Class-D Amplifier Oscillation Absorption Circuit
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Solution Overview
Problem
Class-D amplifiers for high RF ranges face issues with oscillation phenomena and surge voltage, particularly due to the inability of external bypass capacitors to absorb energy from lead-wire and wiring inductances, and internal bypass capacitors restrict current path design, making it difficult to suppress oscillations effectively.
Innovation Solution
An oscillation absorption circuit with an RL parallel configuration is connected to the power source side of the class-D amplifier, using resistance as damping resistance to suppress oscillations and reduce surge voltage without altering the package configuration, by applying low-frequency components via inductance and high-frequency components via resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an external bypass capacitor is used to suppress surge voltage, then surge voltage suppression is improved in low RF range, but it cannot absorb energy from lead-wire and wiring inductances in high RF range
Solution Approach 1:
The patent introduces an oscillation absorption circuit as an intermediary component between the power source and the class-D amplifier. This circuit includes a capacitor connected in parallel with the power source and a resistor connected in series with the capacitor, forming an RC circuit that acts as a mediator to absorb oscillation energy without directly interfering with the bypass capacitor's surge voltage suppression function.
Solution Approach 2:
The patent segments the oscillation suppression function into two separate circuits: one for surge voltage suppression (bypass capacitor) and another for oscillation energy absorption (RC circuit). This segmentation allows each circuit to be optimized for its specific function without compromising the other, resolving the contradiction between surge voltage suppression and oscillation suppression.
2Object-affected harmful factors
If the bypass capacitor is configured to be large to suppress resonance phenomenon, then resonance suppression is improved, but switching loss in MOSFET increases
Solution Approach 1:
The oscillation absorption circuit serves as an intermediary that provides an alternative path for oscillation energy, reducing the burden on the bypass capacitor. This allows the bypass capacitor to be smaller while still achieving effective resonance suppression, thereby reducing switching loss in the MOSFET.
Solution Approach 2:
The patent changes the parameters of the oscillation absorption circuit (resistor and capacitor values) to optimize the balance between resonance suppression and switching loss. By carefully selecting these parameters, the circuit achieves effective oscillation suppression while minimizing the impact on MOSFET switching performance.
3Length of moving object
If internal bypass capacitor is used within the package, then current path length is reduced, but it restricts design flexibility and current path configuration
Solution Approach 1:
The oscillation absorption circuit acts as an intermediary that compensates for the limitations of using an internal bypass capacitor. By adding this external RC circuit, the design gains flexibility in configuring current paths while maintaining effective oscillation suppression, as the RC circuit provides additional oscillation absorption capability.
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 effectively suppresses oscillation phenomena and reduces surge voltage in the high RF range without limiting the current path length within the amplifier package, ensuring stable operation of class-D amplifiers.
Implementation Method 1
resistance being input to the oscillation absorption circuit serves as damping resistance of the oscillation circuit, thereby suppressing the oscillation phenomenon and reducing the surge voltage
Implementation Method 2
an RL parallel circuit including resistance and inductance
Implementation Method 3
an RL parallel circuit including resistance and inductance
Data Source
Figure 1
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AI summary
In a class-D amplifier, oscillation phenomenon is suppressed in a high RF range and surge voltage is reduced. An oscillation absorption circuit is connected on the power supply side of the class-D amplifier circuit, and the class-D amplifier circuit and thus connected oscillation absorption circuit equivalently configure an oscillation circuit. Resistance provided in the oscillation absorption circuit is assumed as damping resistance of the oscillation circuit, thereby suppressing the oscillation phenomenon and reducing the surge voltage. The oscillation absorption circuit is made up of the RL parallel circuit of resistance and inductance. The oscillation absorption circuit and the class-D amplifier circuit constitute the oscillation circuit, and the resistance of the oscillation absorption circuit constitutes the damping resistance of the oscillation circuit in the high RF range.