Motor Driver Brake Circuit for Low-Power Reliable Stop Hold
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Solution Overview
Problem
Existing motor drivers for brushed DC motors lack an efficient mechanism to maintain the motor in a stopped state with minimal power consumption and without risking damage to the switching components.
Innovation Solution
The motor driver incorporates a brake circuit with a comparator and switches that monitor and control the terminal voltage of the motor, allowing the motor to be maintained in a short circuit braking state with the high-side and low-side transistors turned off, thus reducing power consumption and preventing component damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the motor is maintained in a stopped state with transistors turned off, then power consumption is reduced, but the motor may not remain reliably stopped without additional control mechanisms
Solution Approach 1:
The brake circuit includes a comparator that continuously monitors the terminal voltage of the motor and compares it against a reference voltage. When the terminal voltage exceeds the reference voltage, the comparator triggers the switch to connect the motor terminals to ground, ensuring the motor remains reliably stopped. This feedback mechanism allows the system to maintain the motor in a stopped state with minimal power consumption while automatically correcting any deviations from the desired state.
Solution Approach 2:
The brake circuit automatically monitors and controls the motor stopping state without requiring continuous external control signals. The comparator and switch form a self-regulating system that maintains the motor in a stopped state by autonomously detecting voltage conditions and activating the braking function when needed, thereby reducing power consumption while ensuring reliable stopping.
2Reliability
If the motor is held in a short circuit braking state, then the motor remains stopped, but switching components may be damaged due to excessive current
Solution Approach 1:
The brake circuit is pre-configured with a switch connected in parallel with the motor terminals and a diode oriented to conduct during braking. When the comparator detects that the terminal voltage has dropped below the reference voltage, the switch is activated to create a controlled short circuit path. This preliminary setup ensures that when braking is needed, the current follows a predetermined safe path through the diode and switch, preventing uncontrolled current spikes that could damage the transistors while maintaining reliable motor stopping.
Data Source
AI summary
A motor driver for driving a motor includes: a half-bridge output stage including a high-side transistor and a low-side transistor, the motor being connected to a connection terminal to which the high-side transistor and the low-side transistor are connected; and a control circuit configured to monitor a terminal voltage of the connection terminal. The control circuit is configured to turn off the high-side transistor and turn on the low-side transistor, and initiate a brake mode to stop the motor. In the brake mode, when the terminal voltage is lower than a first setting voltage, the control circuit is configured to connect the connection terminal to an electric potential capable of maintaining the motor in a stopped state with the high-side transistor and the low-side transistor turned off.