Switch Control Device for Converter Overcurrent Protection
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Solution Overview
Problem
Conventional converters face issues with malfunction prevention due to leading edge current (LEC), which lengthens the minimum turn-on state maintaining time (Tmin.on) and can lead to peak current exceeding the maximum limit, causing potential damage, especially when the output terminal is overloaded or short-circuited, and this is exacerbated by the inclusion of leading edge blanking (LEB) and abnormal overcurrent protection (AOCP) circuits.
Innovation Solution
A switch control device and method that utilize a first signal generator producing a signal maintained at a high level initially and gradually lowered, combined with a pulse width modulation (PWM) controller comparing current signals to control the switch operation, effectively preventing malfunctions by generating a Leading Edge Envelope (LEE) signal that allows for quicker sensing of current levels and reduced peak values during overloads or short circuits without the need for LEB and AOCP circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a leading edge blanking (LEB) circuit is used to prevent malfunction caused by leading edge current, then the converter can operate safely during LEC generation, but the minimum turn-on state maintaining time (Tmin.on) is lengthened by the LEB time
Solution Approach 1:
The patent extracts and removes the LEB circuit and AOCP circuit from the converter system. Instead of using these separate protection circuits that lengthen Tmin.on, the invention implements a simplified control method where the controller directly manages the main switch turn-off timing based on current detection, eliminating the time-consuming LEB period while maintaining safety through precise current monitoring and control.
2Ease of operation
If the main switch is turned off after current limit delay time (TCLD) from when current reaches maximum limit, then the controller has time to process the current limit signal, but the peak current may exceed the maximum current limit (ILIM) causing potential damage
Solution Approach 1:
The patent applies preliminary action by having the controller prepare and execute the main switch turn-off command immediately when the current limit is detected, without waiting for a delay period. The controller monitors the current through the sense resistor and directly responds to current limit conditions by turning off the main switch, preventing peak current exceedance while providing sufficient processing time through direct signal routing and immediate response mechanism.
3Reliability
If LEB circuit and AOCP circuit are included in the converter design, then the converter can protect against leading edge current and overcurrent conditions, but the device complexity and cost increase
Solution Approach 1:
The patent merges the functions of the LEB circuit and AOCP circuit into a single integrated control mechanism within the controller. The controller combines current sensing, current limit detection, and main switch control functions into one unified system, eliminating the need for separate LEB and AOCP circuits. This integration maintains comprehensive overcurrent protection while significantly reducing device complexity and component count.
Solution Approach 2:
The controller is designed with multi-functionality to perform both the protection functions previously requiring separate LEB and AOCP circuits. The single controller handles current sensing, current limit detection, timing control, and main switch management, making it a universal protection and control unit that replaces multiple specialized circuits, thereby reducing overall system complexity while maintaining comprehensive protection capabilities.
Data Source
AI summary
A switch control device, a switch control method, and a converter using the same are disclosed. The converter includes: a switch; an energy transfer element that converts input energy into output energy according to a switching operation of the switch; and a switch control device that generates a first signal, which is maintained at a first level during a first interval starting from a first time at which the switch is turned on by using a feedback signal corresponding to the output energy and is then gradually lowered from the first level to the feedback signal during a second interval, and controls the switching operation of the switch by using a second signal corresponding to a current flowing at the switch and the first signal. A malfunction due to an LEC can be effectively prevented, and the converter and the converter controller can be implemented to be compact and low-priced.