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Content by Robert K
Robert K
Member Since: June 21, 2006
Blog Posts: 47
Posts: 4

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All (51)           Blogs (47)           Comments (4)          
Power Tip 74: Interleaving Gets More Power From a Flyback
Power Tips  
8/18/2014   4 comments
In his final Power Tip, Robert Kollman looks at the number of benefits to be gained from interleaving a flyback power supply design.
Power Tip 73: Synchronizing Makes for Well-Behaved Power Supplies
Power Tips  
7/28/2014   1 comment
Synchronizing your power system offers a number of benefits, including reduced filtering costs and lower EMI.
Power Tip 72: Select the Right Rectifiers for Multiple Output Flybacks
Power Tips  
7/2/2014   Post a comment
The output rectifiers influence cross regulation over load and temperature, efficiency, and transformer design, so their choice is an important design aspect.
Power Tip 71: Synchronous Boost Labors the High-to-Low Transition
Power Tips  
5/19/2014   Post a comment
There are a lot of papers out there describing the switching waveforms in a synchronous buck regulator. However, there are not many for the boost.
Power Tip 70: Use Weighted Feedback in Multiple-Output Supplies to Meet Regulation Specs
Power Tips  
4/2/2014   3 comments
You may not need to use multiple control loops to meet regulation requirements of multiple-output power supplies.
Power Tip 69: A Simple Oversight Can Ruin EMI Performance
Power Tips  
3/12/2014   4 comments
It's pretty easy to find 100-fF capacitors as a parasitic element in your power supply. You need to recognize that you'll have to address them in order to have an EMI-compliant power supply.
Power Tip 68: Pick the Right Turns Ratio for a Fly-Buck Converter
Power Tips  
2/18/2014   Post a comment
The Fly-Buck is a convenient choice for a simple isolated bias voltage, but you need to be careful when considering running at high duty ratios.
Power Tip 67: Improve Discontinuous Flyback Efficiency With Synchronous Rectifiers
Power Tips  
1/28/2014   Post a comment
You cannot make a self-driven synchronous rectifier for the discontinuous flyback converter. There are both current transformer-driven and semiconductor circuits to accomplish this. The latter have a size and cost advantage, but may need a buffer to properly interface with the high voltage and currents found in power supplies.
Power Tip 66: Reduce EMI From an Offline Power Supply Cost-Effectively
12/24/2013   Post a comment
The obvious ways to reduce emissions are to reduce the amplitude of the switching voltage waveform, to divert the current with a shield or capacitor, and/or to add a series impedance. We apply the first two techniques to demonstrate we can build a low-power, AC input adapter to meet EMI emissions without a common-mode inductor.
Power Tip 65: Power Supply Implications of Envelope Tracking
Power Tips  
11/20/2013   Post a comment
Envelope tracking requires a high-bandwidth power supply with the ability to source and sink current, which complicates the design.
Power Tip 64: Compensate for Cable Drop Without Remote Sensing
Power Tips  
10/9/2013   2 comments
It is possible to put a positive load line on a power supply with a handful of inexpensive parts. In many cases, the added complexity of this circuit is small compared to remote sensing, and it is safer.
Power Tip 63: Testing High-di/dt Power Supplies
Power Tips  
9/18/2013   2 comments
Testing low-voltage, high-current power supplies is quite a challenge, due to inductance and active load capabilities. The two main challenges are minimizing load inductance in the test setup and to taking a proper voltage measurement.
Power Tip 62: Boost or Flyback for Extreme Conversion Ratios?
Power Tips  
8/14/2013   Post a comment
Boost controllers have a limited conversion, ratio set by the minimum off-time of the controller and the operating frequency. So what do you do when you run up against this limit?
Power Tip 61: Watch the Conversion Ratio on Boost Converters
Power Tips  
7/2/2013   Post a comment
Violating limited conversion ratio of boost controllers causes all sorts of proplems. Consider interleaving boost power stages instead to increase effective switching frequency.
Power Tip 60: Three simple split-rail power supply topologies
Power Tips  
6/6/2013   4 comments
Here are three power-supply topology options to meet these types of requirements with varying degrees of performance and costs.
Power Tip 59: Save check-out time with a good power supply layout
Power Tips  
5/2/2013   Post a comment
You can destroy a well-designed power supply with a sloppy layout. There are high power switching circuits as well as sensitive analog circuitry in a power supply, and mixing the two can result in chaotic operation.
Power Tip 58: Power supply grounding--which camp are you in?
Power Tips  
4/4/2013   4 comments
If you want to start a heated discussion between a group of power supply engineers, all you need to do is ask them how they layout the grounds in a power supply.
Power Tip 57: Design a flyback primary switch snubber
Power Tips  
3/14/2013   1 comment
Here's how to best control the voltage stress on the primary switch in a single-ended flyback converter.
Power Tip 56: Estimate PWB interconnect inductance
Power Tips  
2/20/2013   3 comments
Having a ground-plane layer reduces trace inductance and is critical for optimal performance in power supplies. Here's why.
Power Tip 55: Compensate a low-noise power supply having a two-section filter
Power Tips  
1/17/2013   Post a comment
In this Power Tip, Robert Kollman at Texas Instruments discusses using P-Spice in closing the feedback loop around such a filter.
Power Tip 54: Use 2-section filter for low-noise power supply
Power Tips  
12/17/2012   4 comments
Some low-noise applications may require the power supply output ripple voltage to be less than 0.1 percent of the output voltage. These low ripple requirements easily can translate into filter attenuations of significantly greater than 60 dB, which cannot be practically met with a single stage.
