2 Current Limiting Diode Manufacturers in 2022

What Is a Current Limiting Diode?

A current limiting diode is an electronic component that allows a constant current to flow when the voltage is within a specified range. It is sometimes called a "CRD" from the initial letters of another name it goes by, "current regulator diode." There are many electronic devices, such as LEDs, that require a constant current during operation. CRDs are used in such electronic devices.

Current limiting diode is generally used for relatively small currents, such as 1 mA to 15 mA, but there are also current limiting diodes capable of delivering large currents, such as 500 mA. However, care must be taken to avoid heat generation during operation and consequent damage to components.

Uses of Current Limiting Diodes

Diodes are basic electronic components used in various electronic devices. Some electronic devices require a constant current to flow while being driven. For example, LEDs vary in luminance depending on the amount of current flowing through them, so the amount of current flowing through the circuit must be kept constant in order to stabilize the luminescence. Current limiting diodes are used in such current-driven electronic components and devices. Current limiting diodes are also used in battery charging/discharging circuits and leakage circuit breakers (earth leakage circuit breakers).

Principle of Current Limiting Diodes

From 0 to a certain voltage, the current of current limiting diodes increases as the voltage increases. However, once the voltage enters a certain region, the current value becomes constant. The current value at this time is called "pinch-off current" and is one of the values that represent the characteristics of current limiting diodes.

The voltage at which 80% of the pinch-off current value is given is called the "shoulder voltage," and a voltage greater than the shoulder voltage must be applied to maintain a constant current. Note that, as shown in the above figure, even current limiting diodes are not a constant current diode when a large voltage is applied, and the current again increases with an increase in voltage.

Note that applying a voltage so large that it exceeds the constant-current range will damage the diode, so care must be taken when actually using the diode with respect to the size of the voltage.

Types of Current Limiting Diodes

Current limiting diodes can operate from voltages as low as 1 V to as high as 100 V. A variety of low-current diodes are available, including those with different pinch-off current magnitudes and those with reduced pinch-off current value fluctuations. Generally, constant current values of 1 mA to 15 mA are available. On the other hand, current limiting diodes for large currents are also sold, capable of delivering constant currents of 350 mA and 500 mA.

When using current limiting diodes, care must be taken to avoid heat generation during operation. Heat is generated according to the magnitude of the product of voltage and current, and in some cases, this can cause damage to the current limiting diodes. Also, when multiple current limiting diodes with different pinch-off current values are connected, the device may not operate as expected or may be damaged if the circuit is not properly configured.

Other Information on Current Limiting Diodes

Types of Diodes

There are many types of diodes. Here is a brief description of typical diodes other than current limiting diodes.

• Rectifier Diodes
  Normally, each household has its own AC power supply, which is used to power electrical and electronic equipment. Except for incandescent lamps, hair dryers, and other devices that operate directly on AC, rectifier diodes are used to convert AC to DC. Rectifier diodes are often used at relatively high voltages, so the forward voltage VF is large, and some can handle large currents, but those for large currents are quite large and require heat dissipation. Rectifier diodes are often used in modules for full-wave rectification, bridge rectification, etc., and are also available as full-wave and bridge modules.
• Switching Diodes
  These small diodes are mainly used in switching circuits and are enclosed in glass and leaded in appearance. Since they are intended for switching operation, their reverse recovery time trr is shorter than that of rectifier diodes.
• Constant Voltage Diodes
  Normally, diodes are used with a forward voltage applied, but current limiting diodes are used with a reverse voltage applied. When a reverse voltage is applied to a constant-voltage diode, current begins to flow rapidly at a certain voltage. This voltage becomes stable at the Zener voltage (breakdown voltage) and is used as a reference voltage, etc.
• Light Emitting Diode (LED)
  You are probably familiar with the light-emitting diode, which won the Nobel Prize in Physics in 2014 for the invention of the blue light-emitting diode by a Japanese national. This LED, together with the existing red and green LEDs, now has the three primary colors of light, enabling full-color LEDs and white LEDs, which have dramatically expanded the uses of LEDs.