Relaxation Oscillator Startup Circuit to Prevent Deadlock
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Solution Overview
Problem
Conventional relaxation oscillators face a deadlock situation during startup, preventing the generation of complementary periodic square wave signals.
Innovation Solution
The relaxation oscillator is modified to include a voltage-controlled current circuit, a latching circuit, and a combinational logic circuit with transistors and capacitors, which allows for controlled startup and avoids the deadlock situation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional relaxation oscillator circuit is used, then the circuit structure is simple, but the oscillator cannot start up normally due to deadlock situation
Solution Approach 1:
The patent applies preliminary action by adding a start-up circuit that pre-charges the capacitor to a specific voltage level before the main oscillation begins. This preliminary charging action ensures that the capacitor voltage exceeds the threshold voltage required to activate the positive feedback mechanism, thereby breaking the deadlock situation and enabling reliable startup without requiring complex additional control circuits.
Solution Approach 2:
The patent introduces an intermediary component (start-up circuit with transistor and resistor) that mediates between the power supply and the main oscillation circuit. This intermediary provides a controlled initial current path to charge the capacitor, acting as a bridge that enables the transition from static power-on state to dynamic oscillation state, thus resolving the startup deadlock while maintaining overall circuit simplicity.
2Productivity
If the capacitor voltage remains below the threshold voltage, then the circuit remains stable, but the oscillation cannot be generated
Solution Approach 1:
The patent applies preliminary anti-action by designing a circuit that intentionally creates an initial voltage condition opposite to the stable low-voltage state. The start-up circuit forces the capacitor voltage above the threshold level, effectively preventing the system from remaining in the stable but non-oscillating low-voltage state, thereby ensuring oscillation generation while the positive feedback mechanism maintains subsequent stability through hysteresis.
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 modified relaxation oscillator successfully generates complementary periodic square wave signals by avoiding the deadlock situation during startup, ensuring normal operation.
Implementation Method 1
the capacitor C starts to be charged from (−β×Vss)... the capacitor C is charged to (β×Vdd)... the capacitor C starts to be discharged from (β×Vdd)
Implementation Method 2
The voltage at the negative input terminal of the operational amplifier 110 is V−. The voltage at the positive input terminal of the operational amplifier 110 is V+... the voltage V− at the negative input terminal of the operational amplifier 110 is lower than the voltage V+ at the positive input terminal of the operational amplifier 110
Data Source
AI summary
A relaxation oscillator includes a start-up circuit. During the start-up period of the relaxation oscillator, two output signals from the relaxation oscillator are controlled to be complementary signals by the start-up circuit according to a control signal. Consequently, the relaxation oscillator can be started up successfully. The relaxation oscillator can generate periodic square wave signals. Moreover, during the start-up period of the relaxation oscillator, the generation of the deadlock situation can be avoided.