16-05-2012, 04:40 PM
DC-DC Switching Boost Converter
[attachment=22185]
Introduction
Purpose of the Project
Efficiency, size, and cost are the primary advantages of switching power converters
when compared to linear converters. Switching power converter efficiencies can run
between 70-80%, whereas linear converters are usually 30% efficient. The DC-DC
Switching Boost Converter is designed to provide an efficient method of taking a
given DC voltage supply and boosting it to a desired value.
The voltage source provides the input DC voltage to the switch control, and to the magnetic field storage element. The switch control directs the action of the switching element, while the output rectifier and filter deliver an acceptable DC voltage to the output.
Specifications
Design engineers working in today’s high tech environment have to deal with a rapidly changing market of electronic products and components. As new technology develops, integrated circuits function faster and are smaller in size. However, many integrated circuits still require a voltage of 12 volts in order to function. The DC-DC Switching Boost Converter will take a 5 Volt DC voltage supply with 10 % tolerance and deliver 12 Volts across the load. The maximum output ripple will be 2% of the output voltage, while the maximum current delivered to the load will be 100 mA. The circuit will operate with a minimum efficiency of 70%.
Design Procedures
General Boost Converter Configuration
Several different boost converter designs have been developed in the past. In order to achieve the results specified for this project, the output voltage of the converter
When the transistor is conducting, current is being drawn through the inductor. At this time energy is being stored in the inductor. When the transistor stops conducting the inductor voltage flies back or reverses because the current through the inductor cannot change instantaneously. The voltage across the inductor increases to a value that is higher than the combined voltage across the diode and the output capacitor. As soon as this value is reached, the diode starts conducting and the voltage that appears across the output capacitor, is higher than the input voltage.
Component Functions
The inductor shown in Fig. 2 acts as the magnetic field storage element shown in Fig. 1. It stores energy in its core material. The ideal PWM functions as the switch
control and the transistor acts as the switch element. A diode and an output capacitor are used to perform the function of the output rectifier and filter block.
Design Details
Detailed Circuit Description and Function
The MC33063 control chip manufactured by Motorola was used for the switch control. Appendix 1 shows the data sheet for this control chip. This particular chip was chosen because of the minimum number of external components required to implement the design. The transistor shown in Fig. 2 is internal to the control chip. Therefore, an external switch will not be required. This device also consists of a 1.25 V reference regulator, a comparator, and a controlled duty cycle oscillator. The oscillator charges and discharges an external timing capacitor. The upper threshold of the timing capacitor is equal to the reference regulator voltage of 1.25 V.
[attachment=22185]
Introduction
Purpose of the Project
Efficiency, size, and cost are the primary advantages of switching power converters
when compared to linear converters. Switching power converter efficiencies can run
between 70-80%, whereas linear converters are usually 30% efficient. The DC-DC
Switching Boost Converter is designed to provide an efficient method of taking a
given DC voltage supply and boosting it to a desired value.
The voltage source provides the input DC voltage to the switch control, and to the magnetic field storage element. The switch control directs the action of the switching element, while the output rectifier and filter deliver an acceptable DC voltage to the output.
Specifications
Design engineers working in today’s high tech environment have to deal with a rapidly changing market of electronic products and components. As new technology develops, integrated circuits function faster and are smaller in size. However, many integrated circuits still require a voltage of 12 volts in order to function. The DC-DC Switching Boost Converter will take a 5 Volt DC voltage supply with 10 % tolerance and deliver 12 Volts across the load. The maximum output ripple will be 2% of the output voltage, while the maximum current delivered to the load will be 100 mA. The circuit will operate with a minimum efficiency of 70%.
Design Procedures
General Boost Converter Configuration
Several different boost converter designs have been developed in the past. In order to achieve the results specified for this project, the output voltage of the converter
When the transistor is conducting, current is being drawn through the inductor. At this time energy is being stored in the inductor. When the transistor stops conducting the inductor voltage flies back or reverses because the current through the inductor cannot change instantaneously. The voltage across the inductor increases to a value that is higher than the combined voltage across the diode and the output capacitor. As soon as this value is reached, the diode starts conducting and the voltage that appears across the output capacitor, is higher than the input voltage.
Component Functions
The inductor shown in Fig. 2 acts as the magnetic field storage element shown in Fig. 1. It stores energy in its core material. The ideal PWM functions as the switch
control and the transistor acts as the switch element. A diode and an output capacitor are used to perform the function of the output rectifier and filter block.
Design Details
Detailed Circuit Description and Function
The MC33063 control chip manufactured by Motorola was used for the switch control. Appendix 1 shows the data sheet for this control chip. This particular chip was chosen because of the minimum number of external components required to implement the design. The transistor shown in Fig. 2 is internal to the control chip. Therefore, an external switch will not be required. This device also consists of a 1.25 V reference regulator, a comparator, and a controlled duty cycle oscillator. The oscillator charges and discharges an external timing capacitor. The upper threshold of the timing capacitor is equal to the reference regulator voltage of 1.25 V.