Category Archives: DC-DC Converter

Power Brick: #GoldStandard Heat Sinks for DC/DC Converters

Power Brick

ATS Power Brick heat sinks are the #GoldStandard for cooling eighth, quarter, half, and full brick DC/DC power converters. (Advanced Thermal Solutions, Inc.)


Advanced Thermal Solutions, Inc. (ATS) has a line of Power Brick heat sinks (available through Digi-Key Electronics and Arrow) that are specially designed to cool eighth-, quarter-, half-, and full-sized DC to DC power converters and power modules. Power Brick heat sinks feature ATS’ patented maxiFLOW™ design, which reduces the air pressure drop and provides greater surface area for more effective convection cooling.

Power Brick heat sinks are a critical component for the optimal thermal management of electronic devices because DC/DC power converters are used in many applications and across a number of industries, including communications, health care, computing, and more.

DC/DC converters are electronic circuits that convert direct current (DC) from one voltage to another. Converters protect electronic devices from power sources that are too strong or step up the level of the system input power to ensure it runs properly. The process works by way of a switching element that turns the initial DC signal into a square wave, which is alternating current (AC), and then passes it through a second filter that converts it back to DC at the necessary voltage.

As explained in an article on MaximIntegrated.com, “Switching power supplies offer higher efficiency than traditional linear power supplies. They can step-up, step-down, and invert. Some designs can isolate output voltage from the input.”

When converting electrical input to the proper voltage, DC/DC converters operate at a specified efficiency level, with some energy lost to heat. ATS Power Brick heat sinks provide the necessary step of dissipating that heat away from the converter to lower the junction temperature. This will optimize the performance of the component and ensure the longevity of the converter.

Anodization boosts Power Brick heat transfer capability

The pleasing gold color that has made Power Brick one of the most popular lines of heat sinks for DC/DC converters stems from the anodization process that ATS uses for its heat sinks. Anodization, as noted in an earlier blog post on this site, “changes the microscopic texture of a metal, making the surface durable, corrosion- and weather-resistant.”

Surface anodization works by turning the metal into the anode (positive electrode) of an electrolytic circuit. By passing an electric current through an acidic electrolytic solution, hydrogen is released at the cathode (negative electrode) and oxygen is released at the anode. The oxygen on the surface of the metal anode forms a deposit of metal oxide of varying thickness – anywhere from 1.8-25 microns.

The previous article explained, “The advantages of surface anodizing are the dielectric isolation of the cooling components from their electronics environment, and the significant increase in their surface emissivity.”

The emissivity coefficient of an anodized surface is typically 0.83-0.86, which is a significant boost from the standard coefficient of aluminum (0.04-0.06). By increasing the emissivity of the metal, there is also a significant enhancement of the metal’s radiant heat transfer coefficient.

The eye-catching gold color of ATS Power Brick heat sinks is added during the anodization process.

maxiFLOW™ design gives Power Brick an edge

Anodization of heat sinks is a standard practice to ensure that the metal components can withstand the rigors of dissipating heat from high-powered components. The feature that gives an ATS Power Brick heat sink the significant edge on its competitors is its patented maxiFLOW™ fin geometry, which has higher thermal performance for the physical volume it occupies compared to other heat sink designs.

maxiFLOW™ design is a low-profile, spread-fin array, which offers greater surface area for convection cooling. While it offers more surface area, it does not require additional space within the electronics package. This is an important feature in today’s electronics devices, which have an ever-increasing component density and in which space is always at a premium. This is an especially important feature for designers that want to cool DC/DC converters but are limited in the amount of available room.

Independent testing at Northeastern University of various heat sink designs demonstrated that maxiFLOW™ had the lowest thermal resistance for natural and forced convection, particularly when air flow velocity was below two meters per second. For heat sinks with the same base dimensions and fin height, maxiFLOW™ performed the best.

