Frederik Dostal, Subject Purposes Engineer
Reply: There are present limiting ICs accessible.
In some energy administration functions, exact present limiting is required. That is vital both to guard the power supply, for instance, if an intermediate circuit voltage requires overload safety in order that it may reliably provide different system components with power, or to guard a load that may trigger injury as a result of overcurrent in a fault situation.
In the search for a appropriate dc-to-dc level of load regulator to meet this requirement, only a few voltage converters with adjustable present restrict are discovered in the marketplace. Whereas adjustable present restrict is extra usually discovered on controller designs with exterior energy switches, all built-in options seldomly supply such operate. Additionally, adjustable present limits usually would not have very excessive accuracy. As well as, the present limiters in dc-to-dc converter ICs often solely restrict the inductor present and never the enter or output present of the facility provide. Such an built-in present restrict is designed to guard “simply” the switching regulator itself from destruction in a fault situation. The present restrict lies above the nominally specified most output present and generally has a comparatively low accuracy. That is enough for shielding the switching regulator, however usually not enough to be used as an adjustable present limiter.
Determine 1. System in which the present circulate to or from a switching regulator wants to be restricted.
A versatile resolution to this drawback is so as to add an adjustable present restrict through a further part such because the LTC7003. Relying on the utility, accuracies of roughly 15% can be achieved. The LTC7003 is a high-side N-channel MOSFET static change driver. By means of its adjustable present restrict and its present monitoring operate, it’s superb for including present limiting to widespread dc-to-dc converters. Determine 2 exhibits the usage of the LTC7003 limiter for monitoring the output present of an ADP2370. The ADP2370 is a step-down dc-to-dc converter.
Determine 2. Present limiting added through an LTC7003 driver part.
Typically, high-side present sense amplifiers will also be used for measuring a small voltage drop through a present sense resistor within the energy path. They’ll measure currents with a really excessive accuracy. Nonetheless, with nearly all of them, the permissible voltage distinction between the 2 current-sensing connections may be very small. When such a basic present sense amplifier is utilized in an influence provide during which quick circuits can happen as a result of load, the voltage throughout the sense resistor can rapidly go exterior the permissible vary. On this case, an answer such because the LTC7003, which is permitted to be used in an influence provide, is healthier. Right here, the LTC7003 is designed in such a method that a big voltage distinction is permitted on the SENS inputs. The LTC7003 additionally affords the opportunity of interrupting the facility path by the elective N-channel MOSFET Q1 if the set present threshold is reached. Determine 3 exhibits an LTC7003 resolution with an exterior N-channel MOSFET to interrupt the facility path when a set present threshold is reached.
Determine 3. Circuit with the LTC7003 for limiting present.
By means of the IMONoutput, a voltage that is proportional to the present circulate by the sense resistor is offered. This voltage is in respect to the system floor and corresponds to the voltage throughout the sense resistor multiplied by an element of 20. The voltage lies between 0 V and 1.5 V. This voltage can be utilized with a further exterior op amp to feed into the suggestions circuit of a switching regulator. On this method, the output voltage of the dc-to-dc converter will be diminished in proportion to the present stage sensed by the LTC7003. This possibility is proven in Determine 3 in a grayed-out circuit.
With its fascinating capabilities, the LTC7003 is appropriate for monitoring, limiting, and disconnecting provide traces in quite a few totally different techniques.
In regards to the Creator: Frederik Dostal studied microelectronics on the College of Erlangen in Germany. Beginning work within the energy administration enterprise in 2001, he has been energetic in varied functions positions together with 4 years in Phoenix, Arizona, the place he labored on switch-mode energy provides. He joined © Analog Units in 2009 and works as a discipline functions engineer for energy administration at Analog Units in München. He will be reached at frederik.dostal@analog.com.
