![]() With the Arduino's ADC we will read a value between, next, in the code we map that value from 1 to 244 which are the values used with the analogWrite function of the arduino. With this potentiometer we will choose the output value between 1 and 12 volts since the maximum input voltage in this case is 12V. So the main goal is to learn how the circuit, the feedback and the PWM signal work in order to achive the desired output. As you can see in the schematic above we have a potentiometer connected to the analog input A0. The Arduino NANO already has a 5V linear voltage regulator that will lower the efficiency of the circuit. Sincerely, this circuit has no other sense but to learn. That's why this configuration is called step down converter. So te only posible output will be equal or lower than the input. The duty cycle of the PWM can have values between 0 and 1. So we've obtain that the output is the input multiplied by the duty cycle. That means that the On current is equal to the Off current. Ok, now if we want to obtain the output depending on the input and the duty cycle of the PWM all we have to do is to make the sum of the On and Off current equal to 0. So once again using the next figure formulas we obtain the current of the OFF part. In this case the voltage across the inductor is the output voltage. If the switch is closed again before the inductor fully discharges (on-state), the voltage at the load will always be greater than zero. During the off-state, the inductor is discharging its stored energy into the rest of the circuit. The "increase" in average current makes up for the reduction in voltage, and ideally preserves the power provided to the load. This current, flowing while the input voltage source is disconnected, when concatenated with the current flowing during on-state, totals to current greater than the average input current (being zero during off-state). The stored energy in the inductor's magnetic field supports the current flow through the load. The decreasing current will produce a voltage drop across the inductor (opposite to the drop at on-state), and now the inductor becomes a Current Source. When the switch is opened again (off-state), the voltage source will be removed from the circuit, and the current will decrease. As we can see in the next figure we obtain the ON current through the inductor. But we also know that the inductor voltage is the inductance L multiplied by the inductor current derivate. When the switch is ON the inductor will charge up and the voltage on the inductor will be the difference between the output and the input. If the switch is opened while the current is still changing, then there will always be a voltage drop across the inductor, so the net voltage at the load will always be less than the input voltage source. During this time, the inductor stores energy in the form of a magnetic field. Over time, the rate of change of current decreases, and the voltage across the inductor also then decreases, increasing the voltage at the load. This voltage drop counteracts the voltage of the source and therefore reduces the net voltage across the load. When the switch is first closed (on-state), the current will begin to increase, and the inductor will produce an opposing voltage across its terminals in response to the changing current. In the ON part, the switch is closed as we can see in the next figure where the diode is open becasue the cathode voltage is higher than the anode. In order to study how it works, we will divide it in two stages. We have the Buck converter circuit in the next figure where we can see the switch, inductor and capacitor and of course we add a load to the output. But first let's study a little bit of theory. The switch will be a MOSFET transistor and to create the PWM signal we will use a 555 timer in the PWM configuration, boost adjustable controller or one Arduino NANO. ![]() The circuit is very basic using just one diode, an inductor and a capacitor. In this tutorial we will learn how to build and how a DC to DC buck converter works. To reduce voltage ripple, filters made of capacitors (sometimes in combination with inductors) are normally added to such a converter's output (load-side filter) and input (supply-side filter). It is a class of switched-mode power supply (SMPS) typically containing at least two semiconductors (a diode and a transistor, although modern buck converters frequently replace the diode with a second transistor used for synchronous rectification) and at least one energy storage element, a capacitor, inductor, or the two in combination. A buck converter (step-down converter) is a DC-to-DC power converter which steps down voltage (while stepping up current) from its input (supply) to its output (load).
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