# What is fold back current limiting?

## What is fold back current limiting?

“Foldback” current limiting reduces the short circuit current whilst still allowing full output current during normal regulator operation, thereby giving more efficient use of the pass element’s SOA. and so foldback ratios of greater than 2 or 3 are impractical for low-voltage regulators.

How do you draw a current limiting circuit?

Basic constant current limiting circuit The circuit for the power supply current limiter uses a sense resistor placed in series with the emitter of the output pass transistor. Two diodes placed between the output of the circuit and the base of the pass transistor provide the current limiting action.

### What is foldback circuit?

The Fold-back Protection Circuit shown in the blue ellipse as “Current Limit” protects the LDO regulator from damage by overcurrent if the output pin (VOUT) and the ground pin (GND) are shorted. It consists of the overcurrent protection circuit and the short current protection circuit.

How do I limit the current on my power supply?

A common method that has been implemented to limit the output current from power supplies is to monitor the output current and reduce the output voltage when the current limit is reached while maintaining the maximum output current (Figure 4).

#### How does a current limiting device work?

According to the 2020 NEC/NFPA 70, current limiting overcurrent protective device is defined as, “A device that, when interrupting currents in its current-limiting range, reduces the current flowing in the faulted circuit to a magnitude substantially less than that obtainable in the same circuit if the device were …

What is LM317 transistor?

The LM317 is an adjustable 3−terminal positive voltage regulator capable of supplying in excess of 1.5 A over an output voltage range of 1.2 V to 37 V. This voltage regulator is exceptionally easy to use and requires only two external resistors to set the output voltage.

## How does a limiting circuit work?

Figure 1 shows a simple current limiting circuit. As the current through the two diodes in series begins to rise, they begin to conduct. This lowers the voltage at the base of the transistor and thus reduces the amount of current passing through the collector – emitter junction and subsequently to the output.

Does diode reduce current?

Depending on the circuit the forward voltage drop of a forward biased diode can reduce the current a similar amount as reducing the supply voltage by the forward diode drop. But in other circuits the diode drop will have zero effect on current flow.

### How can we reduce the current without change in power?

Resistors in series would drop the voltage. Instead you can connect a resistor in parallel that can draw 180mA of current while allowing 20mA to charge the battery. A resistor in parallel with a current source and one in series with a voltage source are duals of each other – they have exactly the same behavior.

What is dropout voltage in regulator?

The dropout voltage is the minimum voltage required across the regulator to maintain regulation. A 3.3 V regulator that has 1 V of dropout requires the input voltage to be at least 4.3 V. The input voltage minus the voltage drop across the pass element equals the output voltage.