The final project for EE 413 will help us practice and effectively implement all the skills we have learned about the design process while keeping in mind sustainability of the system. The DC to DC converter design should receive a range of input voltages, 3V – 20V, and output a constant value of 13.8V. Our program will measure all voltages and currents of the design by supplying the input through the desired range and then calculating the efficiency and regulation of the system.
Defineproject needs and requirements
General Needs:
self-explanatory
accurate
sustainable
rapid operation
consider all users
easy to use
cost efficient
safety
To enhance productivity and efficiently collect data of a power supply, and that we test the full capabilities of a DC to DC converter.
Developspecifications and state constraints
The design for the boost/buck controller will be running at smaller voltages than what industry would normally use. The reason for testing with a smaller range is that the power supply we're using limits the maximum supply voltage to 20V. To account for problems with currents and powers of the system, implementing voltage divider circuits at the load side to maintain a lower current will fix this issue. We must keep the current below 3A to ensure that we don't damage the equipment or receive false readings. Furthermore, it was suggested that we use the keithley power supply since its range extended all the way to 80V, however, the Keithley can only handle 500mA max and that would not meet our needs. Since we are limited to this particular lab equipment with the GPIB interface, we must restrict our testing to these conditions. Though we do have these restrictions, this project should still help, since all the preliminary testing can be completed using the smaller voltage range to see if the electronics are functioning correctly.
Circuit should receive 3 - 20V on the input
Circuit should output a constant value of 13.8V
Test software should display measurements
Voltages, currents, efficiency, and regulation
Maybe ripple
Circuit should comply with all general requirements in the above section
Compared Circuitry: (Method used to Design)
1.) Boost-Buck Converter:
The boost-buck converters allow for a large input voltage range and can hold the output voltage at the desired level with high efficiency. Shown are 2 of the wide range controller chips we found from Linear Technology and from National Semiconductor. LM5118 - 3 - 75V Buck-Boost DC/DC controller LTM4607 - 4.5 - 36Vin, 24Vout High Efficiency Buck-Boost DC/DC µModule
2.) Flyback Converter
The flyback converter has some advantages over the Boost/Buck converters above like the fact that when implemented they isolate the systems electronics from surges in grid power, however, this converter does not allow for a large enough input voltage range to meet our requirements.
3.) Voltage Regulator
4.) Voltage Doubler
5.) Amplifiers
Systems utilizing the ideas 3, 4 and 5 would not work for our specifications. Since we define that the output voltage maintains the value of 13.8V with any input voltage from 3 - 20V, then we cannot use linear devices like these in which the ouput voltage would vary with input voltage.
Chosen Design:
Boost-Buck Converter- LM5118
We needed a large input range for the large range of voltages we expect from the generator attached to the excerise bike.
The LM5118 provided for a larger input range and also used a lot less complicated circuitry in the 2 switch boost-buck design, so we thought the easier path works better for a smaller time frame.
Given more time we should analyze the benefits of Linear Technologies more complicated design to see if there is any real advantage.
We will eventually need to make our system isolated from the wall. There are other options than using a flyback converter for this purpose
We could use an inverter stage after the convert to provide the same effect
Or other isolation techniques
Design Process used in the project:
The design process began by initially defining the scope of the project and the requirements. Since this project will convert energy from a bicycle to electricity for use, the implemented circuit is supposed to take varying voltages from a generator and then output a constant voltage of 13.8V. The range of 3V-20V was selected to meet specifications of that the generator might have. Due to the limiting supply voltage of the power supply in the lab, 20V was the maximum that the circuit will be able to supply for this project. To convert the varying voltages to a constant 13.8V, many designs were considered. After carefully examining the various strategies, we decided to use a buck/boost converter for our design. The next stage was to implement and test the project. Once the project was verified to work, all the documentation was written to support the project.
