Fan Switch Drive Circuit Using Shared PWM to Save MCU Timers
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Solution Overview
Problem
Conventional fan motor drive circuits require multiple timers to achieve high precision in pulse width modulation, leading to increased cost and size due to limited pin resources in micro control units, which is unbeneficial for lightweight and miniaturized electronic products.
Innovation Solution
A switch drive circuit design that utilizes multiple upper and lower arm switch components with drive control units to receive and output pulse width modulation signals, effectively reducing the need for timers in the processor by sharing signal states and frequencies, allowing for efficient control of fan rotational speed with minimal timer usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple timers are used in the micro control unit to achieve high precision PWM signals for driving lower arm switches, then the output precision of PWM signals is improved, but the device complexity and cost increase due to limited pin resources
Solution Approach 1:
The patent introduces a bootstrap circuit as an intermediary component that generates the second PWM signal based on the first PWM signal from a single timer. This mediator approach allows the system to achieve the function of multiple timers using only one timer resource, thereby improving PWM signal precision without increasing device complexity
Solution Approach 2:
The patent combines the functions of multiple timers into a single timer by using the bootstrap circuit to generate multiple PWM signals from one timer output. This merging strategy reduces the number of timer resources needed while maintaining the precision requirements for driving multiple lower arm switches
2Adaptability or versatility
If additional pins with timers are added to support specific fan functions, then the adaptability of the fan is improved, but the package size is enlarged
Solution Approach 1:
The patent makes a single timer resource universal by enabling it to generate multiple PWM signals through the bootstrap circuit. This multi-functionality allows the same timer pin to support multiple fan control functions without requiring additional dedicated pins, thus maintaining adaptability while reducing package size
Solution Approach 2:
The patent merges multiple pin functions into a single pin by using the bootstrap circuit to derive additional PWM signals from one timer output. This consolidation allows the system to support various fan functions without enlarging the package size
Data Source
AI summary
A switch drive circuit capable of saving timers of fan processor is applied to a processor. The switch drive circuit includes multiple upper arm switch components, multiple lower arm switch components correspondingly electrically connected with the upper arm switch components, a first drive control unit and a second drive control unit. The upper arm switch components are driven by a first pulse width modulation signal and a second pulse width modulation signal. The first and second drive control units serve to receive a third pulse width modulation signal and a high-frequency pulse width modulation signal. The third pulse width modulation signal is switched between a high-level state and a low-level state to trigger and turn on the lower arm switch components.