Technical Articles
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An Industrial Vision of Space Use Qualified Converters
Technical Article – Author: H. Huillet
Presentation:
PHASE 1 : Radiation hardened products
- Began working with CEA in 1995
- Project : 2KW 1Mrad power supply
- In parallel, experiments were conducted to evaluate standard hirel 4W modules behaviour under radiation
- Performance achieved : Up to 70KRad total dose
PHASE 2 : Standard Converters Qualification
- Beginning of cooperation with CNES in 1998
- Qualification of 4W and 10W converters for space use. Only potting compound was changed, No re-design
- Manufacturing based on the quality and industrial manufacturing structure of Gaïa – assembly of converters was done on the standard production lines
- Batch qualifications to ensure product consistency and performance
Results achieved :
- Life test : 1000 hours at 85°C, ON
- Thermal cycling : 300 cycles -40/+110°C, 10°C/min, 30 min dwell time
- Cumulated dose : 4.4 kRad @ 200 rad/h
- Damp heat : 85°C/85%RH, 500 Hours
- SEL SEE : Mosfet, op-amp, pwm
Currently, hundreds of converters delivered with units in operation on Rosetta, Deep Impact, microsat satellites like Demeter, Parasol, Essaim…
Limitations of this solution :
- Total dose behavior is very much batch dependent (from 4KRad to 70KRad), mainly related to the use of Bi-CMOS technology for the PWM
- Thermal dissipation not optimized for space use, difficult to evacuate heat by conduction, requires special mounting brackets…
PHASE 3 : Design of a space dedicated converter
2003 : Based on acquired background with CEA and CNES, it is decided to design a converter family (4W, 10W) for space use.
2 converters options were investigated from the technical and the industrial point of vue :
- Option 1 : 3D-stacking
- Option 2 : Open frame with optimal thermal design
Option 1 : 3D Stacking
Option 2 : Open frame with optimal thermal design
Option 1 : 3D Stacking
Prototypes of 4W converters have been designed, with the following conclusions :
Advantages :
- Space qualified technology
- Space qualified production lines
- Ease of mounting, SMD package
- Prototypes of 4W con
Disadvantages and limitations :
- Commutation noise due to proximity effects (400mV
spikes) - Weight around 20gr for a 4W converter
- Thermal dissipation : only possible through board pins, hot spots can not be cooled efficiently. Due to this restriction, it is not possible to design high power converters.
- Potting causes important parameters variations – for example, inductance changes due to constraints
- Production line is not included in a large scale industrial production scheme that would generate cost savings, therefore it is expensive compared to COTS solutions
Option 2 : Open frame with optimal thermal design
This approach was totally industry driven, using the same technologies that Gaia is using for its new standard product ranges :
- Designed according to
ESA-PSS-01-301 derating guidelines - Open frame converter, no potting
- Optimized thermal design, buried thermal drain in the PCB, heat dissipation possible by conduction through chassis mounting
- Bipolar technology
- Manufacturable on Gaïa standard production lines
SGDS04 and SGDS10 families Designed for space applications :
Components derating ESA-PSS-01-301
Dump input
Undervoltage lockout
Inhibition function
Synchronisation function
Adjustable output
Output regulation 0 to 100% load
Permanent output current limitation
Parallel operation (master slave)
Weight 8gr (4W), 10gr (10W)
Operating temperature range -40°c to
+85°c
Heavy ions and ionising dose 20Krad
characterised
Galvanic insulation 500 VDC
Integrated LC filter
EMI MIL-STD-461C with recommended
external filter
Space Architecture Modules
Advantages :
- Low output noise (60mV ripple + spikes)
- Due to bipolar technology, total dose caracterised to 20KRad
- No potting brings lightweight, higher reliability and higher consistency in production
- Simple assembly process, no mezzanine boards
- Possibility to design higher output power versions – no limitation due to the technology
- Manufactured on standard production lines used for other Gaia products leads to huge costs savings
Industrial approach : The assurance of space grade quality
- Design according to the ESA design rules
- Initial design validation :
- electrical, thermal, mechanical
- reliability (life-test, thermal cycling)
- radiations (heavy ions, total dose)
- Components production in consistent batches for a 3 year production
- approved suppliers
- radiation batch qualification
- drying of plastic case components and packing in dry pack
- nitrogen storage
- Purchasing of PCBs to approved suppliers (i.e. SYSTRONIC)
- Manufacturing of consistent batches :
- consistency of assembly through the use of automated assembly lines
- consistency of consumeables (solder pastes, glues…)
- Assembly by a qualified sub-contractor with periodic audits :
- Detailed flowcharts under control of Gaïa
- Re-inforced and monitored controls
- traceability and recording of all manufacturing operations
- Electrical tests with recording of results at -40/+85/+25°C
- Batch qualifications :
- life test 2000 h
- Thermal cycling : 500 cycles -40/+85°C
- DPA ( RX and visual inspections, micro-sections)
- Nitrogen storage of converters