Electrical Power Supply Matrix Systems
This article highlights AEPS-GROUP electrical power supply systems with GaN technology instead of GaAs technology for a reduction in APAR power consumption.
Distributed electrical power supply systems consisting of a specified set of modules may be easily arranged on a drawing’s horizontal surface as a schematic image in order to analyse and optimize the system structure.
Recently, however, consumers designed for distributed electrical power supply system have appeared. Their schematic images have a strongly expressed spatial matrix structure consisting of lines and columns with power supply modules located at their crossing points. Power supply systems for active phased array radars and those for supercomputers are typical examples of these rapidly developing structures.
The author is the first to suggest using the term “distributed electrical power supply matrix systems” (DEPSMS) to identify such systems. Our companies, united under the brand of AEPS-GROUP, deal exactly with such power supply systems.
The key element of the APAR DEPSMS is a transmitting-receiving module (TRM) which determines as much as 90% of the APAR price, weight and performance. Nowadays, the number of APAR TRM units in aircraft exceeds 2,000 and reaches 10,000 or more in ground equipment.
A typical modern TRM consists of UHF components (transmitter, receiver, phase shifter) and a controlling / signal conditioning microprocessor. An LF component ergonomically located in the TRM is also included. This is the bank of energy storage capacitors providing intermittent energization for the UHF transmitter (pulsed power supply modes – duration of hundreds of nanoseconds to milliseconds, tens to 4-5 duty ratio).
It is extremely important to miniaturize the TRM as its width and height (the average length being 150 to 250 mm) together with the liquid and air cooling components (denoting the conventional side of the square formed with the TRM width and height as ∆L) may not exceed the emitted APAR half-wave length, i.e., ∆ L . Table 1 shows the typical values of ∆ L accounting for the actual sizes of the cooling element for different APAR frequency ranges.
| Range symbol | Emission frequency, GHz | Wave length, mm | ∆ L, mm |
| S | 2 - 4 | 150 -75 | 70 - 33 |
| C | 4 - 8 | 75-37.5 | 33 - 15 |
| X | 8 - 12 | 37.5 - 25 | 15 - 9 |
Table 1: Typical values of ∆ L accounting for the actual sizes of the cooling element
Nowadays, we have learned to accommodate UHF microcircuits in a 9-11 mm wide strip. Taking into account the necessity of a metal case to screen TRM UHF radiation from the adjacent TRMs (the EMC problem) with walls at least 0.5 mm thick (the heat removal problem), it can be affirmed that the UHF portion of the TRM with ∆ L = 10…12 mm will be implemented soon.
Figure 1: DC/DC module JETD25, a module prototype accommodated in the TRM, width ∆L=21.5 mm, dimensions=23x33x10 mm.
One of the obstacles on the way towards miniaturization of the TRM (i.e., weight and APAA price reduction and EMC improvement) is the extremely difficult miniaturization of the power supply modules and their energy storage capacitors. Reducing the dimensions of transformers and throttles for power supply modules operating at frequency ranges 10,000 times less than those of the UHF portion is an extremely difficult task. For example, the best AEPS-GROUP DC/DC and AC/DC type modules for APAR have a ∆L exceeding 21.5 mm and 47 mm, respectively (Figs. 1, 2, 3, 4). This means that, as of yet, it is impossible to create a completely decentralized (which is desirable from the overall APAR reliability point of view) C and X range DEPSMS using AEPS-GROUP modules – time and expensive research are required.
Figure 2: DC/DC module JETD50, a module prototype accommodated in the TRM, width ∆L=21.5 mm, dimensions=23x51x10 mm.
Figure 3: AC/DC module JETA60, a module prototype with PFC for APAR TRM, width ∆L=47 mm, dimensions=101x51x18 mm.
Figure 4: AC/DC / DC/DC module TESAV50 with two alternative input voltage circuits without/with PFC (option), dimensions w/o external capacitor = 83x53x13 mm
That is why only 4 to 6 GHz max. frequency decentralized APAR DEPSMSs based on single-channel TRMs are currently feasible.
Nowadays, proven technical solutions able to bypass the prohibition for APAR dimensions exceeding the emitted half-wave length can be used for APAR operating frequencies above 6 GHz. Specifically, these are multichannel TRMs. Their 2-channel or 4-channel TRM common case accommodates 2 power supply modules connected in series or in parallel providing for elementary (with all the following consequences) power supply module back-up.
In this case we obtain a decentralized DEPSMS with a reliability coefficient which is very close to 1, at the cost of having a complicated TRM and worse EMC.
Manufacturing large quantities of complicated and expensive multichannel type modules instead of single-type simple TRMs adapted for robotic production is hardly a promising business venture.
