Switched Capacitor Circuit With Pre-Charge for Stable Capacitance
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Solution Overview
Problem
Existing capacitor circuits face challenges in precisely and stably adapting capacitance for stable modulation of carrier signals, particularly in Bluetooth Low Energy transmitters, due to parasitic parameters and non-ideal switching behaviors.
Innovation Solution
A capacitor circuit design that includes a switching element and a control unit to pre-charge the intermediate node before transitioning to the OFF state, compensating for charge transfer and maintaining a stable capacitance by ensuring a high off-resistance, thereby reducing charge leakage and capacitance drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a switching element is used to adapt capacitance values, then the capacitance can be changed, but charge leakage occurs during switching transitions causing instability
Solution Approach 1:
The control unit performs preliminary charge transfer to the intermediate node before the switching element transitions from ON to OFF state. This advance action compensates for the charge that will be transferred to the intermediate node during switching, thereby maintaining stable capacitance values and preventing instability caused by charge leakage.
Solution Approach 2:
The control unit monitors the switching state and dynamically adjusts the charge transfer amount based on the switching element's state. This feedback mechanism ensures that the charge compensation is precisely matched to the charge leakage, maintaining stable capacitance adaptation throughout the switching process.
2Adaptability or versatility
If the switching element transitions from ON to OFF state, then capacitance changes, but voltage fluctuations occur at the intermediate node
Solution Approach 1:
The control unit transfers charge to the intermediate node in advance, before the switching element transitions. This preliminary charge transfer counteracts the voltage drop that would otherwise occur at the intermediate node during the switching transition, thereby maintaining voltage stability while enabling capacitance switching.
3Measurement precision
If precise capacitance control is implemented, then frequency modulation accuracy improves, but additional charge transfer control circuitry is required
Solution Approach 1:
The control unit performs multiple functions: it controls the switching element's ON/OFF state, calculates the required charge compensation amount, and executes the charge transfer to the intermediate node. By consolidating these functions into a single control unit, the patent achieves precise capacitance control for accurate frequency modulation while minimizing the increase in device complexity.
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
Enables precise and stable capacitance switching with reduced power consumption and die area, maintaining capacitance accuracy and frequency stability in oscillator circuits.
Implementation Method 1
the switching element exhibits an on-resistance between the first terminal and the second terminal during the ON state and an off-resistance between the first terminal and the second terminal during the OFF state
Implementation Method 2
to transfer an electrical charge to the intermediate node, which is adapted to at least partially or fully compensate an electrical charge that is transferred (from the switching element) to the intermediated node
Data Source
AI summary
The present document describes a capacitor circuit (100) which comprises a capacitor element (124) that is arranged between an intermediate node (122) and a reference potential (111), and a switching element (121) which comprises a first terminal that is coupled to the intermediate node (122) and a second terminal that is coupled to the reference potential (111) during the ON state of the switching element (121). Furthermore, the capacitor circuit (100) comprises a control unit (110, 210) which is configured to cause a transition from the ON state to the OFF state of the switching element (121) at a switching time instant; and, within a bias interval that is prior to the switching time instant, to transfer an electrical charge to the intermediate node (122), which is adapted to at least partially compensate an electrical charge that is transferred to the intermediated node (122) during the transition from the ON state to the OFF state of the switching element (121).