DC/DC Converter Variable Frequency Control
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Solution Overview
Problem
Resonant converters face efficiency reduction and potential damage at light loads due to increased switching loss and IGBT stress, requiring complex control circuits to maintain operation across all load ranges without overvoltage application.
Innovation Solution
A DC/DC converter design with a single switch leg operating at high frequency for light loads and multiple switch legs at lower frequency for rated loads, utilizing a gate drive circuit with adjustable snubber capacitors and a controller for precise switching frequency management, allowing zero voltage sensing and reduced switching loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the switching frequency is increased to lower the output voltage in continuous conduction region, then the output voltage control is improved, but the switching loss increases rapidly
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The controller dynamically adjusts the switching frequency based on the output voltage feedback, allowing the resonant converter to operate at optimal frequencies for different load conditions, thereby reducing switching losses while maintaining precise voltage control
Solution Approach 2:
The patent changes the operating parameters of the resonant converter by adjusting the switching frequency according to the load conditions. By varying the frequency parameter within a controlled range, the system achieves both precise voltage regulation and reduced energy loss at different operating points
2Measurement precision
If the switching frequency is increased to reduce output current from 4A to 2A, then the output current control is improved, but the IGBT loss increases and efficiency is reduced
Solution Approach 1:
The system dynamically adjusts the switching frequency based on real-time output current measurements and load conditions. This dynamic frequency adjustment allows the IGBTs to operate within safe parameters while achieving precise current control, preventing overheating and damage
Solution Approach 2:
The patent implements feedback control where the output current is continuously monitored and fed back to the controller. The controller uses this feedback to adjust the switching frequency and duty cycle, ensuring precise current regulation while protecting the IGBTs from excessive stress and damage
3Power
If multiple switch legs are operated together at lower frequency for rated load, then the power handling capability is improved, but the circuit complexity increases
Solution Approach 1:
The patent divides the power conversion function into multiple independent switch legs that can operate independently or in combination. Each switch leg is a self-contained module with its own controlling signal generator, allowing flexible configuration to match the load requirements while maintaining manageable circuit complexity through modular design
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
Enables high precision control and reduced ripple in output voltage across all load ranges, minimizing energy delivery to the load and preventing IGBT damage, while maintaining efficiency and simplicity in circuit design.
Implementation Method 1
The resonant converter uses a resonant phenomenon of an inductor Lr and a capacitor Cr
Implementation Method 2
a gate drive circuit applying a switching signal to a terminal for turning-on/off control of the power semiconductor switching element, wherein a value of snubber capacitor for preventing a rapid voltage increase of the first switch leg is designed to be smaller than a value of the snubber capacitor of the one or more second switch legs such that zero voltage sensing of the gate drive circuit of the first switch leg is faster than zero voltage sensing of the gate drive circuit of the one or more second switch legs
Data Source
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AI summary
Provided is a high precision DC/DC resonant converter with a wide load range, including: a first switch leg having one end connected to an anode terminal of a DC power source and the other end connected to a cathode terminal of the DC power source to independently operate at a switching frequency used in an application of an output voltage for no load or a light load equal to or less than a rated load and operate to reduce a ripple of the output voltage at a frequency equal to or less than the switching frequency used in the application of the output voltage for no load or the light load equal to or less than the rated load; and one or more second switch legs having one end connected to the anode terminal of the DC power source and the other end connected to the cathode terminal of the DC power source to operate at a switching frequency for the rated load or a frequency equal to or less than the switching frequency used in the application of the output voltage for no load or the light load that the first switch leg takes charge of. The resonant converter can stably operate with high efficiency even in a light load using a switch leg taking charge of the light load.