What is Bleeder Resistor : Working and Its Applications

In most situations, when a device is turned off which is in powered mode. The filter capacitor used in the device keeps some energy at the output. If any person unexpectedly touches the power plug of the device then he may get an electric shock from the plug system. So to overcome this problem, a bleeder resistor is used. This resistor is connected across the capacitor in parallel for discharging the energy which is stored at the output. This article discusses an overview of the bleeder resistor, a circuit with working.

What is a Bleeder Resistor?

This resistor is a standard and high-value resistor and it is used in the filter circuit for discharging the capacitor. The capacitor discharging is very essential in the circuit because they can give current shock ever after the power supply is turned off. So it is mandatory to employ a resistor namely a bleeder resistor to overcome the current shocks. So these resistors are used for safety purposes.


Bleeder Resistor Circuit

To know the importance of this resistor, here we are giving brief information regarding the application of the bleeder resistor.

In the following circuit, the supply is given through the rectifier which means the rectifier’s o/p is connected as an input to the circuit. So here the rectifier’s output is pulsating DC.


Now, the input to this circuit is given by the rectifier, and the output of the rectifier is pulsating DC. Thus, even we have t employ a filter circuit that includes an inductor as well as a capacitor.

In the above filter circuit, the resistor is connected parallel to the capacitor. If we have not connected this resistor parallel to the capacitor, it may give a shock to the operator. Once the power supply is given to the circuit, then the capacitor in the circuit will start charging. If we cannot use


Role in Power Supply

The main reason behind this electric shock from the circuit is, once the power is supplied to the circuit, the capacitor gets charged up to its peak value. Once the power supply is detached from the circuit, then the capacitor still gets charging due to the stored energy previously.

So, we require this bleed resistor to discharge the capacitor properly once detach the power supply. As a result, a standard value of the bleeder resistor is connected with the capacitor in parallel, which aids while discharging after the restriction of power.

How to Choose a Bleeder Resistor?

To choose an appropriate resistor, we have to consider the connection among the momentary voltage (Vt) across the capacitor, the resistance (R) intended for discharge, and ‘Vu’ is the primary voltage, the momentary time‘t’ & the whole capacitance of the capacitor is ‘C’. Then, the following equation is used for calculating the resistor value.

Vt = 𝐕u * 𝒆(−𝒕/𝑹𝑪)

There is frequently an exchange among the working speed of the resistor & the amount of power loss within the bleeder. Lesser resistance values of bleeder can provide us a quicker time to attain safe voltages as the power of the circuit is getting down, however, they will also misuse extra power throughout the operation.

Applications of Bleeder Resistor

The uses of the bleed resistors mainly include the following.

  • For the purpose of safety from electric shock
  • This resistor is used in voltage regulation
  • This resistor is used in voltage division

Thus, this all about an overview of the bleeder resistor which is used for safety, voltage regulation and voltage division? Here is a question for you, what is the significance of this resistor?