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Exxelia introduces the CCM family at ESA / SPCD 2022

Magnetic components for space applications, optimized for multi output Flyback transformers

SUMMARY

  • Introduction : evolution of magnetic components in space

Definition – How to satisfy it?

  • Part 1 : Family qualification by ESA/CNES

Why choose Technology Flow over QPL products?

Qualification steps.

  • Part 2 : Performance characterization of CCM technology

Thermal behavior.

Frequency response and Current saturation (standard CCM inductors).

  • Part 3 : Optimization for multi output Flyback transformers

The cross regulation problem or voltage deviations on some outputs.

PhD thesis definition – Different stages of work – Present and future results.

  • Conclusion

Components that meet present and future customer needs

 

WHAT IS A CCM?

 

CCM family : INTRODUCTION

 

What are the new technical needs and constraints for specific transformers?

 

First : Applications with more outputs.

Need for more In/Out pins.

More different voltages and power levels.

 

Second : Increase in the power to volume and power to weight ratios.

We can no longer take large safety margins.

  →  need to know all the technical limitations of the product.

Reliability, internal heating, frequency response, current saturation.

 

Third : Development time is getting shorter

Breadboards/Prototypes must work the first time  →  design method must be accurate.

Even specific products must avoid qualification time.

  →  have to be already qualified before BreadBoard/Prototype step.

 

Part 1 : ESA qualification 

 

 

  • CCM family : What is this, and what is it for?

1 technology for 5 shapes

Ferrite circuit around windings wound in a bobbin, cabled on a leadframe and moulded.

For both standard and custom components

Different types of functions : inductors (DMC, CMC), pulse/SMPS/measurement transformers

  →  QPL qualification not adapted  Technology Flow is better

 

  • What is a Technology Flow?

Exxelia must prove that CCM technology is space compliant.

1st step Evaluation (Exxelia), 2d step Qualification (ESA/CNES).

Exxelia has to define : bill of materials / manufacturing process / design rules and list of tests to be performed.

 

Bill of materials

3 key raw materials : Bobbin, leadframe and magnetic circuit.

Other materials : wires, solid insulation, glue/resin/varnish, weld, ink, package.

 

Manufacturing process

3 key steps : winding, cabling, moulding.

Other steps : gluing, assembling, marking, testing, packaging.

 

Design rules

All theoretic actions the designer has to do upstream to prevent surprises downstream.

 

Test campaigns

All those in Charts F4 SG1, SG2 and SG3.

Thermal shocks, Temperature rise, Overload, Soldering heat, Vibrations, Mechanical shocks Operating life, Permanence of marking, Solderability, Terminal strength, Dielectric, Moisture.

 

  • Summary of work carried out

- More than 100 components designed, manufactured, and tested

  many configurations of  functions / shapes / tests.

- Some components destroyed to identify security margins

  on thermal, mechanical, dielectric aspects.

- Evaluation took several years to complete

 Result :  Qualification was successful on first try.

 

  • Conclusion

Respecting BOM, process and design rules qualified  ... Exxelia has the right to offer any function in CCM shapes without any mandatory testing for customer.

 

Part 2 : CCM technology performances

 

 

  • Security margins must be reduced

Maximum permissible loss value  →  leads to internal heating (Tmax <  125 °C).

Maximum operating frequency  →  above resonant frequency component is no more inductive.

Saturation curve  →  which inductor value at which excitation current?

 

  • How can these characteristics be determined ?

We decided to carry out 3 experimental campaigns :

  1. Thermal resistance determination for each of 5 shapes.
  2. Inductance versus frequency curves for standard inductors.
  3. Inductance versus current curves for standard inductors.

 

  • Thermal resistance Rth of CCM4, CCM5, CCM6, CCM20 and CCM25

  • Definition of test conditions

Use of inductors with one winding connected to all pins one side.

 

Measurements in vacuum are very complex.

  →  in natural convection in the air first.

Copper losses (heating source) only.

