Non-isolated Power Supply Zero Current Detection
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Solution Overview
Problem
Conventional non-insulated power supply devices for LED lighting face challenges in controlling output current independently of input voltage fluctuations, leading to increased component count and cost due to the need for additional terminals and parts for zero current detection.
Innovation Solution
A non-insulated power supply device configuration that includes a switching element, an inductor, a rectification element, a current-voltage conversion element, and a control circuit with a smoothing circuit and voltage comparison circuit to detect zero current timing using a single external terminal, allowing optimal switching and improved power efficiency without increasing the number of parts or terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a transformer is used to detect zero current timing, then zero current detection accuracy is improved, but the number of parts and footprint increase
Solution Approach 1:
The patent extracts the zero current detection function from the transformer and implements it using only the inductor's terminal voltage. By monitoring the voltage across the inductor terminals, the system can detect when current reaches zero without requiring a separate transformer, thus removing unnecessary components while maintaining detection accuracy.
Solution Approach 2:
The inductor serves multiple functions: it performs current-to-voltage conversion for control purposes and simultaneously provides zero current detection capability through its terminal voltage. This multi-functionality eliminates the need for dedicated detection components, reducing overall device complexity.
2Difficulty of detecting and measuring
If two external terminals are used for zero current detection, then detection capability is improved, but the package pin count and cost increase
Solution Approach 1:
The patent combines the zero current detection function with the existing inductor terminal connections. The control circuit monitors the voltage between the same terminals already used for inductor control, merging detection functionality into existing circuit nodes and avoiding additional external terminals.
Solution Approach 2:
The inductor's own terminal voltage serves the dual purpose of control signaling and zero current detection. The system uses the inductor's inherent electrical characteristics to provide detection information without requiring external detection components or additional terminals.
3Device complexity
If conventional non-insulated power supply control is used, then circuit simplicity is maintained, but output current control becomes dependent on input voltage fluctuations
Solution Approach 1:
The patent implements feedback control by continuously monitoring the inductor's terminal voltage to detect zero current timing. This feedback mechanism allows the control circuit to adjust switching timing dynamically, ensuring stable output current control that is independent of input voltage fluctuations while maintaining circuit simplicity.
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
Enables efficient power supply by detecting zero current timing accurately and adapting to input voltage fluctuations, reducing switching noise and maintaining power efficiency without additional components, thus optimizing switching control.
Implementation Method 1
an inductor connected in series with or in parallel to the load; turn on the switching element so as to allow current to flow to the inductor, and thereafter to turn off the switching element so as to allow the discharge current from the inductor to flow to the rectification element and the load
Implementation Method 2
a current-voltage conversion element connected in series with the switching element; the voltage that is generated from the current flowing through a switching transistor Q1 by current-to-voltage conversion with a sense resistor Rs
Implementation Method 3
a rectification element connected such that a discharge current from the inductor can flow to the load while the switching element is off
Data Source
AI summary
A control circuit that controls a switching element includes a first terminal to which a voltage produced by conversion of current flowing through the switching element by a current-to-voltage conversion element is input, a second terminal to which the voltage of a point of contact of an inductor and rectification element or a voltage proportional thereto is input, a filter for smoothing the voltage input into the second terminal, and a voltage comparison circuit for comparing the voltage smoothed by the filter and the voltage input into the second terminal. The control circuit performs control such that the switching element is switched from off to on near the point where the inductor current becomes zero based on the voltage comparison circuit output and the switching element is switched from on to off in response to the voltage applied to the first terminal reaching a prescribed voltage.