LC Oscillator Capacitor Precharge for Fast Duty-Cycled Startup
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Solution Overview
Problem
Oscillator circuits in IR-UWB applications face challenges with high power consumption due to startup time and inefficiencies, particularly in duty-cycled operations, where ring oscillators are less energy-efficient and LC oscillators require many cycles to reach steady-state, and existing solutions do not adequately address phase noise and power management.
Innovation Solution
An LC circuit with an adjustable capacitive circuit and inductive circuit connected in a loop, where a switching circuit prevents or enables oscillation by charging the capacitive circuit, allowing for near-instantaneous startup and reduced power consumption by limiting capacitor charging and maintaining node voltages within a rail-to-rail supply voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LC oscillators are used for energy efficiency, then power consumption is reduced, but startup time increases significantly as they require many cycles to reach steady-state
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitive circuit to a specific voltage level before oscillation is enabled. This preparation step ensures that when the oscillator starts, the capacitive circuit is already in the correct initial state, allowing immediate oscillation without requiring many cycles to reach steady-state. The switching circuit charges the capacitive circuit to a voltage equal to the supply voltage before enabling oscillation, which eliminates the prolonged startup period typical of LC oscillators.
2Loss of time
If ring oscillators are used for fast startup, then startup time is reduced, but power consumption increases due to lower energy efficiency
Solution Approach 1:
The patent applies parameter changes by dynamically controlling the initial voltage state of the capacitive circuit through the switching circuit. By changing the voltage parameter of the capacitive circuit to match the supply voltage before enabling oscillation, the system achieves instantaneous startup characteristics similar to ring oscillators while maintaining the energy efficiency of LC oscillators. This parameter control allows the oscillator to start immediately without the high power consumption of ring oscillator designs.
3Use of energy by moving object
If duty-cycling is implemented to reduce power consumption, then energy efficiency improves, but oscillator startup becomes a significant component of total power consumption
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitive circuit during the duty-cycle enable transition. When the duty-cycle control signal activates the oscillator, the switching circuit has already prepared the capacitive circuit with the appropriate voltage, eliminating the need for high-power startup sequences. This allows the oscillator to consume minimal power during duty-cycled operation while achieving instantaneous startup when needed.
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 reduces phase noise by over one order of magnitude compared to ring oscillators, lowers power consumption, and enables fast startup in duty-cycled applications, such as IR-UWB communication systems, while maintaining stable oscillation frequencies.
Implementation Method 1
an oscillating signal is generated by an LC circuit having an inductive circuit and an adjustable capacitive circuit connected in a circuit loop
Implementation Method 2
an oscillating signal is generated by an LC circuit having an inductive circuit and an adjustable capacitive circuit connected in a circuit loop
Data Source
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AI summary
In an example embodiment, an apparatus includes an LC circuit having a capacitive circuit and an inductive circuit connected in a circuit loop. In a first mode, a switching circuit in the inductive circuit provides a charge voltage across the LC circuit and prevents oscillation of the LC circuit by opening a switch in the circuit loop. In a second mode, the switching circuit enables the oscillation of the LC circuit by closing the switch in the circuit loop. The adjustable capacitive circuit includes capacitive branch circuits configured to contribute a first amount of capacitance when enabled. For each capacitive branch circuit, an initialization circuit couples the set of capacitors to a respective reference voltage in response to the capacitive branch circuit being disabled and the switching circuit operating in the first mode.