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In many power supplies and circuits it is advantageous and even necessary to monitor the currents flowing in, out, or through a power supply circuit. For example, monitoring for transient overcurrent conditions in the output a DC-DC converter to trigger protection circuitry or to monitor the resonant tank current for control of a Resonant LLC circuit.

While many AC current sense solutions exist on the open market, the current sense transformer can be an appealing solution in many applications. A combination of low primary DCR, low core losses (due to typically low core flux densities), and small secondary currents give rise to a simple, effective, and low-cost method of sensing AC current.

The operation of a current sense transformer is relatively straight-forward but often misunderstood.  A current sense transformer typically has two windings each of which passes through a ferromagnetic core. The primary winding (typically one turn) is designed with low resistance and is in series with the current that is being measured. The secondary winding (typically ranging from twenty to two hundred turns) has higher DCR and carries the much lower current which will be sensed via a burden resistor ( ) that is in series with the secondary winding. The sensed voltage () can then be fed to a comparator or other IC to take the appropriate action. A typical application circuit can be seen below, although it is possible for the rectifying diode to be omitted depending on the sensing requirements:

Pulse expands its range of surface mount current sense transformers with the introduction of its first safety standard compliant products with high isolation and enhanced insulation.

Using the Pulse patented sidecar construction developed for our high isolation transformer series, the PH9500 series utilizes this unique packaging style to offer basic insulation with 8.2mm creepage in a 14x13x8.8mm form factor. The rated current is 10Arms and with turns ratios of 1:65 and 1:100 are available. Please see PH9500 data sheet for further details.

The PH9505 uses a unique construction where the primary winding which is molded into the plastic base forming a solid insulation barrier. This allows the part to be compact, 13.6x12.8x14.4mm, and achieve reinforced insulation per IEC60664/IEC60950-1 for a working voltage up to 300Vrms. The low DCR primary allows for a rated current of 30Arms with a range of turns ratios from 1:50 to 1:180. Please see the PH9505 datasheet for further details.

With the proliferation of high voltage battery packs in automotive and energy storage applications the demand for compact,  high isolation voltage transformers is growing exponentially. These devices, traditionally used to isolate signals between low voltage and high voltage circuits and provide voltage to gate drive and IGBT circuits, are now one of the critical devices keeping high voltage systems isolated and safe. The wide variety of electric transportation systems and electric charging, along with the equally varied energy storage systems such as solar and wind battery backup, creates an equally varied set of electrical, mechanical and safety specifications for these low power isolation transformers. Pulse Electronics has developed, in conjunction with our end-customers and 3^rd party power IC partners, multiple catalog platforms to meet the industries need.

To select the appropriate transformer is it necessary to understand the end-application safety specifications, mechanical constraints and the electrical requirements. From a customer standpoint the mechanical constraints are the most obvious and will be dictated by the end-product dimensions and may define the maximum transformer height/length/width. The electrical requirements of the transformer will depend on the selected switching topology (push-pull, h-bridge, f-bridge, flyback), the input and output voltages, switching frequency and output power. In general, these electrical requirements are well understood and with a wide range of topologies, volt-usec ratings, package sizes and turns ratios a catalog solution from Pulse is is readily available. Often, it is the safety specifications which cause customers the most confusion as there are often multiple standards in play (IEC61558-1, IEC61558-2, IEC6064-1, IEC62368-1) and unfamiliar terminology (working voltages, insulation levels, creepage and clearance distances). Fortunately, Pulse datasheets detail the conformance of each platform in terms of the relevant standard, insulation levels, isolation voltages and applicable safety distances. Pulse also has experienced safety engineers on staff and we are able to assist with any questions.

Our new low power isolation transformer overview provides easy access to all of our commercial and automotive grade catalog surface mount options. Modifications to catalog parts can be made by contacting us here. 

Pulse Electronics expands its range of surface mount common mode chokes with the introduction of the PA5140/41 series. Using the fully automated round wire coil forming technology developed for its existing high current inductor product line, these new series offer the highest available current in a surface mount package. Two platforms have been developed, the 18x19x19mm EP18 and the 23x23x23mm EP22 which offer inductances from 110uH to 470uH, with currents up to 32A. These EP cores have been designed around the coil dimension to minimize the component size, offering a higher-density inductance/current solution. The high permeability ferrite material minimizes the number of turns (and therefore the DC resistance) resulting in a much higher current rating that other similarly sized common mode chokes.

Due to the continuing uncertainty caused by CoVid-19, and in an effort to ensure that we act in a socially responsible manner to protect the health of our employees, business partners and community members, Pulse Electronics has made the difficult decision to withdraw from APEC 2020. Pulse looks forward to participating in APEC 2021 in Phoenix, AZ.

Pulse Electronics continues the expansion of our composite core power inductor products adding four new platform sizes. These new products offer extremely high energy storage density 1300uJ/cm3, current ratings in excess of 39Apk and range in size from 4.3 x 4.3 up to 16.8 x 15.8.  Available in both commercial grade (-40C to 130C) and automotive grade (-55C to 155C) these products are ideally suited for any high performance applications in the communications, computing, industrial, and automotive market segments. Composite core inductors offer superior performance over similar molded powder inductors due to the high density core materials and low loss winding structure and retain the desired soft saturation characteristics.

The demand for electric vehicles, for both personal and commercial transportation, continues to grow and with this growth comes increased pressure on designers of on-board chargers (OBC) and DC/DC inverters to ensure the battery packs are efficiently utilized.  This reality, in turn, puts renewed focus on the power magnetic components that are used to provide isolation and voltage conversion throughout the vehicle.  

The need to ensure that these high power magnetics are optimized in terms of density, weight, efficiency and cost along with the increased usage of resonate mode switching topologies dictates the use of advanced 3D design techniques. It is no longer possible to create a viable design using 2D iterative equations. Pulse Electronics employs our expertise and vast design experience to provide leading edge power magnetics. 

Pulse Electronics is excited to introduce a new series of automotive grade, molded power inductors.  The PM434X series is ideal for high current, non-isolated DC/DC converters and voltage regulators.  This new inductor series expands on our existing commercial grade platforms by offering a fully certified IATF alternative offering the same superior electrical performance. It includes PM4340, PM4341, PM4342, PM4343, PM4344 & PM4345 offering 6 sizes with footprints spanning from 17x17mm down to 6x6mm and a low 2.0mm minimum profile.  These products are suitable for a wide range of automotive applications including seating, safety, lighting, entertainment and any other applications limited to 130C maximum temperature.

The PA/PM540x and PA/PM544x series is our newest line of Molded Power inductors. Designed for high efficiency applications in industrial, communications, computing, and automotive markets. These platforms have low power loss, excellent shielding and can handle high transient current spikes.Ranging in size from 3.7x3.4mm to 14x12.8mm they add to Pulse's existing molded inductor platforms. These new series of parts are available in both commercial grade (PA540x) and automotive grade (PM540x). Production lead time is approximately 12-14 weeks, and samples are available upon request. 

Automotive Grade Reinforced Insulation EP7 Platform

Pulse Electronics has released an automotive grade IATF certified version of our popular PH9185 series of high isolation voltage transformers.The PM2190.XXXNL series is suitable for a wide range of low power automotive applications where high voltage safety isolation is critical such as Battery Management Systems (BMS) and communication modules.