Capacitive Load Discharge Circuit with Pre-Charged Capacitor
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Solution Overview
Problem
Existing DC-DC converters for piezo injection valves face challenges in fully discharging capacitive loads due to limited discharge current as the load voltage decreases, leading to residual charges and increased thermal stress, especially in high-energy and high-injection-rate applications.
Innovation Solution
Incorporating an additional capacitor connected in series with the capacitive load and a down-up converter, where the additional capacitor is charged to a voltage matching the load voltage, allowing it to contribute to the discharge current and facilitate complete discharge without high thermal stress, and using a filter circuit to reduce peak current demands on the additional capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional DC-DC converter is used to discharge the capacitive load, then the discharge process is simple, but the discharge current becomes limited as the load voltage decreases, preventing complete discharge and leaving residual charges
Solution Approach 1:
The patent applies preliminary action by pre-charging an additional capacitor to a voltage matching the load voltage before the discharge process. This additional capacitor then contributes to the discharge current, enabling complete discharge of the load even when the load voltage becomes very low. The pre-charged capacitor acts as a supplemental energy source that maintains discharge capability throughout the entire discharge range.
2Reliability
If the discharge current is increased to fully discharge the load, then complete discharge is achieved, but thermal stress increases significantly
Solution Approach 1:
The patent introduces an additional capacitor as an intermediary element that mediates the discharge process. This capacitor shares the discharge current burden with the load, allowing the load to be fully discharged without requiring excessively high current that would cause thermal stress. The intermediary capacitor absorbs part of the stress and enables a more distributed, thermally-friendly discharge approach.
3Reliability
If an additional capacitor is added to enable complete discharge, then discharge performance improves, but device complexity increases
Solution Approach 1:
The additional capacitor in the patent serves multiple functions: it contributes to discharge current, enables complete discharge of the load, and can be recharged from the load in subsequent cycles. This multi-functionality justifies the added component, as it performs several critical roles that improve overall system reliability without requiring a completely complex circuit redesign.
4Productivity
If the converter operates in high-injection-rate applications, then productivity increases, but residual charges and thermal stress increase due to limited discharge capability
Solution Approach 1:
The patent enables continuous operation at high injection rates by ensuring complete discharge of the capacitive load in each cycle. The additional capacitor maintains discharge capability throughout the entire discharge range, preventing residual charges that would limit the speed and continuity of successive injection cycles. This continuous complete discharge capability supports sustained high-productivity 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
This configuration enables nearly complete discharge of the capacitive load down to 0 V with reduced thermal stress and efficient recovery of stored charge, minimizing power losses and extending the working range of the DC-DC converter.
Implementation Method 1
an additional capacitor CSHIFT, which is connected in series with the capacitive load CPIEZO and a down-up converter BUCK/BOOST, is charged with a voltage VSHIFT matching the load voltage
Implementation Method 2
using a filter circuit to reduce peak current demands on the additional capacitor
Data Source
AI summary
A capacitive load charging/discharging device, including a first capacitor, a down-up converter including a first and a second switching element connected across the first capacitor, wherein a connecting point of the switching elements is connected to a first output terminal of the converter through a main coil. The device further includes an output circuit with a capacitive load arranged between first and second output circuit terminals, which are connected to output terminals of the converter. A discharge circuit is formed with the output circuit, the main coil and the second switching element, including an additional capacitor which is connected to a charging circuit for charging to a specified voltage, wherein the polarity of the voltage corresponds to that of the load voltage in the charged state of the capacitive load.