Definition, Operation , Working , Buck converter , Step up Configuration ,Step up Regulator Boost converter, Inverter configuration , Buck boost configuration ,Switch mode summary ,Advantages ,Disadvantages and Appplications

1. Definition:-
A voltage regulator that using a switching element to transform a supply
into an alternating current which is then converted to a different voltage
using capacitors ,inductors and other elements ,then converted back to
the DC .The circuit includes regulation and filtering components to
insure a steady current.

2. 1:- Step Down Regulator (Buck Converter)
2:- Step Up Regulator(boost Converter)
3:- Inverting Regulator (Buck Boost
Converter)

3. 
OPERATION:-

4. 
 It uses a transistor as a switch that alternately connects and
disconnects the input voltage to a inductor.
 When the switch is turns ON the input voltage is connected to
the inductor .The difference between input and output voltage
is then forced across the inductor causing current through the
inductor to increase.
 During the ON time the inductor current flows into both load
and the output capacitor (the capacitor charges during this
time).
 When the switch is turns OFF the input voltage applied to the
inductor is removed . Since the current in the inductor cannot
change instantly the voltage across the inductor will adjust to
hold the current constant.
WORKING

6. The input end of the inductor is forced negative in voltage by the
decreasing current , eventually reaching the point where the diode
is turned ON . The inductor current then flows through the load
and back through the diode.
The capacitor discharges into the load during the OFF time,
contributing to the total current being supplied to the load (the
total load current during the switch OFF time is the sum of
inductor and capacitor current. )
The current through the inductor ramps up when switch is ON
and ramps down when switch is OFF . The DC load current from
the regulated output is the average value of the inductor current.

8. 
When output voltage V out is tries to decrease the ON time of Q1
is increased , causing an additional charge on C to offset the
attempted decrease .
The output voltage is expressed as:-
V out =(t on/T)V in
The off time is given by:-
T=t on + t off
When V out tries to increase the ON time of Q1 is decreased ,
causing the capacitor to discharge enough to offset the attempted
increase.

10.  It is also called a “BOOST CONVERTER”
 It takes a DC input voltage and produces a DC out put
voltage that is higher in value then the input (but of the
same polarity).
Step Up Configuration

11. 
Step up Regulator

13. 
Out Put Current And
Load Power
 The important deign of boost converter is that the output load
current and the switch current are not equal , and the
maximum available load current is always less then the current
rating of the switch transistor.
 It should be noted that the maximum to total power available
for conversion in any regulator is equal to the input voltage
multiplied times the maximum average input current .(which is
less then the current rating of the switch transistor.
 Since the output voltage of the BOOST is higher than the
input voltage . It follows that the output current must be lower
than the input current.

14. 
The Inverter
Configuration
 It is also called “BUCK BOOST ” converter.
 It is step up type regulator.
 It takes a DC input voltage and produce a DC output
voltage that is opposite in polarity to the input.
 The negative output voltage can be either larger or smaller
in magnitude than the input voltage.

16. 
Buck Boost Working
 When the switch is ON the input voltage is forced across the
inductor causing an increasing current flow through it .
During the ON time the discharge of the output capacitor is
only the source of load current.
 This requires that the charge is lost from the output capacitor
during the on time be replenished during the OFF time.
 When the switch is turned Off the decreasing current in the
inductor causes the voltage at the diode to swing negative . This
action turns ON the diode allowing the current in the inductor
to supply both the output capacitor and the load.
 The load current is supplied by the inductor when the switch is
OFF and by the output capacitor when the switch is ON