Rectifier Arrangement Using Schottky Diodes for Generator Pre-Excitation
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Solution Overview
Problem
The existing rectifier systems in motor vehicle generators, particularly those using silicon pn diodes, face issues with temperature-dependent reverse currents leading to excessive DC voltage components during pre-excitation, which can cause delayed or incorrect generator start-up due to the diodes' varying temperatures.
Innovation Solution
Employing Schottky diodes, such as trench MOS barrier junction (TMBS) or trench junction barrier Schottky (TJBS) diodes with voltage-independent reverse saturation currents, which maintain a stable DC phase voltage by suppressing voltage-dependent reverse current components, ensuring the rectifier operates within safe voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If silicon pn diodes are used in the rectifier bridge, then the rectifier can handle large currents, but the reverse current increases with temperature and reverse voltage, causing the DC component of phase voltage to exceed permissible values during pre-excitation
Solution Approach 1:
The patent changes the material parameter of the diodes from silicon pn diodes to Schottky diodes (TMBS or TJBS), which fundamentally alters the reverse current characteristics. Schottky diodes exhibit voltage-independent reverse saturation current, contrasting with the voltage-dependent reverse current of silicon pn diodes. This parameter change resolves the contradiction by maintaining low reverse currents even at elevated temperatures and reverse voltages, preventing DC component excursions during pre-excitation while retaining high current handling capability.
2Adaptability or versatility
If the reverse current of diodes is temperature-dependent, then the diodes can operate at various temperatures, but the DC component of phase voltage rises above maximum permissible values when diodes are at different temperatures
Solution Approach 1:
The patent changes the temperature dependence parameter of reverse current by transitioning from silicon pn diodes to Schottky diodes. Schottky diodes exhibit minimal temperature dependence in their reverse saturation current, unlike silicon pn diodes whose reverse current increases significantly with temperature. This parameter change ensures that even when diodes operate at different temperatures, the DC component of phase voltage remains controlled within permissible limits.
3Device complexity
If silicon pn diodes are used, then the rectifier structure is simple and well-established, but the controller cannot reliably recognize starting speed due to excessive DC component in phase voltage
Solution Approach 1:
The patent changes the electrical parameter characteristics of the rectifier diodes from silicon pn type to Schottky type (TMBS/TJBS). This change fundamentally alters the reverse current behavior, making it independent of reverse voltage and less temperature-sensitive. The result is that the DC component of phase voltage remains low during pre-excitation, enabling the controller to accurately detect the AC component and reliably recognize starting speed, while maintaining a relatively simple rectifier structure.
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 solution effectively keeps the DC phase voltage below permissible limits, ensuring reliable generator start-up by minimizing the impact of temperature variations on diode reverse currents, thus stabilizing the rectification process.
Implementation Method 1
Employing Schottky diodes, such as trench MOS barrier junction (TMBS) or trench junction barrier Schottky (TJBS) diodes with voltage-independent reverse saturation currents
Implementation Method 2
rectifier arrangement for a motor vehicle generator... B6 AC bridges are usually used as rectifiers for rectification
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to a rectifier arrangement, particularly for a generator, having a bridge arrangement with a prescribable number of rectifier elements, wherein at least one rectifier element (D1+ - D6-) is a rectifier element having a characteristic curve independent of a blocking voltage at least in a prescribable range, and one of the negative diodes (D1+ - D6-) comprises a greater blocking saturation current than the associated positive diode, for example, and at least one of the negative diodes is placed at a location in the rectifier at which the temperature is increased.