Testing has demonstrated that maxiFLOW™ can produce 20 percent lower junction temperatures and 40 percent lower thermal resistance than other heat sink designs. Utilizing maxiFLOW™ allows ATS Power Brick heat sinks to meet the industry standard base plate temperature of 100°C.
For more information about maxiFLOW™, watch the video below:

Power Brick meets industry standards

In the DC/DC market, there are a number of standard footprints that manufacturers use to offer flexibility for designers in choosing a vendor and in laying out a PCB. ATS has addressed the industry standard footprints with its Power Brick heat sinks. This will facilitate the use of the heat sinks for thermal management.

By optimizing the thermal management and meeting industry standards, Power Brick heat sinks can provide cost savings and reduce MTBF. Rather than having to over-design a system or a layout, engineers can turn to Power Brick as a thermal solution.

It is not only the industry standard footprints that Power Brick heat sinks have matched but also the standard hole patterns, which meet the standards set by the Distributed-power Open Systems Alliance (DOSA) to make assembly easy. The three millimeter holes (and soon 3.5 mm) match up to sizes commonly used in power brick manufacturing to ensure the proper connection for the heat sink (to avoid increasing the thermal resistance) and also to avoid using additional space in the tight confines of a PCB.

For the above reasons, Power Brick heat sinks are the “gold standard” for cooling DC/DC converters. Learn more in the video below:

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

References

i http://uk.rs-online.com/web/generalDisplay.html?file=automation/dc-converters-overview&id=infozone
ii https://www.maximintegrated.com/en/app-notes/index.mvp/id/2031
iii https://www.qats.com/cms/2010/11/09/how-heat-sink-anondization-improves-thermal-performance-part-1-of-2/
iv https://www.qats.com/cms/wp-content/uploads/2013/09/Qpedia_Oct08_How-Air-Velocity-Affects-HS-Performance.pdf

Industry Tips for Placing DC/DC Converters on PCB

DC/DC Converters

This article outlines industry tips and suggestions about placing DC/DC power converters on a PCB with other components. (Advanced Thermal Solutions, Inc.)

The design of a printed circuit board (PCB) that includes isolated DC to DC power converters is an important consideration to ensure the optimal performance of a system. Engineers have to be concerned with parasitic impedance and capacitance, the effects of the electromagnetic field created by the power converter on nearby components, as well as voltage accuracy, environmental noise reduction, and limiting radiated electro-magnetic interference (EMI).

This electromagnetic effect can cause significant voltage drops and improper design of a PCB could force engineers to make potentially costly changes (in terms of design time and budget), such as additional circuitry or upgrades to external components like power switches and capacitors.(i)

There are many advantages to using DC/DC converters and engineers adding these power bricks to a PCB do not have to be experts on power supply design, since the Distributed-power Open Systems Alliance (DOSA) has defined the industry standards for footprints and pinouts. Engineers know ahead of time how much space to dedicate and how the converter will be connected to the board.(ii)

“The brick typically comprises all the components (apart from filter circuits) required for a switching power supply including MOSFET switches, energy storage components, and switching controller,” writes Steven Keeping of Electronic Products on DigiKey.com. “By selecting a brick, an engineer does not have to worry about the intricacies of switching power supply design. The supplier has done all the work to ensure the unit operates optimally.”

While much of the work has been done by the manufacturer of the DC/DC converter to ensure its proper function, the engineer designing the system still has to consider the converter’s placement on a board carefully.

Parasitic Resistance, Impedance, and Capacitance

The most prominent issue that DC/DC converters can cause on a PCB is parasitic resistance, capacitance, and impedance. The power module creates an electromagnetic field that could disrupt the performance of components within its boundaries. As noted above, this could cause an unwanted voltage drop for the system and force more external power to be pushed through the converter.

According to a report published by members of the Institute of Electrical and Electronics Engineers (IEEE) from Georgia Tech University, “Short and wide routing traces have lower parasitic resistances and inductances and therefore superimpose less ill-fated effects to the system. As a result, to reduce the parasitic resistance and inductance, the first rule in PCB layout is to place connected power components as close as possible and in a way that their interconnection lengths are minimal.”(iii)

An article on DigiKey.com adds, “The signal traces should not be routed underneath the module, unless they are sandwiched between ground planes, to avoid noise coupling. Similarly, to prevent any coupling, no component should be placed under the module.”(iv)

The IEEE report continued, “Ground planes are effectively close high-speed return paths for average forward signal paths, but arbitrarily increasing the ground plane may not necessarily reach critical nodes. In PCB technologies with more than two layers, middle layers are normally dedicated to ground planes, thereby decreasing their distance to high-current forward switching paths.”

