DC/DC Converter Soft Start for Bus Capacitor Precharge
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Solution Overview
Problem
Existing DC/DC converters in vehicles require a precharge circuit to charge high-voltage bus capacitors, which reduces the reliability and increases costs of the power supply circuit.
Innovation Solution
A voltage conversion circuit with a soft start module and failure isolation module that converts low-voltage direct current into high-voltage direct current to charge the bus capacitor, eliminating the need for a precharge circuit and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a precharge circuit is disposed in the power supply circuit to charge the high-voltage bus capacitor, then the main relay can be protected from burning, but the reliability of the power supply circuit is reduced
Solution Approach 1:
The patent combines the precharge function with the DC/DC converter by integrating a first switch between the first battery and the output filter capacitor. This allows the DC/DC converter to perform both voltage conversion and precharging operations, eliminating the need for a separate precharge circuit and thereby improving reliability while reducing complexity.
Solution Approach 2:
The DC/DC converter is designed to serve multiple functions: it can convert voltage from high-voltage to low-voltage mode during normal operation, and switch to precharge mode by activating the first switch to charge the output filter capacitor. This multi-functionality removes the need for dedicated precharge circuitry.
2Reliability
If a precharge circuit is disposed in the power supply circuit, then the high-voltage bus capacitor can be charged before vehicle start, but costs of the power supply circuit are increased
Solution Approach 1:
The patent merges the precharge circuitry into the existing DC/DC converter structure by adding a first switch. This integration eliminates the need for separate precharge components (such as dedicated precharge resistors and switches), thereby reducing overall circuit costs while maintaining the protective function against relay burning.
3Power
If the DC/DC converter converts high-voltage direct current to low-voltage direct current, then power can be supplied to low-voltage components, but the output filter capacitor cannot charge the high-voltage bus capacitor when the vehicle is started
Solution Approach 1:
The patent implements dynamic operational modes in the DC/DC converter. The converter can switch between a first working mode (voltage conversion from high-voltage to low-voltage) and a second working mode (precharge by charging the output filter capacitor through the first switch). This dynamic adaptability allows the same circuit to fulfill both power conversion and precharge functions based on vehicle startup conditions.
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 solution enhances the reliability of the power supply circuit by eliminating the precharge circuit, reducing costs, and preventing damage to components while ensuring normal vehicle operation.
Implementation Method 1
a low-voltage direct current output by a battery on a low-voltage direct current side of a DC/DC converter may be converted into a high-voltage direct current by the voltage conversion circuit
Implementation Method 2
a rated voltage of the output filter capacitor is equal to a first preset voltage
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~4
AI summary
Embodiments of this application provide a voltage conversion circuit, a control method, a DC/DC converter and a device. The voltage conversion circuit includes a failure isolation module, a soft start module, and a voltage conversion module. The voltage conversion module includes an output filter capacitor. Both a first terminal of the failure isolation module and a first terminal of the soft start module are connected to a positive electrode of a first battery, both a second terminal of the failure isolation module and a second terminal of the soft start module are connected to a first terminal of the output filter capacitor, and a second terminal of the output filter capacitor is connected to a negative electrode of the first battery. The soft start module is configured to connect the first battery and the output filter capacitor, so that the first battery charges the output filter capacitor. The failure isolation module is turned on when the output filter capacitor is charged by the first battery and a voltage of the output filter capacitor is greater than or equal to a second preset voltage, so that the voltage conversion module converts a low-voltage direct current output by the first battery into a high-voltage direct current to charge a high-voltage bus capacitor. In the embodiments of this application, reliability of a power supply circuit on a vehicle is improved.