Battery Pack Connection Detection Using Rectified Voltage
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Solution Overview
Problem
Existing contactless battery charging systems face challenges in accurately determining whether a battery pack is attached to a device or alone, and in calculating the remaining battery capacity, due to issues with current detection and amplifier offset voltage, especially at high battery voltages and low charging currents.
Innovation Solution
The battery pack incorporates a connection decision section and a current path switch to alter the charging current path based on whether it is connected to a device, using rectified voltage to determine connection status and avoid errors, and includes a method to communicate remaining capacity data to the device for accurate display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current flow detection is used to determine connection status, then connection judgment can be made, but measurement precision deteriorates due to amplifier offset voltage and low charging current
Solution Approach 1:
The patent introduces a load resistor as an intermediary element to convert the detection problem from direct current measurement to voltage measurement. The load resistor creates a measurable voltage drop that can be detected by the amplifier, serving as a mediator between the charging circuit and the detection system. This resolves the contradiction by making the detection possible through an intermediate physical quantity transformation.
Solution Approach 2:
The patent changes the detection parameter from direct current measurement to voltage measurement across a load resistor. By transforming the physical quantity being measured (from current to voltage), the system overcomes the amplifier offset voltage issue that plagues direct current detection, especially at low charging currents. This parameter transformation enables accurate connection status determination.
2Ease of operation
If contactless charging is implemented, then charging convenience is improved, but device complexity increases due to additional coils and control circuits
Solution Approach 1:
The battery pack's receiving coil and control circuit are designed to serve multiple functions: contactless power reception, connection status detection, and communication with the charging pad. By making these components multi-functional, the patent reduces the need for separate dedicated components, thereby limiting the increase in device complexity while maintaining charging convenience.
Solution Approach 2:
The patent combines the detection and charging functions into a single integrated system. The same receiving coil used for power transfer also serves as the detection element for connection status, and the control circuit manages both charging control and communication protocols. This merging of functions reduces component count and system complexity.
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 solution enables reliable judgment of the battery pack's connection status and accurate computation of remaining capacity, reducing errors caused by amplifier offset and low current issues, and allows for efficient communication of battery status to the device.
Implementation Method 1
magnetically couples a receiving coil in a battery pack placed on a charging pad with a transmitting coil in the charging pad to transmit power by magnetic induction
Data Source
AI summary
A battery pack having a contactless charging circuit (95) that rectifies power received by a receiving coil (1), and a battery pack control section (91) with a connection decision section. The battery pack control section (91) is configured to judge whether or not the battery pack is connected to the body of a battery powered device (101) based on the rectified voltage of the contactless charging circuit (95). This decision utilizes the fact that the charging circuit is in a no-load condition and the rectified voltage is high when the battery pack is not connected to the battery powered device, and allows reliable judgment of whether or not the battery pack (90) is attached to the battery powered device.