Detection for overload protection circuit


Nowadays, the visible LED display on the street, LED has been integrated into every corner of life, as well as decorative LED lights and LED lights, LED lights can be seen everywhere.

In some physics experiments, LED technology is sometimes needed, but traditional LED circuits are difficult to achieve significant efficiency during the experiment. However, some LED light-emitting display detection circuits with overload protection can play a role in physical experiments.


This article will combine the circuit diagram to analyze an LED light-emitting display detection circuit that can protect the circuit from overload. As shown in Figure 1, A and B in the circuit are the current input terminals to be tested. Transistors VQ1, VQ3 and VQ2, VQ4 form a common-emitter direct-coupled DC amplifier on both sides, and LEDs VD1~VD5 and VD6~VD10 serve as display components for current in two directions. When the measured current flows from the input terminal A to the B, the base potential of the transistor VQ2 decreases, the operating current decreases, and then the VQ4 is turned off, and the light-emitting diodes VD6~VD10 have no operating current and do not emit light.

overload protection
overload protection

At this time, the base potential of VQ1 rises, so that VQ1 and VQ3 are in an amplified state, and sufficient current flows through the collector of VQ3, and the light-emitting diodes VD1 to VD5 are electrically conductively displayed. The brightness and the number of illuminations of the LED are approximately proportional to the current flowing at the input. That is, when the input current is small, the number of light-emitting diodes is small and the brightness is small; when the input current is large, the number of diodes that emit light is large and the brightness is large. When the input current changes from small to large, the order of illumination is VD1, VD2~VD5, and the brightness correspondingly changes from small to large; when the input current changes from large to small, the brightness of the LED is correspondingly darkened until extinguished, the order is VD5, VD4 ~VD1, more vivid and intuitive.

When the input current B flows to A, the operating currents of the transistors VQ1 and VQ3 decrease, the light-emitting diodes VD1 to VD5 do not emit light, and the VQ3 and VQ4 are in an amplified state, and the light-emitting diodes VD6 to VD10 emit light, and the process is the same as the foregoing process. The VQ1, VQ3, VD1~VD6 and VQ2, VQ4, VD6~VD10 work correspondingly on both sides, clearly showing the magnitude and direction of the measured current. In order to meet the needs of the demonstration experiment, three range gears are also available for selection and diode overload protection. After reading this article, I believe that you have a better understanding of this LED lighting detection circuit that can provide overload protection for the circuit. This circuit is especially capable of supporting LED circuits in physical experiments and is more efficient than ordinary LED circuits.

If you happen to encounter this problem, it may take a few minutes to read this article, I believe there will be unexpected gains. Although LEDs are everywhere in life, there are still some shortcomings in LEDs that require our designers to have a more specialized knowledge base in order to design products that are more in line with life.

Difference Between Overcurrent Protection and Overload Protection

Overcurrent protection is protection against excessive currents or current beyond the acceptable current rating of equipment. It generally operates instantly. Short circuit is a type of overcurrent. Magnetic circuit breakers, fuses and overcurrent relays are commonly used to provide overcurrent protection.

Overload protection is a protection against a running overcurrent that would cause overheating of the protected equipment. Hence, an overload is also type of overcurrent. Overload protection typically operates on an inverse time curve where the tripping time becomes less as the current increases. Overload relays as well as “slow blow” fuses are commonly used to provide overload protection.

Some devices provide both overcurrent and overload protection. A thermal-magnetic circuit breaker has both thermal (overload) and magnetic (overcurrent) elements. Both elements operate as described above. Likewise the dual element fuse has both instantaneous and inverse time characteristics in the same fuse providing both overcurrent and overload protection.

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