It also recommended using parallel connections for the supply ground, load ground, and measurement instrument’s ground rather than series connectors that are potentially unreliable and that can add impedance between nodes. The report stated, “Undesired noise and high temperature gradients across the PCB usually result when problems with supply ground connections exist.”

DC/DC converters regulate the voltage supply to the system from external power supplies, which makes accuracy a critical component of its performance. In order to ensure the optimal accuracy, it is recommended that the feedback sense terminal is connected as close to the load as possible. It is this voltage that will be converted.

(Advanced Thermal Solutions, Inc.)

Radiated Electromagnetic Interference

Another major concern for placing a DC/DC converter on a PCB is the amount of radiated electromagnetic interference (EMI) is emitted from the module. This is limited by industry standards (CISPR in Europe and FCC in the U.S.) but, as converters work by converting input voltage to AC before converting it back to DC at the correct voltage, there is an electromagnetic field that is produced when the converter is in use.

To minimize the effects of this EMI, “High-frequency nodes should be as short as possible. The metal paths act as antennas and their frequency range is directly proportional to their length. High frequency signal-return paths should be as close as possible to their respective forward paths. The two traces will therefore generate equal but opposite magnetic fields, canceling each other and hence reducing radiated EMI.”(v)

Tim Hegarty, writing for EDN Network, said, “A passive shield layer is established by placing a ground plane as close as possible to the switching loop by using a minimum dielectric thickness. The horizontal current flow on the top layer sets up a vertical flux pattern. The resulting magnetic field induces a current, opposite in direction to the power loop, in the shield layer.

“By Lenz’s Law, the current in the shield layer generates a magnetic field to counteract the original power loop’s magnetic field. The result is an H-field self-cancellation that amounts to lower parasitic inductance, reduced switch-node voltage overshoot, and enhanced suppression of EMI. Having an uninterrupted, continuous shield plane on layer 2 underneath and at closest proximity to the power loop offers the best performance.”(vi)

On DigiKey.com, Steve Taranovich of Electronic Products Magazine wrote, “The input of a DC/DC power module is a constant power at low frequencies. As the voltage decreases, current increases. This will present negative impedance at the input source. The converter will oscillate when the combination of the input filter’s impedance and the power module impedance becomes negative, causing a mismatch to occur. One way to prevent this is to ensure that the output impedance of the filter is much smaller than the input impedance of the power module at all frequencies.”(vii)

Another issue related to electromagnetic field is ground bounce, which is produced by changing magnetic flux due to the fast-changing currents. One of the solutions to prevent this problem, which could cause noise in video and audio devices, is to ensure that “true ground” is at the low end of the load and that all the other points are part of the ground return. In a two-layer PCB, Jeff Barrow of Analog.com also suggests, “A well-planned cut in the ground plane will constrain the return current to a minimum loop area and greatly reduce the bounce. Any residual bounce voltage that is developed in the cut return line is isolated from the general ground plane.”(viii)

Conclusions

Industry standard DC/DC converters have made adding a power supply to a PCB easier for engineers in terms of known sizes and connections. The footprint of a power module is known, but engineers still have important considerations to make before deciding where it should be placed. Keeping in mind the effects of parasitic impedance, capacitance, and resistance and ensuring that the electromagnetic interference will not surpass industry standards or affect other components on the board will ensure optimal performance of the system as a whole.

Using the design tips that are listed here, engineers are well on their way to creating an effective PCB layout with a DC/DC converter. Using Advanced Thermal Solutions, Inc. (ATS) Power Brick heat sinks will ensure the proper thermal management of the converters and of the board.
Learn more about Power Brick heat sinks at https://www.qats.com/eShop.aspx?productGroup=0&subGroup=2&q=Power%20Brick.

