Adaptive Ramp ADC for Low-Light Image Sensor Readout

The patent applies dynamics by making the conversion process adaptive rather than static. The system dynamically adjusts the conversion strategy based on real-time assessment of the signal level. A decision circuit evaluates whether the input signal represents a low or high light level, and accordingly selects between two different conversion modes: multiple rapid conversions for low light levels or a single standard conversion for high light levels. This dynamic adaptation resolves the contradiction by optimizing the number of conversions based on actual signal conditions rather than always using the maximum number of conversions.

The patent changes the parameter of conversion count based on signal characteristics. By introducing a decision phase that assesses the signal level, the system modifies the conversion parameter (number of conversions) according to the actual measurement conditions. For low light levels where noise reduction is critical, the parameter is set to multiple conversions; for high light levels where speed is more important, the parameter is reduced to a single conversion. This parameter change strategy eliminates the need to always perform the maximum number of conversions.

The patent makes the ramp duration dynamic rather than fixed. Instead of always using a long ramp duration to ensure adequate resolution for all signals, the system dynamically adjusts the ramp duration based on the signal level. For low light level signals that require higher precision, the system uses multiple conversions with appropriately timed ramps. For high light level signals, a single conversion with standard ramp duration suffices. This dynamic approach maintains adequate resolution while improving overall conversion throughput.

The patent applies partial action by using multiple rapid conversions only when necessary (for low light levels), rather than always using the full conversion sequence. The decision circuit determines whether the full multiple-conversion process is needed or if a single conversion is sufficient. This partial application of the multi-conversion strategy maintains resolution where needed while avoiding unnecessary conversion cycles that would reduce conversion rate for signals that don't require it.

The patent segments the conversion process into distinct phases: a decision phase that assesses signal level, and subsequent conversion phases that execute different strategies based on the decision. This segmentation allows the circuit to handle different signal types with appropriate specialized processing rather than requiring a single complex circuit design. The decision circuit acts as a gateway that routes signals to appropriate conversion modes, effectively segmenting the overall measurement process.

The decision circuit serves as an intermediary between the signal input and the conversion process. Rather than directly connecting the input signal to a fixed conversion circuit, the decision circuit mediates by evaluating the signal characteristics and controlling which conversion mode is activated. This intermediary component enables the system to achieve high dynamic range capability while maintaining relatively simple circuit structures, as the decision circuit uses basic comparison logic rather than complex adaptive circuitry.