AC-DC Converter Primary Side OVP Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
During the startup of AC-DC converters, the output voltage on the secondary side of the transformer is not regulated until the secondary side controller powers up, leading to potential over-voltage conditions that exceed manufacturer ratings for components.
Innovation Solution
An over-voltage protection (OVP) system is implemented, including a primary side controller with an OVP circuit and voltage divider, which compares the reduced voltage to a reference OVP voltage and turns off the gate driver if it exceeds the threshold, preventing over-voltage conditions by disconnecting the gate voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the secondary side controller is not powered up during startup, then the output voltage is not regulated, but this leads to over-voltage conditions that exceed component ratings
Solution Approach 1:
The patent implements preliminary over-voltage protection action by monitoring the output voltage on the secondary side before the secondary side controller is powered up. The primary side controller detects over-voltage conditions and asserts an OVP output to turn off the gate driver, preventing damage to secondary side components before they can occur.
Solution Approach 2:
The patent uses feedback by continuously monitoring the output voltage on the secondary side through a voltage divider circuit. The monitored voltage is fed back to the primary side controller, which compares it against a reference voltage threshold and automatically triggers protection action when over-voltage conditions are detected, creating a closed-loop protection system.
2Reliability
If the primary side controller monitors output voltage and turns off the gate driver, then over-voltage protection is provided, but this requires additional circuit components
Solution Approach 1:
The patent achieves multi-functionality by integrating the over-voltage protection function into the existing primary side controller. The controller performs both its primary function of controlling the power conversion and the additional function of monitoring output voltage and providing over-voltage protection, eliminating the need for a separate dedicated protection circuit.
Solution Approach 2:
The patent uses a voltage divider circuit as an intermediary to safely step down the high output voltage on the secondary side to a level that can be monitored by the primary side controller. This intermediary circuit enables voltage monitoring across the isolation barrier without requiring direct electrical connection between primary and secondary sides.
Data Source
AI summary
A system includes a transformer having a primary winding and an auxiliary winding at a primary side of an AC-DC converter, the auxiliary winding reflecting an output voltage of a secondary winding of the transformer. A primary side controller includes an over-voltage protection (OVP) pin and an OVP circuit. A voltage divider includes a first resistor coupled between the auxiliary winding and the OVP pin and a second resistor coupled between the first resistor and a ground. The voltage divider provides, to OVP pin, a reduced voltage that is proportional to the output voltage. In absence of a pulse signal from a secondary side controller, the OVP circuit turns off a gate driver that drives a primary switch in response to the OVP voltage exceeding a reference OVP voltage. The primary switch is coupled between the primary winding of the transformer and the ground.