Class-AB Amplifier Bandwidth Synchronization for Thermal Protection
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Solution Overview
Problem
Existing synchronization methods for temperature protection in amplifiers with capacitive load fail to accurately synchronize bandwidth reduction across multiple amplifiers, leading to premature activation of temperature protection in systems with varying amplifier temperatures, and require multiple control pins.
Innovation Solution
A synchronization circuit and method that utilize a rank selector to synchronize a common bandwidth control signal across multiple amplifiers using only one control pin, where the internal control signal with the highest rank determines the bandwidth reduction, allowing the hottest amplifier to dictate the necessary bandwidth control for temperature protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a weighted sum of temperatures from multiple amplifiers is used to control bandwidth, then temperature protection is activated, but the protection activates at a lower temperature than necessary when multiple amplifiers are hot
Solution Approach 1:
Instead of using a weighted sum of temperatures that activates protection too early, the patent inverts the approach by selecting the maximum temperature among all amplifiers. This ensures protection activates only when the hottest amplifier reaches the critical threshold, avoiding premature activation while maintaining reliable protection.
Solution Approach 2:
The patent uses a common control terminal that is copied and connected to all amplifier circuits. This single terminal receives and distributes the bandwidth control signal to all amplifiers simultaneously, ensuring synchronized temperature protection across multiple channels without requiring separate control pins for each amplifier.
2Adaptability or versatility
If separate control pins are used for each amplifier's temperature protection, then each amplifier can be controlled independently, but the device complexity and pin count increase
Solution Approach 1:
The patent merges the control functions of multiple amplifiers into a single common control terminal. All amplifiers share this terminal and receive the same bandwidth control signal, which is generated based on the maximum temperature among all amplifiers. This reduces the pin count from N separate pins to just one common pin while maintaining synchronized protection.
Solution Approach 2:
The common control terminal serves multiple functions: it acts as the control input for all amplifiers simultaneously, distributes the bandwidth control signal to all channels, and eliminates the need for multiple separate control pins. This universal terminal provides adaptability for controlling multiple amplifiers while minimizing device complexity.
3Reliability
If bandwidth reduction is applied to all amplifiers when any one reaches high temperature, then temperature protection is ensured, but signal integrity and color balance may be compromised
Solution Approach 1:
The patent implements a feedback mechanism where the temperature of each amplifier is monitored and fed into a maximum selector circuit. The bandwidth control signal is adjusted based on this feedback, reducing bandwidth only when necessary (when the maximum temperature reaches the threshold) and maintaining full bandwidth when temperatures are acceptable, thus preserving signal integrity while providing protection.
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 synchronized temperature protection across multiple amplifiers with reduced pin count, ensuring adequate protection against overheating while maintaining signal integrity by using the hottest amplifier's temperature to determine the required bandwidth reduction.
Implementation Method 1
power dissipation in the output transistors increases with signal frequency, which, in turn, gives rise to temperature increase of the amplifier due to the self-heating effect of power dissipation
Data Source
AI summary
The present invention relates to a synchronization circuit for an integrated amplifier provided with a bandwidth control in accordance to a bandwidth control signal, wherein said synchronization circuit comprises a control terminal for a control signal and rank selector means connected to an internal control signal and being configured to emboss said internal control signal to said control terminal, if said internal control signal has a higher rank in accordance to a predetermined ranking criteria in comparison to said control signal. Further, the present invention relates to a respective synchronization method for continuously communicating and synchronizing of a common control signal for multiple circuits. One preferred application of the invention is in temperature protection by a synchronized bandwidth control for multiple class-AB amplifiers by means of only one additional terminal pin per amplifier. In such multi-channel amplifier configuration, the hottest amplifier dictates the amount of bandwidth reduction. By the invention the individual amplifiers can communicate about their individual temperatures, by which the temperature of the actual hottest amplifier and the respective required bandwidth reduction is determined and provided to each individual amplifier for a synchronized bandwidth reduction. Thus, in three channel RGB-amplifiers the signal integrity is advantageously maintained.