Isolated Power Converter Secondary-Side Load Switch Protection
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Solution Overview
Problem
Existing isolated power converters face challenges in efficiently managing power delivery and voltage protection, particularly when there is a sudden disconnect of the supply voltage, leading to potential over-voltage conditions that can damage load circuitry.
Innovation Solution
Incorporating a load switch on the secondary side of the isolated power converter, controlled by secondary-side control circuitry that uses an opto coupler to draw power and switch the load switch into an OFF mode when the supply voltage is disconnected, thereby limiting power output and preventing over-voltage damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the secondary-side control circuitry is disconnected from the supply voltage during a fault condition, then the control circuitry cannot function to regulate power output, but the load remains unprotected from over-voltage damage
Solution Approach 1:
The patent implements preliminary action by providing an additional power source that is pre-configured to activate when the primary supply voltage is disconnected. This additional power source is ready in advance to take over the function of driving the load switch into the OFF mode, ensuring continuous protection capability without requiring complex real-time switching logic or multiple control circuits.
2Object-affected harmful factors
If the load switch remains in ON mode during supply voltage disconnection, then power delivery continues uninterrupted, but over-voltage conditions can damage the load circuitry
Solution Approach 1:
The patent uses an intermediary approach by introducing an additional power source that acts as a mediator between the supply voltage disconnection event and the load switch control. This intermediary power source enables the control circuitry to maintain its protective function even when the primary power supply is disconnected, allowing the load switch to be properly controlled into the OFF mode to prevent over-voltage damage while providing a controlled interruption rather than uncontrolled power delivery cessation.
3Reliability
If primary-side control circuitry limits power output, then over-voltage protection is provided, but the response time is insufficient to prevent damage during sudden disconnects
Solution Approach 1:
The patent applies preliminary action by pre-configuring the additional power source to immediately activate when supply voltage disconnects, enabling the control circuitry to rapidly drive the load switch OFF without waiting for primary-side detection and response. This preliminary preparation of the backup power source eliminates the response time delay inherent in primary-side control mechanisms, providing instantaneous protection while maintaining full power delivery capability during normal operation.
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
This solution effectively blocks the current path to the load during fault conditions, preventing over-voltage damage and ensuring safe power delivery by using an additional power source when the supply voltage is absent, thus enhancing the protection mechanisms of the isolated power converter.
Implementation Method 1
an opto coupler configured to draw power and charge another node of the secondary-side control circuitry when the load switch is in an ON mode
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An apparatus for delivering power to a load, which comprises an isolated power converter that converts input power on a primary side to output power and a supply voltage at a node on a secondary side. On the secondary side, a load switch is located on a current path to the load. A secondary-side control circuitry controls the load switch to operate in an ON mode in which current is provided to the load, and in response to a fault condition corresponding to an effective sudden disconnection of the supply voltage, switches the load switch into an OFF mode in which the current path to the load is blocked.