Switched Driver Circuit With Capacitor Boosting for Low Ripple
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Solution Overview
Problem
Conventional driver circuits for transducers often require large inductance to prevent saturation during peak current flow, which can be undesirable due to size constraints and increased ripple in switching amplifiers.
Innovation Solution
A driver circuit with a network of switching paths and capacitors that allows selective connection and boosting of input voltages, enabling operation in multiple modes with reduced voltage differences between switching voltages, thereby minimizing ripple and inductance requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an inductor is included as a separate component in the output path to suppress switching ripple, then ripple suppression is improved, but the inductance value must be relatively large which increases device size and complexity
Solution Approach 1:
The patent extracts the inductance function from a separate physical inductor component and implements it using the inherent inductance of the voice coil in piezoelectric or ceramic transducers. This eliminates the need for a separate inductor component while maintaining ripple suppression functionality.
Solution Approach 2:
The voice coil of the transducer serves dual purposes: it acts as both the actuator element for sound generation and as the inductor for ripple suppression. This multi-functional approach eliminates the need for dedicated ripple suppression components.
2Object-affected harmful factors
If an inductor is included as a separate component in the output path to suppress switching ripple, then ripple suppression is improved, but device complexity increases
Solution Approach 1:
The patent removes the separate inductor component from the circuit, thereby reducing component count and circuit complexity while maintaining the essential inductance function for ripple suppression.
Solution Approach 2:
The transducer's own voice coil provides the inductance needed for ripple suppression, making the system self-sufficient and eliminating the need for additional passive components.
3Power
If the driver circuit operates with large voltage differences between switching voltages, then output voltage range is improved, but voltage ripple increases
Solution Approach 1:
The patent changes the operating parameters by using smaller voltage differences between switching levels and compensates by adjusting duty cycle and switching frequency to maintain the required output voltage range, thereby reducing voltage ripple.
Solution Approach 2:
The patent uses high-frequency periodic switching with adjusted duty cycles to achieve the desired average output voltage while maintaining smaller voltage swing amplitudes, which reduces ripple content.
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 the maximum voltage ripple and allows for a given output voltage range with lower input voltage requirements, enhancing efficiency and reducing the need for large inductors.
Implementation Method 1
each of the first capacitor and the second capacitor can be selectively connected in series between the first and second input nodes to be charged to the input voltage
Implementation Method 2
the first input node can be selectively coupled to a first selective boost node by a path that includes the first capacitor in series
Data Source
AI summary
The application describes a switched driver (401) for outputting a drive signal at an output node (402) to drive a load such as a transducer. The driver receives respective high-side and low-side voltages (VinH, VinL) defining an input voltage at first and second input nodes and has connections for first and second capacitors (403H, 403L). A network of switching paths is configured such that each of the first and second capacitors can be selectively charged to the input voltage, the first input node can be selectively coupled to a first node (N1) by a path that include or bypass the first capacitor, and the second input node can be selectively coupled to a second node (N2) by a path that includes or bypasses the second capacitor. The output node (402) can be switched between two switching voltages at the first or second nodes. The driver is selectively operable in different operating modes, where the switching voltages are different in each of said modes.