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Rezo Bragin
Rezo Bragin

Low Cost Reverse Polarity And Over Current Protection (Corrected)



The MAX17527A offers adjustable protection boundaries for systems against input voltage faults and overcurrent faults. In addition, the MAX17527A offers a programmable power limiting function. Input-voltage faults (with positive polarity) are protected up to +60V by an internal nFET featuring low ON-resistance (30mΩ typ). The device features fixed or programmable overvoltage lockout (OVLO) and undervoltage lockout (UVLO) thresholds by using internal or external voltage-dividers. Factory preset internal fixed thresholds can be invoked by connecting the OVLO and/or UVLO pin(s) to GND. Input undervoltage protection can be programmed between 5.5V and 59V, while the overvoltage protection can be independently programmed between 6V and 60V.




Low Cost Reverse Polarity and Over Current Protection (Corrected)



Input reverse-polarity protection is realized using an external nFET that is controlled by the MAX17527A. The magnitude of reverse-polarity voltage protection is dependent on the operating load-bus voltage (VOUT) and the voltage blocking capability of the external nFET. For example, for protection down to a -55V input range with VOUT = 30V, an external nFET rated at 85V is needed. The external nFET is also needed for the optional reverse-current protection. If reverse polarity protection and reverse-current protection are not needed, SN must be connected to IN and GN must be left unconnected. The MAX17527A is tolerant against accidental output reverse-polarity application due to incorrect wiring across the output terminals.


The MAX17527A evaluation kit (EV kit) is a fully assembled and tested circuit board that demonstrates the MAX17527A high accuracy adjustable power limiter with integrated 30mΩ field-effect transistor (FET) in a 20-pin 5mm x 5mm TQFN-EP package. The EV kit can be configured to demonstrate adjustable overvoltage (OV), undervoltage (UV), overcurrent (OC), different current-limit types, reverse output voltage, and power limit features. The EV kit also features an external N-Channel field-effect transistor (nFET) for reverse input voltage and reverse current protection evaluation.


Non-isolated, switch mode design. Step up from 12VDC to 24VDC at 10 Amps DC with very low energy consumption. Small size and light weight. Protected against overload, short circuit, reverse polarity and high voltage and transient suppression on input side.


The protection ensures that the components are not damaged by accidental swap of the power supply connections. There are various methods that differ in operation, efficiency and complexity. While some like a diode or circuit breaker provides only the reversal voltage protection, others such as the protection ICs provide the reverse voltage, over current, and overvoltage protections.


Protection ICs such as the LTC 4365 are designed to protect sensitive circuits from reverse polarity, over current and over voltages. The ICs blocks the undesired current or voltage and only allows the safe voltages to pass through.


Note that your wish not to have a fuse makes a huge difference in cost: otherwise a fuse + power zener diode would do the reverse and over voltage protection, and a current triggered thyristor crowbar would do over-current.


It is my suggestion that the reverse polarity protection can best be provided via a series Schottky diode in the Vin+ supply line. I also suggest that you design your over voltage detector and over current detector in a manner that leaves the GND of the circuit intact. Someday when your project ideas turn into a real product that you must take off to a lab for emissions and immunity testing you will really appreciate using design techniques that keep a single GND, GND planes and chassis/enclosure references.


Unlike incandescent light bulbs, which illuminate regardless of the electrical polarity, LEDs will only light with the correct electrical polarity. When the voltage across the p-n junction is in the correct direction, a significant current flows and the device is said to be forward-biased. If the voltage is of the wrong polarity, the device is said to be reverse biased, very little current flows, and no light is emitted. LEDs can be operated with alternating current, but they will only light on the half of the AC cycle where the LED is forward-biased. This causes the LED to turn on and off at the frequency of the AC supply.


Most LEDs have relatively low reverse breakdown voltage ratings compared to standard diodes, so it may be easier than expected to enter this mode and cause damage to the LED due to overcurrent. However, the cut-in voltage is always less than the breakdown voltage, so no special reverse protections are necessary when driving an LED directly from an AC supply when properly current-limited for forward-biased operation.


