MIL Grade EMC Filter for DC/DC Converters
2023. 6. 16
DC/DC-converters are electronic devices that can change a direct current (DC) voltage into another DC voltage. They can act like an isolating transformer or a step-up or step-down transformer but with direct current instead of alternating current (AC) supplies.
1. About DC/DC Converters
DC/DC-converters are electronic devices that can change a direct current (DC) voltage into another DC voltage—in other words, they can act like an isolating transformer or a step-up or step-down transformer but with direct current instead of alternating current (AC) supplies. As transformers only work with AC, all DC/DC converters are internally DC-to-AC-to-DC modules:
Fig. 1: Basic layout of a DC/DC-converter
As DC/DC converters contain switching elements (transistors) to generate the internal AC waveform, their input and output currents are pulsating in nature which generates electromagnetic interference (EMI). Electromagnetic compatibility (EMC) filters are specialized circuits designed to ensure effective management of EMI and allow the converter to pass the EMC tests with sufficient margin below the maximum permitted limits. Their primary function is to suppress unwanted electromagnetic signals, preventing interference that could disrupt or degrade the performance of sensitive electronic equipment.
2. About MIL-STD-461G
Military-grade compliant EMC filters are engineered to meet stringent army, airforce and navy standards, with high-quality components and rigorous testing to ensure reliability in extremely harsh environmental and operating conditions. With their exceptional EMI-suppression capabilities, these filters play a crucial role in safeguarding critical military systems and optimizing their overall electromagnetic compatibility.
The United States Military Standard (MIL-STD) applicable for EMC is MIL-STD-461 (Requirements for the Control of Electromagnetic Inter¬ference Characteristics of Subsystems and Equipment). The current, most up-to-date version of this standard is referred to as MIL-STD- 461G, although many legacy projects still use the older version, MIL-STD-461E.
The United States Military Standard (MIL-STD) applicable for EMC is MIL-STD-461 (Requirements for the Control of Electromagnetic Inter¬ference Characteristics of Subsystems and Equipment). The current, most up-to-date version of this standard is referred to as MIL-STD- 461G, although many legacy projects still use the older version, MIL-STD-461E.
3. Classes and Lebels of MIL-STD-461G
MIL-STD-461G establishes classes and test levels to define the limits for EMC in various military platforms. These classes and their corresponding limits apply to a wide range of military vehicles, including:
Ground Vehicles:
Class A: Non-critical systems with moderate emission and immunity requirements.
Class B: Combat vehicles with intermediate emission and immunity requirements.
Class C: Mission-critical systems, such as command and control units, with the strictest emission and immunity requirements.
Aircraft:
Class A: Non-critical avionics and systems meeting moderate limits.
Class B: Critical avionics with intermediate emission control and immunity requirements.
Class C: Vital systems, including flight control and communication equipment, meeting the strictest limits for emission and immunity.
Submarines:
Class A: Non-critical systems with moderate emission and immunity requirements.
Class B: Critical subsystems with intermediate emission control and immunity requirements.
Class C: Vital systems such as navigation and communication equipment, subject to the strictest emission and immunity requirements.
Ground Vehicles:
Class A: Non-critical systems with moderate emission and immunity requirements.
Class B: Combat vehicles with intermediate emission and immunity requirements.
Class C: Mission-critical systems, such as command and control units, with the strictest emission and immunity requirements.
Aircraft:
Class A: Non-critical avionics and systems meeting moderate limits.
Class B: Critical avionics with intermediate emission control and immunity requirements.
Class C: Vital systems, including flight control and communication equipment, meeting the strictest limits for emission and immunity.
Submarines:
Class A: Non-critical systems with moderate emission and immunity requirements.
Class B: Critical subsystems with intermediate emission control and immunity requirements.
Class C: Vital systems such as navigation and communication equipment, subject to the strictest emission and immunity requirements.
4. Requirements Matrix
MIL-STD-461G specifies a comprehensive set of test procedures aimed to fulfill the US Department of Defense (DoD) specifications and requirements, depending on the sphere of operation. The test procedures are broken up into four groups: radiated emissions (RE), conducted emissions (CE), radiated susceptibility (RS), and conducted susceptibility (CS). The name of a procedure consists of the two-letter abbreviation representing its group followed by a code, for example CS101 denotes the test “Conducted Susceptibility, Power Leads.”
A = Applicable
S = Specified in procurement
L = Limited applicability
Blank = Not applicable
| Equipment | CE101 | CE102 | CE106 | CS101 | CS103 | CS104 | CS105 | CS114 | CS115 | CS116 | CS117 | CS118 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Surface Ships | A | A | L | A | S | L | S | L | S | A | L | S |
| Submarines | A | A | L | A | S | L | S | L | S | L | S | S |
| Aircraft, Army | A | A | L | A | S | S | S | A | A | L | A | |
| Aircraft, Navy | L | A | L | A | S | S | S | A | A | L | A | |
| Aircraft, Airforce | A | L | A | S | S | S | A | A | L | A | ||
| Space Systems | A | L | A | S | S | S | A | A | L | |||
| Ground, Army | A | L | A | S | S | S | A | A | S | |||
| Ground, Navy | A | L | A | S | S | S | A | A | S | |||
| Ground, Airforce | A | L | A | S | S | S | A | A |
Table 1: MIL-STD Conducted Emissions and Susceptibility Matrix
A = Applicable
S = Specified in procurement
L = Limited applicability
Blank = Not applicable
| Equipment | RE101 | RE102 | RE103 | RS101 | RS103 | RS105 |
|---|---|---|---|---|---|---|
| Surface Ships | A | A | L | L | A | L |
| Submarines | A | A | L | L | A | L |
| Aircraft, Army | A | A | L | A | A | L |
| Aircraft, Navy | L | A | L | L | A | L |
| Aircraft, Airforce | A | L | A | |||
| Space Systems | A | L | A | |||
| Ground, Army | A | L | L | A | ||
| Ground, Navy | A | L | L | A | L | |
| ... | ... | ... | ... | ... | ... | ... |
Table 2: MIL-STD Radiated Emissions and Susceptibility Matrix
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