Buck converter using pic microcontroller and IR2110
Buck converter using pic microcontroller and IR2110 , In this article you will learn everything you need to design a buck converter. you will learn following things in this article
- what is buck converter ?
- how to design buck converter ?
- what are applications of buck converter ?
- how to select components like diode , switch, inductor and capacitor for buck converter ?
- how to select or design gate driver circuit or IC?
- How to use microcontroller for PWM generation?
I hope that after reading this article you will be able to design your own buck converter according to your requirement.
what is buck converter ?
buck converter is non isolated converter which is used to step down DC voltageIt is actually serve the purpose of step down DC transformer. Buck converter is used only for low power applications due to some reasons of efficiency issues, inductor size and capacitor size. It is beyond the scope of this article to discuss what is the reason behind . you can find answer of this question from many books on power electronics.Buck converter have very high efficiency for low power applications
Applications of buck converter ?
There are plenty of application of buck converter in switch mode power supplies and many other. some of the applications are given below
- mppt charge controller
- step down DC converter
- LED drivers
- regulated power supplies and many others.
How to design buck converter ?
In this section you will learn how to design a Buck converter. before designing buck converter you should have a theoretical knowledge of buck converter. how buck converter works and how to calculate value of inductor, capacitor, frequency and duty cycle of switch. If you don’t know anything about buck converter I recommend you to read chapter 5 of M.H Rashid book on power electronics.
Let’s proceed to practical design of Buck converter. A simple circuit diagram of buck converter with control mechanism is shown below.This is a simple circuit diagram of buck converter you have came across many time while reading about Buck converter in plenty of books.But in practical buck converters there are many other components used to get regulated step down voltage.These books don’t discuss the practical implementation of buck converter. After reading this reading you will be able to design buck converter.
In circuit diagram given below inductor, capacitor and diode can be found easily from market. Inductor should be ferrite core or iron core for high current or power applications. Before selection of diode you should take care of turn on and turn off time of diode. Diode switching time from turn on to turn off and vice versa should be fast. I recommend you to use schotty diode, becuase it have fast reverse recovery time and low forward conduction losses. You can also use another switch instead of diode. This type of buck converter is called synchronous buck converter. Another components used in this circuit diagram is switch. Switch is most important component of any dc to dc converter. By controlling turn on and turn off time of switch we actually control voltage at the output of buck converter. Now the question is how to select this switch?
This switch can be any semicondutor device from transistor, MOSFET and IGBT. Selection of these components depends on power rating of buck converter. Usually MOSFET is used in practical buck converters due to its low on state resistance, high switch frequency and high power handling capability. PWM controller shown in circuit diagram is used to control turn on and turn off time of switch. In other words it is uses to control duty cycle of PWM. PWM stands for pulse width modulation. I have posted a separate article on pulse with modulation. If you don’t know about pulse width modulation and duty cycle I recomend you to read following read before reading this article further.
Now let’s move to another componets need to design buck conveter. If you are using MOSFET as a switch, you can use MOSFET either as low side MOSFET driver or high side MOSFET driver. Now you must be thinking why we need of MOSFET driver when MOSFET can be turn on by applying voltage signan to its base. Bcause MOSFETs are voltage controlled devices. They have high gate to source impedence. To get high swithcing speed of MOSFET gate driving circuit is used. Another reason to use gate driver circuit is that if you are using microcontroller for PWM generation, the output of microcontroller PWM is 5 volt and to drive MOSFET we must apply voltage to gate of MOSFET between 10.5 volt to 12 volt. So gate driver circuit is also used to tranaslate voltage level of PWM square wave. Mosfet can be used either in low side or high. If load is connected to source pin of MOSFET it is called high side configurati0n and if load is connected to drain pin of MOSFET it is called low side configuration. There are many gate drivers IC available in market. But we are using IR2110 of international rectifiers as a gate driver of MOSFET. If you want to know more about gate drivers circuits and How to use IR2110 for high side and low side driver of MOSFET check this article.
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