Battery Voltage Detection Circuit Using Capacitive Coupling
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Solution Overview
Problem
Existing battery voltage detecting circuits face challenges in precisely detecting battery voltages while minimizing cost, as they require high-voltage operational amplifiers and high-precision ADCs, leading to increased expenses and voltage-dependent resistor issues.
Innovation Solution
A battery voltage detecting circuit utilizing operational amplifiers without applied DC voltage, employing capacitors for differential amplification and switching circuits to manage transient currents, allowing for precise voltage detection without the need for high-voltage components and high-precision converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If high-voltage operational amplifiers are used to detect battery voltages up to 5V, then voltage detection range is improved, but circuit cost increases
Solution Approach 1:
The battery voltage detection is divided into two stages: first, a voltage divider circuit divides the high battery voltage (up to 5V) to a lower level suitable for standard operational amplifiers; second, a capacitor couples the divided voltage to the operational amplifier input, blocking DC components while allowing AC signal transmission. This segmentation allows use of low-voltage, low-cost operational amplifiers instead of expensive high-voltage types.
Solution Approach 2:
A capacitor is introduced as an intermediary component between the voltage divider and the operational amplifier. This capacitor couples the divided voltage signal while blocking DC components, enabling standard low-voltage operational amplifiers to handle high-voltage battery signals without requiring expensive high-voltage rated components.
2Ease of manufacture
If gain of operational amplifier is reduced to make it non high-voltage type, then component cost decreases, but output voltage becomes too low for ADC conversion
Solution Approach 1:
Before the signal enters the operational amplifier, a voltage divider circuit pre-adjusts the high battery voltage to a suitable lower level. This preliminary voltage division ensures that when the signal passes through the low-gain operational amplifier, the final output voltage remains within the optimal range for ADC conversion, eliminating the need for high-precision (and expensive) ADCs.
Solution Approach 2:
The voltage divider circuit changes the voltage level parameter of the battery signal before amplification. By dividing the voltage to an appropriate level beforehand, the system can use operational amplifiers with lower gain (reducing component cost) while still achieving sufficient output voltage for ADC conversion.
3Loss of energy
If resistors with high resistance values are used to suppress battery discharge current, then energy loss decreases, but voltage-dependent resistance effects increase detection error
Solution Approach 1:
The patent replaces the traditional resistor-based current suppression method with a capacitor-based coupling method. Instead of using high-resistance resistors that suffer from voltage-dependent effects, the capacitor couples the voltage signal while blocking DC current. This substitution eliminates the harmful voltage-dependent resistance effects while still suppressing battery discharge current.
Solution Approach 2:
The patent changes the electrical parameter approach from resistance-based current suppression to capacitance-based coupling. By using a capacitor to block DC components while allowing AC signal transmission, the system achieves current suppression without the voltage-dependent resistance effects that plague high-value resistors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise battery voltage detection at a lower cost by eliminating the requirement for high-voltage operational amplifiers and high-precision ADCs, while maintaining detection accuracy even when voltages are reduced due to increased load.
Implementation Method 1
a first capacitor having one end connected to one input terminal of the operational amplifier... an energizing circuit configured to be energized with a transient current flowing into the first capacitor
Implementation Method 2
a second capacitor having one end connected to an output terminal of the operational amplifier and the other end connected to the one input terminal of the operational amplifier
Data Source
AI summary
A battery voltage detecting circuit includes: a first capacitor having one end connected to one input terminal of an operational amplifier; a second capacitor having one end connected to an output terminal of the operational amplifier and the other end connected to the one input terminal of the operational amplifier; a third capacitor having one end connected to the other input terminal of the operational amplifier; a fourth capacitor having one end applied with a reference voltage and the other end connected to the other input terminal of the operational amplifier; and a switching circuit configured to electrically connect the one input terminal of the operational amplifier to the one end of the first capacitor after the transient current has stopped flowing.