Motor Protecting Circuit Diverts Residual Current to Ground
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Solution Overview
Problem
In electronic products, residual currents during motor commutation can damage transistors and generate noise due to the configuration of transient voltage suppressor diodes, which charge input capacitors and lead to overheating.
Innovation Solution
A motor protecting circuit with a rotor position detector, output circuit, driver circuit, and overvoltage detector circuit is implemented, where high-side and low-side transistors are grouped and controlled to divert current to ground when an overvoltage is detected, preventing damage from flowing back to the power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transient voltage suppressor diode or Zener diode is connected between the power supply voltage source and the bridge circuit to prevent residual current from flowing to the power supply, then the power supply is protected, but the residual current charges the input capacitor causing inrush voltage that damages transistors and generates noise
Solution Approach 1:
The patent introduces an overvoltage detector circuit as an intermediary component that monitors the voltage across the input capacitor and controls the switching of high-side and low-side transistors based on overvoltage conditions. This mediator prevents the harmful inrush voltage from damaging transistors while still allowing the diode to protect the power supply, thus resolving the contradiction between power supply protection and transistor safety.
Solution Approach 2:
The overvoltage detector circuit implements feedback control by continuously monitoring the voltage across the input capacitor and providing control signals to the driver circuit. When overvoltage is detected, the feedback mechanism triggers the switching of transistors to divert the residual current away from charging the capacitor further, preventing inrush voltage damage while maintaining power supply protection.
2Stability of the object's composition
If the diode configuration is used to block residual current from the power supply, then power supply stability is improved, but inrush voltage damages circuit components
Solution Approach 1:
The overvoltage detector circuit performs preliminary detection of voltage conditions before the inrush voltage can cause damage. By monitoring the voltage across the input capacitor in advance and triggering protective switching actions when overvoltage thresholds are approached, the system prevents component damage while maintaining power supply stability through the diode's current blocking function.
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
The solution effectively prevents transistor damage and noise by ensuring current flows to ground instead of the power supply during overvoltage events, thereby protecting the motor components.
Implementation Method 1
the overvoltage detector circuit is connected to the controller circuit and coupled to the power supply voltage of the output circuit. When the overvoltage detector circuit determines that the power supply voltage of the output circuit is higher than a voltage threshold, the overvoltage detector circuit outputs an overvoltage detected signal to the controller circuit.
Implementation Method 2
the driver circuit is configured to drive the output circuit. The controller circuit, according to the overvoltage detected signal, controls the driver circuit to turn on the high-side transistor and the low-side transistor in one of the plurality of groups, or to turn on the high-side transistors and the low-side transistors in some or all of the plurality of groups, at the same time.
Data Source
AI summary
A motor protecting circuit is provided. A first terminal of each of high-side transistors is coupled to a power supply voltage. A second terminal of each of low-side transistors is grounded. Second terminals of the high-side transistors are respectively connected to first terminals of the low-side transistors. An overvoltage detector circuit is coupled to the power supply voltage of an output circuit. When the overvoltage detector circuit determines that the power supply voltage of the output circuit is higher than a voltage threshold, the overvoltage detector circuit outputs an overvoltage detected signal to a controller circuit. According to the overvoltage detected signal, the controller circuit controls a driver circuit to turn on at least one of the high-side transistors and at least one of the low-side transistors at the same time.