H-Bridge Driver Mode Switching for Low-Noise Motor Control
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Solution Overview
Problem
H bridge circuits used in motor drives, such as voice coil motors, generate high-frequency noise due to the high switching frequency in PWM control, which can be problematic for peripheral circuitry.
Innovation Solution
An H bridge driver circuit that switches between PWM mode and constant voltage mode using a switching signal, allowing for control of motor current direction and voltage, with PWM mode controlling the duty ratio and constant voltage mode maintaining output voltage, enabling efficient motor drive based on device requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PWM control with high switching frequency is used to control motor current, then the responsiveness and control precision are improved, but high-frequency noise is generated which interferes with peripheral circuitry
Solution Approach 1:
The patent applies dynamics by making the control method adjustable between two modes (PWM mode and constant voltage mode) based on operational conditions. The control circuit dynamically selects the appropriate mode: PWM mode for high responsiveness and precision, constant voltage mode for noise reduction. This dynamic adaptation resolves the contradiction by allowing the system to optimize between control precision and noise generation depending on the situation.
Solution Approach 2:
The patent changes the control parameter from fixed PWM switching to variable control mode selection. By introducing a mode selection mechanism that switches between PWM control (high frequency, high precision) and constant voltage control (low frequency, low noise), the system can adjust its operational parameters to resolve the contradiction between control precision and noise generation.
2Speed
If the upper transistor is turned on and off at high frequency in PWM mode, then the output current control responsiveness is improved, but high-frequency noise is generated
Solution Approach 1:
The control circuit dynamically switches between PWM mode (fast switching, high responsiveness) and constant voltage mode (slow switching, low noise) based on operational requirements. This dynamic mode selection allows the system to achieve high responsiveness when needed while minimizing noise generation during other operations, resolving the contradiction between speed and harmful factors.
Solution Approach 2:
The patent uses periodic PWM switching at high frequency for rapid current control when responsiveness is critical, while alternatively using less frequent switching in constant voltage mode when noise reduction is prioritized. This periodic alternation between different switching frequencies and modes resolves the contradiction between responsiveness and noise generation.
3Device complexity
If a single control mode is used, then the control circuit is simple, but the adaptability to different operational requirements is limited
Solution Approach 1:
The control circuit achieves multi-functionality by incorporating both PWM control capability and constant voltage control capability within a single circuit. The mode selection mechanism allows the same circuit to perform different control functions based on operational requirements, thereby increasing adaptability without proportionally increasing complexity. This universal design resolves the contradiction between simplicity and adaptability.
Solution Approach 2:
The control circuit is designed to be dynamically configurable between different operational modes. By introducing mode selection switches and control logic that can adapt the circuit's behavior based on requirements, the system achieves high adaptability while maintaining reasonable complexity through structured design. This dynamic configurability resolves the contradiction between circuit simplicity and operational adaptability.
Data Source
AI summary
A PWM mode for turning on and off two output transistors by an output of a high impedance circuit and a constant voltage mode for controlling voltages at two output terminals by an output of an op amp are provided. Then, the two modes are switched by a switching signal.