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 Safety / Protection Circuits
Safety / Protection:  # - G        H - Q        R - Z


Last Updated: October 24, 2017 02:55 PM
Circuits Designed by Dave Johnson, P.E. :

Circuit Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was. . . Circuit by Dave Johnson P.E.-March, 2002

Detects Low Voltage 120VAC Power Line  -  This hobby circuit will turn on a beeper when the line voltage drops below 100 volt AC . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Circuit Protects FPGAs from killer Spikes -  04/23/98 EDN Design Ideas:  NOTE: File contains multiple circuits scroll to find this circuit.   A project using Xilinx FPGAs brought an interesting problem to light.  When you turn on the board, one FPGA in three succumbs to this problem.  A lot of frustration and testing uncovered a negative-going spike (Figure 1) in the 5V line from the DC/DC converter.  The system uses a DC/DC converter __ Circuit Design by Nelson Nguyen, Anritsu Corp, Morgan Hill, CA

Circuit Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was. . . Circuit by Dave Johnson P.E.-March, 2002

Circuit protects system from overheating -  11/08/01 EDN Design Ideas:  The two-chip circuit in Figure 1 provide as fan control and overtemperature warning and shutdown signals to protect systems from excessive heat.  The circuit monitors the temperature of the pc board and the die temperature of a CPU, an FPGA, or another IC with an on-chip temperature-sensing transistor __ Circuit Design by Kerry Lacanette, Maxim Integrated Products, Sunnyvale, CA

Circuit provides flexible gain ranges -  06/21/01 EDN Design Ideas:  Certain designs need a programmable-gain amplifier with a wide gain range and high accuracy and common-mode rejection.  Usually, its wise to exploit a programmable-gain instrumentation amplifier, such __ Circuit Design by Luo BenCheng, Chinese Academy of Sciences, Beijing, China

Circuit provides reverse-battery protection -  12/21/00 EDN Design Ideas:  A universal problem in battery-operated devices is the threat of damage when an end user (never an engineer) inserts the battery backward.  You can avoid damage by inserting a single diode or by using a diode-bridge configuration, but those fixes waste power and reduce the supply voltage by adding one or two diode drops between the battery and the supply rail.  An alternative solution not only protects against battery-reversal damage, but also automatically corrects the reversal (Figure 1).   __ Circuit Design by John Guy, Maxim Integrated Products, Sunnyvale, CA

Circuit Safely Deep Discharges NiCd Battery -  NIC d batteries possess an undesirable memory effect caused by partial discharges.  The remedy is to do a complete discharge before charging again.  Figure 1 shows a simple circuit which performs this feat.  Although relatively straightforward in concept, the circuit has three redeeming features: 1) it is powered by the battery being discharged.2) After the battery is fully discharged current drain is only about 4 uA, usually well below the self-discharge of a battery alone.3) Near end-of-charge the LED flashes.9publised 04/29/99 EDN-Design idea)  __ Designed by Jim Hagerman, Science & Technology International, Honolulu, HI

Circuit safely Deep-discharges NiCd battery  -  04/29/99  EDN-Design ideas   NOTE:  Scroll to find this circuit.   Nickel-cadmium (NIC d) batteries can possess an undesirable memory effect due to partial discharges. The remedy is a complete discharge before charging again. Figure 1a shows a simple circuit that performs this feat.  __ Circuit Design by Jim Hagerman, Science & Technology International, Honolulu, HI

Circuit Secures Bootstrap Operation Under Light Load -  05/12/11  EDN Design Ideas:  Additional circuit lets a capacitor charge, preventing voltage dips.  A previous Design idea highlights a potential issue of a bootstrap IC under light-load or prechargedload operation (Reference 1).  The circuit in Figure 1, with the additional circuit in the green box, fixes the problem of a voltage dip in the bus-voltage signal.  The waveforms in Figure 2 demonstrate how this problem takes place in buck converter IC 1B when its output voltage, VBUS, dips below the regulation point at a fixed rate under no load.  By inspecting the other traces in Figure 2, you can conclude that the dip of VBUS occurs __ Circuit Design by Chee H How, Kuala Lumpur, Malaysia

Circuit-breaker handles voltages to 32V -  25-May-00 EDN Design Ideas:  The simplicity of low-side current monitoring can mask the advantages of a high-side approach.  You can monitor load currents in a power supply, a motor driver, or another power circuit on either the high or the low side (ground].  However, don't let the ease of low-side monitoring cause you to overlook __ Circuit Design by Greg Sutterlin and Craig Gestler, Maxim Integrated Products, Sunnyvale, CA

Complete 12V Automotive Undervoltage, Overvoltage & Reverse-Supply Protection -  The LTC4365 is a unique solution that elegantly and robustly protects sensitive circuits from unpredictably high or negative supply voltages.  The LTC4365 blocks positive voltages as high as 60V and negative voltages as low as 40V.  Only voltages in the safe operating supply range are passed along to the load.  The only external__ Linear Technology/Analog Devices App Note, Sep 19th 2011

