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1000 Watt EBRR Power Chip

EBRR - Electric Bicycle Road Racing on Go Kart tracks.

Background

In order for EBRR to become a reality it had been missing an essential piece of technology. Since ebikes vary in their power output it's necessary in order to achieve fairness to have some means to limit the power of the ebike to 1000 watts of input.

Circuit History

In the earliest days of circuit design people used analog circuits cobbled together so that voltage and current were combined to produce an approximate power result. I say "approximate" because analog circuits tend to be inaccurate. This earliest design has fallen completely out of favor.

The next step was to switch to a digital conversion process which also lost precision due to the conversion of analog to digital signals. While the digital technique was an improvement over the original analog approach it still was combersome and inaccurate.

The most recent concept is to use modern chip fabrication techniques to precisely control the creation of a dedicated chip using analog techniques to arrive at a power figure. Since chips can be produced to very high precision they can actually minimize the inaccuracies at the source.

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Digi-Key - LT2940IMS#PBF-ND (Manufacturer - LT2940IMS#PBF)

http://cds.linear.com/docs/Datasheet/2940f.pdf

4V to 80V High Side Sense, 100V Max

The LT®2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power. Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate forward and reverse power flow.

An integrated comparator with inverting and noninverting open-collector outputs makes the LT2940 a complete power level monitor. In addition, an output current proportional to the sensed high side current allows current monitoring. The current mode outputs make scaling, filtering and time integration as simple as selecting external resistors and/or capacitors.

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Power/current monitor enables board and system-level optimization

12/15/2009 9:33 PM EST

Milpitas, Calif.—Linear Technology Corp. has introduced the LT2940, a power and current monitor for 4V to 80V systems.

According to Linear, the LT2940 provides the necessary circuits to accurately measure, monitor, and control power in situations in which both the current and voltage may vary due to supply voltage uncertainty, component parametric changes, transient conditions or time-varying signals.

Unlike traditional power monitors that rely on data converters and multiplying registers to calculate power, the LT2940 uses a true four-quadrant analog multiplier that results in what the company says is a 5% power measurement accuracy and 3% current measurement accuracy, ensuring that boards and systems achieve optimum power efficiency and reliability.

The LT2940 is suitable for use in line cards and servers, power-sense circuit breakers, power control loops and a wide variety of metering applications.

Pricing: Starts at $2.05 each in 1,000 piece quantities.

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Notice that the chip came into existence not long ago in Dec 2009.