Delta Electronics Series H48SA manual Design Considerations, Input Source Impedance

DESIGN CONSIDERATIONS

Input Source Impedance

The impedance of the input source connecting to the DC/DC power modules will interact with the modules and affect the stability. A low ac-impedance input source is recommended. If the source inductance is more than a few μH, we advise adding a 33 to 100 μF electrolytic capacitor (ESR < 0.7 Ω at 100 kHz) mounted close to the input of the module to improve the stability.

Layout and EMC Considerations

Delta’s DC/DC power modules are designed to operate in a wide variety of systems and applications. For design assistance with EMC compliance and related PWB layout issues, please contact Delta’s technical support team. An external input filter module is available for easier EMC compliance design. Below is the reference design for an input filter tested with H48SA12025NN A to meet class B in CISSPR 22.

Schematic and Components List

+	CY1		Vin(+) Vo(+)
CX	CX1	Cin	H48SA12025	LOAD
Vin		L2
L1
-	CY1		Vin(-) Vo(-)
			CY

CX is 4.7uF ceramic cap;

CX1 is 4.7uF ceramic cap;

CY is 3.3nF ceramic cap;

CY1 is 4.7nF ceramic cap;

L1 is common-mode inductor, L1=0.08mH;

L2 is common-mode inductor, L1=0.24mH;

Test Result

Test result is in compliance with CISPR 22 class B, which is shown as below:

Vin=48V, Io=25A,

Yellow line is quasi peak mode;

Blue line is average mode.

DS_H48SA12025_05052008

Safety Considerations

The power module must be installed in compliance with the spacing and separation requirements of the end- user’s safety agency standard, i.e., UL60950, CAN/CSA-C22.2 No. 60950-00 and EN60950:2000 and IEC60950-1999, if the system in which the power module is to be used must meet safety agency requirements. When the input source is 60 Vdc or below, the power module meets SELV (safety extra-low voltage) requirements. If the input source is a hazardous voltage which is greater than 60 Vdc and less than or equal to 75 Vdc, for the module’s output to meet SELV requirements, all of the following must be met:

ŠThe input source must be insulated from any hazardous voltages, including the ac mains, with reinforced insulation.

ŠOne Vi pin and one Vo pin are grounded, or all the input and output pins are kept floating.

ŠThe input terminals of the module are not operator accessible.

ŠIf the metal baseplate is grounded the output must be also grounded.

ŠA SELV reliability test is conducted on the system where the module is used to ensure that under a single fault, hazardous voltage does not appear at the module’s output.

Do not ground one of the input pins without grounding one of the output pins. This connection may allow a non-SELV voltage to appear between the output pin and ground. The power module has extra-low voltage (ELV) outputs when all inputs are ELV. This power module is not internally fused. To achieve optimum safety and system protection, an input line fuse is highly recommended. The safety agencies require a fuse with 30A maximum rating to be installed in the ungrounded lead. A lower rated fuse can be used based on the maximum inrush transient energy and maximum input current.

Soldering and Cleaning Considerations

Post solder cleaning is usually the final board assembly process before the board or system undergoes electrical testing. Inadequate cleaning and/or drying may lower the reliability of a power module and severely affect the finished circuit board assembly test. Adequate cleaning and/or drying is especially important for un-encapsulated and/or open frame type power modules. For assistance on appropriate soldering and cleaning procedures, please contact Delta’s technical support team.

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