A single-phase active-clamped (AC) push-pull converter is a type of power electronic circuit used for DC-DC voltage conversion. It combines elements of both push-pull and active-clamp converter topologies to provide improved performance in terms of efficiency, voltage regulation, and reduced stress on components.
Here's a description of the operation of a single-phase active-clamped push-pull converter:
Topology Overview:
The active-clamped push-pull converter consists of two main arms, often referred to as the "primary side" and the "secondary side." Each side includes a pair of switching devices (usually MOSFETs or IGBTs), a transformer, and a clamp circuit.
Primary Side Operation:
On the primary side, two switching devices are connected in a push-pull configuration. These devices are controlled in a complementary manner, so when one is turned on, the other is turned off. This ensures that the input DC voltage is applied alternately to the primary winding of the transformer, creating a square wave AC voltage across the primary winding.
Transformer Operation:
The transformer couples the energy from the primary side to the secondary side. It typically has a center-tapped secondary winding. The AC voltage from the primary side induces a voltage in the secondary winding, which is then rectified to provide the desired DC output voltage.
Secondary Side Operation:
The secondary side includes a diode bridge rectifier that converts the AC voltage across the secondary winding of the transformer into a pulsating DC voltage. This DC voltage is then filtered by a capacitor to provide a smoother output voltage.
Clamp Circuit:
The distinctive feature of the active-clamped push-pull converter is the clamp circuit. This circuit includes a clamping switch (often a MOSFET) and a clamp capacitor. The purpose of this circuit is to actively control the voltage spikes that can occur when the primary-side switches turn off. These voltage spikes are often a result of transformer leakage inductance and parasitic capacitance.
Clamping Operation:
As the primary-side switches turn off, the energy stored in the transformer's leakage inductance and parasitic capacitance can lead to voltage spikes. The clamp circuit mitigates these spikes by turning on the clamping switch, creating a path for the energy to be transferred to the clamp capacitor. This action limits the voltage across the primary-side switches and reduces stress on them.
Control and Regulation:
The operation of the active-clamped push-pull converter requires careful control and regulation of the switching devices. The timing and synchronization of the primary and secondary side switches, as well as the clamping switch, are crucial to achieving efficient and stable conversion.
Benefits of a single-phase active-clamped push-pull converter include reduced voltage stress on primary-side switches, improved efficiency due to reduced switching losses, and better voltage regulation due to controlled clamp action. However, the complexity of control and the need for additional components like the clamp circuit are considerations when implementing this topology.