Motor Current Control Circuit with Voltage Detection for Transistor Protection
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Solution Overview
Problem
In electronic products, the heat generated by circuit components can lead to overheating of transistors in fan driver circuits, potentially damaging them due to inadequate current control in motor systems.
Innovation Solution
A motor current controlling circuit with a voltage detection mechanism, comprising a bridge circuit, zero current detector circuit, driver circuit, and controller circuit, which includes a Hall sensor and current limiting circuit to accurately monitor and control motor currents, preventing overheating by adjusting commutation times and current thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the driver circuit switches transistors to drive the motor, then the motor can rotate and cool the circuit components, but the transistors are heated up by the circulated heated air and may be damaged due to overheating
Solution Approach 1:
The patent implements a feedback mechanism by detecting the voltage at the node between the low-side transistor and motor, determining whether motor current equals zero, and using this information to control the switching timing of the bridge circuit. This closed-loop feedback ensures transistors are switched at appropriate moments, preventing excessive current and overheating damage.
Solution Approach 2:
The patent applies preliminary action by detecting the zero current condition before switching the transistors. The controller circuit determines whether motor current is zero in advance of the switching operation, and only permits switching when the current is zero, thereby preventing harmful current spikes before they can occur.
2Reliability
If the driver circuit accurately obtains motor current values and switches transistors appropriately, then transistor damage from excessive current is prevented, but the device complexity increases due to additional detection and control circuits
Solution Approach 1:
The patent applies self-service by using the existing motor current flowing through the circuit to generate the detection signal. The zero current detection is achieved by monitoring the voltage at the existing node between the low-side transistor and motor, rather than requiring separate current sensing components. The system uses its own operational parameters for self-diagnosis and control.
Solution Approach 2:
The patent implements multi-functionality by using the same node voltage detection for multiple purposes: determining motor current status, controlling transistor switching timing, and protecting against overcurrent conditions. The controller circuit integrates these functions, allowing one circuit element to serve multiple protective and control roles.
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 prevents transistor damage by accurately monitoring and controlling motor currents, ensuring they do not exceed safe limits, thereby extending the lifespan of electronic components.
Implementation Method 1
The Hall sensor is configured to sense a positive voltage and a negative voltage that are generated with a change in magnetic field strength from rotation of a rotor of the motor, so as to output a Hall signal
Data Source
AI summary
A motor current controlling circuit having a voltage detection mechanism is provided. A first terminal of a first low-side transistor is connected to a second terminal of a first high-side transistor. A node between the first terminal of the first low-side transistor and the second terminal of the first high-side transistor is connected to a first terminal of a motor. A first terminal of a second low-side transistor is connected to a second terminal of a second high-side transistor. A zero current detector circuit detects a voltage of the node and determines whether or not a current flowing through the motor is equal to a zero value to output a zero current detected signal according to the detected voltage. A controller circuit controls a driver circuit to turn on or off the high-side transistors and the low-side transistors according to the zero current detected signal.