Bistable Standby Circuit Reducing Component Count and Energy Consumption
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Solution Overview
Problem
Existing standby circuits in electric appliances are costly and require a large number of components, which is inefficient for reducing energy consumption during standby states.
Innovation Solution
A bistable circuit using two transistors in pass-gate configuration, with a p-type and n-type BJT, and a feedback diode, to control a switch and manage direct voltage supply to electronic modules, reducing component count and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a switch is used at the power supply output to break the direct voltage line during standby, then energy consumption is reduced, but the cost and component count increase
Solution Approach 1:
The circuit uses the leakage current inherently present in the AC/DC power supply to automatically trigger the standby mode without requiring additional sensing components. The power supply's own leakage current serves the dual purpose of charging the capacitor and detecting standby conditions, eliminating the need for separate voltage detection circuits or sensors.
Solution Approach 2:
The invention extracts and utilizes the otherwise wasted leakage current from the power supply as a useful signal for controlling the standby mode. By capturing this small current through a high-value resistor and capacitor, the circuit transforms a parasitic effect into a functional mechanism for automatic power management.
2Device complexity
If manual button press is required to reset the switch, then the circuit can be simplified, but user interaction is required instead of automatic reset
Solution Approach 1:
The circuit automatically resets itself by utilizing the same leakage current that triggered the standby mode. When mains power is restored or continuously present, the leakage current charges the capacitor again, automatically resetting the transistor and restoring power to the load without requiring any user intervention.
Solution Approach 2:
The circuit exhibits periodic automatic resetting behavior based on the presence of mains voltage. The capacitor charges and discharges in cycles, creating automatic on-off-reset sequences that eliminate the need for manual buttons while maintaining simple circuitry.
3Device complexity
If high-value resistor and capacitor are used to detect standby mode, then component count is reduced, but the circuit becomes more sensitive to electronic noise
Solution Approach 1:
The circuit incorporates a feedback mechanism where the transistor's collector is connected to the base through a feedback resistor. This positive feedback reinforces the transistor's state once triggered, creating a bistable condition that resists noise-induced false triggering. The feedback ensures that once the transistor switches, it remains in that state until the capacitor fully charges or discharges.
Solution Approach 2:
The high-value capacitor acts as a time-constant element that filters out short-duration noise spikes. By requiring a sustained voltage level over the capacitor's charge time constant, the circuit inherently rejects transient electronic noise that would otherwise trigger false standby modes.
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
The solution provides a low-cost, efficient method to manage direct voltage supply, reducing energy consumption by using a minimal number of components and maintaining stability against electronic noise.
Implementation Method 1
a capacitor being charged through a high-value resistor when the electric appliance is in the standby state
Implementation Method 2
the transistor being in a first state when a voltage level at a base of the transistor exceeds a threshold value and being in a second state when the voltage level at the base does not exceed the threshold value
Data Source
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AI summary
The present invention relates to an electric standby circuit (4) for an electric appliance. The circuit comprises a switch (41) adapted to open and close an electric connection between a first input (IN1) and an output (OUT) of the circuit (4), and a bistable circuit electrically connected to the switch in order to control the opening and closing thereof. The bistable circuit comprises a first BJT transistor (Q19) of the pnp type and a second BJT transistor (Q12) of the npn type. The first transistor (Q19) is connected to the first input (IN1) through the emitter, and the collector of the first transistor (Q19) is connected to the base of the second transistor (Q12) through a first resistor (R39). The collector of the second transistor (Q12) is connected to the switch (41) and to a second input (IN3) through a second resistor (R40). The base of the first transistor (Q19) is connected to the second input (IN3) through a third resistor (R38).