NMOS Battery Charging Circuit for Fast-Charge Heat Reduction
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Solution Overview
Problem
Conventional PMOS transistors used in battery pack charging circuits exhibit high internal resistance and temperature rise during high-current fast charging, necessitating additional cooling devices, which increase volume and cost.
Innovation Solution
Employing an NMOS transistor with a body diode and a switch control unit to control the charging circuit, utilizing a power supply unit and optional components like a controller, voltage regulator, and temperature/communication units to manage charging efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PMOS transistors are used to control the charging circuit, then the charging port voltage can be ensured to be zero when not in use and overvoltage prevention is achieved, but the internal resistance is relatively large and temperature rise is high during fast charging, requiring additional cooling devices
Solution Approach 1:
The patent inverts the conventional approach by using NMOS transistors instead of PMOS transistors for charging control. NMOS transistors have lower internal resistance and generate less heat during high-current fast charging, eliminating the need for additional cooling devices while maintaining charging safety through the body diode's reverse blocking capability
2Reliability
If PMOS transistors are used to control the charging circuit, then charging safety is ensured, but additional cooling devices are required which increase the volume and cost
Solution Approach 1:
The patent inverts the conventional approach by using NMOS transistors instead of PMOS transistors for charging control. NMOS transistors have lower internal resistance and generate less heat during high-current fast charging, eliminating the need for additional cooling devices while maintaining charging safety through the body diode's reverse blocking capability
Solution Approach 2:
The patent extracts and eliminates the cooling devices from the charging circuit by using NMOS transistors that inherently generate less heat, simplifying the overall system structure and reducing cost
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
The NMOS transistor-based solution reduces heat generation, lowers power consumption, and eliminates the need for cooling devices, providing low-cost, high-efficiency charging with strong over-current capability and discharge prevention.
Implementation Method 1
The first control switch is an NMOS transistor Q11 with a body diode
Implementation Method 2
The switch control unit is connected with a gate, the source, and the drain of the first control switch and controls on-off of the first control switch by sampling a voltage between the source and the drain of the first control switch
Implementation Method 3
An output end of the power supply unit is connected with a power source end of the switch control unit and configured to supply power to the switch control unit
Data Source
AI summary
The disclosure provides a battery charging circuit, a battery pack and a battery pack charging system. The battery charging circuit includes a first control switch, a switch control unit and a power supply unit. The first control switch is arranged between the charging positive terminal and the positive electrode of the battery pack, or between the charging negative terminal and the negative electrode of the battery pack, and it is an NMOS transistor with a body diode. The switch control unit is connected to the gate, source, and drain of the first control switch and controls the on-off of the first control switch by sampling a voltage between the source and the drain of the first control switch. The output end of the power supply unit is connected to the power source end of the switch control unit to supply power to the switch control unit.