The Boost Converter Optimization

The Boost Converter

Edward Dy Jay Lee

Stevens Institute of Technology

SYS 655 - Robust Engineering Design

Spring 2009

Dr. Caroline Lubert

May 8, 2008

Table of Contents

1 Project Formulation 3

2 Definition of Ideal Function 4

2.1 Input Power 4

2.2 Output Power 4

2.3 Ideal Function Equation 4

3 S/N Ratio 5

4 Noise Factors 5

External 5

Internal 5

5 Noise Strategy 6

6 Control Factors 6

6.1 Duty Cycle 7

6.2 Frequency 7

6.3 Inductance 7

6.4 Capacitance 7

7 Orthogonal Array 8

8 Optimization Experiment 9

9 Data Analysis 10

10 Prediction and Verification 12

10.1 Prediction 12

10.2 Verification 12

11 References 14

List of Figures

Figure 1: PSPICE Schematic of a Boost Converter 3

Figure 2: P-Diagram of the System 8

Figure 3: Duty Cycle Factor Effect 10

Figure 4: Frequency Factor Effect 10

Figure 5: Inductance Factor Effect 11

Figure 6: Capacitance Factor Effect 11

List of Tables

Table 1: Boost Convert Noise Factor 6

Table 2: L9 Orthogonal Array 8

Table 3: Control Factors & Levels 9

Table 4: Parameter Optimization Experiment Results 9

Table 5: Verification Test Results 12

1 Project Formulation

With the rapid advancement of computer and electronics technology in the past few decades, a vast number of newer electronic devices have been developed that required different input voltages to function properly. Engineers started to develop new power supply designs that would be able convert AC voltage to DC voltage as well as convert DC voltages to a higher or lower DC voltage, called DC/DC converters. One such example of a DC/DC converter is the Boost Converter.

The basic function of a boost converter allows a lower DC input voltage to be stepped up to a higher DC voltage. Laws of physics dictate that energy can neither be created nor destroyed. So in the case of the boost converter, the higher DC voltage that is produced by the system means the output current will be lower than the input current. The focus of this design optimization will be the efficiency of the boost converter's power transformation. Efficiency is the most important function of a power supply. Any engineer can create a crude electronic design that can step up or lower a voltage, but the efficiency will not be tolerable. The loss in power will result in poor quality and financial loss for the customer.

Figure 1: PSPICE Schematic of a Boost Converter

Input power and output power is calculated by the formula: Power = Voltage x Current. The power is measured in Watts. The focus of the design optimization will be to maximize the output power so the efficiency of the power supply can be maximized as well. Robust Engineering techniques will be utilized to find the optimum design for the boost converter. The ideal function, control factors, noise, S/N ratio will be discussed in the design optimization. Then the orthogonal array experiment via PSPICE simulation will be conducted. The results of the experiments will be then analyzed and discussed that will lead to a prediction of the optimum design for the boost converter. The optimum design will be then tested to verify the results.

2 Definition of Ideal Function

Ideally, power transmission and power transformation should be one hundred percent efficient. The input power that is applied to the boost converter is fully transmitted and transformed to the converter's output. There are no losses in energy and therefore there is no quality loss on the system.

Power (in) = Power (out)

2.1 Input Power

The total power applied at the input can be measured by using the P=V*I formula. Basically, the voltage (V) is the DC voltage that is supplied by V1 in the schematic and current (I) is the current that is being drawn from V1. After running the circuit's simulation, the applied current can be measured and multiplied with the input voltage to attain the input power applied to the converter.

2.2 Output Power

The output power will be measured from the load resistor (R1) of the circuit. The load resistor acts as an electronic device that is being powered by the boost converter. By measuring the voltage applied at R1, the current can be attained by using Ohm's law: V = I*R. PSPICE will also allow us to directly measure the current running through the load resistor and the output power can be then calculated.

2.3 Ideal Function Equation

The equation for the ideal function is the formula used to measure power efficiency.

Y = Pout/Pin

In the ideal case, the output power is equal to the input power. However, attaining one hundred percent efficiency in a power supply system is not realistic. There are noises that act