Bandgap Voltage Reference Circuit Startup Current Reduction
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Solution Overview
Problem
Bandgap voltage reference circuits with startup circuits consume significant startup current, especially in battery-operated devices that are frequently powered on and off, leading to reduced battery life due to increased current consumption.
Innovation Solution
A bandgap voltage reference circuit design that includes an output current controller to maintain output current to the output terminal regardless of the voltage difference between input terminals when the output voltage is below a threshold, eliminating the need for a startup circuit by ensuring the output voltage reaches the second stable point during power-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a startup circuit is provided to forcibly supply startup current to raise output voltage to the second stable point, then the bandgap voltage reference circuit can prevent stopping operation at the first stable point, but current consumption is increased especially in battery-operated apparatus
Solution Approach 1:
The invention extracts and removes the startup circuit from the bandgap voltage reference circuit. By analyzing the circuit characteristics, the patent determines that the operational amplifier's inherent characteristics and the P-N junction voltage differences naturally drive the circuit to the second stable point without requiring an external startup circuit, thereby eliminating the source of excessive current consumption
Solution Approach 2:
The bandgap voltage reference circuit is designed to self-start without external assistance. The operational amplifier, combined with the P-N junction circuits, automatically generates the necessary voltage differences during power-up to drive the output voltage to the second stable point, making the circuit self-sufficient and eliminating the need for a separate startup circuit
2Ease of operation
If startup current is supplied to forcibly raise output voltage on startup, then the output voltage reaches the desired voltage level, but battery life is reduced due to increased current consumption during repeated power-on and off operations
Solution Approach 1:
The startup circuit is completely removed from the design. The patent demonstrates that the bandgap voltage reference circuit naturally achieves reliable power-up operation through the inherent characteristics of the operational amplifier and P-N junction circuits, which generate sufficient voltage differences during startup to drive the system to the desired stable point without external startup assistance
Solution Approach 2:
The invention changes the operating parameters during startup by utilizing the natural voltage differences between P-N junctions and the operational amplifier's gain characteristics. These parameter changes enable the circuit to automatically transition from the first to the second stable point during power-up, achieving reliable operation without the high current consumption associated with traditional startup circuits
Data Source
AI summary
A bandgap voltage reference circuit comprising: a first P-N junction circuit generating a first voltage which changes according to a first characteristic; a second P-N junction circuit generating a second voltage which changes according to a second characteristic different from the first characteristic; an amplifier receiving the first and second voltages at a pair of input terminals and changing the amount of an output current provided from a high-voltage power supply to an output terminal according to a difference voltage between the first and second voltages, wherein an output voltage at the output terminal is provided to the first and second P-N junction circuits; and an output current controller causing the amplifier to provide the output current to the output terminal regardless of the difference voltage when the output voltage equals to or is smaller than a threshold voltage.