Constant Voltage Generator Circuit for Stable Low-Dropout Switching
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Solution Overview
Problem
Existing constant voltage generator circuits face issues with unintended mode transitions and malfunctions due to changes in output voltage or current, leading to accuracy deterioration and increased chip area requirements.
Innovation Solution
A constant voltage generator circuit is designed with a transistor, first and second amplifier circuits, a protection circuit, and a control circuit. The second amplifier circuit operates at a higher speed than the first and only engages when the output current reaches specific threshold levels, while a protection circuit limits output current and a control circuit manages the operation of the second amplifier circuit to prevent mode transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a reference voltage source is shared between circuits with voltage potential fluctuations, then chip area is reduced, but noise is superimposed on the reference voltage source causing output voltage changes and unintended mode transitions
Solution Approach 1:
The patent segments the reference voltage supply by providing separate reference voltage sources for the first circuit (with voltage fluctuations) and the second circuit (without voltage fluctuations). This segmentation prevents noise coupling from the first circuit to the reference voltage source used by the second circuit, thereby avoiding unintended mode transitions while maintaining reasonable chip area through selective separation.
2Object-affected harmful factors
If the transistor size connected to the reference voltage source is reduced to suppress noise, then noise superimposition is reduced, but mismatch between transistors increases and characteristic variation of comparator or differential amplifier increases
Solution Approach 1:
The patent segments the circuit into two independent reference voltage systems: one for the comparator/differential amplifier (first circuit) and one for the main operation (second circuit). By providing a dedicated reference voltage source for the comparator that is isolated from voltage fluctuations in the main circuit, the patent allows the transistor size in the main circuit to be reduced for noise suppression without affecting the matching accuracy of transistors in the comparator, as they operate from separate reference voltages.
3Reliability
If an offset is given to the differential amplifier to prevent mode switching, then mode transitions are prevented, but output voltage accuracy deteriorates
Solution Approach 1:
The patent segments the control functions by separating the comparator (which detects mode transitions) from the differential amplifier (which controls output voltage). The comparator uses its own dedicated reference voltage source that is isolated from fluctuations, allowing it to accurately detect mode transitions without requiring a large offset. This segmentation enables the differential amplifier to maintain high output voltage accuracy without needing to compensate for large offsets, as the mode transition detection is handled independently by the comparator with its stable reference voltage.
Data Source
AI summary
A constant voltage generator circuit includes a first amplifier circuit that drives a transistor controlling an output current based on a reference voltage; a second amplifier circuit that drives the transistor based on the reference voltage from the power source; a protection circuit that limit an output current flowing through the load from the transistor; and a control circuit that controls operation of the second amplifier circuit. The control circuit controls the second amplifier circuit to operate or not to operate based on a relationship between the output current and predetermined first or second threshold. The second amplifier circuit further includes a first operation voltage potential fixing circuit that fixes an operation voltage potential of an internal node of the second amplifier circuit during non-operation thereof.