Current Source Delay Circuit for Stable Power-Off Sequencing
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Solution Overview
Problem
Existing discharge control circuits for devices with multiple power supplies face challenges in controlling the power-off sequence due to dependence on load capacity and resistance, leading to potential reversal of power supply potentials and parasitic element activation, which is not freely adjustable and is affected by temperature and power voltage variations.
Innovation Solution
A discharge control circuit with logic circuits and delay circuits that use transistors with temperature- and voltage-independent logic thresholds, combined with a current source circuit and capacitor to set delay times, allowing for flexible control sequences and reducing current consumption by cutting off charging current after a predetermined delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a delay circuit with fixed current ratio is used to control power-on and power-off sequences, then the delay time is determined at manufacturing, but the control sequences cannot be freely set and the delay time depends on power voltage changes
Solution Approach 1:
The patent makes the delay circuit dynamically adjustable by introducing a control terminal that accepts external control signals. The delay time and control sequences can be freely set by changing the control signal, transforming the fixed manufacturing parameter into a dynamically adjustable parameter that adapts to different operational requirements.
2Reliability
If discrete components are used to constitute a discharge circuit, then the power-off sequence can be controlled, but the circuit complexity increases and the discharge time depends on load capacity and resistance
Solution Approach 1:
The patent integrates multiple functions into a single semiconductor integrated circuit chip. The delay circuit, discharge control, and power sequence management are all incorporated into one universal component that can control both power-on and power-off sequences, eliminating the need for separate discrete components and reducing overall circuit complexity.
3Loss of time
If a constant current source is used in the delay circuit, then the delay time can be maintained, but the current value changes as power voltage changes and temperature variations occur
Solution Approach 1:
The patent employs a feedback mechanism where the delay circuit monitors the actual delay time and power voltage conditions, and automatically adjusts the current output to maintain the prescribed delay time. The control terminal receives feedback about operating conditions and modifies the current source output accordingly, ensuring stable delay performance despite voltage or temperature variations.
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 effectively prevents potential reversal of power supply potentials, allows for flexible setting of power-on and power-off sequences, and maintains stable operation despite temperature and voltage fluctuations, thereby preventing parasitic element activation and optimizing discharge control.
Implementation Method 1
a current source circuit which is independent of a power voltage or temperature and which is suitable for constituting a delay circuit
Data Source
AI summary
A discharge control circuit includes discharge elements, logic circuits, and at least one delay circuit. Each of the logic circuits controls turning-on and turning-off the discharge elements based on a control signal inputted externally. The delay circuit delays an output signal of a first logic circuit among the logic circuits. The discharge control circuit pulls out charges from a corresponding terminal in response to turning-on of the discharge elements. A signal delayed by the delay circuit is inputted to a second logic circuit among the logic circuits so that the discharge elements are controlled in a predetermined order by one control signal.