MOS Transistor Gate Control for Battery Charging
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Solution Overview
Problem
Existing control devices for power transistors in battery charging systems suffer from significant Joule losses and voltage drops due to the internal diodes, leading to inefficient charging and potential damage to the transistors.
Innovation Solution
A control device for power transistors is developed, featuring an amplification circuit with biasing currents injected into the drain and source inputs to maintain a linear operating mode, reducing voltage drops and Joule losses by using an equal number of semiconductor junctions and feedback loops for stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the transistor is controlled using conventional switching method, then the charging function is achieved, but significant Joule losses and voltage drops occur due to the internal diode
Solution Approach 1:
The patent applies dynamics by transitioning the transistor from static switching (off/on states) to dynamic linear mode operation. The control device continuously adjusts the gate voltage to maintain the transistor in a linear operating state, enabling precise control of current flow and eliminating the need for the parasitic diode to conduct, thereby reducing Joule losses and voltage drops while preventing transistor damage
Solution Approach 2:
The patent changes the operating parameter of the transistor from binary switching (0V or Vcc gate voltage) to continuous linear control (variable gate voltage). The control device monitors the drain-source voltage and dynamically adjusts the gate voltage to maintain the transistor in linear mode, changing the operational state from discrete to continuous, which eliminates diode conduction losses and enables precise charging control
2Ease of operation
If the internal diode is used for current flow, then the charging path is established, but the voltage drop around 0.7V causes unequal charging voltage between batteries
Solution Approach 1:
The control device dynamically adjusts the gate voltage to maintain the transistor in linear mode, enabling real-time compensation for voltage drops. This dynamic control ensures that the charging voltage can be precisely regulated to be equal across parallel batteries, eliminating the 0.7V diode drop issue and enabling accurate charging control
Solution Approach 2:
The patent substitutes the passive diode-based current path with an active transistor-based controlled path. Instead of relying on the parasitic diode's fixed 0.7V drop, the system uses the transistor's controllable channel to conduct current, replacing the passive diode mechanism with an active controlled switch that can maintain precise voltage equality between batteries
Data Source
AI summary
A device for controlling (10) a power transistor (5), comprises: an amplifying device (15) for monitoring the transistor gate (5) via an output control signal, the device including: a first input connected to the transistor drain, the whole assembly forming a first circuit portion; a second input connected to the transistor source, the whole assembly forming a second circuit portion. The control device comprises means for producing a polarizing current (I1, I2), the current being injected into the first and second inputs (NEG, POS) so as to offset the drain-source voltage measurement and maintain a linear operating mode of the output control signal, prior to opening the transistor, and the same number of N semiconductor junctions in the first and second circuit portions. The device is applicable in particular on battery charging devices.