Common uses of current limiters
Current limiters are used in different ways depending on the application and requirements. Common use cases include:
- Electronic equipment protection: Current limiters protect components, circuits, and power supplies. For example, adding a current limiter to a circuit prevents excessive current from damaging components or causing fire. Current limiters can be placed at the power input or at specific circuit nodes; select the appropriate type and current rating for the application.
- Power management: Current limiters help stabilize power output and protect power devices. For example, fuse-type current limiters at the power input can prevent overcurrent from damaging power equipment or systems.
- Charger protection: Current limiting devices control output current in chargers. In mobile phones, tablets, and electric vehicles, current limiting prevents overcurrent that could damage chargers or batteries.
- Fiber-optic communications: In fiber-optic systems, optoelectronic current limiters control optical signal power and drive current to avoid fiber damage or optoelectronic device overload.
- Component protection: Current limiters protect passive components such as resistors and capacitors, and semiconductor devices such as diodes and transistors, from overcurrent. By selecting an appropriate current limiter and placing it in series with the protected device, excessive current flow can be restricted.
Principle of current limiting
When the voltage u1 across resistor r1 is greater than the supply voltage uc, a voltage e2 is induced across r2. This induced electromotive force is proportional to the voltage v across r2.
1. Capacitor c.
2. Inductor l3 and capacitor c4, and their impedances are r1, v, c1, and c2 respectively.
Then two induced electromotive forces will appear across resistor r2: e2- = e1 + - e2. The voltage drops satisfy u1 = +u2 = -ui.
In a loop with two power sources and two loads: e1- = ei + ie; e2- = ei - (ie). Because two oppositely biased higher-order harmonic components appear in the loop, the output exhibits larger amplitude ripple. To reduce the output amplitude variation to meet grid requirements, the input side must be filtered. This leads to the use of filter circuits.
To improve system electromagnetic immunity, reliability, and equipment lifetime, additional measures should be taken to enhance system robustness and reliability.
How to disable current limiting
If it is necessary to prevent a current limiter from limiting, consider the following approaches:
- Replace the current limiter: Choose a current limiter with a higher current rating to replace the existing device. A higher rated limiter will allow greater current to pass without engaging limiting.
- Bypass the current limiter: Reconfigure wiring or circuit connections to route current around the limiter. Before bypassing, fully understand the limiter's role and design intent to avoid damaging the circuit or causing an overload.
- Adjust limiter parameters: Some current limiters provide adjustable parameters via knobs, switches, or other controls. Consult the limiter specifications and instructions to determine how to adjust its settings correctly.
- Check the circuit load: Current limiting is based on the connected load. If the load exceeds the limiter's rated range, the limiter will engage. Verify that the load is appropriate and, if necessary, reduce it so it operates within the limiter's range.
- Check the supply: The supply voltage and available current can affect limiter behavior. Ensure the power source is stable and meets the limiter's requirements so the limiter functions as intended without unnecessary limiting.