Current Limit Protects Power Bus -  12/12/97 EDN Design Ideas:  Protects a power bus from a load short within a guaranteed2 sec response Time __ Circuit Design by Ron Lenk, Temic/Siliconix, Santa Clara, CA

Current limiter provides latch-up signal -  01/01/98 EDN Design Ideas:  Current-limiting circuit both signals a latch-up condition and prevents latch-up-induced overcurrent destruction of a CMOS IC or group of IC s __ Circuit Design by Hartmut Henkel, von Hoerner & Sulger GmbH, Schwetzingen, Germany

Data acquisition system uses fault protection -  04/15/04  EDN Design Ideas:  ensitive systems, such as those in aircraft, must withstand fault conditions, thereby avoiding component and system damage, because a sensor failure could cause a catastrophic event to occur.  A channel protector, comprising two n- __ Circuit Design by Catherine Redmond, Analog Devices, Limerick, Ireland

DC Changeover System with Battery Protection Unit -  Emergency lights commonly available in the market come with battery over-charging protection but no discharging protection.  Here is a circuit that protects the battery from over-charging as well as over-discharging.__ Electronics Projects for You

DC Fault Protection for Audio Amplifiers -  Circuit ideas how to replace traditional CD protection relays with MOSFETs __ Designed by R.G. Keen

Deep Discharge Protection for 12 V Batteries -    NOTE: Must register on this site __ Designed by Published in Elecktor July/Aug, 2010

Design Notes 503: Dual DC/DC Controller for DDR Power with Differential VDDQ Sensing & 50mA VTT Reference -  11/01/13  EDN-Design Notes   Solid-state circuit breaker for microcontrollers.  The LTC3876 is a complete DDR power solution, compatible with DDR1, DDR2, DDR3, and DDR4 lower voltage standards.  The IC includes VDDQ and VTT DC/ DC controllers and a precision linear VTT reference.  A differential output sense amplifier and precision internal reference combine to offer an accurate VDDQ supply.  The VTT controller tracks the precision VTTR linear reference with less than 20mV total error.  The precision VTTR reference maintains 1.2% regulation accuracy, tracking one-half VDDQ over temperature for a 50mA reference load.   __ Circuit Design by Ding Li

Detect & Disconnect Overvoltage -  04/25/96 EDN Design Ideas:  The circuit in Fig.1 protects circuits and systems with power supplies that may exceed safe limits.  One example is small consumer products that use external ac adapters; it's easy to mistakenly plug in the wrong adapter.  Another example is a portable system that uses a rechargeable battery pack.  if the battery pack is absent or fails to open during recharging, a high-compliance charger can deliver excessive voltages to the system __ Circuit Design by Kerry Lacanette, National Semiconductor Corp, Santa Clara, CA

Detects Low Voltage 120VAC Power Line  -  This hobby circuit will turn on a beeper when the line voltage drops below 100 volt AC . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Double the protection of a laser driver using a 1V power supply -  04/09/13 EDN Design Ideas:  Drive a laser pointer with a single cell discharged to as low as 1V, and improve safety reliability with redundant current control transistors.   __ Circuit Design by liao taishan

Dual Comparator Thermally Protects Lithium-Ion Battery -  18-Sep-03 EDN Design Ideas:  Most manufacturers recommend that you don't change lithium-ion batteries at temperatures lower than 0C or higher than 50C.  You can monitor both thresholds by adding a thermistor and dual (window] comparator to a lithium-ion battery charger (Figure 1).  Set the low-temperature trip point at 2 __ Circuit Design by Mike Hess, Maxim Integrated Products, Sunnyvale, CA

Dual DC/DC Controller for DDR Power with Differential VDDQ Sensing & 50mA VTT Reference -  11/01/13  EDN-Design Notes   Solid-state circuit breaker for microcontrollers.  The LTC3876 is a complete DDR power solution, compatible with DDR1, DDR2, DDR3, and DDR4 lower voltage standards.  The IC includes VDDQ and VTT DC/ DC controllers and a precision linear VTT reference.  A differential output sense amplifier and precision internal reference combine to offer an accurate VDDQ supply.  The VTT controller tracks the precision VTTR linear reference with less than 20mV total error.  The precision VTTR reference maintains 1.2% regulation accuracy, tracking one-half VDDQ over temperature for a 50mA reference load.   __ Circuit Design by Ding Li

Electronic Breaker -  This circuit uses the on-resistance of the MOSFET as the current sensor.  Reset it by removing the input power or the load.  The circuit draws no current unless tripped.   __ Designed by Andrew R. Morris

