Welcome to the Biricha WDS User Guide
Design stable analog and digital power supplies in minutes!
This is an installation and help guide for WDS. For more information about WDS and its capabilities, please click here.
Getting Started
Tutorials
- Analog Voltage Mode Buck Converter Design using WDS
- Example Digital Voltage Mode Buck Controller Design
- LTspice Simulations from WDS
- Isolated Power Supply Design Tool with WDS
Installation Guide
1. Downloading and Installing WDS
Go to Biricha WDS and download WDS.
After downloading the WDS setup files, extract the zip and run “setup.exe”.
You may recieve a warning from Windows – click “Run” to proceed.
Then, click “Next”.
Please read the end-user license agreement (EULA) carefully. If you agree with the terms, select “I Agree” and click “Next” to continue. If you do not agree with the terms of the EULA then you should not proceed with the installation.
Select the installation folder for WDS. The default installation folder is your “Program Files” directory. Click “Next” to continue.
Click “Next” to proceed with the installation.
You may receive a message about User Account Control from Windows, if so, click “Yes” to proceed with the installation.
The installation is now complete. Click “Close” to exit the installer.
3. Setting up Licensing
If you have an activation code, then got to Help -> License and then paste your activation code into the relevant box. This will activate WDS.
If you do not have an activation code then WDS will run in trial mode. Under trial mode you have fill access to all functions of WDS; the only limitation is that the input and output voltages are locked.
4. Updating WDS
In future, if your license file permits, WDS will prompt you when updates are available. Please ensure that you always update to the latest version.
Using WDS
Concept
- To begin, the user should select their preferred topology and enter an input voltage, output voltage and output current specification
- WDS will then calculate all other parameters based on this
- The user will then select parts from their supplier and then enter the actual values into WDS
- Generally speaking the design should start on the “Specification” tab and work through the tabs systematically. I.e. “Specification” to “Transformer” to “Semiconductor” to “Output Filter” to “Controller Design” etc.
- The ideal calculated values will automatically update as the users enters the actual values (such as selected transformer turns ratio, output capacitor, inductor, etc)
Combo Boxes
- Combo boxes, such as the one shown below, are used to switch between WDS calculated values and user defined values
- WDS will use whatever value is currently active in the combo box
- For your convenience, the nearest preferred values are calculated for many components and these can be selected by clicking the arrow to the right of the combo box
WDS calculated values are shown with a blue background
If the user overwrites this with their own value, the background color changes to white:
The user can always switch back to the default WDS calculated value by clicking the arrow to the right of the combo box and selecting the value next to the text “(default)”
- The locked text boxes on the left hand column indicated the original WDS calculated value and allow the user to compare the calculated value to the user defined value (if entered)
Voltage Mode Buck
In this tutorial, we will design a voltage mode Buck converter.
Please see the Using WDS section for more information on using WDS.
Specification
On the “Specification” tab, enter the following specification into the relevant fields under “Converter Specification”:
Again on the “Specification” tab, enter the following specification into the relevant fields under “Control Parameters”:
As you update the values, WDS will automatically update the design and show the associated Bode plot in the Frequency Response tab.
Now move onto the “Semiconductors” tab, enter the following specification into the relevant fields under “Primary Switch”; these are the actual parameters of the FETs that we are using on the board. Important: for now, please ignore the values in the left hand column; these are calculated values based on your specification and will get updated as you input various parameters in the future tabs.
These are the values for the semiconductor switches that we are using on the Biricha Buck board used in our workshops.
Again on the “Semiconductors” tab, enter the following specification into the relevant fields under “Diode/Switch”:
Output Filter
Now click on the “Output Filter” tab. On the “Output Filter” tab, enter the following specification into the relevant fields under “Output Filter Inductor “:
Again this is the parameters of the Würth inductor that we are using on the Biricha Buck board.
Also on the “Output Filter” tab, enter the following specification into the relevant fields under “Output Filter Capacitor “:
Note that we are using 2x220uF caps and we measured the ESR to be around 70mΩ for 1 capacitor. So the ESR of 2 in parallel will be around 34.5mΩ.
