The Buck Step Down Voltage Converter

 

In Dc circuits, the usual inputs are of 5 or 12 volts, but this is not necessarily the desired input and, hence a need for something to step down the dc voltage occurs. For example, we need 3.3v for a microcontroller input. Now, this is simple if we just add a 3.3v line regulator with a 12v rail. Let us say for further clarity that the microcontroller has to power a strip of LEDs. Each LED consumes about 20mA, and a long strip will consume an amp easily. If calculate the power dissipated by the formula

P = (V_in – V_out) * I_out

The power comes out to be 8.7 watts which is a lot and the total efficiency of the circuit comes to be 38 % which is not acceptable. At this point, an engineer would wonder if there is such a device that steps down voltage efficiently.

Introduction to Buck Converters and There Working

A device that can efficiently step down voltage already exists and it’s called a Buck converter or step down voltage regulators. In essence, a Buck converter does the job of a few transistor switches and an inductor.

The Buck converter works similarly to a PWM dimmer. Lights being dimmed by PWM are a good example here, small duty cycle PWM means the load gets a small average voltage and high duty cycle PWM means the voltage seen by the load is high too.  

But this constant fluctuation in the PWM between high voltage and ground is not something delicate loads like ICs and microcontrollers would like. Now connecting an RC filter does give a clean output and is also directly proportional to the PWM duty cycle.

But the drawback of using an RC filter is that it limits the current and the energy wasted is in the form of heat, just like the linear voltage regulator. So to counter this we use an LC filter instead, which changes the resistor with an inductor. So the capacitor resists changes in the voltage and the inductor resists changes in the current resulting in a smooth DC output.

The working of the buck converter can be broken down into two steps

  First, the switch is in the on position letting the current flow to the capacitor, causing it to charge up. However, due to the presence of the inductor between the capacitor and the source, the current is limited, which results in the voltage not increasing instantly across the capacitor hence the voltage never equals the full source voltage during this switching cycle.

Secondly, now the switch is in the open position, now the current across the inductor can’t change instantly so we observe a voltage across it. This voltage charges the capacitor and the load across the diode, maintaining current throughout this cycle.

RD602 Buck Voltage Converter

The RD602 Buck Voltage Converter is a digital signal generator that supports PC software control (windows 7/8/10). The digital power supply can be monitored via a computer. It has the following features

·         12A high current power supply

·         2.4 inch LCD screen

·         Keypad and encoder potentiometer

·         Battery charging terminals

It also has a high precision sampling chip, and the manufacturers keep optimizing the product’s software and hardware algorithm to give stable and accurate measurements. In addition, it comes with overcurrent protection (OCP) and overvoltage protection (OVP), which, when set, will shut down the converter if the output exceeds the set values to protect the load. The data is displayed in numbers and real-time curves.