Using LM317 with Overvoltage Protection

The circuit diagram
shows the over voltage protection as a feature of LM317 linear voltage

Over voltages come from several source or factors which are usually
in the form of transients. Transients are represented in spikes which
are short and fast disturbance or change in the voltage and current

It only occurs in circuits containing conductance and capacitance.
The causes are typically from power outages, short circuits, tripped
circuit breakers, lightning spikes, inductive spikes and other
malfunctions from power company.


Circuit Diagram

As an example using a 12V battery source, the LM317 voltage
regulator can be used to obtain 6 Volts. To protect any device from over
voltage, there are ways such as adding relays or a zener diode. A relay
switch functions by opening or closing under the command of another
circuit. But finding a relay that would limit the output from 6 V to 12 V
is not easy.

Fortunately, zener diodes are more abundant. A 6.2V zener diode
rating can be used to surpass any excessive voltage set by the voltage
regulator, to prevent more damage to the circuit. The components will be
as follows:

ZD1 – 6.2 Volts
R1 – 1K ohms
R2 – 1K ohms
T1 – NPN Transistor (low power)
T2 – NPN Transistor (acts as a switch)

Every circuit design needs to be tested carefully as to avoid
further damage to the equipment that will be connected. The trial can be
done by using a multimeter, and gradually increasing the circuit
voltage. Once the circuit turns off the supplied voltage, take note of
the reading which will signify the threshold voltage of the zener diode.


Logic PSU With Over-Voltage Protection

A simple 5 Volt regulated PSU featuring overvoltage protection. The 5 volt regulated power supply for TTL
and 74LS series integrated circuits, has to be very precise and
tolerant of voltage transients. These IC’s are easily damaged by short
voltage spikes. A fuse will blow when its current rating is exceeded,
but requires several hundred milliseconds to respond. This circuit will
react in a few microseconds, triggered when the output voltage exceeds
the limit of the zener diode. This circuit uses the crowbar method,
where a thyristor is employed and short circuits the supply, causing the
fuse to blow. This will take place in a few microseconds or less, and
so offers much greater protection than an ordinary fuse.

Circuit diagram:

Logic PSU With Over Voltage Protection Circuit

Logic PSU With Over-Voltage Protection Circuit Diagram

If the output voltage exceed 5.6Volt, then the zener diode will
conduct, switching on the thyristor (all in a few microseconds), the
output voltage is therefore reduced to 0 volts and sensitive logic IC’s
will be saved. The fuse will still take a few hundred milliseconds to
blow but this is not important now because the supply to the circuit is
already at zero volts and no damage can be done. The dc input to the
regulator needs to be a few volts higher than the regulator voltage. In
the case of a 5v regulator, I would recommend a transformer with
secondary voltage of 8-10volts ac. By choosing a different regulator and
zener diode, you can build an over voltag trip at any value.


Overvoltage Protection

When a sensitive circuit
must under no circumstances have too high a supply voltage applied,
then some means of disconnecting the supply must be provided. One way to
achieve this is to trigger a thyristor to blow a fuse. A less
destructive alternative possibility is to use a MOSFET to disconnect the supply. An over-voltage protection IC, the LTC1696 from Linear Technology (,
has recently become available, which is suitable for triggering and
driving such a device. It operates from a power supply in the range 2.7 V
to 27 V and can be connected to the unregulated input of a voltage
regulator. Two voltages can be monitored using feedback pins FB1 and
FB2, suitably divided down using potential dividers.

The trigger threshold for both FB1 and FB2 is +0.88 V. The value of
the upper resistor in the potential divider can be calculated using the
following formula: R1 = 33 kΩ× [(VLIMIT – 0.88 V)/0.88 V] The value of the capacitor connected to the TIMER/RESET
pin sets the delay before the protection is triggered. The charging
current for this capacitor depends non-linearly on the amount by which
the voltage exceeds the threshold value. The greater the over-voltage,
the faster the IC triggers. Once triggered the IC remains in that state
until either the input voltage is removed or the internal latch is
cleared using the MOSFET connected to the TIMER/RESET input.


Battery Overvoltage Protection IC

Battery Overvoltage Protection IC

Battery Overvoltage Protection IC

The bq2946xy family of products is a secondary level voltage monitor and protector for Li-Ion battery pack systems. The cell is monitored for over voltage condition and triggers an internal counter once the OVP threshold is exceeded and after a fixed set delay the out is transitioned to a high level. The output is reset (goes low) if the cell voltage drops below the set threshold minus the hysteresis.