How the Project Works and What it Does:
It is our goal to create a Boost/Buck converter to help harness the energy that would otherwise be wasted in the new Cal Poly gym. When a person uses a machine, he/she puts energy into that system. In the past, students have created a generator that will capture this energy from the excersie bike, but we still need to convert that varying voltage into a steady useable voltage. To create power the voltage generated must be held constant at a value of 13.8V; this is a major problem since that voltage varies from 0 to around 25V depending on the level of intensity of the user’s workout. Therefore, it is our job to design an electronic system that will boost those voltages from 0 to 13.8V to 13.8V and buck those voltages from 13.8 to 25V down to 13.8V so that the battery is constantly charging during the entire duration of the user’s workout. Benefits for the entire design are obvious: we are making use of energy that would normally stop with the gym equipment, so it is environmentally friendly. We will design the system so is costs the school $0 with hopes of doing even better than that. Also, we will design the system so that it meets general safety requirements, specifically; the system will not pose any threat to shock the user and will tolerate spills on or around the machine without posing a threat to the user.
Schematic:
Figure1: Schematic of our Project
Simulation of a Similar Circuit using LTM4607:
Circuit Used for Simulation (Downloaded from Linear Technology - Simulation Models for LTM4607- Link to model)
Figure 2. Circuit used for Simulation
Input Deck - Netlist for Simulation
This simulation was created by Chris Henry and Henry Ung for Project 3 of EE413.
L1 N001 N002 3.3µ Rser=1m
R1 N004 0 7.5m
R2 0 N008 6.153K
V1 IN 0 5
C1 N010 0 .01µ
R3 N006 N005 100K
C2 IN 0 150µ Rser=35m
C3 IN 0 10µ Rser=20m
C4 OUT 0 180µ Rser=32m x2
R4 N005 N009 4.64K
R5 N009 0 1.21K
R6 IN N003 51K
D1 0 N003 1N750
C5 OUT 0 22µ Rser=5m x2
XU1 N008 OUT 0 N001 IN N002 N004 N004 0 N006 N005 N009 N003 N010 N003 N007 NC_01 0 0 NC_02 LTM4607
Rload OUT 0 10
.model D D
.lib C:\PROGRA~1\LTC\LTSPIC~1\lib\cmp\standard.dio
.tran 10m startup
The equipment that we are using for our final project consists of the Agilent DC power supply, the Agilent multimeter, and the Fluke multimeter. The Agilent multimeter will measure the current and the Fluke multimeter will measure voltages. The reason the Agilent multimeter will be used to be measure the current as opposed to having the Fluke do it is because the Agilent has higher current capabilities than the Fluke does. Since this project is a DC based project, there is no need to use an oscilloscope. The goal of this project is to measure input power, output power and efficiency. Since this is the case, just measuring voltages and currents is all that is needed.
When developing and testing the system, writing the VI’s to ensure that the unit was capable of collecting data was first. After the unit properly acquired data from the instruments, calculations were programmed into the VI for input power, output power and efficiency. The VI was then programmed to output the raw data to a text file.
How does the Test Suite Work:
The test suite takes a starting input voltage, stopping input voltage, a voltage input step, and power supply current limit. After the values are inputted into the VI, the system will calculate input power, output power, and efficiency. It will also graph these values for the user to see. It then programs the instruments to the starting voltage and collects the data for that input voltage. After it completes one iteration, the input voltage increases by the step input and repeats the tests again.
Pedaling patterns: The user may not pedal at a constant rate.
Water Spills: The chassis for the electrical equipment needs to be encased in a water proof capsule.
Ripple Output makes the pedaling jumpy for the user: User needs to experience the normal operation of the exercise bike. The pedals cannot jump in resistance in certain places.
Sustainability Analysis: Explain how your design idea or applications related to the design contribute to or prevent sustainability [6]. Reference [7] and others on Blackboard™ [8]-[20] provide helpful information.
In general, the design idea seems to prevent sustainability of the Earth due to its cost in raw materials, from construction; however, the way the design applies in the world can change that. The DC-DC converter will be used in a system that harnesses the power created by a person riding a stationary bike in a gym. It takes a fluctuating DC voltage created by a generator attached to the wheel of the stationary bike as an input, and converts this fluctuating voltage to a single DC value with small ripple on the output. In this way it helps to create electrical power that would otherwise need to be created in a large power plant that operates completely inefficiently causing destruction to the raw materials in the environment. Furthermore, our design uses a controller that does not require independent rails to operate and will work with only the input from the generator. Thus there will be no cost in power to turn “on” the device. Stated below is a more in-depth analysis of the product’s sustainability qualities.
Consider issues related to Energy, Environment, Economics, and social or political Equity, four “E”s of sustainability.
