Switching Power Supply Rectifier Voltage Clamp Transient Mitigation
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Solution Overview
Problem
Switching power supplies face issues with voltage spikes due to imperfect electromagnetic coupling in transformers, leading to excessive stress on rectifiers, which existing solutions like higher voltage diodes, RC snubbers, clamp windings, and active clamp circuitry either dissipate power inefficiently or are costly and complex.
Innovation Solution
A circuit with a voltage clamp configuration using clamp diodes and capacitors or Zener diodes to set a clamp voltage, effectively reducing voltage transients by providing a short-circuit path for high-level voltage spikes, while also harvesting some energy to improve power supply efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher voltage diodes are used to mitigate voltage spikes, then rectifier stress is reduced, but power dissipation increases due to higher forward voltage drop
Solution Approach 1:
The patent introduces an intermediary voltage clamp circuit between the transformer output and rectifier. This clamp circuit, comprising a clamp winding, clamp diode, and capacitor, acts as a mediator that captures and redirects voltage spike energy away from the rectifier, preventing both stress and unnecessary power dissipation in the rectifier diode.
Solution Approach 2:
The voltage clamp circuit converts the harmful voltage spike energy into a beneficial form by redirecting it through the clamp diode to charge the capacitor. This transformed energy can then be reused or safely dissipated, turning the originally harmful transient energy into a useful resource that protects the rectifier without wasting power.
2Reliability
If RC snubbers are used to reduce voltage stress, then rectifier protection is improved, but device complexity and component size increase
Solution Approach 1:
The patent merges the voltage spike mitigation function with the transformer structure itself by incorporating a clamp winding into the transformer core. This integration eliminates the need for separate RC snubber circuits, reducing overall circuit complexity while maintaining effective rectifier protection through the combined transformer-clamp system.
3Reliability
If clamp windings or active clamp circuitry are used to mitigate voltage transients, then rectifier stress is reduced, but device complexity and cost increase
Solution Approach 1:
The patent merges the voltage spike mitigation function with the transformer structure itself by incorporating a clamp winding into the transformer core. This integration eliminates the need for separate RC snubber circuits, reducing overall circuit complexity while maintaining effective rectifier protection through the combined transformer-clamp system.
Solution Approach 2:
The clamp winding is designed to automatically activate during voltage transient events without requiring external control signals or complex circuitry. The passive components (clamp diode and capacitor) self-regulate the voltage spikes, making the system self-service and eliminating the need for active control mechanisms.
4Reliability
If RCD clamps are used to clamp voltage transients, then rectifier protection is improved, but adaptability is reduced as they may only clamp freewheeling rectifier diodes
Solution Approach 1:
The voltage clamp circuit designed in the patent is universally applicable to different rectifier configurations. By placing the clamp circuit at the transformer output stage, it can protect various types of rectifiers (bridge rectifiers, full-wave rectifiers, etc.) and different rectifier diode arrangements, making the solution versatile and adaptable to multiple applications.
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 effectively clamps voltage transients, reducing rectifier stress and improving power supply efficiency by dissipating some energy as heat and delivering a portion of the clamped energy to the output load, thus addressing the inefficiencies and costs of existing methods.
Implementation Method 1
a voltage clamp, configured to clamp, to a clamp voltage set by the voltage clamp, a first voltage transient and a second voltage transient of the AC signal
Implementation Method 2
A switching power supply includes a transformer having a primary winding to receive a switched input current and a secondary winding, followed by a rectifier. Electromagnetic coupling between the primary winding and the secondary winding is imperfect.
Data Source
AI summary
A circuit to rectify an alternating current (AC) signal produced by an output coil of a transformer responsive to an input current in an input coil of the transformer comprises: an output node and a return node coupled to an output load; a first rectifier, coupled to a first terminal of the output coil and the return node, to rectify the AC signal to supply a current to the output node when the input current is ON; a second rectifier, coupled to a second terminal of the output coil and the return node, to rectify the AC signal to supply a current to the output node when the input current is OFF; and a voltage clamp to clamp a first voltage transient and a second voltage transient of the AC signal that occur at the first terminal and the second terminal when the input current is switched OFF and ON.