Motor Pre-Driver Current Limiting Circuit for Transistor Overheating
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Solution Overview
Problem
In electronic products, motor driver transistors are prone to overheating and damage due to excessive current flow, which existing cooling systems fail to adequately address, leading to potential circuit component damage.
Innovation Solution
A current limit protecting system for a motor pre-driver that includes a current limiting circuit and controller circuit, which senses current through a sensing resistor, compares it to a threshold, and controls switch components to prevent overheating by performing a rest protection procedure when excessive current is detected during specific working periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fans are configured to cool down circuit components, then heat dissipation is improved, but the transistors are still heated up by circulated air and damaged by excessive current
Solution Approach 1:
The current limiting circuit performs preliminary protection by detecting excessive current before it causes transistor damage. The system proactively limits current flow through the sensing resistor and controller circuit, preventing the harmful effect of overheating and current-induced damage before it occurs.
Solution Approach 2:
The sensing resistor serves as an intermediary element to detect current flow. By placing the sensing resistor in series with the transistors, the system can indirectly monitor current levels and trigger protection mechanisms without directly interfering with the transistor operation, thus preventing damage while maintaining system functionality.
2Ease of operation
If transistors are switched by controller circuit, then motor control is achieved, but excessive current flows through transistors to common voltage causing damage
Solution Approach 1:
The current limiting circuit implements feedback control by continuously monitoring current through the sensing resistor and comparing it against a reference voltage. When excessive current is detected, the system automatically adjusts the switching signals to limit current flow, providing closed-loop protection that maintains motor control while preventing transistor damage.
Solution Approach 2:
The protection mechanism performs preliminary action by detecting excessive current conditions before they cause transistor damage. The current limiting circuit anticipates potential harm and takes preventive measures by limiting current flow through the switching transistors, ensuring safe operation during motor control operations.
3Reliability
If current flowing through transistors is limited, then transistor protection is improved, but system complexity increases with additional circuits
Solution Approach 1:
The current limiting function is implemented locally at the motor driver stage rather than throughout the entire system. By placing the sensing resistor and current limiting circuit only in the motor control path, the system achieves transistor protection with minimal additional complexity, affecting only the specific area where protection is needed.
Solution Approach 2:
The sensing resistor acts as a simple intermediary that enables current detection without adding complex circuitry. This passive component provides a straightforward method for monitoring current flow and triggering protection mechanisms, maintaining system simplicity while achieving reliable transistor protection.
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
Effectively limits current flow through switch components, preventing overheating and ensuring stable operation of single phase motors by alternately turning on/off switches during fixed periods, thereby extending the lifespan of transistors and maintaining system stability.
Implementation Method 1
A second terminal of the second high-side switch and a second terminal of the second low-side switch are connected to a first terminal of a sensing resistor. A second terminal of the sensing resistor is grounded.
Data Source
AI summary
A current limit protecting system and method of a motor pre-driver are provided. A current limiting circuit detects a current of a resistor that is connected to a motor, and then compares the current of the resistor with a current threshold to output a current comparing signal. When a controller circuit determines that the current of the resistor is larger than the current threshold according to the current comparing signal, and a working period of a first signal of a first node or a working period of a second signal of a second node of the motor reaches a preset value, a first high-side switch and a second high-side switch are turned off, and a first low-side switch and a second low-side switch are alternately turned on. As a result, a temperature of the motor generally reduces.