Energy: Energy is the key issue that our project deals with. The creation of electrical power through clean, green manipulation of an already existing system in which the only by product is sweat. When used in the Cal Poly gym the combined generation of electrical power by all the stationary bikes should create enough power to at least power the LCD screens displaying the video that the users watch. The energy that it would have taken to power these video displays in thus saved and thus the power company needs to create less. Furthermore, the DC-DC converter is self powered, so no power is wasted on powering the electronics.
Environment: The environment benefits greatly from our product. Currently, the most prevailing way to create the electrical power in America is through large power plants that burn fossil fuels. These power plants have a large adverse effect on the environment. They use up the raw materials provided by the Earth and pollute the Earth with harmful by products. Knowing this many people have created “green” ways to create power without harming the environment such as solar, wind, etc. Our project fits as one of these green products. The system creates power from energy that would otherwise be wasted and has no harmful by products other than the materials used in the construction; however, the design will also take this into account and make sure that waste is minimal.
Economics: Economic attributes are obvious in such a design. Using electricity costs money, so once the school starts using our product the school will decrease its need for electricity and thus decrease the amount of money that it spends to power the gym. More to the point, the project will pay itself off and start to pay the school back over its lifetime, so the school will actually make money off of using our design. The power companies will see economic losses from the implementation of the design since the need for power will have diminished, however, we deal on such a small scale they probably will not notice.
Equity: The definition, as described by dictionary.com, of equity is something that is fair and just for all, socially and politically. There may be some problems with equity in our design, since we undercut the power companies profits by making a system that performs the job better than what they have. We do live in a free market, however, and if a better solution to the school’s need for electricity is out there than it is unrealistic to believe that the school would choose the more expensive option. If the power company even complains about the product, it may only serve to make them think of ways to create power in a “green” fashion also. Even though, as previously stated, the small power we are generating will probably go unnoticed by the power companies.
Explain to what extent the design idea embodies the green engineering design principles
Engineer processes and products holistically, use systems analysis, and integrate environmental impact assessment tools.
We will design the system in a way that minimizes environmental impact. The product already generates power in a green fashion, which helps the environment as discussed above, but also we will design the converter so that the waste involved at the end of the lifetime is minimal also.
Conserve and improve natural ecosystems while protecting human health and well-being.
The design reduces the need for electrical power to be generated, thus decreasing the need for people to plunder the world to find more fossil fuels to burn to create more power.
Use life-cycle thinking in all engineering activities.
The application must either be recyclable or must not impact the environment corrosively when moved to a waste facility
Ensure that all material and energy inputs and outputs are as inherently safe and benign as possible.
Since the design idea deals with high voltages and high power, the circuitry must pose no threat to the user in the way of shocking or sparking while operating or just sitting idlely. Also, the application case would have to be designed to not pose any danger to the user. (for example: sharp edges)
Minimize depletion of natural resources.
The system is very small and will use the smallest amount of materials possible to accomplish its goals as a converter of DC voltages.
Strive to prevent waste.
As stated previously, we will choose the materials so that the product will either be recyclable or will decompose quickly in a landfill.
Develop and apply engineering solutions, while being cognizant of local geography, aspirations, and cultures.
It is American culture to want new and improved electronic devices and new ways to provide energy, we will provide that.
Create engineering solutions beyond current or dominant technologies; improve, innovate, and invent (technologies) to achieve sustainability.
We harness the power from an exercise machine to power electronics in the gym.
Actively engage communities and stakeholders in development of engineering solutions.
We have already been recognized by Cal Poly and they will be implementing our design in the new gym expansion taking place soon.
Bill of Materials:
Table 1:Parts required for the project listed with ratings, product numbers, and costs.
PCB Design:
Figure 11: 1st Draft PCB Layout, still need to change traces of higer current's thickness
User Manual:
How to use the prototype and test suite.
Prototype
The Prototype has been designed to require minimal work for the user. The three wires exposed away from the bread board are GND, VIN, and VOUT colored white, red, and black respectively. To setup the circuit the user just connects the system's GND to the GND pin and then connects the VIN to the DC voltage supplied. The regulated voltage is read on the output wire, VOUT.
Test Suite
After connecting the prototype to the test equipment, input a starting voltage ranging from 3V-20V and a stop voltage from 3V-20V. If the starting voltage is greater than the stopping voltage, the step voltage must be a negative properly gather data correctly. If the starting voltage is less than the stopping voltage, the step voltage must be positive. Now, select the proper current limits for the tests (as high as 1.5A). Hit the run button at the top for the software to collect data. Switching data output tab will display real-time data and plot three graphs when the software completes data collection.
