Relaxation Oscillator Circuit With Integrated Reference Branch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing relaxation oscillators for RFID transponders face high current consumption due to additional consumer circuits and oscillation amplitude limitations, which deviate from the theoretical minimum consumption, and suffer from parasitic capacitance and overshoot phenomena.
Innovation Solution
A low-power relaxation oscillator design integrates a reference voltage generator within the current branch using a reference resistor and employs a current mirror comparator with transistors operating in strong inversion, reducing current consumption and allowing arbitrary oscillation amplitude adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional consumer circuits (reference voltage generator, comparators) are added to achieve oscillation function, then oscillation capability is improved, but current consumption increases beyond theoretical minimum
Solution Approach 1:
The reference voltage generator is merged with the current branch by placing the reference resistor in series with the storage capacitor within the same current path. This allows the reference voltage to be derived from the same reference current that charges the capacitor, eliminating the need for separate current paths and reducing total current consumption.
Solution Approach 2:
The reference current serves multiple functions simultaneously: it charges the storage capacitor to generate the ramp voltage, and it passes through the reference resistor to generate the reference voltage for comparison. This multi-functionality reduces the need for additional dedicated current sources.
2Use of energy by moving object
If oscillation amplitude is reduced to minimize current consumption, then power consumption decreases, but oscillation amplitude becomes linked to fixed transistor parameters
Solution Approach 1:
The oscillation amplitude is determined by the reference voltage, which can be adjusted by changing the reference resistor value or the reference current. This allows independent control of amplitude without being constrained by fixed transistor gate-source voltages, enabling both low power operation and amplitude adjustability.
3Use of energy by moving object
If storage capacitance is reduced to approach theoretical minimum consumption, then current consumption decreases, but parasitic capacitance effects become significant
Solution Approach 1:
The current mirror comparator uses transistors operating in strong inversion mode with optimized dimensions to minimize their parasitic capacitance contributions. By carefully selecting transistor sizes and operating conditions, the harmful parasitic effects are reduced while maintaining the low storage capacitance necessary for low power consumption.
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 design achieves reduced current consumption close to theoretical minimums without compromising supply voltage or temperature stability, with a period of oscillation dependent only on the reference resistor and storage capacitor, minimizing parasitic capacitance effects.
Implementation Method 1
a first module (21) comprising a ramp generator formed by a current source (31) and a storage capacitor (32), supplied by the current source via a current branch and defining a ramp voltage
Implementation Method 2
a reference voltage generator (34) resulting from adding a reference resistor (33) to said current branch, so that the reference voltage is defined by the current supplied by said current source and passing through the reference resistor
Implementation Method 3
a voltage comparator (10, 11) for comparing the ramp voltage with the reference voltage
Implementation Method 4
an asynchronous flip-flop (12) receiving, at a first input, the output signal of the comparator of the first module and, at a second input, the output signal of the comparator of the second module and outputting alternately charging control signals for the capacitance of the first module and for the capacitance of the second module
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The oscillator has a primary module (21) including a ramp generator formed by a reference current source (31) and a storage capacitor (32) defining ramp voltage (Vramp1). A comparator comprising transistors (m1, m2) compares the ramp voltage with reference voltage. A reference voltage generator (34) is formed by adding reference resistors (33, 43) on a reference current branch such that the reference voltage is defined by reference current (Iref) passing through the resistors.