Current Mirror Pre-Charging for Fast Power Amplifier Enable
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Solution Overview
Problem
Current power amplifiers with large capacitances in portable communication devices experience slow enable times due to the need for a small current to charge a large capacitance in current mirrors, which affects stability and noise performance.
Innovation Solution
A system and method for pre-charging current mirrors using a controller that provides both a first current and an additional current based on a reference voltage, allowing for rapid charging of capacitances associated with current mirrors, thereby reducing turn-on time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large capacitance is used in the current mirror to meet stability and noise performance requirements, then the stability and noise performance are improved, but the enable time becomes slow because a relatively small current must charge a relatively large capacitance
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitance associated with the current mirror before the current mirror is fully activated. A pre-charge current is provided to charge the capacitance to a predetermined voltage level in advance, so that when the current mirror becomes active, the capacitance is already partially or fully charged, significantly reducing the enable time while maintaining the large capacitance value needed for stability and noise performance
Solution Approach 2:
The patent implements dynamics by making the charging current dynamic rather than static. The charging current is adjusted based on the charging state of the capacitance - initially providing a larger pre-charge current to quickly charge the capacitance, then reducing the current as the capacitance approaches the target voltage level. This dynamic current adjustment optimizes both the speed of charging and the accuracy of the final voltage level
2Reliability
If a relatively small current is used to charge the capacitance, then the current mirror operates safely without excessive current stress, but the charging speed becomes slow
Solution Approach 1:
The patent implements dynamics by making the charging current dynamic rather than static. The charging current is adjusted based on the charging state of the capacitance - initially providing a larger pre-charge current to quickly charge the capacitance, then reducing the current as the capacitance approaches the target voltage level. This dynamic current adjustment optimizes both the speed of charging and the accuracy of the final voltage level
Solution Approach 2:
The patent applies preliminary action by pre-charging the capacitance associated with the current mirror before the current mirror is fully activated. A pre-charge current is provided to charge the capacitance to a predetermined voltage level in advance, so that when the current mirror becomes active, the capacitance is already partially or fully charged, significantly reducing the enable time while maintaining the large capacitance value needed for stability and noise performance
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 pre-charging system significantly reduces the turn-on time of current mirrors from approximately 22 microseconds to 2.2 microseconds, enhancing the stability and noise performance of power amplifiers in portable communication devices.
Implementation Method 1
coupling a voltage-to-current converter to an input of a current mirror, the voltage-to-current converter generating a bias current that is proportional to the voltage at an input of the voltage-to-current converter
Data Source
AI summary
A system for pre-charging a current mirror includes a controller configured to provide a first current and an additional current to a current mirror to rapidly charge a capacitance associated with the current mirror based on a reference voltage or control signals. A power amplifier module includes at least one current mirror and a controller. A capacitor is coupled to the current mirror. The controller provides a bias current in an amount proportional to an input to a voltage-to-current converter. The controller receives a control signal that directs the controller to apply one of a pre-charge voltage and a nominal voltage to the voltage-to-current converter.