Voice Coil Motor Current Sensing Circuit Integration
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Solution Overview
Problem
Conventional Voice Coil Motor (VCM) control systems in hard disk drives rely on external resistors to measure drive current, which can be inefficient and limit the integration of current sensing within the control circuit, hindering precise control and feedback loops.
Innovation Solution
The integration of a current sensing circuit within the control integrated circuit, utilizing H-bridge and current sensing circuits operating at different power supply voltage levels, allows for internal sensing of drive current and improved feedback control, enabling more precise current control and reduced external component reliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external resistors are used to measure drive current, then current sensing can be achieved, but device complexity increases and integration is limited
Solution Approach 1:
The patent merges the current sensing function with the control integrated circuit by integrating a sensing circuit internally. The sensing circuit includes a sense amplifier and current mirror circuits that are fabricated on the same semiconductor substrate as the H-bridge circuit, eliminating the need for external resistors and reducing device complexity while maintaining measurement capability
Solution Approach 2:
The patent introduces current mirror circuits as intermediary elements that replicate the drive current from the H-bridge circuit. These current mirrors transfer the current information to the sense amplifier through internal circuitry, enabling current measurement without external components and resolving the contradiction between measurement precision and device complexity
2Device complexity
If current sensing is integrated within the control circuit, then device complexity reduces, but measurement precision may be compromised
Solution Approach 1:
The patent replaces the mechanical/external resistor-based sensing system with an integrated electronic sensing circuit. The sense amplifier and current mirror circuits use electronic field effects to measure current, achieving both integration and precision by substituting external physical components with on-chip electronic measurement mechanisms
Solution Approach 2:
The patent changes the operating parameters of the sensing circuit by providing separate power supply voltages to the H-bridge circuit and the sensing circuit. This parameter separation allows each circuit to operate at optimal voltage levels, maintaining measurement precision while achieving integration and reducing overall device complexity
3Productivity
If H-bridge and sensing circuits operate at different power supply voltage levels, then integration efficiency improves, but circuit design complexity increases
Solution Approach 1:
The patent segments the control circuit into distinct functional blocks operating at different voltage levels: the H-bridge circuit operates at a first power supply voltage while the sensing circuit operates at a second power supply voltage. This segmentation allows independent optimization of each block while maintaining overall integration, improving productivity without excessive complexity increase
Solution Approach 2:
The integrated control circuit achieves multi-functionality by incorporating both the H-bridge driver circuit and the current sensing circuit on the same semiconductor substrate. The circuit can simultaneously perform current driving and current measurement functions at different voltage levels, improving integration efficiency while managing design complexity through unified fabrication processes
Data Source
AI summary
A current sensing circuit includes: a first controlled device; a first controlled device; a first current mirror configured to cause a first mirror current to flow through a first load device based on a first control signal received by the first controlled device; a second controlled device; a second current mirror configured to cause a second mirror current to flow through a second load device based on a second control signal received by the second controlled device; and an amplifier configured to output a voltage signal based on the first mirror current flowing through the first load device and the second mirror current flowing through the second load device. The first control signal is substantially proportional to a first drive signal applied to a first controlled remote device, and the second control signal is substantially proportional to a second drive signal applied to of a second controlled remote device.