PFC Bus Voltage Control for Cooler DC-DC Converter Operation
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Solution Overview
Problem
Existing power converters face thermal risks and efficiency losses due to increased switching frequency and heat generation in the DC-DC converter circuit when handling high alternating current voltages, particularly in harsh working conditions.
Innovation Solution
Implementing a hybrid modulation mode that adjusts direct current voltage based on the output efficiency of the DC-DC converter circuit, using a first reference value less than the peak alternating current voltage, and switching to a passive rectification state when the instantaneous voltage exceeds this value, thereby stabilizing the DC-DC converter operation and optimizing heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the direct current voltage of the direct current bus is raised to ensure stable operation of the PFC circuit under high alternating current input voltage, then the PFC circuit operates stably, but the DC-DC converter circuit operates in high-frequency and large turn-off current state, causing sharp increase in loss and thermal risk
Solution Approach 1:
The patent implements dynamic adjustment of the direct current bus voltage based on the instantaneous alternating current input voltage. When the AC input voltage is high, the DC bus voltage is dynamically reduced to a specific value range (400V-430V) rather than maintaining a fixed high voltage, thereby reducing the voltage stress and switching loss in the DC-DC converter circuit while ensuring stable operation of the PFC circuit through coordinated control of the switch transistors.
Solution Approach 2:
The patent changes the operating parameters of the power conversion system by adjusting the direct current bus voltage level according to the AC input voltage conditions. By changing the DC bus voltage from a fixed high value to a dynamically adjusted value within 400V-430V range, the system optimizes the operating point of the DC-DC converter to reduce switching losses and thermal risk while maintaining PFC circuit stability.
2Reliability
If the working frequency of the DC-DC converter circuit is increased to be far away from the resonance point, then the circuit operates stably, but heat generated by switch transistor and resonant cavity increases, increasing thermal risk
Solution Approach 1:
The patent converts the potential harmful effect of operating near resonance into a beneficial feature by intentionally operating the DC-DC converter circuit at a working frequency close to the resonance frequency. This resonance operation reduces the required switching frequency and consequently reduces the switching losses and heat generation in the switch transistors and resonant cavity, while maintaining stable operation through proper control of the switch transistor timing and duration.
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 hybrid modulation mode reduces switching frequency by 20% and improves efficiency by 1%, effectively preventing thermal risks and enhancing the stability and reliability of the power converter, especially in harsh conditions, while allowing for optimized component design.
Implementation Method 1
The power factor correction circuit is configured to: convert an input alternating current voltage into a direct current voltage
Implementation Method 2
The direct current-to-direct current converter circuit is configured to: perform voltage conversion on the direct current voltage
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5b
AI summary
This application provides a power converter and a control method thereof. The power converter includes a power factor correction circuit, a direct current-to-direct current converter circuit, and a controller. In a hybrid modulation mode, the controller directly determines, based on output efficiency of the direct current-to-direct current converter circuit, a first reference value of a direct current voltage output by the power factor correction circuit, and generates a first PWM signal based on the first reference value. The first reference value is less than a peak value of an alternating current voltage input by the power factor correction circuit, and pulling down the direct current voltage can ensure a stable operating state of the direct current-to-direct current converter circuit. When an instantaneous value of the alternating current voltage is less than the first reference value, a turned-on/turned-off state of at least one switch transistor in the power factor correction circuit is controlled by using the first PWM signal. When the instantaneous value of the alternating current voltage is greater than or equal to the first reference value, the at least one switch transistor in the power factor correction circuit is controlled to keep in the turned-on state, so that the power factor correction circuit operates in a passive rectification state.