Power Supply Input Circuit Using Avalanche Overvoltage Protection
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Solution Overview
Problem
Existing power supply systems face inefficiencies and high losses when dealing with overvoltages, particularly in three-phase networks, due to the limitations of varistors and traditional switching transistors, which lead to increased harmonic content and energy losses.
Innovation Solution
An input circuit with a switching element, inductance, and active switch unit that periodically switches between conductive and blocked states, allowing current flow only when the breakdown voltage is exceeded, generating avalanche energy to handle overvoltages efficiently without additional switches, thus enhancing dielectric strength and reducing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If varistors are used for overvoltage protection in the input stage, then overvoltage impulses are limited and sensitive circuits are protected, but very high currents are diverted and significant impulse power loss occurs
Solution Approach 1:
The patent changes the operating parameters of the switching transistor by utilizing its avalanche breakdown capability. The transistor is designed to operate in the avalanche region during overvoltage events, where it can withstand high voltages and divert currents without suffering excessive power loss. This parameter change allows the transistor to handle overvoltage protection more efficiently than varistors, reducing impulse power loss while maintaining protection reliability
Solution Approach 2:
The patent replaces the passive varistor-based overvoltage protection mechanism with an active switching transistor controlled by a control circuit. Instead of relying on the voltage-dependent resistance of varistors, the system uses the switching transistor's controlled conductivity and avalanche breakdown characteristics. This substitution enables more precise control over the protection mechanism, allowing the system to limit overvoltage impulses while minimizing energy loss through intelligent switching and avalanche operation
2Reliability
If switching transistors are used for overvoltage protection, then circuit protection is achieved, but high harmonic content and energy losses occur
Solution Approach 1:
The patent replaces conventional switching transistor protection methods with a controlled avalanche operation mode. Instead of using the transistor in traditional switching modes that generate significant harmonics, the system utilizes the transistor's avalanche breakdown characteristic in a controlled manner. The control circuit manages the transistor to operate in avalanche region during overvoltage events, which provides protection while generating fewer harmful harmonics compared to conventional switching approaches
Solution Approach 2:
The patent changes the operating mode of the switching transistor from conventional switching to controlled avalanche operation. By adjusting the operating parameters to utilize the avalanche breakdown region, the transistor can provide overvoltage protection with reduced harmonic generation. The control circuit monitors and adjusts the transistor's operation to maintain it in the appropriate mode, minimizing harmful harmonic content while ensuring circuit protection
3Reliability
If additional switches like IGBTs are added for overvoltage protection, then voltage resistance is improved, but device complexity and component count increase
Solution Approach 1:
The patent makes the existing switching transistor multi-functional by enabling it to handle both normal operation and overvoltage protection tasks. Through controlled avalanche operation, the same transistor that performs switching functions during normal operation also provides overvoltage protection when needed. This eliminates the need for additional protection switches like IGBTs, maintaining voltage resistance while reducing device complexity and component count
Solution Approach 2:
The patent merges the overvoltage protection function with the existing switching transistor. Instead of adding separate protection components, the system combines the protection capability into the already-present transistor by utilizing its avalanche breakdown characteristic. The control circuit integrates the protection function into the existing switching control, allowing one component to serve multiple purposes and thereby reducing overall device complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides high efficiency and improved voltage resistance during overvoltages, reducing energy losses and harmonic content, allowing for reliable operation in supply networks with 400 to 500V alternating voltage without the need for additional components like IGBTs, resulting in a compact and efficient design.
Implementation Method 1
current flow through the switching element in the blocked state is permitted if a predetermined breakdown voltage at the switching element is exceeded
Data Source
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AI summary
The present invention relates to an input circuit (ES) for a power supply. An input voltage (Ue) of the input circuit (ES) is converted into an output voltage (Ua) of the input circuit (ES) by periodically switching a switching element (SE) between a conducting and a blocked state. An inductor (L) arranged in series with the switching element (SE) is at least partially traversed by a current (IL) during a switching period of the switching element (SE). This current (IL) charges an output-side capacitance (Ca), from which the output voltage (Ua) is provided. When the switching element (SE) is blocked, the current is taken over by an active switching unit (FD). Furthermore, current flow (IAVAL) through the switching element (SE) in the blocked state is permitted if a predetermined breakdown voltage (Ud) across the switching element (SE) is exceeded.If an overvoltage is detected at the input of the input circuit (ES), the switching element (SE) can be switched to the off state. The resulting current flow (IAVAL) can be conducted into the inductor (L) of the input circuit (ES), thereby switching off the active switching unit (FD). The switching element (SE) and the inductor (L) are dimensioned such that, in the event of an overvoltage, a so-called avalanche energy is generated at the switching element (SE), which allows the switching element (SE) to withstand the current (IL) flowing through the inductor (L) for the duration of the overvoltage.