Diode Loss Detection for Synchronous Output Stage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a need to detect an open-circuit condition in a rectifying diode separated from an integrated circuit in switch-mode power converters to prevent dangerous pulsed voltages and ensure safe operation, particularly in applications like automotive environments where a separate diode is used.
Innovation Solution
A series arrangement of a resistor and a switch is coupled in parallel with the diode, with a comparator configured to assert an output signal when a current through the resistor crosses a threshold level, triggering the controller to shut down the power converter, allowing operation in continuous conduction mode even at low load currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a diode is externally coupled to an integrated circuit, then the integrated circuit size is reduced and safety is improved, but the complexity of detecting open-circuit conditions increases
Solution Approach 1:
A sense resistor is introduced as an intermediary element in series with the externally coupled diode. This resistor mediates between the diode and the integrated circuit, enabling voltage-based detection of diode health status without requiring direct complex monitoring of the diode itself. The voltage drop across the sense resistor serves as an indirect indicator of diode conduction state.
Solution Approach 2:
The patent replaces direct electrical connection monitoring with voltage threshold comparison. Instead of using complex electrical monitoring circuits to detect diode open-circuit conditions, the system uses a comparator circuit that simply compares the voltage across the sense resistor against a reference threshold, substituting mechanical/electrical complexity with a simpler voltage comparison mechanism.
2Loss of energy
If a synchronous output stage is used, then power efficiency is improved, but the risk of substrate current injection and latch-up increases
Solution Approach 1:
The detection circuit performs preliminary monitoring of the diode's health status before substrate current injection can cause latch-up. By continuously checking the voltage across the sense resistor and comparing it against thresholds, the system can detect diode failures early and shut down the synchronous output stage before dangerous substrate currents develop.
Solution Approach 2:
The patent implements a feedback mechanism where the voltage across the sense resistor is continuously monitored and fed back to the comparator. This feedback loop allows the system to dynamically adjust its operation based on diode health status, enabling the synchronous output stage to operate efficiently under normal conditions while automatically shutting down when diode failure is detected, thus preventing latch-up.
3Stability of the object's composition
If continuous conduction mode is enabled at low load currents, then output voltage regulation is improved, but power dissipation in the integrated circuit increases
Solution Approach 1:
The patent changes the operational parameters of the synchronous output stage by introducing a sense resistor with specific resistance value and configuring the comparator with appropriate threshold levels. This parameter configuration enables the system to maintain continuous conduction mode at low load currents while limiting power dissipation through the sense resistor, achieving a balance between output voltage regulation stability and energy loss.
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 detects and responds to an open-diode condition, ensuring safe operation and reducing power dissipation in the integrated circuit, while enabling continuous conduction mode at low or no load conditions, thus preventing substrate current injection and maintaining system functionality.
Implementation Method 1
A first input terminal of a comparator is coupled to a first terminal of the resistor and a second input terminal of the comparator is coupled to a second terminal of the resistor. The comparator is configured to assert an output signal when a current through the resistor crosses a threshold current level
Data Source
AI summary
An embodiment of the invention relates to a switch-mode power converter including an inductor and an external rectifying diode. A series arrangement of a resistor and a switch are coupled in parallel with the external rectifying diode. The resistor and the switch enable continuous conduction mode, even at substantially no output current. A comparator senses a current level in the resistor. When the current level crosses a threshold level, the power converter is shut down. The current level is sensed with a second resistor coupled to a current source to produce a current sensing arrangement dependent on a ratio of resistances. Advantageously, the current level is sensed with clamp circuits coupled to the comparator, each clamp circuit including a series circuit arrangement of a field-effect transistor with a gate coupled to a voltage source.