Power Tip 53: Use P-SPICE to design your power supply control loop
Power Tips  
11/26/2012   Post a comment
In this Power Tip, we use P-SPICE to design a control loop for the integrated, synchronous buck switcher.
Power Tip 52: Making over the wall wart
Power Tips  
9/28/2012   5 comments
With worldwide sales of cell phones closing in on 2 billion per year, the cell phone charger’s size, cost and efficiency is under scrutiny.
Power Tip 49: Avoid these common multi-layer ceramic capacitor pitfalls
Power Tips  
8/31/2012   7 comments
Multi-layer ceramic (MLC) capacitors have become extremely popular in power electronics due to their small size, low equivalent series resistance (ESR), low cost, high reliability, and high ripple current capacity.
Power Tip 51: Be aware of capacitor parasitics
Power Tips  
8/31/2012   1 comment
Power supply ripple and transient specifications establish the requirements for the amount of capacitance you will need.
Power Tip 50: Avoid these common aluminum electrolytic capacitor pitfalls
Power Tips  
7/30/2012   9 comments
Aluminum electrolytic capacitors remain a popular choice in power supplies due to their low cost. However, they have limited life and are sensitive to both hot and cold temperature extremes.
Power Tip 48: Tame conducted common-mode emissions in isolated switchers – Part 2
Power Tips  
6/18/2012   Post a comment
We continue our discussion of common-mode currents which started in Power Tip 47.
Power Tip 47: Tame conducted common-mode emissions in isolated switchers (Part 1)
Power Tips  
5/11/2012   Post a comment
Understand the danger these difficult-to-control emissions can cause, and how to minimize them
Power Tip 46: Time your synchronous-buck FETs properly
Power Tips  
4/13/2012   9 comments
Understand how turn on/off timing for high- and low-side gate drives affect efficiency
Power Tip 45: Handling high dI/dt load transients, Part 2
Power Tips  
3/16/2012   Post a comment
Understand the options and tradeoffs when dealing with this common situation
Power Tip 44: Handling high dI/dt load transients, Part 1
Power Tips  
2/17/2012   Post a comment
Understand how to handle this common circuit challenge, which is an increasingly important hazard
Power Tip 43: Discrete devices—a good alternative to integrated MOSFET drivers (Part 2)
Power Tips  
1/15/2012   1 comment
The humble, inexpensive discrete transistor can be a cost- and performance-effective choice, and better in some ways than a more-highly integrated component.
Power Tip 42 (Part 1): Discrete devices—a good alternative to integrated MOSFET drivers
Power Tips  
12/9/2011   8 comments
The humble, inexpensive discrete transistor can be a cost- and performance-effective choice, and better in some ways than a more-highly integrated component.
Power Tip 41: Powering DDR memory
Power Tips  
11/13/2011   3 comments
Understand the special requirements and tradeoffs when supplying this unique load
Power Tip 40: Common-mode currents and EMI in non-isolated power supplies
Power Tips  
10/14/2011   4 comments
Understand the role of this "type" of current flow as an EMI source
Power Tip 39: You get more than just better efficiency by going synchronous
Power Tips  
9/16/2011   4 comments
Understand the virtues of synchronous power-conversion topologies
Power Tip 38: Simple latch circuit protects power supplies
Power Tips  
8/12/2011   3 comments
Understand how to design and configure a latch which has this use, and many others
Power Tip 37: Trade AC-line range for input-capacitor ripple current
Power Tips  
7/12/2011   Post a comment
Understand the relationship between these two critical parameters
Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
Power Tips  
6/17/2011   11 comments
Understand why higher voltage is a better choice, and how to achieve it.
Power Tip 35: Minimize transformer interwinding capacitance effects
Power Tips  
5/9/2011   7 comments
Understand how this capacitance develops, why it is a problem, and what can be done about it
Power Tip 34: Design a simple, isolated bias supply
Power Tips  
4/1/2011   7 comments
Understand how the asymmetrical, half-bridge flyback (aka flybuck) configuration can provide multiple benefits in many situations
Power Tip 33: Beware of circulating currents in a SEPIC coupled-inductor – Part 2
Power Tips  
3/10/2011   Post a comment
Understand how leakage inductance requirements for this DC/DC converter topology
Power Tips #5: Buck-boost design uses a buck controller
Power Tips  
8/4/2010   Post a comment
A negative output voltage buck-boost, sometimes called a negative flyback, operating at 50% duty-cycle provides an output voltage equal to the input voltage, only opposite in polarity.
Power Tip #4: Damping an Input Filter " Part 2 of 2
Power Tips  
9/29/2008   3 comments
The source impedance of an input filter should be at least 6dB less than the input impedance of a switching regulator as a safety margin to minimize the chance for oscillation.
Power Tip #3: Damping the input filter --- Part 1
Power Tips  
9/5/2008   1 comment
Here's how to inhibit oscillations in a switching supply.
Power Tip #2: Taming a noisy power supply
Power Tips  
8/3/2008   1 comment
Focus on the electrical and physical design of the error amp, reference amp, and ramp circuits to minimize problems.
Power Tip #1: Picking the right operating frequency for your power supply
Power Tips  
7/7/2008   1 comment
Low-frequency designs tend to be the most efficient, but are the largest and most costly. Moving higher in frequency improves size and cost at the expense of circuit losses.

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