HDD Write Preamplifier Switching With Programmable Slew Rate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional HDD preamplifier circuits face a tradeoff between switching speed and power consumption, with large switching currents required for fast transitions leading to high power consumption and slower switching speeds due to increased resistor values needed for lower currents, and lack of slew rate control without varying the output write current.
Innovation Solution
The implementation of a hard drive write preamplifier using static current sources and FET or BJT switches, where static current sources create static reference voltages and switches are coupled to resistors to generate output currents, allowing for reduced power consumption and programmable slew rates without affecting the output write current magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If large switching currents are used to achieve fast switching speed, then switching speed is improved, but power consumption increases
Solution Approach 1:
The patent applies dynamics by making the slew rate programmable and variable. The circuit transitions from a static design to a dynamic one where the slew rate can be adjusted based on requirements. This is achieved through a variable current source that can be programmed to provide different current levels, allowing the switching speed to be optimized without always using maximum current, thus reducing average power consumption while maintaining the capability for fast switching when needed.
Solution Approach 2:
The patent changes the parameter of switching current from a fixed large value to a variable value that can be programmed. By using a variable current source with programmable slew rate, the system can adjust the current magnitude according to the specific switching requirements. This parameter change allows the system to use smaller currents for non-critical switches, reducing power consumption, while still providing large currents when fast switching is required.
2Use of energy by moving object
If smaller current sources are used to reduce power consumption, then power consumption is reduced, but switching speed decreases due to larger resistor values needed
Solution Approach 1:
The patent overcomes this contradiction by introducing a dynamic, programmable current source that can adapt its output current based on the switching requirements. Instead of being locked into a fixed current level, the system can dynamically adjust the current magnitude. This allows the use of smaller currents for routine operations to save power, while still providing the capability to rapidly increase current for fast switching when needed, thus resolving the tradeoff between power consumption and switching speed.
Solution Approach 2:
The patent implements preliminary action by pre-programming the variable current source with appropriate slew rate values for different switching scenarios. The system prepares multiple current levels in advance, allowing it to quickly switch between power-efficient mode (smaller currents) and high-speed mode (larger currents) based on the specific switching task, without needing to physically change components or resistors.
3Device complexity
If fixed current sources are used, then circuit simplicity is maintained, but slew rate control is lost
Solution Approach 1:
The patent applies universality by designing a variable current source that can serve multiple functions: it can operate in a fixed mode for simple applications and a variable mode for applications requiring slew rate control. The programmable current source acts as a multi-functional element that combines the simplicity of a fixed current source with the flexibility of a controllable current source, allowing the same circuit to adapt to different performance requirements without needing separate circuits for each function.
Solution Approach 2:
The patent introduces dynamics by transforming the static fixed current source into a dynamic variable current source with programmable slew rate. This dynamic element allows the circuit to adapt its behavior based on control signals, providing slew rate control capability while maintaining a relatively simple overall circuit architecture. The variable current source can be programmed to provide fixed currents when simplicity is needed or variable currents when slew rate control is required.
Data Source
AI summary
A hard drive write preamplifier includes a first differential pair of PNP BJTs having a first PNP BJT and a second PNP BJT; a first tail current source coupled into emitter of the PNP BJTs of the first differential pair; a second differential pair of NPN BJTs having a first NPN BJT and a second NPN BJT; a second tail current source coupled into the emitters of the NPN BJTs of the second differential pair; wherein a collector of each of the PNP BJTs of the first differential pair are coupled to a corresponding collector the NPN BJTs of the second differential pair; a first shift up PNP BJT having emitter coupled to the collector of a first PNP BJT of the first differential pair; a second shift up PNP BJT having an emitter coupled to the collector of the second PNP BJT of the first differential pair.