Electronic fuse emulates fast- or slow-blow fuses -  11/09/00 EDN Design Ideas:  The electronic-fuse circuit in Figure 1 combines the properties of a current transducer and a solid-state relay to disconnect low power at preset levels.   Using this circuit lets.   PDF contains multiple circuits, scroll to find the one of interest __ Circuit Design by John A Hasse, Colorado State University, Fort Collins, CO

Emergency Light with Charger -  White LEDs are replacing the conventional incandescent and fluorescent bulbs due to their high power efficiency and low operating voltage.  These can be utilised optimally for emergency lamp and vehicle turning...__ Electronics Projects for You

Emergency Stop -    NOTE: Must register on this site __ Designed by Published in Elecktor July/Aug, 2010

Enhanced Security Bike LED Light -  Adds movement detection and visual effects to enhance visibility to motorists.3 LEDs flash simultanuously in normal mode.  Various light effects when a small movement or direction change is detected.  All 3 LEDs light up for 1, 5 sec when braking occurs. __ Designed by Michel Bavin

Ensure Safety In Power-On Operation -  04/24/03  EDN Design Ideas:  Buck converter handles battery-backup system - Computers find universal use in industrial-control systems.  During power- and start-up sequences (booting], the outputs of such control systems may yield uncontrolled pulses before the  __ Circuit Design by Jean-Bernard Guiot, DCS AG, Allschwil, Switzerland

Equip switchers with overcurrent protection -  06/24/99 EDN Design Ideas:  Overcurrent protection is usually a necessary design feature of a switch-mode power supply to safeguard both the switcher and the load.  Most PWM control ICs  have internal overcurrent-protection circuits, and you can typically add auxiliary circuits around the IC to enhance this protection.  For example, simple circuits enhance the operation of the common family of UC3842/3/4/5 (Unitrode Corp, www.unitrode.com) PWM-control ICs  (Figure 1).    __ Circuit Design by Robert N Buono, Buono Consulting, Ringwood, NJ

External components provide true shutdown for boost converter -  16-Mar-06 EDN Design Ideas:  An additional MOSFET and resistor solves the problem by opening the unwanted current path during shutdown __ Circuit Design by Navid Mostafavi, Maxim Integrated Products Inc, Sunnyvale, CA

Failed Power Light -  This back-up lamp stays off as long as light falls on the CdS photocell from either the NE-2 or from room ambient light.  So, if the power fails at night, the lamp will light.  The 6 volt lamp should be directed away from the photocell __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Fast Electronic Fuse -  A fast electronic fuse designed to operate on 230V AC with an adjustable trip current.   __ Designed by Miroslav Adzic-Serbia Montenegro

Fault-latch protects switchers -  02/19/04  EDN Design Ideas:  Many power-supply designers like to have a regulator latch off in the event of an overcurrent situation or other fault condition.  Yet, many PWM controllers do not internally support this latch-off function.  Most do, however, have a __ Circuit Design by Craig Varga, National Semiconductor, Phoenix, AZ

Folds back current during fault conditions -  11/28/02  EDN Design Ideas:  You can use monolithic linear regulators at currents lower than 5A for most applications.  Most manufacturers of these devices integrate current-limiting and thermal shutdown to prevent damage during fault conditions.  For currents greater than 5A, most linear supplies use controllers that allow the user to select the pass element to handle different current requirements __ Circuit Design by Martin Galinski, Micrel Semiconductor, San Jose, CA

For want of protection Devices -  02/03/97 EDN-Design Feature  A variety of devices protects sensitive circuits against overvoltage or overcurrent conditions, thereby preventing overheating, avalanche breakdown, and device burnouts.   __ Circuit Design by Design Feature by Bill Travis, Senior Technical Editor

Fuse Monitor/Alarm -  a simple way to see if a fuse has blown without removing it from its holder __ Designed by Andy Collison

Ground Fault Indicator -  Check out your AC Outlets for Possible Hazzards.   __ Designed by G.L. Chemelec

Ground Fault Interrupter -  App Note MP1851 June 1992__ National Semiconductor

Guard Against Battery Reversal -  07/06/95 EDN Design Ideas:  The circuit in Fig 1 protects a battery-operated system in two ways  Q1 prevents damage from the flow of reverse current that could occur if you install the battery backward, and Q3 prevents the excessive current flow that could occur with a sudden load increase or a short circuit.  A properly installed battery fully enhances Q1 by pulling i __ Circuit Design by Dana Davis, Maxim Integrated Products, Sunnyvale, CA

Guard Amplifier outputs against overvoltage -  07/05/07  EDN Design Ideas:  An automotive-protection circuit withstands repeated insults of direct short circuits to the full battery voltage __ Circuit Design by John Guy, Maxim Integrated Products, Sunnyvale, CA

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Safety / Protection:  # - G        H - Q        R - Z

 


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