How the prototype and test suite work.
Prototype
As seen in the schematic shown above, an input voltage come into the circuit on the VIN wire and the controller chip, LM5118, sense if the voltage is below or above 13.8V. If the voltage is lower than 13.8V the loop containing the top MOSFET in a boost configuration switches on and off until the output reaches the desired voltage, and when the voltage is higher than the 13.8V the loop containing the lower MOSFET creates a Buck configuration that pulls the output voltage down to the desired voltage.
Test Suite
The test suite works by collecting the input voltage, input current, output voltage, and output current. After the software finishes collecting the data, the suite will calculate input power, output power and efficiency. Data also outputs to a text file that excel can import. Under the data output tab, where the graphs are located, there is a sustainable mode. This mode saves CPU resources by not creating an array of data and outputting the values to the graphs on the display.
Troubleshooting
If after inputting all the data into the software, none of the instruments are responding, make sure that all instruments hooked up on the GPIB connection are on. If the instruments do not respond still, restart the computer and retry the software again. If the graphs do plot or the real-time data does not update actively, make sure that sustainable mode is not on by accident. This feature saves CPU resources and energy by not updating the graphs or real-time data.
If no ouput appears in the graphs and realtime data and you wanted to see information, check the sustainability mode button on the front panel.
Still if no output appears then check to make sure the circuit is hooked up correctly as discussed above.
If the current seems to limit at a certain point that you dont want it to, then check the current limit text box on the front panel and make sure the desired limit is inputed.
If your data seems sparse then decrease the size of your increment in the 1st page of the front panel.
The range of the boost-buck converter is only from 3 to 50V, so if your input voltage exceeds this range we cannot be responsible for strange outputs.
Project 3
Chris Henry, cahenry@calpoly.eduHenry Ung, hung@calpoly.edu
Introduction/Objective:
The final project for EE 413 will help us practice and effectively implement all the skills we have learned about the design process while keeping in mind sustainability of the system. The DC to DC converter design should receive a range of input voltages, 3V – 20V, and output a constant value of 13.8V. Our program will measure all voltages and currents of the design by supplying the input through the desired range and then calculating the efficiency and regulation of the system.Define project needs and requirements
General Needs:To enhance productivity and efficiently collect data of a power supply, and that we test the full capabilities of a DC to DC converter.
Develop specifications and state constraints
The design for the boost/buck controller will be running at smaller voltages than what industry would normally use. The reason for testing with a smaller range is that the power supply we're using limits the maximum supply voltage to 20V. To account for problems with currents and powers of the system, implementing voltage divider circuits at the load side to maintain a lower current will fix this issue. We must keep the current below 3A to ensure that we don't damage the equipment or receive false readings. Furthermore, it was suggested that we use the keithley power supply since its range extended all the way to 80V, however, the Keithley can only handle 500mA max and that would not meet our needs. Since we are limited to this particular lab equipment with the GPIB interface, we must restrict our testing to these conditions. Though we do have these restrictions, this project should still help, since all the preliminary testing can be completed using the smaller voltage range to see if the electronics are functioning correctly.Compared Circuitry: (Method used to Design)
1.) Boost-Buck Converter:The boost-buck converters allow for a large input voltage range and can hold the output voltage at the desired level with high efficiency. Shown are 2 of the wide range controller chips we found from Linear Technology and from National Semiconductor.
LM5118 - 3 - 75V Buck-Boost DC/DC controller
LTM4607 - 4.5 - 36Vin, 24Vout High Efficiency Buck-Boost DC/DC µModule
2.) Flyback Converter
The flyback converter has some advantages over the Boost/Buck converters above like the fact that when implemented they isolate the systems electronics from surges in grid power, however, this converter does not allow for a large enough input voltage range to meet our requirements.
3.) Voltage Regulator
4.) Voltage Doubler
5.) Amplifiers
Systems utilizing the ideas 3, 4 and 5 would not work for our specifications. Since we define that the output voltage maintains the value of 13.8V with any input voltage from 3 - 20V, then we cannot use linear devices like these in which the ouput voltage would vary with input voltage.