  →  DC current excitation / measurement of Rwind.

Component on PCB / all pins soldered  / no glue / no copper except for large current paths.

Component in a (pierced) box inside a ventilated oven  / temperature controlled.

 

  • Measurement bench

Measurements realised for each of 5 shapes.

2 L values  /  5 Tenv : 25, 50, 75, 100, 125 and 150°C  / up to 15 meas. points for each Tenv.

 

  • Complements and further work

Results applied for all CCM components  /  We have a math model air convection → vacuum.

3D simulations in progress to validate these curves  …  1st results are promising.

Measurements in vacuum are planned.

 

  • Frequency behavior for CCM4, CCM5, CCM6, CCM20 and CCM25 standard inductors

 

  • Definition of test conditions

Use of inductors with one winding connected to all pins one side.

Constant excitation, between 100µT and 1mT.

Components soldered on a brass plate.

RLC meter calibrated after 1 hour functioning.

 

Measurement device

 

  • Measurements realised for each of 5 shapes

2 L values  / up to 15 meas. points for each inductor value.

 

 

  • Result overview
    • Majority of inductors are usable at least up to 1MHz.
    • All of inductors are usable at least up to 400kHz.

 

  • Saturation behavior for CCM4, CCM5, CCM6, CCM20 and CCM25 standard inductors

 

  • Definition of test conditions

Use of inductors with one winding connected to all pins one side.

0,5 phase shift full bridge DC supply.

DC+AC (300kHz) excitation with duty cycle > 0,5.

ΔI constant as long as no saturation.

Period nb controlled to achieve desired DC current.

L value measured with current rise slope.

 

  • Measurements realised for each of 5 shapes

2 L values  / 2 Tenv, ambiant and 125°C / up to 15 meas. points for each Tenv.

2 types of curves L function of Idc or Imax (Idc+ΔI/2).

 

  • Result overview

Big ≠ between 25 and 125 °C : taking account of thermal behavior of ferrite is mandatory.

Main interest : to detect the beginning of saturation.

 

Part 3 : multi Flyback optimization

 

 

  • What are voltage deviations also named cross regulation problem ?
  1. At nominal point of load, some output voltages are different from theoretical values.
  2. If power level at regulated output varies, some non-regulated output voltages values vary.
  3. Current waveform on some auxiliary outputs is very different from theoretical triangle shape.

 

  • Observation :

The more different output / voltage levels / power levels …

The greater the probability to have voltage deviations.

Actual solution : linear regulators.

  →  more volume/weight, less efficiency, more heating.

 

  • Charge :  Transformer is mostly responsible

Problem seriousness depends on application and even on piece inside a manufacturing batch.

Magnetic root cause (transformer), but power electronics consequence (converter).

  →  need to work in both electromagnetism and power electronics.

 

  • Exxelia decided to manage a PhD thesis on this subject

Aims :

  1. Understand scientific problem, Identify root causes (transformer, other components?),
  2. Find solutions, Take account of voltage deviations in design and manufacturing process

Partners : G2Elab laboratory, D. Motte Michellon student, CNES, Steel Electronique

 

  • PhD step 1 : Understanding the scientific problem, identify root causes

Study of magnetic behavior of several transformers

  →  use of FLUX finite element simulation software

Identification of a circuit model compliant with several softwares (Psim, Spice, other)

  →  extended Cantilever magnetostatic model

Calculation of all output voltages for different transformers/converters

  →  use of Psim circuit software

 

  • Result of analysis :
  •  3/4 problem comes from transformer : magnetic coupling between all secondaries
  •  1/4 problem comes from drawbacks of some other components of converter

 

  • Actions :
  1.   Creating an analytic model to take account of leakage inductances between secondaries,
  2.   Use this model to quick calculate all output voltages.

 

  • PhD step 2 :  Finding theoretical and industrial solutions

We identified relationship between   CCM winding process, couplings between secondaries and voltage deviations.

We identified which other components and which drawbacks are concerned.

