Converter's resting power consumption reduced by 50%

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A power converter that maintains its efficiency at currents ranging from 500pA to 1mA has been unveiled by researchers from MIT's Microsystems Technologies Laboratories (MTL). Application areas include the IoT and body-powered electronics.

"Typically, converters have a quiescent power, which is the power that they consume even when they're not providing any current to the load," says researcher Arun Paidimarri. "My converter can maintain efficiency over a wide range of currents."

The design is a step-down converter that accepts inputs ranging from 1.2 to 3.3V and reduces them to between 0.7 and 0.9V.

"It's based on packets of energy." Paidimarri explains. “You have switches, an inductor, and a capacitor in the power converter, and the switches turn on and off."

The control circuitry for the switches includes a circuit that measures the output voltage of the converter. If the output voltage is below a threshold, the controllers throw a switch and release a packet of energy.

If no device is drawing current from the converter, or if the current is going to a simple, local circuit, the controllers might release between one and a couple hundred packets per second. But if the converter is feeding power to a radio, it might need to release 1million packets a second.

The converter can run the switch controllers at a range of rates. The circuit that monitors the converter's output voltage contains a voltage divider, which siphons off a little current from the output for measurement.

Siphoning current lowers the converter's efficiency, so the divider is surrounded by a block of additional circuit elements, which grant access to the divider only for the fraction of a second that a measurement requires.

According to the researchers, the result is a 50% reduction in quiescent power consumption compared to previous designs and a tenfold expansion of the current-handling range.