SMPS Active Load Detection Circuit Reducing Dummy Resistor Loss
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Solution Overview
Problem
Conventional switching mode power supplies (SMPS) suffer from inefficiencies due to constant current flow through a dummy resistor regardless of load, leading to switching losses and heat generation, which are not effectively addressed by existing technologies.
Innovation Solution
The SMPS incorporates an active load detection function that branches current to a dummy resistor only when the rectified voltage or current exceeds a predetermined value, using a detecting unit to notify a controlling unit to adjust the switching frequency and reduce power supplied to the primary coil, thereby minimizing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current is continuously supplied to the dummy resistor in conventional SMPS, then the output voltage can be maintained, but power loss and heat generation increase
Solution Approach 1:
The patent applies dynamics by making the dummy resistor's current path dynamically controllable through a switching element. The resistor is connected in parallel with the switching element, allowing the system to switch between two states: when the switching element is off, current flows through the dummy resistor to maintain output voltage; when the switching element is on, current is diverted away from the dummy resistor, reducing power loss. This dynamic configuration resolves the contradiction between maintaining voltage stability and reducing energy waste.
Solution Approach 2:
The patent applies local quality by creating different operational conditions for different parts of the circuit based on load status. The controlling unit detects load conditions and selectively activates the dummy resistor current path only when needed (during no-load or light-load conditions). This localized control ensures that the dummy resistor functions only where and when necessary for voltage stabilization, while avoiding unnecessary power consumption in other operational states.
2Power
If switching frequency is maintained at constant high level, then power delivery capability is improved, but switching losses increase
Solution Approach 1:
The patent applies dynamics by implementing variable switching frequency control based on detected load conditions. The controlling unit adjusts the switching frequency of the switching element according to the actual power demand: higher frequencies when load requires more power delivery, and lower frequencies when load is minimal or absent. This dynamic frequency adjustment maintains adequate power delivery capability while minimizing unnecessary switching operations that cause energy loss.
Solution Approach 2:
The patent applies periodic action by using pulse-width modulation (PWM) technique where the switching element operates in periodic on-off cycles. The duty cycle and frequency of these periodic actions are dynamically adjusted based on load detection, allowing the system to deliver power in controlled pulses rather than continuous operation, thereby reducing average switching losses while maintaining required power delivery capability.
3Device complexity
If dummy resistor is always connected, then circuit simplicity is maintained, but efficiency deteriorates under no-load conditions
Solution Approach 1:
The patent applies dynamics by introducing a controllable switching element that dynamically alters the circuit configuration based on operational conditions. The switching element acts as a dynamic connector that can either include or exclude the dummy resistor from the current path, transforming the circuit from a static to a dynamic structure. This dynamic approach maintains relative simplicity while dramatically improving efficiency under no-load conditions by eliminating unnecessary current flow through the dummy resistor.
Solution Approach 2:
The patent applies taking out by selectively removing the dummy resistor from the active circuit path when it is not needed. The switching element enables the dummy resistor to be extracted from the current flow path during no-load or light-load conditions, while remaining available for connection when output voltage stabilization is required. This selective extraction eliminates wasted power consumption without permanently complicating the circuit structure.
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 approach reduces energy consumption by minimizing power loss through the dummy resistor and lowering switching frequency when no load is present, thereby reducing heating and inefficiencies in the SMPS.
Implementation Method 1
supplying AC power input to a primary coil of a transforming element, then to a secondary coil of the transforming element
Data Source
AI summary
A switching mode power supply (SMPS) with an active load detection function which supplies AC power input to a primary coil of a transforming element, then to a secondary coil of the transforming element, and then rectifies and outputs the AC power is provided. The SMPS comprises a controlling unit for controlling switching frequency by changing the time constant of a switching unit depending on the current and reducing the amount of power supplied to the primary coil of the transforming element. The current at a terminal of a resistor can be controlled under a cross condition, and the current flowing to the resistor can be controlled when in a normal state, thereby preventing energy loss which always occur in the resistor. The switching frequency during a standby state can be reduced to reduce switching loss.