For the moment, one method of winding CCM to avoid worst cases of voltage deviations and to minimize variations from one piece to another applied since 01/01/2022 for all designed Flyback in CCM.

In progress, a software to optimize (minimize) voltage deviations and to identify best cases of CCM winding processes.

    →  Increase of know-how for customer benefit.

 

CCM family : CONCLUSION

 

 

  • Whatever the function you need

Component is already qualified  →  Reliability and security.

Many pins  ==  many input/output possibilities.

You know its thermal behavior  →  have a good idea of its energy/power limit.

 

  • For inductor applications

You can have standard or custom components.

You know frequency and current responses.

 

  • For multi output Flyback transformers

Design method focused on :

  1. meeting customer’s need as close as possible,
  2. volume and weight reductions.

 

Understanding voltage deviations  =  problem minimization + ability to assist customer.

 

                                                                CCM technology is well adapted for space   …  and we continue to improve it.

 

 

 

Autor : Bruno COGITORE  –  Jean PIERRE

Magnetic Expert / Innovation  –  Space product Manager  •  Exxelia Magnetics

 

Published on 05 Oct 2021 by Stephane PERES

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Understanding Electrical Transients in Magnetics Electrical transients are sudden, short-duration spikes in voltage or current. They can arise from various sources such as lightning strikes, switching operations, or inherent instabilities within the system. These transients can cause severe stress on magnetic components, leading to potential malfunctions or catastrophic failures.   Causes of Electrical Transients Electrical transients can originate from external factors like environmental conditions or input/output operations. Internally, they can be caused by the natural response of the system&#39;s reactive components: resistors, inductors, and capacitors. These components, governed by the laws of physics, react to changes in state variables, resulting in oscillations, amplification, or decay of signals.   Effects on Magnetic Components Magnetic components, such as transformers and inductors, are particularly susceptible to transients. For instance, transformers can exhibit parasitic components that affect their response to sudden voltage or current changes. These parasitic elements can cause amplification, oscillation, or even breakdown under transient conditions.   Mitigating Transient Threats Effective mitigation of transient threats involves understanding the behavior of magnetic components under dynamic conditions and implementing design strategies to counteract these effects.   Component Functions and Response Resistors: Dissipate energy to manage power levels. Inductors: Generate opposing voltages to slow current changes. Capacitors: Absorb or release charge to stabilize voltage changes. The induced voltage and current in inductors and capacitors are inversely proportional to the circuit&#39;s time constant. A smaller time constant means faster energy transfer, which can lead to higher transient voltages or currents.   Transformer Design Considerations Transformers must be designed to handle dynamic impedance transformations and provide necessary isolation. Realistic transformer models must account for parasitic components, which can significantly influence their behavior during transients. High voltage transformers, for instance, are prone to series resonance due to leakage inductance and self-capacitance, leading to oscillations and potential saturation.   Practical Mitigation Techniques High Bandwidth Instruments: Use to detect latent transient amplification and persistent ringing during normal operations. Worst Case Analysis: Evaluate bias currents and flux density for worst-case scenarios, including maximum voltage and temperature conditions. Current Transformer Verification: Ensure that protection circuits can detect transient overcurrents despite reduced output due to saturation. Residual Magnetization Control: Verify that residual magnetization does not impair operation, ensuring sufficient headroom for magnetization. Design of Experiments (DOEs), Risk Reduction Tests (RRTs), and Accelerated Stress Tests (ASTs): Implement these throughout the design stages to mitigate risks effectively. Protective Components: Use components like MOVs (Metal Oxide Varistors) to safeguard circuits from lightning-induced transients.   Countering threats from transients in magnetics requires a thorough understanding of the underlying causes and the implementation of robust design strategies. By employing high bandwidth detection instruments, performing worst-case analyses, and integrating protective measures, engineers can significantly reduce the risk of transient-induced failures in magnetic components. Adopting a proactive approach to design and testing ensures the resilience and reliability of electrical systems in the face of transient threats.
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