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

References

i http://rincon-mora.gatech.edu/research/pcb.pdf
ii http://www.digikey.com/en/articles/techzone/2012/dec/an-introduction-to-board-mounted-dcdc-converter-bricks
iii http://rincon-mora.gatech.edu/research/pcb.pdf
iv http://www.digikey.com/en/articles/techzone/2012/jul/proper-pcb-layout-minimizes-noise-coupling-for-point-of-load-converter-modules
v http://rincon-mora.gatech.edu/research/pcb.pdf
vi http://www.edn.com/design/power-management/4439749/3/DC-DC-converter-PCB-layout–Part-2
vii http://www.digikey.com/en/articles/techzone/2011/dec/conducted-and-radiated-emissions-reduction-techniques-for-power-modules
viii https://pdfs.semanticscholar.org/e3bb/49a1403b2da7d3d77e7024f7be208ee3a732.pdf

New maxiFLOW DC-DC Brick Heat Sinks Ideal for Military-COTS Applications

ATS has recently launched a new product line of maxiFLOW heat sinks, specially designed to cool DC-DC converters. The new line of heat sinks can be used with Vicor’s DC-DC converter Bricks, including their military-COTS applications.

Vicor’s Maxi, Mini, and Micro series DC-DC converters are relied upon by over eight thousand OEMs for their proven performance, broad coverage of input and output voltages, ease of mechanical mounting and thermal management flexibility. These converter modules use advanced power processing, control, and packaging technologies to provide the performance, flexibility, and ruggedness expected in a Military COTS product. High frequency ZCS/ZVS switching, advanced power semiconductor packaging, and thermal management provide high-power density with low noise and high efficiency.

maxiFLOW Heat Sink for Half Brick DC-DC Converters

 

ATS’ patented maxiFLOW technology cools millions of BGAs and other PCB components. The same technology is now available for cooling eighth, quarter, half and full brick modules, such as the Micro, Mini, and Maxi series from Vicor. Unlike other converter heat sinks, the patented maxiFLOW heat sink design reduces air pressure drop and provides greater surface area, increasing thermal performance by 30-200%.

Vicor’s Micro, Mini, and Maxi DC-DC Converters

Vicor’s offering of full, half, and quarter-brick modules feature a patented low noise design with the highest reliability and power density available. Fully encapsulated, Maxi, Mini and Micro series DC-DC converters utilize a proprietary spin fill process that assures complete, void free encapsulation making them suitable for the harshest environments. Two grades (H & M) are available with temperatures to -55°C operating and -65°C storage. H & M-Grade modules are qualified to the stringent environmental tests of MIL-STD-810 and MIL-STD-202 and undergo 100% Environment Stress Screening.

By combining technology from industry leaders Vicor and ATS, it can be ensured that DC-DC converters will have superior performance in the harshest environments, which is vital for military and aerospace applications.

To learn more about maxiFLOW Brick DC-DC converter heat sinks, please visit our Power Brick Heat Sink Page or email ats-hq@qats.com, or call us 781-769-2800.

New maxiFLOW Heat Sinks for Cooling DC-DC Converters


ATS now provides maxiFLOW heat sinks specially designed to cool eighth, quarter, half and full brick size DC-DC converters. The patented maxiFLOW heat sink design reduces air pressure drop and provides more surface area for more effective convection (air) cooling. The same ATS maxiFLOW technology is used in heat sinks cooling millions of BGAs and other PCB components,

The brick DC-DC converter heat sinks offer a range of fin patterns, directions and profiles to match different height and weight restrictions and airflow patterns. All of these heat sinks are protected with a gold anodized finish.

Each heat sink is provided pre-assembled with a layer of Chomerics T766 Thermflow phase change thermal interface material to enhance heat transfer from brick to heat sink. All of these heat sinks also come with three sets of screws in lengths of 5, 6 and 8 mm for varied attachment situations. The heat sinks pre-drilled hole patterns fit all major DC-DC converter designs.

DC-DC converters are circuits which convert direct current (DC) from one voltage level to another. They are extensively used in electronic devices serving communications, computing, data storage, health care, industrial equipment, instrumentation and test and measurement. Heat sinks are typically required to keep the converters running within safe operating temperatures.