Operation of Freewheeling Diodes
The Freewheeling diode circuit is shown below,
Freewheeling diode
The Inductor and resistor are connected across a Freewheeling diode. An ideal flyback diode will have a very large high forward current; which helps control the voltage variations from burning out the diode, the inductor’s power supply is convenient for reverse breakdown voltage and low forward voltage drop. Depending on the instruments being used and the purpose for which the equipment is being utilized, voltage flow can be 10 times that of the power source’s voltage.
The freewheeling diode in the circuit is reverse-biased by the external potential during operating conditions when the switch is closed. Freewheeling diode does not play any crucial role under normal or steady-state conditions. But in the existence of a Freewheeling diode when the switch is opened, the voltage over the inductor forward biases the freewheeling diode.
Need for Freewheeling Diode
In the circuit shown above, External potential is applied when the switch closes, then the diode in the circuit becomes forward biased and current flows through the load Resistance and Inductance.
An inductor is a wire loop that conducts electricity and produces a magnetic field as current passes through it. The inductor carries the energy in the form of an electromagnetic field. The magnetic field created by the current passing through the inductor when the switch is closed then causes the device to fully charge. This resulted in a break in the circuit’s current flow, which ended the previously created magnetic field.
Lenz’s law states that this field creates an opposing current in the circuit, which creates a negative potential across the inductor. This potential is called Flyback voltage. This voltage across the inductor is noticeably higher than the potential that the external source first applied. This results in a rapid current flow through the circuit, which builds up a large reverse voltage across the switch and the diode and may cause damage to other circuit components.
The voltage spike over the inductor is:
where,
L = inductance
di/dt is the rate of change of current over the inductor.
Then the voltage across the inductor and the flow of current through the circuit carry the relation of direct proportionality. As a result, a freewheeling diode is connected across the inductor to keep away the damage in the circuit.
Freewheeling Diode
In an Electrical circuit, a Diode is a semiconductor device that acts like a one-way switch (it allows current to flow in one direction and restricts the current to flow in another direction). Semiconductor is made up of p-type and n-type materials. Semiconductors have conductivity between conductors and insulators. To control the Load voltage, a switching element is used to switch at a particular frequency.
A severe high voltage occurs at the time the switching element is activated due to the stored energy within the magnetic field of the inductive load coming across the switching element terminals in switch OFF condition which may destroy the switching element. To distribute this energy, a Freewheeling diode is used. The Load can be short-circuited at the time the switching element is inactivated. The energy stored in the magnetic field is degenerate like heat.
Table of Content
- What is a Freewheeling Diode?
- Basics of Flyback Converters
- Operation
- Importance in Inductive Load Circuits
- Advantages
- Disadvantages
- Applications
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