Transformer DC/DC Converter With Adaptive PWM for Low HV Voltage
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Solution Overview
Problem
Existing DC/DC converters for electric vehicles suffer from high conversion losses and inefficiency at low high-voltage DC voltages, often requiring multiple stages that increase complexity, cost, and space consumption.
Innovation Solution
A DC/DC converter design with a transformer, low-voltage and high-voltage semiconductor bridge circuits, and a control device that adjusts pulse-width modulation frequencies based on detected voltages to optimize power transmission, reducing conversion losses by using different PWM frequencies for low and high-voltage switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage DC/DC converter is used, then the design is simple, but conversion losses are high at low HV DC voltages
Solution Approach 1:
The patent applies dynamics by making the PWM frequency adjustable based on operating conditions. The control device dynamically selects between a first PWM frequency (higher) and a second PWM frequency (lower) depending on the HV DC voltage level and power transmission direction. This dynamic frequency adaptation allows the single-stage converter to optimize conversion efficiency across different voltage conditions without requiring multiple fixed-stage designs.
2Loss of energy
If multiple stages are used to reduce conversion losses, then efficiency improves, but device complexity and space consumption increase
Solution Approach 1:
The patent applies parameter changes by varying the PWM frequency parameter based on operating conditions. The control device adjusts the PWM frequency to a higher value when transmitting power from LV to HV side, and to a lower value when transmitting from HV to LV side. This parameter adaptation enables a single-stage converter to achieve efficiency comparable to multi-stage designs by optimizing the operating parameters rather than adding structural complexity.
3Loss of energy
If PWM frequency is increased for low HV voltages, then conversion efficiency improves, but switching losses increase
Solution Approach 1:
The patent resolves this contradiction through dynamic PWM frequency selection. The control device monitors the HV DC voltage level and power transmission direction, then dynamically adjusts the PWM frequency accordingly. When HV voltage is low and power flows from LV to HV, a higher PWM frequency is used to maintain efficiency. When HV voltage is high or power flows from HV to LV, a lower PWM frequency is used to reduce switching losses. This dynamic adaptation optimizes the trade-off between conversion efficiency and switching losses in real-time.
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 efficient power transmission at low high-voltage DC voltages without additional stages, simplifying the design and reducing costs and space requirements.
Implementation Method 1
a transformer with a low-voltage winding and a high-voltage winding, wherein the low-voltage winding and the high-voltage winding are magnetically coupled
Data Source
AI summary
A DC/DC converter is provided. The DC/DC converter includes a control device for controlling LV semiconductor switches and HV semiconductor switches by means of pulse-width modulated control signals. The control device is configured to detect the LV DC voltage and the HV DC voltage based on the LV DC voltage, the HV DC voltage, and a transformation ratio of a transformer, to determine a theoretical pulse-width modulation duty cycle and to generate a pulse-width modulated control signal as a function of the theoretical pulse-width modulation duty cycle.