Charge-Control IC Backgate Voltage Switching for Battery Back-Flow Prevention
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Solution Overview
Problem
Existing charge-controlling ICs for secondary batteries face issues with back-flow prevention, where input voltage offsets during manufacturing can lead to premature battery charge termination or continuous discharge due to parasitic diode currents, resulting in inefficiencies and incomplete charging.
Innovation Solution
A charge-controlling semiconductor integrated circuit with a current-controlling MOS transistor, a substratum voltage switching circuit, and a voltage comparison circuit that includes an intentional offset to manage backgate voltage, along with a level shift circuit to adjust voltage comparisons, ensuring the backgate is set to a preferable voltage across various control modes to prevent back-flow and ensure full charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a back-flow preventing diode is provided in series with the current-controlling MOS transistor, then back-flow is prevented, but losses in the elements increase
Solution Approach 1:
The patent extracts the back-flow prevention function from the series diode approach and implements it through a separate substratum voltage switching circuit that controls the backgate voltage of the MOS transistor. This removes the need for a series diode and its associated voltage drops, eliminating the energy loss while maintaining back-flow prevention capability.
Solution Approach 2:
The patent changes the control parameter from simple series connection to dynamic backgate voltage control. By switching the substratum voltage between different levels (0V, VDD, or VBAT), the MOS transistor's threshold voltage is dynamically adjusted to prevent back-flow only when necessary, minimizing energy losses during normal operation.
2Reliability
If the backgate voltage is switched based on comparator output, then back-flow is prevented, but input offset in the comparator causes premature charge termination or continuous discharge
Solution Approach 1:
The patent applies preliminary anti-action by intentionally adding an offset voltage to the comparator's reference input. This pre-compensates for the inherent input offset, ensuring that the comparator makes accurate decisions about when to switch the backgate voltage, thereby preventing both premature charge termination and continuous discharge conditions.
Solution Approach 2:
The patent introduces an offset voltage as an intermediary element in the comparator circuit. This offset voltage acts as a mediator that compensates for the comparator's inherent inaccuracies, allowing the voltage comparison function to operate accurately despite manufacturing variations and temperature effects.
3Adaptability or versatility
If the current-controlling MOS transistor remains on during input voltage drop, then the battery can discharge through the IC, but power efficiency decreases
Solution Approach 1:
The patent implements dynamic control of the MOS transistor's substratum voltage based on real-time comparison of input and output voltages. When the input voltage drops below the output voltage, the substratum voltage is switched to prevent back-flow, dynamically adapting the transistor's operation to prevent battery discharge while maintaining power efficiency during normal charging conditions.
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
This configuration effectively prevents back-flow and ensures the battery is fully charged by managing backgate voltage and input voltage offsets, improving power efficiency and preventing continuous discharge during charging.
Implementation Method 1
a voltage comparison circuit to compare the input voltage and the output voltage
Implementation Method 2
a current-controlling MOS transistor connected between a voltage input terminal and an output terminal, and controlling a current flowing from the input terminal to the output terminal
Implementation Method 3
there is a possibility that a reverse current (back-flow) flows to the input terminal side through a parasitic diode existing between a drain and backgate (substratum or well region)
Data Source
AI summary
A charge-controlling semiconductor integrated circuit includes a current- controlling MOS transistor which is connected between a voltage input terminal and an output terminal and controls flowing current, a substratum voltage switching circuit connected between the voltage input/output terminal and a substratum to which an input/output voltage is applied, and a voltage comparison circuit to compare the input/output voltage. The charge-controlling semiconductor integrated circuit controls the substratum voltage switching circuit based on an output of the voltage comparison circuit, and the voltage comparison circuit includes an intentional offset in a first potential direction. A level shift circuit to shift the output voltage to a potential direction opposite to the first potential direction is provided in a preceding stage of a first input terminal of the voltage comparison circuit, and the input voltage is input to a second input terminal of the voltage comparison circuit.