Controller Design
On the “Controller Design” tab, WDS has selected a Type III compensator. The automatic pole/zero placement algorithms have calculated the location of the poles and zeros such that the loop will achieve the crossover frequency and phase margin specification concurrently, i.e. WDS has designed a compensator that will give a crossover of 10kHz and a phase margin of 55 degrees. As shown below:
Note that in this tab WDS asks for the PWM ramp height which has been set to 1.8V
Note that this value is chip dependant. For the UC3823 chip that we are using the typical value from the datasheet is 1.8V.
If not already in context, click on the “Frequency Response” tab on the right hand side to view the simulated Bode plot. Under the “Bode Plot” section of this tab, make sure that only “Loop” is ticked. This will display the simulated loop response. See that the simulated crossover frequency and phase margin are displayed at the top of this tab.
Analog (Non-Isolated)
Click on the “Analog (Non-Isolated)” tab. The component values required for the Type III compensator have been automatically calculated.
In this example we will be using the UC3823 PWM controller from TI to implement the controller.
The voltage reference from this chip is 5.1V (from the datasheet). But, in this example, we divide this by 2 using a potential divider. Therefore in WDS please make sure that the “Error Amplifier Reference Voltage” is set to 2.55V.
Circuit Tab (right hand pane)
In WDS, click on the “Circuit” tab (right hand pane) and view the circuit diagram for the Type III compensator. Please study the circuit diagram and identify the location of the Type III compensator components.
Frequency Response
Click on the “Frequency Response” tab again to view the Bode plot. Then observe how the Bode plot changes as you type in the Nearest Preferred Values (NPVs) used in the actual circuit in to the relevant boxes in the “Controller Component Values” section of the “Analog (Non-Isolated)”. The component values are shown below:
WDS will always use the user defined values instead of calculated values. So now that you have changed the component values to their NPVs, your crossover and phase margin will also have changed. The simulated crossover frequency and phase margin have changed because you have now entered the values of the components used on the actual PCB, which are slightly different to those calculated by WDS. Thus your compensator poles and zeros are slightly different from the ones calculated by WDS.
Power Loss Budget Tab (right hand pane)
This tab toughly estimates the total power loss in various components of the power supply.
Total power loss budget (PLB) is estimated based on the user’s efficiency requirements and this is displayed at the bottom light hand side of the WDS window. A warning is displayed of the losses exceed the total PLB.
Summary Tab (right hand pane)
This is the final summary of your design. It includes all the parameters calculated by WDS including all the voltage and current stresses on the devices in addition to all the frequency repose Bode plots.
When your design is complete, you can save this as an rft file by pressing the “Save Summary As” button or insert on your own reports by simply copying and pasting.
Finally pressing “Generate and Email Transformer Design to” allows you to generate an email with all the parameters relevant to the transformer which you can send to your magnetics supplier of choice.
Spice Simulation Tab (right hand pane)
This is an extremely power full feature full explanation of the available simulations is given when you click on this tab.
Digital Voltage Mode Buck
In this tutorial, we will design a digital controller using WDS.
Please see the Using WDS section for more information on using WDS.
Specification
On the “Specification” tab, enter the following specification into the relevant fields under “Converter Specification”:
Again on the “Specification” tab, enter the following specification into the relevant fields under “Control Parameters”:
As you update the values, WDS will automatically update the design and show the associated Bode plot in the Frequency Response tab.
Semiconductors
Now move onto the “Semiconductors” tab, enter the following specification into the relevant fields under “Primary Switch”; these are the actual parameters of the FETs that we are using on the board. Important: for now, please ignore the values in the left hand column; these are calculated values based on your specification and will get updated as you input various parameters in the future tabs.
These are the values for the semiconductor switches that we are using on the Biricha Buck board used in our workshops.
Again on the “Semiconductors” tab, enter the following specification into the relevant fields under “Diode/Switch”:
Output Filter
Now click on the “Output Filter” tab. On the “Output Filter” tab, enter the following specification into the relevant fields under “Output Filter Inductor “:
Again this is the parameters of the Würth inductor that we are using on the Biricha Buck board.
Also on the “Output Filter” tab, enter the following specification into the relevant fields under “Output Filter Capacitor “:
Note that we are using 2x220uF caps and we measured the ESR to be around 70mΩ for 1 capacitor. So the ESR of 2 in parallel will be around 34.5mΩ.