Device Uses
  • 2nd-Level Protection in Li-Ion Battery Packs in:
    • Tablets
    • Slates
    • Portable Equipment and Instrumentation
  • Single-Cell Monitor for Secondary Protection
  • Fixed Programmable Delay Timer
  • Fixed OVP Threshold
    • bq294602 = 4.35 V with 4-s Delay Timer
    • bq294622 = 4.45 V with 4-s Delay Timer
    • bq294682 = 4.225 V with 4-s Delay Timer
    • bq294604 = 4.35 V with 6.5-s Delay Timer
    • bq294624 = 4.45 V with 6.5-s Delay Timer
    • bq294684 = 4.225 V with 6.5-s Delay Timer
  • High-Accuracy Overvoltage Protection:
    ± 10 mV
  • Low Power Consumption ICC ≈ 1 µA


  • Low leakage current per cell input < 100 nA
  • Small package footprint
    • 6-pin SON

1988 Mercedes Benz E190 Fuse Box Diagram

1988 Mercedes Benz E190 Fuse Box

1988 Mercedes Benz E190 Fuse Box Diagram

1988 Mercedes Benz E190 Fuse Box Map

1988 Mercedes Benz E190 Fuse Box Map

Fuse Panel Layout Diagram Parts: combination relay, heatable rear window, turn signal, wiper, relay window opener, air conditioning, overvoltage, protection.


Protect Car Electronic Modules Using RBO Circuit Protection Device

is one of reversed battery and overvoltage (RBO) protection device
which has been developed to protect sensitive semiconductors in car
electronic modules. The following circuit diagrams the basic application of the RBO circuit in preventing overvoltages generated by the module from affecting the car supply network.

The basic application of the RBO40 circuit

In the RBO circuitry,
this monolithic multi-function protection has 3 funtions integrated
on-chip, there are reversed battery protection (D1 diode function),
clamping against negative overvoltages, and transil function against
load dump effect (T2 transil function).



Overvoltage Protection Controller

Overvoltage Protection Controller

Overvoltage Protection Controller

Linear Technology Corporation introduces the LT4363, an overvoltage protection controller that provides overvoltage and overcurrent protection to high-availability electronic systems. Supply voltages surge whenever currents flowing through long inductive power buses change abruptly. Also, automotive batteries experience a condition known as load-dump, where the voltage can stay elevated for many milliseconds. Traditional protection circuitry relies on bulky inductors, capacitors, fuses, and transient voltage suppressors. Instead, the LT4363 creates a robust, adaptable, and space-efficient design with simple control of an N-channel MOSFET. Only the controller and the MOSFET suffer the high voltage surge; downstream components can afford lower voltage ratings, thereby saving costs.

The LT4363 controller builds on Linear’s popular first-generation LT4356 device by extending overvoltage protection capabilities beyond 100V without sacrificing overcurrent protection. The LTC4363 reacts quickly to overcurrent and short-circuit faults at the load, limiting the current to a safe value set by a sense resistor.

Armed with a 100V maximum rating and operational capability down to 4V (cold-crank), the LT4363 makes for an ideal barrier against badly behaving supplies. A simple clamp on the controller supply extends protection beyond the native 100V. It even survives reversed battery connections to -60V. During voltage surges, the output is regulated to a voltage set by a resistive divider, allowing the load to operate safely and smoothly through transient events. Overvoltage and undervoltage comparator inputs ensure that the LT4363 remains off outside a user-defined voltage range. To limit the thermal stress on the power MOSFET, the LT4363 uses a VDS–accelerated fault timer. If the fault persists, a warning is issued before the MOSFET is shut off. By limiting the MOSFET gate slew-rate with a resistive-capacitive (RC) network, the controller can be adapted for inrush control in Hot Swap™ applications. In the shutdown state the LT4363 sips just 7µA of supply current, preserving battery life. A built-in thermal shutdown occurs around 150°C.

The LT4363 is available in two options: the LT4363-1 latches off after a fault, whereas the LT4363-2 will retry after a long cool-down period. Specified over the full commercial and industrial temperature ranges, the LT4363 is offered in 12-pin DFN (4mm x 3mm) and MSOP packages, and a 16-pin SO package with enhanced high-voltage pin spacing. Pricing begins at $2.48 each for 1,000-piece quantities and the device is now available in production quantities. For more information, visit

Summary of Features: LT4363
  • Withstands Surges Over 100V with Vcc Clamp
  • Wide Operating Voltage Range: 4V to 80V
  • Adjustable Output Clamp Voltage
  • Fast Overcurrent Limit: Less Than 5µs
  • Reverse Input Protection to –60V
  • Adjustable UV/OV Comparator Thresholds
  • Low 7µA Shutdown Current
  • Shutdown Pin Withstands –60V to 100V
  • Adjustable Fault Timer
  • Controls N-Channel MOSFET
  • Less Than 1% Retry Duty Cycle During Faults (LT4363-2)
  • 12-Lead MSOP, (4mm x 3mm) DFN &
  • 16-Lead SO Packages