A flyback converter is an isolated buck-boost converter used in AC and DC applications. It rapidly switches between on and off states, using a MOSFET and diode to control the switching. It can have multiple outputs, but a snubber circuit may be needed to reduce ringing voltage. Current mode control is essential for stabilizing output power, while voltage mode control requires waveform analysis and computer-based design principles.
A flyback converter is a buck-boost converter in which the electrical current is isolated, preventing the transfer of energy between the inputs and outputs. It is used in both alternating current (AC) and direct current (DC) applications. A transformer is formed within the circuit by dividing the inductor, and flyback converters are used in high-power systems, such as computers and televisions, to allow them to use as little power as possible. They are preferred primarily because they use fewer components than other electrical devices and are relatively inexpensive to include.
The flyback converter works by rapidly switching between on and off states. A metal oxide semiconductor field effect transistor (MOSFET) and diode are used to control the switching. When the converter is turned on, a transformer stores energy and then releases it when the unit is turned off. Tight coupling of the primary to the secondary windings minimizes leakage inductance or current drop due to magnetic flux between the misaligned windings. In a flyback converter, the energy generated by it is released as heat.
When the flyback converter switch is in the on state, the primary input of the transformer and the input voltage source are connected. When off, the switch allows energy to move from the transformer to the converter output. With the energy stored in the transformer, multiple outputs can be included. The converters also have a rail that loads to power the transformer via pulse width modulation.
Allowing for low power consumption, the conversion of electrical energy by a flyback converter is suitable for devices operating from 50 to 100 watts. Each added output consists of its own winding, diode, and capacitor, and multiple outputs can add enough voltage to increase leakage inductance. The ringing voltage caused by this can be reduced by a snubber circuit. This ensures adequate protection based on the type of transistor used.
Removing the diode from the system classifies the unit as a flyback transformer, used to drive a plasma lamp or voltage multiplier. In general, the converter and control circuit must each be isolated on a flyback converter. Current mode control is essential to stabilize the output power. Signals for voltage mode control are created using an optocoupler on the circuit or using an additional coil winding. Adjusting voltage and current modes is important for items such as phone chargers, which require high accuracy that is achieved using in-depth waveform analysis and computer-based design principles.
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