Three-Phase Motor Inverter Feedback Control for Reverse Current Protection
Solution Overview
Problem
Three-phase motor driving circuits face issues with reverse currents flowing back to the power source, potentially damaging MOS switches due to back electromotive force, which existing protective measures like Zener diodes and capacitors do not fully address.
Innovation Solution
A three-phase motor driving circuit and method that includes an inverter circuit, control circuit, turn-off module, turn-off confirmation module, and turn-on logic unit, which adjusts the voltage of the output node to prevent reverse currents by detecting and regulating the output current, allowing the lower bridge switch to be turned off only when the current stops flowing, and enabling feedback mode to avoid sink current states and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the lower bridge switch is turned off without feedback control, then the switching speed is improved, but reverse current flows back to the power source causing voltage spikes that damage MOS switches
Solution Approach 1:
The patent applies preliminary action by detecting the output current direction before turning off the lower bridge switch. The feedback detection unit monitors whether current is flowing toward the upper bridge switch, and only allows the lower bridge switch to turn off when the current has stopped flowing or is flowing away from the upper bridge switch, preventing reverse current damage before it can occur.
Solution Approach 2:
The patent implements feedback control through a feedback detection unit that continuously monitors the output current direction. When current is detected flowing toward the upper bridge switch, a feedback control signal is generated to delay the lower bridge switch turn-off until the current direction is safe, thereby preventing voltage spikes and reverse current damage while maintaining reliable switching operation.
2Reliability
If protective Zener diode and capacitor are inserted to prevent reverse current, then the reliability of power switch protection is improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent applies self-service by using the motor's own back electromotive force and current characteristics to protect itself. The feedback control system utilizes the natural current decay and direction changes during motor operation to determine when it is safe to turn off the lower bridge switch, eliminating the need for external protective components like Zener diodes and capacitors.
Solution Approach 2:
The patent extracts and removes the protective Zener diode and capacitor components from the circuit by replacing them with an active feedback control mechanism. This extraction simplifies the overall circuit design while maintaining protection functionality through intelligent control rather than passive components.
3Reliability
If feedback mode is activated to detect output current direction, then the protection against reverse current is improved, but the power consumption increases due to continuous monitoring
Solution Approach 1:
The patent applies periodic action by activating the feedback detection mode only at specific moments during motor operation - specifically when the lower bridge switch is about to turn off. The feedback detection is not continuous but is triggered periodically at critical switching transitions, reducing power consumption while maintaining protection effectiveness at key moments.
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 reverse currents from flowing back to the voltage source, reducing the risk of damage to MOS switches and minimizing power consumption by adjusting the output node voltage during motor operation.
Implementation Method 1
The feedback detection unit is configured to, in response to receiving the feedback start signal, detect an output current of the output node of the designated phase circuit
Implementation Method 2
the feedback detection unit outputs a voltage regulation signal to adjust a voltage of the output node to approach the predetermined voltage
Implementation Method 3
changes of magnetic flux on the coil cause a reverse voltage on a coil connector, which is called back electromotive force
Data Source
AI summary
A three-phase motor driving circuit and a three-phase motor driving method are provided. The three-phase motor driving circuit includes an inverter circuit, a control circuit, a turn-off module, a turn-off confirmation module, and a turn-on logic unit. The inverter circuit includes a plurality of phase circuits, each including an upper bridge switch and a lower bridge switch. The control circuit operates in a feedback mode to output a feedback start signal. The turn-off module includes a feedback detection unit, a voltage adjusting unit, and a turn-off logic unit. The feedback detection unit detects an output current of a designated phase circuit, and if the output current flows out, a voltage regulation signal is output until the output current is 0, and a lower bridge turn-off signal is output. The voltage adjusting unit adjusts the voltage of the output node to be close to a predetermined voltage.