DC Motor Drive Circuit Current Control
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Solution Overview
Problem
Conventional DC motor control systems face challenges in accurately determining and controlling low current amplitudes due to offset voltages, leading to errors and noise, especially when using external resistor elements, which also consume power and occupy space.
Innovation Solution
A control system with a drive circuit comprising parallel-connected transistors and a current determination circuit that adjusts the number of transistors to be turned on based on voltage across the drive switch, increasing resistance and improving accuracy in low-current regions without external resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external resistor element is added to determine current value, then current control of DC motor can be performed, but power efficiency decreases due to power consumption by the resistor element
Solution Approach 1:
The invention extracts and eliminates the external resistor element from the system by implementing current determination directly within the drive circuit using the existing transistor structure. The current determination circuit uses the on-resistance of the drive transistor itself to sense current, removing the need for separate external resistors that consume power.
Solution Approach 2:
The drive transistor serves multiple functions: it acts as both the switching element for motor control and the sensing element for current determination. The on-resistance of the same transistor that controls current flow is utilized for current sensing, eliminating the need for dedicated external sensing components.
2Measurement precision
If an external resistor element is added to determine current value, then current control of DC motor can be performed, but device size increases making it difficult to secure disposal space
Solution Approach 1:
The invention merges the current determination function with the existing drive circuit structure. The current determination circuit is integrated into the drive circuit, sharing the transistor and utilizing its on-resistance, thereby eliminating the need for separate external resistor elements and reducing overall device area.
Solution Approach 2:
The drive transistor performs dual functions as both a switching device and a sensing device. By using the same transistor's on-resistance for current sensing, the invention eliminates external sensing components and reduces the device footprint.
3Device complexity
If voltage across drive switch is used to determine current, then current determination can be performed without external resistors, but accuracy decreases in low-current regions due to offset voltages
Solution Approach 1:
The invention dynamically adjusts the circuit configuration based on current magnitude. In low-current regions, it switches to a high-resistance configuration that amplifies the voltage signal for better resolution, while in high-current regions, it uses the normal drive circuit configuration. This dynamic adaptation maintains accuracy across the full current range.
Solution Approach 2:
The invention changes the resistance parameter of the determination circuit based on operating conditions. By switching between different resistance values (high resistance for low current, normal resistance for high current), the system optimizes voltage signal magnitude and measurement accuracy for different current ranges.
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
Enhances current determination accuracy and reduces noise and vibration in low-current driving, allowing for precise control and expanded dynamic range of controllable currents in DC motors.
Implementation Method 1
The current determination circuit determines a current flowing between the first node and the second node
Data Source
AI summary
According to one embodiment, there is provided a control device including a drive circuit and a control circuit. The drive circuit includes a plurality of transistors and a current determination circuit. The plurality of transistors is electrically connected in parallel to each other between a first node and a second node. The first node is connected to a power supply circuit. The second node is connected to a DC motor. The current determination circuit determines a current flowing between the first node and the second node. The control circuit generates a control signal to control a number of transistors to be turned on among the plurality of transistors in accordance with the determined current. The drive circuit drives the DC motor using a current in response to the control signal.