# What kind of circuit is required to increase amperage with variable input voltage?

I am new here and will try to be as specific as possible.

I started doing all kinds of stuff in my car, and wanted to add some led stripes in the interior. I want however that the led stripes are dimming with the rest of the interior lights.

I have found the dimmer line, the voltage varies from 0V (lights out) to 10V -> lights at 100%.

I have tested this with simple LEDs and 4.7 kOhm resistors and everything works correctly. However a whole led stripe will consume considerable more power and I want to make sure that the dimmer doesn't overload / burn.

So I thought I'd build a current amplifier connected to the main 12V of the car (battery line) which takes whatever input voltage the dimmer gives, routes that to the output but with increased current. I've measured the LED stripes at 12 V (10 A should be more than enough to ensure good operation at all voltage levels).

My question is :

How is this circuit called? Can you give me the correct search terms?

Searching for 12V DC amplifier points me to audio amplifier which isn't what I need.

10 A is rather a lot in a car. It's = 12 V x 10 A = 120 W which will be the same as your headlamps.

What you are looking for is a voltage controlled constant current power supply.

Specifications:

• Voltage: 12 V.
• Control voltage: 0 to 10 V.
• Current output: 0 to 10 A (or, if you can split the load, 2 x 0 - 5 A, etc.)

Alternatively you could use a PWM (pulse-width modulation) controller with the full 12 V switched rapidly (faster than the eye can discern) as shown in Figure 1.

Figure 1. PWM signal varying from 80% to 20% to 80% to 0.

Specification:

• Voltage: 12 V.
• Output current: 10 V.
• PWM control: 0 - 10 V. (You could use 0 - 5 V if you divide down your control voltage with a pair of resistors.)
• Are there PWM controllers which can be controlled by voltage? i.e. 0-10V should convert to 0-100% Duty cycle. And in addition how much power can such a controller deliver? – FailedDev Oct 8 '16 at 22:01
• Yes there are and they'll be available from mA to hundreds of amps. – Transistor Oct 8 '16 at 22:10