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Design Tips

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Noninvasive measuring of loop gains

Dr. Ray Ridley, Ridley Engineering

It is always desirable to simplify the measurement process of power supplies, and characterize them without overly invasive testing. This can work for loop gains with limited success, and shows the pitfalls of trying to measure loops noninvasively. Power supply output impedance measurements For
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Date:
02/13/2015
Practical control measurements for the Sepic converter - Part III

Dr. Ray Ridley, Ridley Engineering

Sepic Converter with Voltage-Mode Control This article shows the measured characteristics of Sepic converter using current-mode control, either with a coupled inductor or separate inductors. In the last article of this series, the coupled-inductor Sepic was examined. It
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Date:
12/30/2014
In this video Dr. Ray Ridley of Ridley Engineering talks to Alix Paultre of Power Systems Design at his latest power engineering seminar on the course and its benefits. One of only
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Date:
12/06/2014
Practical control measurements for the sepic converter - Part II

Dr. Ray Ridley, President, Ridley Engineering

This article shows the measured characteristics of coupled-inductor Sepic converters and compares them with a separate inductor Sepic. The coupled-inductor Sepic has less diverse transfer functions, but it is still a challenge to control over a wide range. Publications in the past have discussed the coupled-inductor
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Date:
11/22/2014
Practical control measurements for the sepic converter - Part !

Dr. Ray Ridley, President, Ridley Engineering

Depending on the conditions under which you measure a Sepic converter, it can appear either easy to control, or extremely difficult. Make sure you always make an extended range of measurements on your Sepic design if you wish to ensure avoiding the troublesome regions. Sepic converter with
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Date:
10/21/2014
Source interaction with board-mount converters

Dr. Ray Ridley, President, Ridley Engineering

Board-mount power supplies use multilayer ceramics for both their input and output capacitors. The inherently low ESR values lead to transfer functions with higher Q than converters using electrolytic capacitors, and this can lead to interesting effects when making measurements. Many newcomers to
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Date:
10/20/2014
Loop gain Bode plots and Nyquist diagrams

Dr. Ray Ridley, Ridley Engineering

This article shows the link between loop gain Bode plots and Nyquist diagrams. The Nyquist diagram is a subset of the Bode Plot, omitting crucial design data. The linear scaling of the Nyquist diagram restricts its practicality, and omission of frequency as an explicit variable in the plot is a major drawback. Loop
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Date:
09/23/2014
Interpreting loop gain measurements

Dr. Ray Ridley, President, Ridley Engineering

There have been many dramatic changes in power supply development over the last 20 years, but loop gain measurements remain the key to rugged and aggressive system performance. Understanding how to read a loop gain is important. Loop gain measurements in modern systems Quite
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Date:
04/30/2014
Power Supply Failure Survey â€

Dr. Ray Ridley, Ridley Engineering

In this third article about power supply failures, the magnetics are examined for their contribution to the failure rate. These are usually the least understood of all components, and poor magnetics design can lead to many different failure mechanisms in power supplies. Power
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Date:
04/06/2014
Power supply failure survey â€

Dr. Ray Ridley, President, Ridley Engineering

In this second article about power supply failures, the capacitors are examined for their contribution to the failure rate. The causes of failure for different types of capacitors are discussed. In the last part of this article, the question was asked of group members “Why do power supplies fail?” and the
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Date:
03/03/2014
Results of a power supply failure survey

Dr. Ray Ridley, President, Ridley Engineering

We here at Ridley Engineering recently conducted a survey with a group of almost 3,000 active power supply design engineers to discover the various reasons and circumstances they have encountered power supplies that failed. The experiences the engineers shared with us were very enlightening, and this article
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Date:
02/15/2014
Point-Of-Load Converter Design â€

Dr. Ray Ridley, Ridley Engineering

Point-of-load converters commonly use multilayer ceramic capacitors instead of electrolytic capacitors. The effect of this change is strongly felt in the bulk storage capacitor value, and can lead to unexpected variations in control measurements. Instability can result if input filter capacitors become too small.  Input
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Date:
01/12/2014
Point-Of-Load Converter Design

Dr. Ray Ridley, Ridley Engineering

There has always been a debate about how essential it is to measure the loop of a switching power supply. Some power designers have always resisted this part of development and design validation, claiming they are able to tune a loop properly through step-load testing [1]. While this may have worked with low
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Date:
12/07/2013
Designing snubbers for nonisolated converters

Dr. Ray Ridley, President Ridley Engineering

All power electronics circuits with devices which rapidly turn on and turn off will exhibit voltage ringing when currents are interrupted or initiated. For transformer-isolated designs, the leakage inductance of the transformer usually dominates the ringing inductance, and the first step in snubber design is
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Date:
10/16/2013
Tapped Boost Converter Modeling

