Full-Bridge Circuit Control Signal Reduction
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Solution Overview
Problem
Conventional full-bridge circuits in heat dissipation systems face challenges with weak anti-noise ability due to low voltage elements and complex circuitry requiring four control signals from a micro-processor control unit, limiting cost reduction and reliability.
Innovation Solution
A full-bridge circuit design utilizing two out-of-phase control signals to control all switches, incorporating high voltage switches and driving voltage sources to simplify circuitry and enhance anti-noise ability, allowing for the use of various low-cost elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If low voltage elements are used in the full-bridge circuit, then the circuit can be controlled by a standard 5V MCU output, but the anti-noise ability deteriorates resulting in false operation
Solution Approach 1:
The patent changes the voltage parameter of the MOSFETs from low voltage (4.5V) to high voltage (10V-20V) type. This allows the lower bridge switches to have strong anti-noise ability while the upper bridge switches maintain compatibility with the 5V MCU output through level shifting circuits or voltage division, thus resolving the contradiction between MCU compatibility and anti-noise ability.
2Ease of operation
If four control signals are used to control all switches, then each switch can be precisely controlled, but the circuit complexity increases
Solution Approach 1:
The patent combines the control of two switches (upper and lower in the same leg) into a single control signal through the use of complementary MOSFET pairs or half-bridge configurations. This merging reduces the four control signals to two, simplifying the circuit while maintaining precise control through the inherent complementary switching behavior of the MOSFET pairs.
3Reliability
If high voltage elements are used in the full-bridge circuit, then the anti-noise ability is improved, but the available element selection is limited and cost reduction becomes difficult
Solution Approach 1:
The patent applies different voltage-rated MOSFETs to different parts of the circuit based on their specific requirements. The lower bridge switches use high voltage (10V-20V) MOSFETs for strong anti-noise ability, while the upper bridge switches use standard 5V-compatible MOSFETs since they are directly controlled by the MCU. This local differentiation allows cost optimization by not over-specifying all switches with high voltage devices.
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
The solution simplifies circuitry by reducing the number of control signals needed and improves anti-noise ability by using high voltage elements, preventing false operations and reducing costs through the use of low-cost MOSFETs, while ensuring reliable operation of the heat dissipation system.
Implementation Method 1
a current path of an input voltage Vin includes the switch Q1, the induction coil L, and the switch Q4
Data Source
AI summary
A full-bridge circuit for a heat dissipation system. The heat dissipation system further includes a fan and a control circuit. The control circuit outputs a first control signal and a second control signal. The full-bridge circuit includes a first control line having a first switch and a third switch serially coupled, a second control line includes a second switch and a fourth switch serially coupled, and a induction coil having one terminal coupled between the first and third switches and the other terminal coupled between the second and fourth switches. The ON/OFF states of the first and second switches are controlled by the first and second control signals respectively. The ON/OFF states of the third and fourth switches are controlled by two driving voltage sources respectively.