Regulated Positive Voltage Booster

Posted on Feb 6, 2014

When Q1 is active, a larger current begins to flow through L1 to GND. When Q1 is switched off, the current through L1 trys to remain the same as it was, causing an increased voltage. By varying the PWM duty cycle, the current through L1 and output voltage can be controlled. There are many ways to explain the relationship between PWM (analog output) and output voltage. The simplest way to put it,

Regulated Positive Voltage Booster
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is that as PWM duty cycle increases, the voltage also increases. This is true when the output load remains constant. What the PWM does is control power, and if output current remains constant, then the voltage increases (P=VI). Alternately, at any given PWM if the output current is reduced, the voltage will increase. Without regulation, the output voltage would change as the load changed. Don`t worry about the gain of the transistor. (I`ve tested 2N3904, 2N2222, 2N4124, etc. ) Connecting it correctly, is all that`s important. When the circuit is powered by batteries or the Arduino, the gain of the transistor will have little effect on ouput power. Also note that even though the transistor is rated for 30Vdc (in most cases), it should be safe to use up to 60Vdc for two reasons. 5V logic on the transistor base doesn`t saturate it, so the voltage drop across the transistor is generally less than 1/2 the circuit output voltage. The second reason is that the voltage rises when the transistor is off and not conducting. By the time the transistor is turned back on, the voltage should have dropped back down closer to the input voltage. This is why most 30V NPNs can handle generating 60V. The exact inductance of L1 doesn`t matter. The circuit is capable of using almost any inductor. Any insulated wire wrapped at least 16 times around metal should work, regardless of the wire`s guage (thickness). I don`t even own an inductance meter,...

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