Voltage Regulator Startup Gating Through Op-Amp State Detection
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Solution Overview
Problem
Conventional voltage regulators have a long start-up time and increased semiconductor device size due to the need for a power source voltage-monitoring circuit, which delays operation when the power supply voltage is lower than the operating range.
Innovation Solution
A voltage regulator design that includes a detecting circuit to monitor the operational amplifier's state, preventing the output transistor from conducting when the operational amplifier is not within its operating voltage range, thus avoiding unintended high voltages and eliminating the need for direct power source voltage monitoring, allowing for quicker start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power source voltage-monitoring circuit is included to protect the load circuit, then the load circuit is protected from high voltages, but the start-up time increases and the semiconductor device size increases
Solution Approach 1:
The patent extracts the voltage monitoring function from a separate power source voltage-monitoring circuit and integrates it into the existing operational amplifier circuit. The operational amplifier naturally compares the power source voltage against its internal reference voltage, so no additional monitoring circuit is needed. This eliminates the extra circuitry while maintaining protection functionality.
Solution Approach 2:
The operational amplifier is made multi-functional by having it perform both its primary voltage regulation function and the secondary power source voltage monitoring function. When the power source voltage is insufficient, the operational amplifier cannot operate properly, which automatically prevents the output transistor from conducting, thus protecting the load circuit without requiring a dedicated monitoring circuit.
2Reliability
If a power source voltage-monitoring circuit is included to protect the load circuit, then the load circuit is protected from high voltages, but the semiconductor device size increases
Solution Approach 1:
The patent removes the need for a separate power source voltage-monitoring circuit by utilizing the operational amplifier's inherent voltage comparison capability. The operational amplifier already compares voltages as part of its normal operation, so it can simultaneously monitor the power source voltage without adding extra circuit components.
Solution Approach 2:
The voltage monitoring function is merged with the operational amplifier circuit. The operational amplifier's differential input stage naturally monitors the power source voltage by comparing it against its reference voltage, combining two functions (voltage regulation and voltage monitoring) into a single integrated circuit block, thereby reducing the overall semiconductor device area.
3Reliability
If the voltage regulator waits for sufficient power source voltage before operating, then the load circuit is protected, but the start-up time increases
Solution Approach 1:
The operational amplifier provides continuous feedback monitoring of the power source voltage through its differential input. When the power source voltage rises to a sufficient level, the operational amplifier automatically begins regulating the output voltage. This feedback mechanism eliminates the need for a separate monitoring circuit and associated delay, as the operational amplifier responds immediately when voltage conditions are met.
Solution Approach 2:
The operational amplifier is designed to be ready to operate as soon as the power source voltage reaches the required level, with its internal reference voltage and comparison circuitry already in place. This preliminary preparation allows the voltage regulator to start up quickly without waiting for additional monitoring circuit activation or complex sequencing.
Data Source
AI summary
A voltage regulator includes an operational amplifier that compares a feedback voltage that is proportional to an output voltage and a predetermined reference voltage that corresponds to a desired output voltage. The operational amplifier controls the conduction state of an output transistor according to the comparison. A detecting circuit monitors the operating state of the operational amplifier, and in the case that the operational amplifier is not operating, outputs a signal which causes the output transistor to be placed in a non-conductive state.