Project 1 - Loss calculation for a DC/DC converter-MATLAB

                                                                             Project 1

                                           Loss calculation for a DC/DC converter-MATLAB

                                                                     EV REFRESHER

Q.1

• Extending the learned lessons in previous module, you will be diving into another power electronics concept on your own.

• Design of boost converter, and calculating the loss of different components including power switching device and deriving efficiency of boost converter. This is applicable in power supply industry, electric vehicles etc. where DC-DC converter is required to boost the voltage from DC source. All the aspects of this project with loss calculation, device selection, simulation etc. are industry relevant.

Solution:

BOOST-CONVERTER:

      A boost converter (step-up converter) is a DC-DC power converter that steps up voltage (while stepping down current) from its input (supply) to its output (load).

         It is a class of Switched mode power supply (SMPS) containing at least two semiconductors (a diode and a Transistor) and at least one energy storage element: a capacitor, inductor, or the two in combination.

         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).

                                    Boost Converter Schematic

Simulink Model:

 The following blocks:

• DC Voltage source
• MOSFET
• Diode
• series RLC branch
• Voltage measurement block
• PWM generator
• Display
• Bus selector
• Powergui
• Scope

Conduction Losses:

            Conduction losses are a result of device parasitic resistances impeding the DC current flow in a DC/DC converter. These losses are in direct relationship with the duty cycle.

       When the integrated high-side MOSFET turns on, the load current flows through it. The drain-to-source channel resistance (RDSON) causes power dissipation.

Formula:

                    Conduction Losses: Pc= I² * R *D

were,

p= Power Dissipation

I= Current through MOSFET

R= Resistance in Ohm

D=Duty Cycle= Vout / Vin

Diode losses:

         The diode is forward-biased when the integrated MOSFET turns off. During this time, the inductor current ramps down through the output capacitors, the load and the forward-biased diode. Since the load current is now conducting through the diode, there will be power dissipation in Diode.

This will be calculated by using below

 Formula:

                   Diode Losses: P= Vf * I* (1-D)

were,

Vf= forward voltage

I= Current output

D=Duty Cycle= Vout / Vin

Induction Losses:

  The conduction losses depend on the load current. With heavier loads, the conduction loss in the MOSFET increases and is the dominating factor. Conduction losses plus switching, driver and internal low-dropout regulator (LDO) losses lead to a considerable generation of heat.

 These losses can be calculated by using the below

 Formula:

             Pd= I² * R + {(rl / 12) (D* Vin / F*L)}

were,

I= Current output

D=Duty Cycle= Vout / Vi

F= Frequency

L= Inductance value

Capacitance losses:

        While getting the output through the capacitor we can get some power dissipation in capacitor also.

this power dissipation is determined by using the following

 Formula:

             Pc= {rc* D*(1-D) I² + {rc / 12(1-D)}} *{(Din / C*F)}

were,

I= Current output

D=Duty Cycle= Vout / Vi

F= Frequency

C= Capacitance value

Simulink Model:

Voltage Measurement:

Output: (Scope)

• The output voltage is greater than the input voltage, as shown in the graph above.

• Consequently, the Boost Converter is operating in a proper manner.

• The Below Signal statistics block will show the minimum and highest voltage.

MOSFET VOLTAGE AND CURRENT:

The Mosfet Current Graph will be the top graph from the one above.

The voltage graph will be in the bottom graph.

We can see from the graph that the duty cycle ratio is 0.5.