Describe the operation of a single-phase active-clamped (AC) resonant converter.
1 Answer
A single-phase active-clamped (AC) resonant converter is a type of power electronics circuit used for efficiently converting electrical energy from one form to another. It is often employed in applications such as power supplies, renewable energy systems, and industrial equipment. The primary feature of an active-clamped resonant converter is its ability to minimize voltage stress on the switching devices by using a clamping circuit, leading to improved efficiency and reduced switching losses.
Here's a description of the operation of a single-phase active-clamped resonant converter:
Basic Components:
Input Source: The converter receives input power from an AC source, usually the mains supply.
Full-Bridge Inverter: The input power is connected to a full-bridge inverter, which consists of four switching devices (typically insulated gate bipolar transistors - IGBTs) arranged in a bridge configuration. The full-bridge inverter is responsible for converting the AC input voltage into a high-frequency AC voltage.
Resonant Tank Circuit: Connected to the output of the full-bridge inverter is a resonant tank circuit comprising inductors and capacitors. This circuit establishes a resonant frequency at which energy can be efficiently transferred.
Clamping Circuit: The unique feature of the active-clamped resonant converter is the presence of a clamping circuit. This circuit is designed to actively control and limit the voltage across the main switching devices (IGBTs) during their turn-off transitions.
Operation:
Switching Phase 1 (Turn-On): The active-clamped resonant converter operates using a phase-shift control technique. Initially, two diagonal IGBTs in the full-bridge inverter are turned on. These IGBTs allow current to flow through the resonant tank circuit, which starts to accumulate energy.
Switching Phase 2 (Clamping): Before the energy stored in the resonant tank circuit is fully transferred, the diagonal IGBTs are turned off. However, due to the inductive nature of the circuit, the voltage across the IGBTs tends to rise rapidly. This is where the clamping circuit comes into play.
Clamping Action: The clamping circuit detects the rising voltage and activates an auxiliary clamping switch (usually a fast-switching diode) in parallel with each IGBT. These clamping switches provide an alternate current path for the inductive energy, effectively clamping the voltage across the IGBTs to a controlled level. This significantly reduces voltage stress on the main IGBTs and prevents voltage spikes.
Switching Phase 3 (Turn-Off): Once the voltage is clamped, the main diagonal IGBTs can be safely turned off without encountering excessive voltage spikes. This turn-off process is smoother and generates fewer switching losses compared to a traditional resonant converter.
Energy Transfer and Output: The clamping action allows the resonant energy to be transferred to the output side of the circuit more efficiently. The output voltage can be regulated by adjusting the phase shift between the switching devices in the full-bridge inverter.
By actively controlling the voltage across the main switching devices using the clamping circuit, a single-phase active-clamped resonant converter achieves higher efficiency and improved performance compared to conventional resonant converters, making it suitable for various power conversion applications.
Here's a description of the operation of a single-phase active-clamped resonant converter:
Basic Components:
Input Source: The converter receives input power from an AC source, usually the mains supply.
Full-Bridge Inverter: The input power is connected to a full-bridge inverter, which consists of four switching devices (typically insulated gate bipolar transistors - IGBTs) arranged in a bridge configuration. The full-bridge inverter is responsible for converting the AC input voltage into a high-frequency AC voltage.
Resonant Tank Circuit: Connected to the output of the full-bridge inverter is a resonant tank circuit comprising inductors and capacitors. This circuit establishes a resonant frequency at which energy can be efficiently transferred.
Clamping Circuit: The unique feature of the active-clamped resonant converter is the presence of a clamping circuit. This circuit is designed to actively control and limit the voltage across the main switching devices (IGBTs) during their turn-off transitions.
Operation:
Switching Phase 1 (Turn-On): The active-clamped resonant converter operates using a phase-shift control technique. Initially, two diagonal IGBTs in the full-bridge inverter are turned on. These IGBTs allow current to flow through the resonant tank circuit, which starts to accumulate energy.
Switching Phase 2 (Clamping): Before the energy stored in the resonant tank circuit is fully transferred, the diagonal IGBTs are turned off. However, due to the inductive nature of the circuit, the voltage across the IGBTs tends to rise rapidly. This is where the clamping circuit comes into play.
Clamping Action: The clamping circuit detects the rising voltage and activates an auxiliary clamping switch (usually a fast-switching diode) in parallel with each IGBT. These clamping switches provide an alternate current path for the inductive energy, effectively clamping the voltage across the IGBTs to a controlled level. This significantly reduces voltage stress on the main IGBTs and prevents voltage spikes.
Switching Phase 3 (Turn-Off): Once the voltage is clamped, the main diagonal IGBTs can be safely turned off without encountering excessive voltage spikes. This turn-off process is smoother and generates fewer switching losses compared to a traditional resonant converter.
Energy Transfer and Output: The clamping action allows the resonant energy to be transferred to the output side of the circuit more efficiently. The output voltage can be regulated by adjusting the phase shift between the switching devices in the full-bridge inverter.
By actively controlling the voltage across the main switching devices using the clamping circuit, a single-phase active-clamped resonant converter achieves higher efficiency and improved performance compared to conventional resonant converters, making it suitable for various power conversion applications.