Vehicle HV-LV DC-DC Converter Current Saturation Control
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Solution Overview
Problem
Existing methods for supplying power from a high-voltage (HV) onboard electrical subsystem to a low-voltage (LV) subsystem in vehicles are inadequate, particularly when the HV source has limited power, leading to potential damage and inefficiencies due to circulating currents and transient loading.
Innovation Solution
Implementing an adjustable current saturation value in electrically isolated DC-DC voltage converters, adapting the current saturation based on input power and voltage thresholds, and resetting it to a standard value when the input voltage returns to nominal, to ensure stable power supply to the LV subsystem.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed standard value of current saturation Iout,max is used in the DC-DC voltage converter, then the device structure is simple, but the power supply reliability deteriorates when input voltage drops below nominal voltage
Solution Approach 1:
The current saturation value Iout,max is made dynamically adjustable based on the input voltage level. When Vin drops below the auxiliary voltage Vin,th, the controller automatically reduces Iout,max to a power-adapted value Iout,max|red calculated from the available input power Pin. This dynamic adaptation ensures reliable power supply under varying input conditions without requiring complex manual intervention.
Solution Approach 2:
The controller continuously monitors the input voltage Vin and available input power Pin, and uses this feedback to automatically adjust the current saturation value Iout,max. The feedback mechanism compares the measured Vin against the auxiliary voltage Vin,th threshold and accordingly modifies the current saturation to maintain stable power delivery to the LV subsystem, improving reliability through closed-loop control.
2Reliability
If the current saturation is increased to maintain power supply during voltage drops, then power supply stability improves, but circulating currents and transient loading increase causing potential damage
Solution Approach 1:
The controller changes the current saturation parameter Iout,max based on the input voltage condition. When Vin is below Vin,th, the current saturation is reduced to Iout,max|red = Pin / Vin,th, which limits the output current to a safe level that prevents circulating currents and excessive transient loading. This parameter adaptation maintains power supply stability while eliminating harmful effects.
Solution Approach 2:
The controller preemptively reduces the current saturation Iout,max when detecting low input voltage conditions, before harmful circulating currents can develop. By calculating the available input power Pin and setting Iout,max|red accordingly, the system prevents the occurrence of damaging transient loading and circulating currents rather than reacting to them after they occur.
3Object-affected harmful factors
If the current saturation is reduced to prevent circulating currents, then safety improves, but power delivery capability deteriorates when input voltage is nominal
Solution Approach 1:
The current saturation Iout,max is dynamically adjusted based on real-time input voltage conditions. When Vin returns to the nominal voltage Vin,nom, the controller automatically restores Iout,max to its standard value Iout,max|def, thereby recovering full power delivery capability. This dynamic switching between reduced and standard current saturation ensures both safety during voltage drops and optimal performance during normal operation.
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
Ensures reliable power delivery to the LV subsystem even with a low HV input voltage, reduces loading on electronics, and prevents damage by managing circulating currents, thereby enhancing supply security and efficiency.
Implementation Method 1
electrically isolated DC-DC voltage converter
Data Source
AI summary
A method for supplying power to a low-voltage (LV) onboard electrical subsystem of a vehicle from the high-voltage (HV) onboard electrical subsystem thereof via at least one DC voltage converter with an adjustable current saturation value, wherein an auxiliary voltage that is between a nominal voltage of the HV onboard electrical subsystem and a specified minimal input voltage is set; when an input voltage measured at the DC voltage converter falls below the value of the auxiliary voltage, an associated input power is determined; a power-adapted value of the current saturation is calculated on the basis of the previously determined input power, and is set instead of a standard value of the current saturation; and the current saturation is reset to the standard value only when the input voltage again reaches the nominal voltage of the HV onboard electrical subsystem.