Last Updated on April 24, 2023 by Kevin Chen
Image source ElProcus
A bleeder resistor is a type of resistor that is connected to in parallel with the filter capacitor and is used for discharging electrical charge from the capacitor when power supply is turned off.
The bleeding is considered a safety measure since it ensures that the capacitor does not retain any charge that will be a major risk to people and even other electronic components. This charge has the potential of causing electric shock.
A bleeder resistor is also known safety discharge resistor, capacitor discharge resistor, or safety discharge resistor.
In general, we can say that a bleeder resistor is just a standard resistor that is used for a specific application-it is not a specialized resistor.
Understanding the function of a bleeder resistor
Now you know what a bleeder resistor is. So, what exactly does it do or what are its functions?
To know how it works, let’s assume we have an electric circuit that has a capacitor filter which is connected to the power source. The circuit also has a rectifier diode that determines the direction of the current. When forward-biased mode, the capacitor will get charged.
When in the reverse-biased mode, the capacitor will get discharged hence there will be a continuous flow if current on the terminals. What if the power source is turned off? Well, the capacitor will still have its charges flowing to the terminals. This means that if someone touches those terminals, they may suffer from electric shock.
Now imagine if we have a mechanism to discharge the electric current from the terminals. The problem will be solved. This is where the relevance of a bleeder resistor comes in. The resistor is connected in parallel to the capacitor to provide a discharge path. It will literally bleed the capacitor.
Basically, that is the function of a bleeder resistor.
How does a bleeder resistor work?
Image source Electronics Reference
As we have said, a bleeder resistor works by providing a path for the flow of electric current from the capacitor. This is enhanced by the fact that it is connected in parallel to the capacitor meaning that charges from the terminals will have to pass through the resistor.
When included in the electric circuit, the resistor will act as a load, drawing the current from the capacitor. It will then dissipate this current in the form of heat hence depleting the capacitor of its voltage.
The discharge will continue until the capacitor reaches safe voltage levels. Take note that the choice of resistor used should allow a smooth discharge of the capacitor without affecting the operation of the circuit. For example, a resistor with a low resistance value will be overwhelmed and will allow some current leakage. On the other hand, large resistance will slow down the discharge rate.
In general, the electrical properties of a bleeder resistor allow it to operate perfectly when included in an electric circuit.
The resistance value of a bleeder resistor
We have just mentioned that the resistance value is a key parameter that you should consider when buying and installing a bleeder resistor. The value will determine the suitability of the resistor in a particular circuit.
The value should not be too small or too high for the application. This resistance value of a bleeder resistor is decided at the point of circuit design. Usually, it should be low enough to facilitate a fast discharge rate ad high enough not to interfere with the normal operation of the circuit.
So, how do I choose the proper value of a bleeder resistor?
There is a formula that you can use to work estimate the value:
R=(T*C)/5
Where R is the resistance value , T is the estimated discharge time, C is the capacitance of the capacitor and 5 is considered the safety margin to use.
If we are considering the safe voltage of the capacitor, we will use the formula
R=-t/C*ln(v/Vm).
Still not sure about the resistance value of the bleeder resistor to use? Confirm with the manufacturer of the device. You can also consult an electronics expert for this information.
The resistive value of a bleeder resistor is what is called the bleeder resistance. It varies from one circuit to another. Using the different formulas, you should be in a position to know the bleeder resistance of your resistor.
Consider the power rating of the resistor
Other than the resistance, you should also consider the power rating of the bleeder resistor that you want to buy.
The most critical aspect of power rating is heat management and power dissipation. Will the resistor manage the heat due to the current well or will it overheat?
With a good power rating, there will be a smooth dissipation of power in the circuit. Otherwise, the whole circuit may end up getting damaged due to poor power dissipation.
Bleeder resistors as voltage regulators
The working principle of the bleeder resistors allows them to unction as voltage regulators in electric circuits. This usually happens when the circuit has both the load resistor and bleed resistors connected in parallel.
When the circuit is ON, there will be a voltage drop across the load resistor and when the circuit is OFF, there will be a voltage drop across the bleeder resistor. A combination of the two resistors in a circuit increases the value of the no-load voltage a key factor that is considered when regulating the voltage in the circuit.
The main reason why DC/DC converters have bleeder resistors at their output is mainly because of the voltage regulation property of the bleeder resistor. This is an addition to the fact that these outputs need a faster discharge rate. This is the same reason why you will need a bleeder resistor on the start capacitor.
Application of bleeder resistors
Bleeder resistors are mostly used in high-voltage circuits where the safety of the circuit and its operators needs to be prioritized. Without the resistor, anyone working on such circuits will be easily electrocuted.
These resistors are also used as load balancers and regulators in different devices such as audio equipment and amplifiers.
At this point, you know all the essentials of a bleeder resistor. In case you want to buy these resistors, ensure that you get them from reputable and reliable bleeder resistor suppliers. A premium quality resistor will guarantee your safety and that of the circuit.
If you want to find more Electronic Components Distributors, please check out the following articles:
Electronic Components Distributors In the USA
Electronic Components Distributors In UK
Electronic Components Distributors In China
Electronic Components Distributors In India
Electronic Components Distributors In Singapore
Electronic Components Distributors In Malaysia
Electronic Components Distributors In Vietnam
Electronic Components Distributors In South Korea
- The Ultimate Guide to IRFZ44N MOSFET - April 30, 2024
- AMD Ryzen 5 vs Intel i5: How to Choose the Right Processor? - April 30, 2024
- Where to buy IC chips? The Best Guide? - March 26, 2024
