Battery Current Control Circuit Using Single Switch and Driver Filter
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Solution Overview
Problem
Conventional battery control circuits require multiple MOSFETs and a large pin count protection IC, leading to high costs and inefficient trickle charging due to decreasing charging current as voltage increases during trickle charging.
Innovation Solution
A circuit with a driver and filter that generates pulse signals for controlling battery current, allowing the same switch to handle both normal and trickle charging/discharging modes, reducing the number of switches and drivers, and maintaining a constant filtered DC signal to adjust on-resistance based on duty cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple MOSFETs and individual drivers are used for each switch, then the battery can be controlled in normal and trickle charging/discharging modes, but the circuit cost increases and the protection IC pin count increases
Solution Approach 1:
The patent applies universality by designing a single switch that can operate in multiple modes (normal charging, trickle charging, normal discharging, trickle discharging) through different control signals. The driver circuit generates different types of output signals (PWM for normal mode, DC for trickle mode) to control the same switch, eliminating the need for separate MOSFETs for each mode and reducing overall circuit complexity and cost.
2Ease of operation
If a resistor is used to limit charging current in trickle charging mode, then the charging current can be controlled, but the charging current decreases as battery voltage increases, resulting in longer charging time
Solution Approach 1:
The patent applies dynamics by using a driver circuit that can dynamically adjust its output characteristics based on the charging mode. In trickle charging mode, the driver outputs a DC signal that maintains a constant gate voltage to the switch, thereby maintaining a stable charging current despite changes in battery voltage. This dynamic control mechanism eliminates the current decrease problem associated with fixed resistors.
Solution Approach 2:
The patent changes the control parameter from a fixed resistor value to a dynamically adjustable driver output signal. By switching from PWM mode (for normal charging) to DC mode (for trickle charging), the system can precisely control the switch's on-resistance and maintain a constant charging current throughout the trickle charging process, significantly improving charging efficiency.
3Ease of operation
If separate drivers are used for each MOSFET, then each switch can be independently controlled, but the protection IC requires a large pin count which increases cost
Solution Approach 1:
The patent applies universality by designing a single driver circuit that can control a single switch for all charging and discharging modes. The driver internally generates different control signals (PWM for normal mode, DC for trickle mode) and controls the same switch accordingly, eliminating the need for multiple drivers and significantly reducing the protection IC pin count.
Solution Approach 2:
The patent merges the functions of multiple drivers and switches into a single integrated driver-switch control system. By combining normal mode control and trickle mode control into one driver circuit that outputs different signal types, the design reduces component count and simplifies the protection IC architecture while maintaining full functionality.
Data Source
AI summary
A circuit for controlling a current flowing through a battery includes a driver and a filter coupled to the driver. The driver can generate a pulse signal in a first operating mode and generate a first signal in a second operating mode to control the current through the battery. The filter can filter the pulse signal to provide a filtered DC signal to adjust an on-resistance of a switch in series with the battery based on a duty cycle of the pulse signal in the first operating mode. The filter can receive the first signal and provide a second signal to drive the switch in a linear region in the second operating mode.