Digital Switching Converter Control Circuit
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Solution Overview
Problem
Existing switching converter control circuits for DC/DC converters, particularly those used in LED illumination devices, require external components like sense resistors and filter circuits for load current regulation, which can be inefficient and prone to temperature and aging-related issues, and lack integrated solutions for reduced component count.
Innovation Solution
A digital control circuit that integrates current sensing within the switching converter, using sense transistors to monitor the high and low-side transistor currents, eliminating the need for external sense resistors and filter networks, and employing a digital PWM modulator with a comparator and proportional-integral controller to regulate the load current, allowing for reduced external components and improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external sense resistors and filter circuits are used for load current regulation, then current regulation can be achieved, but device complexity and component count increase
Solution Approach 1:
The patent merges the current sensing function and filter function into the existing switching converter structure by utilizing the source and drain terminals of the high-side and low-side transistors. This eliminates the need for external sense resistors and filter circuits, reducing component count while maintaining current regulation capability through the integrated transistor terminal measurements
Solution Approach 2:
The switching converter transistors serve multiple functions: power switching, current sensing, and filtering. The source and drain terminals of these transistors are used both for their primary switching operation and for measuring current-related voltages, thereby eliminating dedicated external sensing components and reducing overall device complexity
2Measurement precision
If external sense resistors are used for current sensing, then load current can be monitored, but manufacturing cost and device complexity increase
Solution Approach 1:
The current sensing function is merged with the power switching transistors by measuring voltages at their source and drain terminals. This eliminates the need for separate external sense resistors, reducing manufacturing cost and simplifying the bill of materials while maintaining measurement precision through the inherent transistor terminal voltage measurements
3Stability of the object's composition
If filter circuits are added to smooth current sense signals, then output stability improves, but device complexity and component count increase
Solution Approach 1:
The filtering function is merged with the power switching transistors by utilizing their source and drain terminals as both switching elements and filtering nodes. The inherent capacitance and resistance of the transistor terminals provide natural filtering of the sensed signals, eliminating the need for separate external filter circuits while maintaining output stability
Solution Approach 2:
The switching transistors serve dual purposes: power switching and signal filtering. Their terminals are used both for switching operation and for providing filtered current sense signals to the control circuit, thereby reducing overall circuit complexity while maintaining output stability
Data Source
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AI summary
A control circuit for controlling the operation of a switching converter to provide a regulated load current to a load is disclosed. The switching converter includes an inductor and a high-side and a low side-transistor for switching the load current provided via the inductor. The circuit includes: a digital modulator configured to provide a modulated signal having a duty cycle determined by a digital duty cycle value; a current sense circuit coupled to at least one of the transistors and configured to regularly sample a load current value; a comparator, coupled to the current sense circuit and configured to compare the sampled load current value with a first threshold and provide a respective comparator output signal, the first threshold being dependent on a defined desired output current and the comparator output signal being indicative of whether the sampled current value is lower or greater than the desired output current; and a regulator configured to receive the comparator output signal and to calculate an updated digital duty cycle value. Furthermore, a corresponding method for controlling the operation of a switching converter is disclosed.