Controller Design
On the “Controller Design” tab, WDS has selected a Type III compensator. The automatic pole/zero placement algorithms have calculated the location of the poles and zeros such that the loop will achieve the crossover frequency and phase margin specification concurrently, i.e. WDS has designed a compensator that will give a crossover of 15kHz and a phase margin of 50 degrees (after phase erosion). As shown:
Note that we are using 2x220uF caps and we measured the ESR to be around 70mΩ for 1 capacitor. So the ESR of 2 in parallel will be around 34.5mΩ.
If not already in context, click on the “Frequency Response” tab on the right hand side to view the simulated Bode plot. Under the “Bode Plot” section of this tab, make sure that only “Loop” is ticked. This will display the simulated loop response. See that the simulated crossover frequency and phase margin are displayed at the top of this tab.
Digital (Non-Isolated)
Click on the “Digital (Non-Isolated)” tab, enter the following into the relevant fields under “PWM Parameters”
Again on the “Digital (Non-Isolated)” tab, enter the following into the relevant fields under “Sampling Divider and ADC”:
WDS will now be able to calculate the correct scaling factors for the digital controller.
Coeffs
WDS can provide the coefficients in various formats. Generic Fixed and Floating point, TI IQ format, Microchip MCU16, ST MCU32 and Infineon XMC. For the purpose of this example we only present Microchip’s 16 but fixed point format however the general principle stays the same for all other formats.
Click on the “Coeffs (Fixed Point / Microchip)” tab (on the right hand pane of WDS), and select “Normalized (IQ Format)” from the “Controller Type and Output” group as per the image.
WDS will then calculate the correct controller coefficients.
The user simply clicks “Copy Hex to Clipboard” and then pastes the controller coefficients directly into their code.
Implementation and Results
The design is now complete!
The completed WDS file used in this tutorial can be downloaded here.
LTspice Simulations
IWDS allows LTspice simulations in both time domain and frequency domain of your power supply, provided that LTspice is already installed. You can run a spice simulation by clicking in the “Spice Simulation” tab and then “Run LTspice Simulation” in the right hand window:
Important: to import the results of your LTspice Simulation back into WDS you must close LTspice first.
For example if you run a “Frequency Response Simulation” in LTspice by activating it through WDS, after the simulation completed you must close LTspice. You can then click on the “Spice” button on the Bode plot to display the LTspice. In figure below green trace is WDS output and the black trace is the LTspice output imported in WDS.
Isolated Power Supplies
You can design an isolated power supply by simply selecting “Isolated” from the drop box in the Specification tab
Transformer
WDS provides most necessary information such as “turns ratio”, “Volts-us” product etc. so that you or your magnetics design can design you’re the magnetics WDS recommends the transformer turns ratio Primary inductance and leakage. The user can of course change these values after which all calculation will be based on the user’s input. The user can also indicate if a bias winding is needed by filling in the “Bias Winding Voltage” box. Once all design parameters are completed in this tab the user can email this specification to his/her magnetics provider by pressing the “Generate and Email Transformer Design to” button on the “Summary” tab.
Isolated PSU Controller Design
Pole zero placement is identical to non-isolated version. In digital control, WDS assumes that the controller is on the secondary side with zero delay in transmitting the data to the primary side and therefore the design is identical to the non-isolated version. If there is a delay, this can be added in as a “Pure Time Delay” from the specifications tab.
For analog Isolated PSUs, WDS assumes that you will be using a traditional analog optocoupler. The pole zero placement stays identical but you must now add the parameters of your optocoupler. The circuit diagram of the type of isolated power supply that WDS designs is shown on the “Circuit” tab:
Using the above diagram the user must first input the data of their chosen optocoupler. This is done in the “Analog (Isolated)” tab.
Maximum, Typical, Minimum CTR, forward drop across the diode (Vf) and Collector Emitter saturation voltage Vce(sat) are usually available from the manufacture’s datasheet. Copto represents the bandwidth of the opto and usually must be measured. Many good methods for measuring this parameter are freely available on-line.
Vpullup is the reference voltage from the user’s selected controller IC. Based on the above WDS calculates all other parameters which the user can of course change.
Finally, Zener reference voltage Vz must be operated in the breakdown region and therefore its value must be lower than the output voltage of the power supply. All other parameters are either available from the datasheet or are calculated by WDS.