Full Bridge Circuit Prevents Reverse Current in DC Motors
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Solution Overview
Problem
Conventional DC motor drivers experience damage due to reverse current and voltage spikes caused by high rotation rates, leading to reliability and operational range degradation.
Innovation Solution
A full bridge circuit incorporating operational amplifiers and multiplexers is used to control and maintain output voltages, ensuring that motor current decays to zero, preventing reverse current flow by maintaining output voltages at or below the supply voltage, thus avoiding voltage spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotation rate of the DC motor is increased to meet digital product requirements, then the productivity and speed are improved, but reverse current flows back to the power supply causing voltage spikes that damage controllers and drivers
Solution Approach 1:
The patent implements feedback control by monitoring the current flowing through the motor and adjusting the switching signals accordingly. When current exceeds a threshold (indicating potential reverse current), the controller modifies the PWM duty cycle or switch timing to prevent voltage spikes and protect the power supply and control circuitry
Solution Approach 2:
The patent applies preliminary action by using freewheeling diodes or active clamp circuits that are pre-configured to conduct reverse current before it can reach the power supply. The switching sequence is also pre-planned to ensure that body diodes of MOSFETs are conducting before the main switches turn off, providing a safe current path in advance
2Device complexity
If conventional full bridge circuits are used without additional control components, then the device complexity is low, but the output voltage cannot be fixed and reverse current cannot be avoided
Solution Approach 1:
The patent introduces operational amplifiers as intermediary components that compare the actual output voltage with a reference voltage and adjust the switching signals accordingly. This intermediary control mechanism enables precise voltage regulation and reverse current protection without requiring complete redesign of the full bridge circuit topology
Solution Approach 2:
The patent makes the full bridge circuit multi-functional by integrating voltage regulation, current protection, and motor control capabilities into a single system. The same control circuitry that drives the motor also monitors and regulates output voltage, eliminating the need for separate protection circuits
Data Source
AI summary
A full bridge circuit includes a first switch, a second switch, a third switch, a fourth switch, a first controller, a second controller, a first operational amplifier, a first multiplexer, a second operational amplifier, and a second multiplexer. The first controller includes a first output coupled to the first switch. The second controller includes a first output coupled to the third switch. The first operational amplifier includes a first input coupled to the first switch and the second switch, and a second input for receiving a first reference voltage. The second operational amplifier includes a first input coupled to the third switch and the fourth switch, and a second input for receiving a second reference voltage. The first multiplexer is coupled to the first operational amplifier, the first controller, and the second switch. The second multiplexer is coupled to the second operational amplifier, the second controller, and the fourth switch.