Converter Overload and Short-Circuit Sensing Circuit
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Solution Overview
Problem
Existing converter protecting circuits fail to independently control overload and short-circuit current levels, leading to instability and increased risk of device damage due to the reliance on a single sensing circuit for both conditions, which also results in increased PCB area and cost.
Innovation Solution
A separate circuit path is configured for overcurrent and short-circuit sensing at the primary side, using an overcurrent sensing unit, voltage level adjusting unit, rectifying unit, short-circuit sensing unit, and delay unit to independently manage and delay signals for the control circuit, allowing for independent control of overload and short-circuit levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensing circuit is used for both overload and short-circuit detection, then the device complexity is reduced, but the reliability of protection is deteriorated because overload and short-circuit levels cannot be independently controlled
Solution Approach 1:
The sensing circuit is divided into two independent paths: a first sensing circuit for overload detection and a second sensing circuit for short-circuit detection. Each circuit independently processes its respective signal, allowing separate threshold control and protection level adjustment for overload and short-circuit conditions, thereby improving protection reliability without excessive complexity increase.
Solution Approach 2:
The short-circuit sensing function is extracted from the overload sensing circuit. A separate second sensing circuit is implemented specifically for short-circuit detection, while the first sensing circuit handles overload detection. This extraction allows independent optimization of each protection function's parameters and thresholds.
2Measurement precision
If the RC delay time is increased to control turn on/off timing, then the protection response accuracy is improved, but the PCB area increases due to requiring a significantly large smoothing capacitor
Solution Approach 1:
The delay function is segmented from the main sensing circuit and implemented as a separate delay circuit with adjustable RC time constants. This allows precise control of turn on/off timing without requiring an excessively large capacitor in the main sensing path, thereby maintaining protection response accuracy while reducing PCB area occupation.
3Duration of action of moving object
If an electrolytic capacitor is used to increase the smoothing capacitor value, then the RC delay is sufficient for protection operation, but the device life decreases and cost increases due to electrolytic capacitor characteristics
Solution Approach 1:
The capacitor function is segmented into two roles: a small multilayered ceramic capacitor for basic smoothing in the first sensing circuit, and a separate adjustable RC delay circuit for timing control. This segmentation eliminates the need for a large electrolytic capacitor, thereby extending device life and reducing cost while maintaining sufficient RC delay duration for protection operation.
Solution Approach 2:
The RC delay circuit uses adjustable resistors and capacitors to provide variable time constants, allowing the delay duration to be tuned to match different protection requirements without being constrained by fixed electrolytic capacitor values. This parameter adjustability achieves the required delay duration using smaller, more reliable components.
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 enables stable and efficient protection of converters by allowing independent adjustment of overload and short-circuit levels, reducing heat generation and improving device stability by separating the sensing and control of these conditions, thus enhancing the converter's operational reliability.
Implementation Method 1
an overcurrent sensing unit (10) sensing a primary current of a converter, wherein the overcurrent sensing unit includes a sensing capacitor connected in parallel with a resonant capacitor configuring a primary resonant circuit of the converter to sense the primary current
Implementation Method 2
a half wave rectifier circuit, and a resistance dividing circuit. An amount of current flowing to the primary side is sensed as an alternating current (AC) voltage by a capacitor and is half-wave rectified by a diode
Data Source
AI summary
Disclosed herein are an overload and short-circuit sensing circuit and a converter protecting circuit and method. The overload and short-circuit sensing circuit includes: an overcurrent sensing unit sensing a primary current of a converter; a voltage level adjusting unit adjusting a voltage level of the sensed primary current; a rectifying unit rectifying the signal adjusted by the voltage level adjusting unit; a short-circuit sensing unit sensing a current induced to a primary side of the converter due to a short-circuit or an overcurrent at a secondary side of the converter, separately from the overcurrent sensing unit; and a delay unit delaying the signal provided from the rectifying unit and the induced current sensing signal provided from the short-circuit sensing unit and providing the delayed signals to a control circuit for protecting the converter.