Study of heat sink EMI effects in SMPS circuits

Abstract

EMC is an integral part of Switching Mode Power Supply design. An optimal SMPS could be considered as one, which achieves the best possible compromise between power losses and EM1 disturbances, both of which are directly related to the switching speed of the device. Thus the process of finding an acceptable switching speed becomes a critical part of the design process. This paper considers heat sink aspects of this power loss/EMI trade-off.

A CM Filter Configuration for Grid-Tied Voltage Source Converters

“…In all these prevalent methods discussed in literature, the heat sink is typically grounded for safety reasons [1], [2], [6]. Grounding the heat sink can increase the CM currents and potentially aggravate the CM noise [1], [13]. This may necessitate the use of a complicated higher order or a bulkier CM filtering solution.…”

“…Such fault scenarios can be handled either by floating the heat sink or by providing an impedance between the heat sink and ground [14]. A floating or a nongrounded heat sink reduces the CM noise but becomes a source for radiated emissions as it acts like a voltage-driven antenna with respect to ground [13]. Impedance grounding of the heat sink offers a possibility to reduce the CM noise without having an adverse effect on the radiated emissions.…”