Oscillator Circuit Frequency Stability Against Voltage Fluctuations
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Solution Overview
Problem
Conventional oscillator circuits in semiconductor integrated circuits have a high dependence of oscillation frequency on the power supply voltage, which can change due to battery deterioration or other factors.
Innovation Solution
The oscillator circuit includes two charging and discharging circuits with switching and detection mechanisms that alternately perform initialization and discharge operations, starting from the power supply voltage, reducing the oscillation frequency's dependence on the power supply voltage by maintaining consistent initial voltages for capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional oscillator circuit uses a single capacitor charging/discharging mechanism, then the circuit structure is simple, but the oscillation frequency has high dependence on power supply voltage changes
Solution Approach 1:
The oscillator circuit is divided into two independent charging/discharging paths: a first path with a first capacitor, first switching circuit, and first detection circuit; and a second path with a second capacitor, second switching circuit, and second detection circuit. Each path operates independently to charge and discharge its respective capacitor, thereby segmenting the single oscillation mechanism into two parallel mechanisms that collectively improve frequency stability against power supply variations.
Solution Approach 2:
The control circuit alternates the operation of the two charging/discharging paths in periodic fashion. When the first path is performing initialization, the second path performs discharge, and vice versa. This periodic alternation ensures continuous oscillation while maintaining stable frequency by ensuring that at least one capacitor is always in discharge mode, making the oscillation frequency less sensitive to power supply voltage fluctuations.
2Ease of operation
If the capacitor discharge operation is continuous without initialization, then the circuit operation is simple, but the oscillation frequency varies with power supply voltage changes
Solution Approach 1:
Before each discharge operation, the control circuit performs an initialization operation on the capacitor through the switching circuit, setting the capacitor voltage to the power supply voltage Vdd in advance. This preliminary initialization ensures that each discharge cycle starts from a known voltage state, making the discharge time and resulting oscillation frequency independent of previous voltage levels and stable against power supply variations.
Solution Approach 2:
The detection circuit monitors the capacitor voltage during discharge and provides feedback to the control circuit. When the capacitor voltage reaches a predetermined threshold during discharge, the detection circuit signals the control circuit to switch from discharge mode to initialization mode. This feedback mechanism automatically controls the alternating operation of the two paths, ensuring stable oscillation frequency without requiring complex external control.
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 solution ensures a stable oscillation frequency regardless of power supply voltage changes, maintaining accurate clock output with a 50% duty cycle without the need for additional counters.
Implementation Method 1
a first capacitor C1, a first switching circuit SW1, a first detection circuit KC1... a second capacitor C2, a second switching circuit SW2, and a second detection circuit KC2
Implementation Method 2
a P-channel type MOS transistor M10 and an N-channel type MOS transistor M11 forming an inverter... an N-channel type MOS transistor M12 serially connected to these transistors and flowing a reference current I1
Data Source
AI summary
The invention provides an oscillator circuit that reduces the dependence of an oscillation frequency on a power supply voltage. When a first charging and discharging circuit completes its discharge, a terminal voltage of a first capacitor of the first charging and discharging circuit is initialized to a power supply voltage and simultaneously a second charging and discharging circuit starts its discharge. Then, when the second charging and discharging circuit completes its discharge, a terminal voltage of a second capacitor of the second charging and discharging circuit is initialized to the power supply voltage and simultaneously the first charging and discharging circuit starts its discharge. The first and second charging and discharging circuits alternately repeat the initialization and the discharge, and the discharge is always started from the power supply voltage.