LDO Pre-Regulator Bypass Circuit for Wide Input Voltage Range
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Designing electronic devices like smoke detectors that require a wide input voltage range poses challenges due to the need for high voltage devices, which are unsuitable for low current, high-speed applications and result in inefficiencies and increased power consumption when using LDO regulators or DC-DC converters to step down voltages.
Innovation Solution
A pre-regulator circuit that uses a clamp diode on the gate of a pass transistor and a bypass switch to regulate upper supply voltages above a threshold, allowing the LDO to extend its input voltage range without requiring high voltage devices, by bypassing regulation for lower supply voltages and using a comparison circuit to manage the bypass switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If high voltage devices are used to handle wide input voltage range, then the device can operate from 15V AC/DC supply, but it increases power consumption and is unsuitable for low current applications
Solution Approach 1:
The voltage regulation system is segmented into two distinct paths: a bypass path for low voltage operation and a regulation path for high voltage operation. The bypass switch creates a separate conduction path that avoids the power-consuming regulation circuitry when high voltage stepping is not needed, while the regulation path handles voltage reduction only when input voltage exceeds the threshold.
Solution Approach 2:
The system dynamically switches between bypass and regulation modes based on the input voltage level. The bypass switch is controlled to be closed when input voltage is below the threshold (enabling low-power direct connection) and opened when input voltage exceeds the threshold (enabling voltage regulation), allowing the system to adapt its power consumption characteristics to the operating conditions.
2Reliability
If voltage regulation is always applied, then output voltage is protected from harmful high voltages, but power consumption increases and efficiency decreases
Solution Approach 1:
The bypass switch is preliminarily configured to provide a direct low-resistance path from input to output when the input voltage is within the acceptable range. This preliminary configuration ensures that the voltage protection circuitry remains dormant and power-consuming regulation is avoided entirely during normal low-voltage operation, while still maintaining the capability to activate protection when needed.
Solution Approach 2:
The bypass switch acts as an intermediary element that mediates between the input voltage source and the output load. When closed, it provides a preferred low-impedance path that bypasses the power-consuming regulation circuitry. The switch dynamically routes the current based on voltage conditions, enabling the system to achieve both protection and efficiency.
3Device complexity
If LDO regulator is used directly with wide voltage range, then simple circuit design is achieved, but the LDO requires high voltage devices which are unsuitable for low current applications
Solution Approach 1:
The voltage handling function is segmented between the bypass path (handling low voltage directly) and the regulation path (handling high voltage reduction). This segmentation allows the LDO regulator to be designed for low voltage operation only, avoiding the need for high voltage devices while still supporting wide input voltage ranges through the combined bypass-regulation architecture.
Solution Approach 2:
The bypass switch serves as an intermediary that conditions the input voltage before it reaches the LDO regulator. By providing a direct path for low voltage operation and isolating the regulator from high voltage stress, the switch enables the use of low-voltage-optimized LDO devices in applications with wide input voltage ranges.
Data Source
AI summary
An electronic device includes a voltage regulator circuit having a power NFET coupled between an upper supply voltage and a pre-regulator output node and a current source coupled in series with a diode element between the upper supply voltage and a lower supply voltage. A gate of the power NFET is coupled to a first node between the current source and a diode element. A bypass circuit includes a power PFET coupled between the upper supply voltage and the pre-regulator output node. A comparison circuit is coupled to turn the bypass circuit off when the upper supply voltage is greater than a regulation threshold voltage.