Dr. Ray Ridley, Ridley Engineering

As mentioned in the last article of this series [1], Dr. Vatché Vorpérian developed the PWM switch model in 1986, which replaced the need for state-space averaging and greatly simplified the analysis process. It was a very elegant and intuitive modeling approach, which is easily grasped by new students in
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Date:
10/10/2013
PWM Switch Modeling

Dr. Ray Ridley Engineering, Ridley Engineering

Soon after switching power supplies were implemented in industry in the 60s and 70s, it became apparent that they had unique issues with control that defied normal circuit analysis. This gave rise to state-space averaging, a technique with which the two distinct conditions of the power switch and diode could
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Date:
08/18/2013
Ray Ridley on Ridley Engineering's services at PCIM 2013 (Video)

Dr. Ray Ridley, President, Ridley Engineering

In this video, Ray Ridley of Ridley Engineering describes his company's services
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Date:
07/10/2013
Switching power supply primer - Part I - why do you want to build a switching power supply? (Video)

Dr. Ray Ridley, President, Ridley Engineering

In this introductory video on switching power supply design, Dr. Ridley
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Date:
06/14/2013
Flyback Power Supply Development - Part V

Dr. Ray Ridley, President, Ridley Engineering

This article is the fifth of a series in which Dr. Ridley shows the steps involved in designing and building an offline flyback converter. With full input voltage and full load applied, the control-to-output transfer function and loop gain is measured and compared to predictions. Theory and
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Date:
06/01/2013
Frequency Response Analysis - Part III - - How much signal do you need? (Video)

Dr. Ray Ridley, President, Ridley Engineering

In this third part of a series of videos on frequency response analysis,
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Date:
05/21/2013
Flyback Power Supply Development - Part IV

Dr. Ray Ridley, President, Ridley Engineering

This article is the fourth of a series in which Dr. Ridley shows the steps involved in designing and building an offline flyback converter. The power transformer is added to the circuit, and the current sensing and snubbers are designed to operate at full power without excessive stress on the components. Power
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Date:
05/16/2013
Paultre on Power - PCIM 2013 impressions with Ray Ridley (Video)

Dr. Ray Ridley, President, Ridley Engineering

Alix Paultre, Editorial Director of Power Systems Design, and Dr. Ray
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Date:
05/16/2013
Flyback Power Supply Development - Part III

Dr. Ray Ridley, President, Ridley Engineering

This article is the third of a series in which Dr. Ridley shows the steps involved in designing and building an offline flyback converter. The input filter rectifier is simulated to find the design range of the converter, and the transformer design is completed and measured. Input Voltage
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Date:
05/14/2013
Power supply design four-day hands-on workshop (Video)

Dr. Ray Ridley, President, Ridley Engineering

In this video, Dr. Ridley presents the agenda for this unique power supply
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Date:
05/08/2013
Frequency response analysis  - Part II - What frequency range do you need? (Video)

Dr. Ray Ridley, President, Ridley Engineering

In this second part of a series of videos on frequency response analysis,
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Date:
05/03/2013
Frequency response analysis for power supplies - Part I - why do you need it? (Video)

Dr. Ray Ridley, President, Ridley Engineering

In this video, the first part of a series of videos on frequency response
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Date:
05/01/2013
Flyback Power Supply Development - Part II

Dr. Ray Ridley, President, Ridley Engineering

This article is the second of a series in which Dr. Ridley shows the steps involved in designing and building an offline flyback converter. The second part of the series begins testing on the bias and control circuit, and verifies the high-voltage operation of the power FET with a resistive load. Initial
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Date:
03/09/2013
Flyback power supply development: - Part I

Dr. Ray Ridley, President, Ridley Engineering

This article is the first of a series in which Dr. Ridley shows the steps involved in designing and building an offline flyback converter. The first part of the series presents the power supply architecture and schematic, including the control and bias circuits. Flyback power converter The
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Date:
01/15/2013
Input Impedance Measurements and Filter Interactions - Part III

Dr. Ray Ridley, President, Ridley Engineering

In this article, Dr. Ridley continues the discussion of power supplies with input filters. He shows how the presence of a poorly-designed filter has a drastic effect on the loop gain of a voltage-mode controlled system. He also shows that the loop gain of a current-mode system can be a poor indicator of stability
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Date:
01/09/2013
Input Impedance Measurements and Filter Interactions - Part II

Dr. Ray Ridley, President, Ridley Engineering

In this article, Dr. Ridley continues the discussion of power supplies with input filters. He shows how the output impedance of the input filter is measured, and demonstrates the importance of input filter damping. Input Filter Measurements As discussed in the last article
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Date:
11/01/2012

 

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