Chosen Design:
Boost-Buck Converter- LM5118Design Process used in the project:
The design process began by initially defining the scope of the project and the requirements. Since this project will convert energy from a bicycle to electricity for use, the implemented circuit is supposed to take varying voltages from a generator and then output a constant voltage of 13.8V. The range of 3V-20V was selected to meet specifications of that the generator might have. Due to the limiting supply voltage of the power supply in the lab, 20V was the maximum that the circuit will be able to supply for this project. To convert the varying voltages to a constant 13.8V, many designs were considered. After carefully examining the various strategies, we decided to use a buck/boost converter for our design. The next stage was to implement and test the project. Once the project was verified to work, all the documentation was written to support the project.How the Project Works and What it Does:
It is our goal to create a Boost/Buck converter to help harness the energy that would otherwise be wasted in the new Cal Poly gym. When a person uses a machine, he/she puts energy into that system. In the past, students have created a generator that will capture this energy from the excersie bike, but we still need to convert that varying voltage into a steady useable voltage. To create power the voltage generated must be held constant at a value of 13.8V; this is a major problem since that voltage varies from 0 to around 25V depending on the level of intensity of the user’s workout. Therefore, it is our job to design an electronic system that will boost those voltages from 0 to 13.8V to 13.8V and buck those voltages from 13.8 to 25V down to 13.8V so that the battery is constantly charging during the entire duration of the user’s workout. Benefits for the entire design are obvious: we are making use of energy that would normally stop with the gym equipment, so it is environmentally friendly. We will design the system so is costs the school $0 with hopes of doing even better than that. Also, we will design the system so that it meets general safety requirements, specifically; the system will not pose any threat to shock the user and will tolerate spills on or around the machine without posing a threat to the user.Schematic:
Simulation of a Similar Circuit using LTM4607:
Circuit Used for Simulation (Downloaded from Linear Technology - Simulation Models for LTM4607- Link to model)Input Deck - Netlist for Simulation
- This simulation was created by Chris Henry and Henry Ung for Project 3 of EE413.
L1 N001 N002 3.3µ Rser=1mR1 N004 0 7.5m
R2 0 N008 6.153K
V1 IN 0 5
C1 N010 0 .01µ
R3 N006 N005 100K
C2 IN 0 150µ Rser=35m
C3 IN 0 10µ Rser=20m
C4 OUT 0 180µ Rser=32m x2
R4 N005 N009 4.64K
R5 N009 0 1.21K
R6 IN N003 51K
D1 0 N003 1N750
C5 OUT 0 22µ Rser=5m x2
XU1 N008 OUT 0 N001 IN N002 N004 N004 0 N006 N005 N009 N003 N010 N003 N007 NC_01 0 0 NC_02 LTM4607
Rload OUT 0 10
.model D D
.lib C:\PROGRA~1\LTC\LTSPIC~1\lib\cmp\standard.dio
.tran 10m startup
- LTM4607 - 36 VIN, 24 VOUT Buck-Boost DC/DC uModule\nInput: 5V-20V Output: 13.8V @ 1.38A
- Note:\n If the simulation model is not found please update with the "Sync Release" command from the "Tools" menu.\n It remains the customer's responsibility to verify proper and reliable operation in the actual application.\n Component substitution and printed circuit board layout may significantly affect circuit performance or reliability\n Contact your local sales representative for assistance. This circuit is distributed to customers only for use with LTC parts\n Copyright © 2008 Linear Technology Inc. All rights reserved.
.lib LTM4607.sub.backanno
.end
5V Input - With a 10Ohm Load
10V Input - With a 10Ohm Load
20V Input - With a 10 Ohm LoadPictures of the Prototype:
Why we selected the Instruments for the VI:
The equipment that we are using for our final project consists of the Agilent DC power supply, the Agilent multimeter, and the Fluke multimeter. The Agilent multimeter will measure the current and the Fluke multimeter will measure voltages. The reason the Agilent multimeter will be used to be measure the current as opposed to having the Fluke do it is because the Agilent has higher current capabilities than the Fluke does. Since this project is a DC based project, there is no need to use an oscilloscope. The goal of this project is to measure input power, output power and efficiency. Since this is the case, just measuring voltages and currents is all that is needed.
