet Splitter 3.1A Dual USB Car Charger for iPhone6s/6/6 Plus,iPad, Samsung Galaxy S6/S6 Edge and More
Automotive Parts and Accessories (BESTEK)
  • BESTEK Advantage: convert and increase your car cigarette lighter from 1 to 2 sockets as well as 2 USB ports, charging up to 4 devices at once. Excellent Solution...
  • Dual USB Ports with total 3.1A output power for charging your both mobile devices such as iPhone and iPad.
  • 26 inch cord makes it easy for friends in the backseat to grab a charge for their devices
  • Can be used for both 12V DC and 24V DC. Rated Power: 150W. USB Output: 5V DC, 3.1A in total
  • Built-in protective circuits and high quality components prevent the product or your devices from overheating or overloading
DROK DROK 3A/15W Dual Power Adapter 8-22V to 5V Double USB Cable Connector Car Charger For IPhone/iPad/Nokia/HTC
BISS (DROK)
  • Build-in identification resistor for Apple/iPhone/iPad, synchronous rectification, low heat
  • Input Voltage: DC 8-22v;output Voltage: DC 5V
  • Output current: 3A max; output power: 15W max (each USB output 1 5A/7 5W)
  • Protection: reverse polarity protection, overcurrent protection, over temperature protection, short circuit protection
  • Application: use for charging Cell phone, power for electronic device etc

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