Switched-mode Power Supply Gate Drive Control
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Solution Overview
Problem
Existing switched-mode power supply devices face challenges in effectively reducing Electro-Magnetic Interference (EMI) noise and switching loss, particularly due to the continuous operation mode at high load ratios, which affects efficiency and noise levels.
Innovation Solution
The implementation of a switched-mode power supply device that dynamically switches between normal drive and soft drive modes based on load ratio thresholds, using a drive circuit and load ratio detection circuit to control the switching element's gate voltage charging speed, thereby optimizing operation across the full load range and reducing EMI noise without increasing switching loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If normal drive mode is used at all load ratios, then switching speed is maintained, but EMI noise increases and switching loss increases
Solution Approach 1:
The patent applies dynamics by making the drive mode adjustable based on operating conditions. The control circuit dynamically selects between normal drive mode and soft drive mode according to the detected load ratio, allowing the system to adapt its characteristics to different operating states rather than using a fixed drive mode
Solution Approach 2:
The patent changes the gate resistance parameter based on load conditions. In soft drive mode, a larger gate resistance is used to slow down the charging speed of the switching element's gate voltage, reducing EMI noise and switching loss. The control circuit adjusts this parameter dynamically based on the load ratio detection
2Object-generated harmful factors
If soft drive mode is used at all load ratios, then EMI noise is reduced, but switching speed decreases and efficiency drops at high load
Solution Approach 1:
The system dynamically adjusts the drive mode based on load conditions. The control circuit detects the load ratio and switches between soft drive mode (for EMI reduction) and normal drive mode (for high efficiency) appropriately, optimizing performance across different operating ranges
Solution Approach 2:
The gate resistance parameter is changed based on load ratio. When the load ratio is below a threshold, a larger gate resistance is applied to reduce EMI noise. When the load ratio exceeds the threshold, the gate resistance is reduced to maintain high switching speed and efficiency
3Object-generated harmful factors
If gate resistance is increased continuously, then EMI noise is reduced, but switching loss increases and heat generation increases
Solution Approach 1:
The patent applies periodic action by using different gate resistance values in different operating periods. The control circuit periodically evaluates the load ratio and switches between normal drive (lower resistance) and soft drive (higher resistance) modes, applying the appropriate resistance only when needed rather than continuously
Solution Approach 2:
The gate resistance parameter is changed based on operating conditions. The control circuit selects between a first gate resistance value (normal drive) and a second gate resistance value (soft drive) according to the load ratio, optimizing the balance between EMI reduction and switching loss
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
This approach effectively reduces EMI noise and switching loss by employing soft drive at low load ratios and normal drive at high load ratios, ensuring optimal performance and minimizing heat generation and noise levels across the full load range.
Implementation Method 1
a transformer comprising a primary winding to which a DC voltage is applied, the DC voltage generated by rectifying an input voltage from the AC power supply, and a secondary winding that induces a pulse voltage based on operation of a switching element
Data Source
AI summary
A switched-mode power supply device is disclosed including an AC power supply, a transformer including a primary winding and a secondary winding, a switching element electrically connected to the primary winding, a secondary-side rectifying and smoothing circuit that generates an output voltage by rectifying and smoothing the pulse voltage, a load ratio detection circuit that detects if a load ratio is not greater than a load ratio threshold value during steady load, and outputs a drive switch signal based on the detection, and a drive circuit that, on the basis of the drive switch signal, causes the switching element to perform switching operation in one of a normal drive in which a speed of charging a gate voltage is faster and a soft drive in which the speed of charging the gate voltage is slower.