When developing and testing the system, writing the VI’s to ensure that the unit was capable of collecting data was first. After the unit properly acquired data from the instruments, calculations were programmed into the VI for input power, output power and efficiency. The VI was then programmed to output the raw data to a text file.
How does the Test Suite Work:
The test suite takes a starting input voltage, stopping input voltage, a voltage input step, and power supply current limit. After the values are inputted into the VI, the system will calculate input power, output power, and efficiency. It will also graph these values for the user to see. It then programs the instruments to the starting voltage and collects the data for that input voltage. After it completes one iteration, the input voltage increases by the step input and repeats the tests again.Here's the LabView Library for this project:
LabView:
Main VIBlock Diagram of Project:
Hierarchy of Project:
Problems to Consider in Final Design:
Sustainability Analysis: Explain how your design idea or applications related to the design contribute to or prevent sustainability [6]. Reference [7] and others on Blackboard™ [8]-[20] provide helpful information.
In general, the design idea seems to prevent sustainability of the Earth due to its cost in raw materials, from construction; however, the way the design applies in the world can change that. The DC-DC converter will be used in a system that harnesses the power created by a person riding a stationary bike in a gym. It takes a fluctuating DC voltage created by a generator attached to the wheel of the stationary bike as an input, and converts this fluctuating voltage to a single DC value with small ripple on the output. In this way it helps to create electrical power that would otherwise need to be created in a large power plant that operates completely inefficiently causing destruction to the raw materials in the environment. Furthermore, our design uses a controller that does not require independent rails to operate and will work with only the input from the generator. Thus there will be no cost in power to turn “on” the device. Stated below is a more in-depth analysis of the product’s sustainability qualities.
Consider issues related to Energy, Environment, Economics, and social or political Equity, four “E”s of sustainability.
Energy: Energy is the key issue that our project deals with. The creation of electrical power through clean, green manipulation of an already existing system in which the only by product is sweat. When used in the Cal Poly gym the combined generation of electrical power by all the stationary bikes should create enough power to at least power the LCD screens displaying the video that the users watch. The energy that it would have taken to power these video displays in thus saved and thus the power company needs to create less. Furthermore, the DC-DC converter is self powered, so no power is wasted on powering the electronics.
Environment: The environment benefits greatly from our product. Currently, the most prevailing way to create the electrical power in America is through large power plants that burn fossil fuels. These power plants have a large adverse effect on the environment. They use up the raw materials provided by the Earth and pollute the Earth with harmful by products. Knowing this many people have created “green” ways to create power without harming the environment such as solar, wind, etc. Our project fits as one of these green products. The system creates power from energy that would otherwise be wasted and has no harmful by products other than the materials used in the construction; however, the design will also take this into account and make sure that waste is minimal.
Economics: Economic attributes are obvious in such a design. Using electricity costs money, so once the school starts using our product the school will decrease its need for electricity and thus decrease the amount of money that it spends to power the gym. More to the point, the project will pay itself off and start to pay the school back over its lifetime, so the school will actually make money off of using our design. The power companies will see economic losses from the implementation of the design since the need for power will have diminished, however, we deal on such a small scale they probably will not notice.
Equity: The definition, as described by dictionary.com, of equity is something that is fair and just for all, socially and politically. There may be some problems with equity in our design, since we undercut the power companies profits by making a system that performs the job better than what they have. We do live in a free market, however, and if a better solution to the school’s need for electricity is out there than it is unrealistic to believe that the school would choose the more expensive option. If the power company even complains about the product, it may only serve to make them think of ways to create power in a “green” fashion also. Even though, as previously stated, the small power we are generating will probably go unnoticed by the power companies.
Explain to what extent the design idea embodies the green engineering design principles
Bill of Materials:
PCB Design:
User Manual:
How to use the prototype and test suite.How the prototype and test suite work.
Troubleshooting
References:
LM5118 Datasheet: http://www.national.com/ds/LM/LM5118.pdfMOSFET Datasheet: http://www.irf.com/product-info/datasheets/data/irlr024n.pdf
Diode Datasheet: http://www.onsemi.com/pub_link/Collateral/MBR2030CTL-D.PDF
Heat Sink Design Help: http://sound.westhost.com/heatsinks.htm#2
Buying Heat Sinks: http://www.aavidthermalloy.com/products/dctodc/dcdc_Half.shtml
LTM4607 - Simulation Model: http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1424,P39462