The cons also include the forced necessity of using AC/DC type centralized power supply sources for these systems, e.g., inverterbased with backed-up JETA2000 PFC (Fig. 5). The result is a two-staged inversion structure with low duty ratio efficiency.
Figure 5: AC/DC module with JETA2000 with PFC, dimensions=250x140x38 mm
Data published in American magazines represents an excellent example of how difficulties of miniaturizing DEPSMSs consisting of more than 2,000 TRMs hamper 3D APAR implementation on the F22 RAPTOR fighter (Fig. 6).
With the volume/weight of all side-looking airborne radars being 565 dm3/553 kg and with the MSDNE AFAS 16 total power being 530W, the volume/weight of MSDNE represents 40/45 %. It should be noted here that a virtually centralized DEPSMS is used in this example. It possesses critically low reliability and has a high share in the weight of the TRM feeder-type power supply system, but it is lighter than the decentralized system.
Figure 6: Picture of APAR within the F22 fighter
The following are examples of some typical ground and airborne APAR DEPSMS implementations, and how the transistor technology used for the TRM UHF part impacts the key energy indicators of a decentralised MSDNE.
Design 1 (Fig. 7) was developed on the basis of GaAs UHF transistors with their typical 10 V power voltage and 0.2 efficiency. An energy storage capacitor of 3.14 nominal units volume is available (differential power voltage and efficiency are considered when comparing Designs 1 and 2).
Figure 7: DEPSMS for APAR (GaAs)
Design 2 (Fig. 8) was developed on the basis of transistors with 28 V power voltage and 0.5 efficiency typical for GaN technology. An energy storage capacitor of 1 nominal unit volume is available.
Figure 8: DEPSMS for APAR (GaN)
The following parameters are common for both designs: radiated pulse power of each TRM = 10 W, max. frequency = 6 GHz, power supply module efficiency = 0.88, TRM number = 2,000, pulse duty ratio = 5.
The total volume of GaAs-based DEPSMS is 10,280 nominal units or approximately 56 dm3, and together with the centralized backedup inverter including 18 JETA2000 type modules w/ PFC connected in parallel (each having a volume of 1,200 nominal units) we have 21,600 + 10,280 = 31,880 nominal units or approximately 174 dm3.
The total volume of GaN-based DEPSMS is 4,000 nominal units or approximately 21.7 dm3, and together with 9 centralized inverter JETA2000 type modules w/ PFC connected in parallel we have 10,800 + 4,000 = 14,800 nominal units or approximately 80.4 dm3.
| Parameters | GaAs | GaN |
| Total volume of DEPSMS | 10,280 units | 4,000 units |
| DEPSMS total volume | 56 dm3 | 21.7 dm3 |
| Total volume of DEPSMS with centralized backedup inverter | 31,880 units | 14,800 units |
| Total volume of DEPSMS with centralized backedup inverter | 174 dm3 | 80.4 dm3 |
| Energy storage capacitor | 3.14 nominal units (volume) | 1 nominal unit (volume) |
| Power supply voltage | 10 V | 28 V |
| Transistor efficiency | 0.2 | 0.5 |
| Average power consumption of all TRM UHF portions | 20,000 W | 8,000 W |
| Average power consumption of APAR with centralized inverter | 25,244 W | 10,111 W |
| Thermal power dispersion in APAR, excluding antenna | 86,855 W | 10,251 W |
Table 2: Comparison of Design 1 (GaAs) and Design 2 (GaN) parameters
Conclusions:
The results show that using GaN technology instead of GaAs technology can allow for a reduction in APAR power consumption of up to 2.5 times, a reduction in thermal power dispersion of more than 8 times and a reduction in the volume and weight of all components of more than 2 times.
Even today, in 2015-2016, the industry would be able to manufacture APARs based on single-channel GaN TRM operating in S, C and partially in X ranges, with 20,000 W total output UHF-power. JETD25, JETD50, JETA2000 modules produced in series by AEPSGROUP could be used as prototypes of power supply modules for APAR and supercomputers.
AEPS-GROUP TESAV50 modules without/with PFC and JETA60 modules with PFC are rather promising for supercomputers and compact APAR systems – direct operation from 220 V or 3х380 V generators without a centralized inverter becomes possible, dramatically improving dimensional and weight parameters and considerably reducing thermal power dispersion.
The author will be grateful for questions and remarks on this material. Communication should be carried out via www.goncharov-jet.com . All the data in this article have been taken from freely accessible online sources.
About the Author
A.Yu. Goncharov has PhD in Technical Sales and the president of AEPS-GROUP, that is a company with specialization in development and manufacturing of AC/DC and DC/DC power supply units and blocks, which provide unique characteristics for operation in extremely harsh environmental conditions. In the group there are also our trade and production representative offices in Russia: TE LLC and VIP-AG LLC. These companies have a license for the right of local production using AEPS-GROUP technologies.
