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MOSFET air-cooling module for a voltage transient tool

IP.com Disclosure Number: IPCOM000004697D
Publication Date: 2001-Apr-12
Document File: 4 page(s) / 104K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a design for a MOSFET air-cooling module (MACM) for a voltage transient tool (VTT). Benefits include a high efficiency, self-sufficient, localized cooling system that functions in a small area and volume with high current inputs.

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MOSFET air-cooling module for a voltage transient tool

Disclosed is a design for a MOSFET air-cooling module (MACM) for a voltage transient tool (VTT). Benefits include a high efficiency, self-sufficient, localized cooling system that functions in a small area and volume with high current inputs.

The components of the MACM design include:

Inlet fan with high airflow and high static pressure characteristics

Exhaust fan with flexible airflow, low or high depending on design requirements, but low static-pressure characteristics

Thermal-coupled (to MOSFETs), 4-way horizontal airflow optimized cower heat-sink with various embodiments

Plastic module cover over the heat-sink to guide or direct airflow over the heat-sink fins

The cover can also serve as an EMI shield, if required.

The MACM is a self-sufficient unit that provides optimal air-cooling for high power density VTT components using a combination of passive and active technology. A cooling module consists of two fans arranged in a push-pull arrangement. The fans are separated by a nearly-sealed plastic module cover, which contains copper heat-sink(s) thermal-coupled to VTT PCB components, namely MOSFETs. The attachment or thermal-coupling mechanism may vary. Bolting, clips, and press-fittings are some examples. Copper is used in the heat-sink for its high thermal conductivity and thermal inertia (mass heat capacity). The fins are unidirectional and extruded, not pin fins, reducing the significant pressure drop.

The MACM is comprised of three sections, the inlet cooling-air section, the cooling section, and the exhaust-air section (see Figure 1).

A source of forced, cool ambient air is provided by the inlet-fan into the cooling section to remove the heat from the highly concentrated electronic components. Incoming cooling air faces flow resistance, or impedance from VTT components and the heat-sink. A loss in momentum, or pressure drop, occurs against the VTT components and the heat-sink. Therefore, the inlet fan must not only have high volumetric airflow but high static pressure and is generally thicker than the exhaust fan. It is intended to have flexible volumetric airflow but low static-pressure characteristic because an exhaust fan does not face the impedance.

The cooling section has a small volume, less than 125 cc. In one implemented design, it dissipates up to 100 watts from multiple MOSFETs (up to four) and from VTT PCB components (for example, resistors) with an additional wattage of 3-5 watts. The cooling section is topped by a plastic module cover. It ducts the air from the inlet fan, focuses air on the heat-sink fins (and decreases momentum loss, or pressure drop), and then ducts the heated air to the exhaust fan.

Heat is conducted away from the MOSFET to the copper heat sink and then cooled by the forced-cooling air. Incoming cool air also cools other VTT PCB components, i...