Comparator Circuit with Variable Bias Current for Low Power
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Solution Overview
Problem
Conventional comparator circuits face limitations in reducing current consumption, making them unsuitable for semiconductor devices requiring very low current consumption, and similarly, oscillation circuits using comparators are also restricted in achieving low current consumption due to instability and noise issues with multiple current sources.
Innovation Solution
A comparator circuit with a simple configuration utilizing three constant current sources and transistors, where the second constant current source is controlled by a voltage to turn on or off, and the current values of the first and second constant current sources are equal, allowing all current paths to be shut off when the voltage difference between input terminals is positive or negative, thereby reducing current consumption. Additionally, an oscillation circuit incorporating these comparators with a charge/discharge control circuit further minimizes current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the bias current is reduced to suppress current consumption, then current consumption decreases, but response speed decreases
Solution Approach 1:
The patent applies dynamics by making the bias current variable rather than constant. The bias current is dynamically adjusted based on the input voltage level - using a larger current when the input voltage is high (faster response needed) and a smaller current when the input voltage is low (power saving prioritized). This resolves the contradiction by allowing the system to adapt between power consumption and response speed based on operational conditions.
Solution Approach 2:
The patent changes the parameter of bias current from a fixed value to a variable value that depends on input voltage. By changing the current parameter dynamically according to input conditions, the system achieves both low power consumption during idle states and high response speed during active states, resolving the trade-off between these two parameters.
2Reliability
If multiple current sources are used to bias the differential pair and source-grounded amplifier circuit, then the circuit can maintain output state, but it becomes difficult to stably keep the output state due to leak current or noise when current is excessively reduced
Solution Approach 1:
The patent extracts or removes unnecessary current sources from the conventional circuit configuration. Instead of using multiple constant current sources that consume power even when not needed, the invention uses a single variable bias current that is only applied when required for proper circuit operation. This eliminates redundant current consumption while maintaining output state stability through intelligent current management.
Solution Approach 2:
The patent applies dynamics by making the bias current variable rather than constant. The bias current is dynamically adjusted based on the input voltage level - using a larger current when the input voltage is high (faster response needed) and a smaller current when the input voltage is low (power saving prioritized). This resolves the contradiction by allowing the system to adapt between power consumption and response speed based on operational conditions.
3Use of energy by moving object
If the bias current is reduced to very low levels for low current consumption, then power consumption decreases, but the circuit becomes susceptible to leak current and noise affecting stability
Solution Approach 1:
The patent applies dynamics by making the bias current variable rather than constant. The bias current is dynamically adjusted based on the input voltage level - using a larger current when the input voltage is high (faster response needed) and a smaller current when the input voltage is low (power saving prioritized). This resolves the contradiction by allowing the system to adapt between power consumption and response speed based on operational conditions.
Solution Approach 2:
The patent changes the parameter of bias current from a fixed value to a variable value that depends on input voltage. By changing the current parameter dynamically according to input conditions, the system achieves both low power consumption during idle states and high response speed during active states, resolving the trade-off between these two parameters.
Data Source
AI summary
A comparator includes a first constant current source, a first transistor having a drain connected to the first constant current source, a gate connected to a non-inverted input terminal, and a source connected to an inverted input terminal, a second constant current source connected between the inverted input terminal and a second power supply terminal, a second transistor having a source connected to a first power supply terminal, a gate connected to the drain of the first transistor, and a drain connected to an output terminal, and a third constant current source connected between the drain of the second transistor and the second power supply terminal. An oscillation circuit includes comparators in which at least one of the comparators is a comparator described above.