Variable Resistance No-Load Detection Circuit for Switching Power Supplies
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Solution Overview
Problem
Conventional load detecting methods for switching mode power supplies face challenges in accurately determining no-load or light-load conditions due to difficulties in choosing the appropriate resistance value, leading to high power consumption or inaccurate detection.
Innovation Solution
A no-load detecting circuit with a variable resistance circuit and comparison circuits that adjust equivalent resistance based on load status, using transistors in series and parallel to generate a no-load detecting signal, and a reload determining signal to manage power supply operations effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistor is coupled in series to the load for load detection, then the load status can be detected by comparing voltage across the resistor with a preset threshold, but the resistance value is difficult to choose because large resistance causes high power consumption under heavy load while small resistance produces too small voltage to detect accurately under light load
Solution Approach 1:
The patent applies dynamics by making the resistance value changeable based on operating conditions. The variable resistance circuit adjusts its equivalent resistance dynamically: under heavy load conditions, it presents higher resistance to minimize power consumption, while under light load conditions, it presents lower resistance to maintain sufficient detection voltage. This dynamic adaptation resolves the contradiction between detection accuracy and power consumption.
Solution Approach 2:
The patent changes the resistance parameter of the detection circuit based on load conditions. By using a variable resistance circuit whose equivalent resistance can be adjusted (higher under heavy load, lower under light load), the system optimizes both power consumption and detection accuracy across different operating states, directly addressing the technical contradiction.
2Loss of energy
If the resistance is large to reduce power consumption under heavy load, then power loss decreases, but the voltage across the resistor becomes too small to detect accurately under light load
Solution Approach 1:
The variable resistance circuit dynamically adjusts its resistance value based on the operating state. When under heavy load, it adopts a higher equivalent resistance to minimize power loss. When under light load, it switches to a lower equivalent resistance to ensure sufficient voltage for accurate detection. This dynamic behavior resolves the contradiction between power consumption and detection accuracy.
Solution Approach 2:
The resistance parameter is changed according to load conditions. The system uses a variable resistance circuit that presents different resistance values (higher for heavy load, lower for light load) to optimize both power efficiency and detection precision under different operating states.
3Measurement precision
If the resistance is small to maintain sufficient detection voltage under light load, then detection accuracy is maintained, but the power consumption becomes high under heavy load
Solution Approach 1:
The variable resistance circuit dynamically adapts its resistance value to the operating conditions. Under light load, it uses lower resistance to maintain sufficient detection voltage for accurate measurement. Under heavy load, it switches to higher resistance to minimize power consumption. This dynamic adjustment resolves the contradiction between detection accuracy and power efficiency.
Solution Approach 2:
The resistance parameter is dynamically changed based on load status. The system employs a variable resistance circuit that adjusts its equivalent resistance (lower for light load to maintain detection voltage, higher for heavy load to reduce power consumption), thereby optimizing both detection accuracy and power efficiency across different operating states.
Data Source
AI summary
A no-load detecting circuit and the method thereof are disclosed. The no-load detecting circuit may be applied in switching mode power supplies or other circuits. The no-load detecting circuit comprises: a variable resistance circuit coupled in series to a load of the switching mode power supply; and a first comparison circuit coupled to the variable resistance circuit to receive the voltage across the variable resistance circuit, wherein based on the comparison of the voltage across the variable resistance circuit and a first threshold, the first comparison circuit generates a no-load detecting signal indicative of the load status; wherein the equivalent resistance of the variable resistance circuit varies based on the varying of the load of the switching mode power supply.