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Power Designs in Your Hands

Wed, 06/22/2011 - 7:08am
Bonnie C. Baker, Texas Instruments
The process of power supply design can be an over-whelming task from understanding the complexity of your circuit to the challenge of getting help from the chip distributor. As an applications engineer by trade, this article is not going to work in my favor! Here is how you can use available tools to quickly design your own power supply, without asking for any help from the manufacturer – or me. Facing this challenging task has never been as easy as it is today with the available software and hardware tools. The design of your power supply circuits is now in your hands.

For instance, let’s start with the design of a step-down DC/DC circuit. A perfect example of this type of circuit is the TPS54331, a 3A, 28V input, step-down Swift™ DC/DC converter with Eco-mode™. This converter is a 28-V, 3-A non-synchronous buck converter that integrates a low RDS(on) high-side MOSFET. To increase efficiency at light loads, a pulse-skipping Eco-mode feature is automatically activated. A resistor divider programs the hysteresis of the input under-voltage lockout.
The manufacturer’s support behind this product is extensive. The product data sheet for the TPS54331 [1] provides device information, such as typical device characteristics, a detailed description of the product, and circuit design guidance. Beyond the detailed product data sheet, there is also an evaluation module [2]. This module provides a hardware platform (Figure 1) where you can measure and modify the circuit (Figure 2) as you settle into your final circuit design. 

Figure 1. Layout of TPS54331 evaluation module.

Figure 2. Circuit of the TSP54331 evaluation module.

But, before you settle on your final DC/DC converter circuit, you may want to take into consideration a tool like Texas Instrument’s SwitcherPro™ software. The distributor can point you in the right direction to find this software [3]. The SwitcherPro power supply design software has online or desktop versions that allow you to design power supplies with Texas Instruments products. With the SwitcherPro power supply design-software, you can use EVM reference designs which can function as starting points for your custom power supply designs. The desktop application now allows more flexibility in creating power supply designs since there is no need to be connected to the Internet. Now you can design and go at your own pace!
The SwitcherPro software offers a circuit diagram and layout suggestions for your power supply designs. Once you start the software, you will notice the EVM Designs option on the left side of the window. Continuing with our example, you will find the TPS54331 EVM in the given list. Figure 3 shows the SwitcherPro layout suggestion for the TPS54331, DC/DC converter. Both the layout in Figure 1 and the layout in Figure 3 are already tested and proven. 

Figure 3. Layout of TPS54331 from SwitcherPro software.

The SwitcherPro tool offers you the opportunity to change the circuit requirements, and even the component in the schematic. You can do this by copying the EVM design and selecting the edit circuit option. In this view, you are able to change the DC/DC converter’s input minimum and maximum values as well as the output voltage and current requirements. General, stress, efficiency, and loop analysis are available for your review.

To complete this design circle, you can go back to your evaluation module, change the values as suggested by SwitcherPro and test and verify your new circuit. Finally, if you are working on the web, you can easily share your design with others. 

Figure 4. Circuit of the TSP54331 from SwitcherPro software.

I know that the concepts in this article will have the effect of turning me into the “Maytag woman.” But the good news for you is that you can now say, “I can do this power supply design myself!” Let the distributor point you to the right software. From there, the pace of your power supply design is under your control.

References
1. “3A 28V INPUT STEP DOWN SWIFT DC/DC CONVERTER WITH Eco-mode (Rev. C), SLVS839C, Texas Instruments, March 2010.
2. “TPS54331EVM-232 3-A, SWIFT Regulator Evaluation Module,” SLVU247, Texas Instruments, July 2008.
3. SwitcherProTM Switching Power Supply Design Tool: www.ti.com/switcherpro-ca

About the Author

Bonnie C. Baker is a Senior Applications Engineer at Texas Instruments and can be reached at ti_bonniebaker@list.ti.com.
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