The S1500 charger packs several useful features, including a USB port, software update port, safety timer, protection against heat, reverse polarity, short circuit, over-current, and low-input voltage. When combined with a Spektrum Smart battery, this charger really shines by providing much more data than is typically available with a conventional charger.


during practical testing we noticed that setting the current limit with Rcl may be influenced by the bypass resistor to the GND diode when using the TPS274160 with reverse polarity protection as shown in the datasheet. Is a correction of the Rcl needed in that case and what will be the correct calculation / procedure?


Autoformers are used in industries to stabilize voltage and lower the operating cost of equipment. The Autoformer has 5 windings: 2 primary and 3 secondary. All models have surge and spike protection. When the unit is in Automatic and the park or input voltage is 116 volts or below, the output is 10% over the input. When the input is over 118 volts, the output is 2% over the input.


The VIN pin in Arduino boards is a power pin with a dual function. This pin can work as a voltage input for regulated external power supplies that do not use a barrel jack connector. This pin can also work as a voltage output when an external power supply is connected to the barrel jack connector present in some Arduino boards. An important consideration is that the VIN pin is connected directly to the input pin of the onboard voltage regulator on Arduino boards. Since the VIN pin is directly connected to the voltage regulator, the VIN pin does not have reverse polarity protection.


Since 3V3 and 5V pins are directly connected to the onboard's 3V3 and 5V voltage regulators outputs, these pins have no reverse polarity protection. Use them carefully when working as power inputs to avoid damaging your board's voltage regulator.


This option is recommended when a regulated power supply without a barrel jack connector is available. Take into account that using VIN pin should be made carefully since this pin does not have reverse polarity protection. Current is constrained by the regulated power supply and the onboard voltage regulator.


Do not construct a circuit so that overcurrent and burning occur if the NO, NC and SPDT contacts are short-circuited. Also, with SPST-NO/SPST-NC Relays, a short-circuit current may flow for forward/reverse motor operation.Arcing may generate short-circuiting between contacts if there is shortcircuiting because of conversion to the MBB contact caused by asynchronous operation of the NO and NC contacts, the interval between the NO and NC contacts is small, or a large current is left open.


Either an N-channel or a P-channel MOSFET can be used for high-side reverse-battery protection. An N-channel device provides the lowest power loss topology by virtue of its low RDS(ON). However, a gate voltage greater than the battery voltage is needed to turn the MOSFET on. This requires a charge pump as shown in Figure 1, which increases circuit complexity and component cost, and can also introduce EMI challenges. A comparably sized P-channel MOSFET will have a higher RDS(ON) and hence higher power losses but can be implemented with simpler drive circuitry comprising a Zener diode and a resistor.


Although designed to prevent current flow due to reverse-battery connection, the protection device can itself be exposed to potentially damaging transients. While numerous types of switching transients can give rise to pulses of short duration, the most dangerous high-energy pulses are.


These negative transient voltages temporarily subject the protection devices to an avalanche condition. A detailed description of an avalanche condition and its effects on the semiconductor junctions are beyond the scope of this article. However, in simple terms, when a PN junction is subjected to an avalanche condition, the junction breaks down and allows a large amount of reverse current to flow through it. Avalanche can cause irreversible damage if the device is not rated to handle the current and energy involved. In an automotive reverse battery protection application, these avalanche conditions occur due to the magnetic energy stored in inductive loads, such as relays, and any parasitic inductances, making it a limited energy event. Hence, if the device had an adequate avalanche rating it can survive these situations.


A number of approaches are viable when implementing required battery reverse-polarity protection for automotive ECUs. Designers need to take into account factors such as ECU power consumption and cost, to achieve an optimal combination of efficiency, circuit complexity, electromagnetic compatibility and ruggedness. The Super Barrier Rectifier, which has been developed for high-power, high-temperature applications such as automotive, provides a competitively priced alternative to the Schottky diode and can deliver greater efficiency and reliability in situations where low cost, low complexity and freedom from EMI issues, are priorities. 041b061a72


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