DC Power Supply Capacitor Balancing for Stable Load Drive
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Solution Overview
Problem
Conventional DC power-supply devices face challenges in suppressing voltage unbalance between capacitors, leading to unstable load drive and reduced capacitor lifespan when converting alternating current to direct current, especially with high voltage and power consumption inefficiencies.
Innovation Solution
A DC power-supply device is designed with a rectifier circuit, reactors, serially connected capacitors, and a control unit that synchronizes charging to balance voltages between capacitors based on alternating current phases, ensuring stable and efficient direct current supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If detection resistors are used to detect middle-point voltage for capacitor voltage balancing, then voltage unbalance detection is achieved, but power consumption increases and detection accuracy decreases due to resistance value unevenness
Solution Approach 1:
The patent replaces the resistor-based voltage division detection method with a capacitor-based detection method. Instead of using detection resistors to divide voltage and detect middle-point voltage, the invention uses the inherent capacitance of the series-connected capacitors themselves to detect voltage unbalance. This substitution eliminates the power consumption issue of detection resistors while maintaining detection accuracy.
Solution Approach 2:
The patent creates a detection mechanism that uses a copy of the existing capacitor structure rather than introducing separate detection components. By utilizing the capacitive properties of the series-connected capacitors themselves, the system can detect voltage unbalance without adding separate detection resistors, thereby avoiding both power consumption and accuracy degradation issues.
2Use of energy by moving object
If large-size resistors with high resistance are used to suppress power consumption, then power consumption decreases, but detection accuracy deteriorates due to decreased S/N ratio
Solution Approach 1:
The patent fundamentally replaces the resistor-based detection system with a capacitor-based detection system. This substitution allows the system to achieve both low power consumption and high detection accuracy simultaneously, as the capacitive detection method does not suffer from the S/N ratio degradation that plagues high-resistance resistor-based methods.
3Ease of operation
If capacitor voltage is detected for control, then control is executed, but control becomes unstable and capacitor voltage becomes vibrational when power-supply voltage is alternating current
Solution Approach 1:
The patent replaces capacitor voltage detection with middle-point voltage detection using capacitive coupling. This substitution provides inherent immunity to the pulsation components of alternating current power supply, as the middle-point voltage remains stable even when the input voltage amplitude varies. The capacitive coupling naturally filters out the high-frequency pulsations, providing stable detection signals for control execution.
4Loss of energy
If switching frequency is kept low to decrease switching loss, then efficiency increases, but voltage control precision may be affected
Solution Approach 1:
The patent uses a detection mechanism that copies the existing capacitor structure, allowing for accurate voltage unbalance detection without requiring high switching frequencies. The capacitive detection method provides sufficient signal quality even at low switching frequencies, maintaining voltage control precision while minimizing switching losses.
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 effectively suppresses voltage unbalance, enhances capacitor lifespan, and improves reliability by maintaining stable load drive and reducing power consumption.
Implementation Method 1
a rectifier circuit that rectifies the alternating current
Implementation Method 2
a reactor connected to an input side or an output side of the rectifier circuit
Implementation Method 3
a first capacitor and a second capacitor serially connected between output terminals to the load
Data Source
AI summary
To provide a DC power-supply device that can suppress voltage unbalance of a plurality of capacitors serially connected between both terminals of a load, achieve stable drive of the load and long life of the capacitors, and contribute to high reliability, in a configuration in which an alternating current is converted into a direct current and is supplied to a load, and a refrigeration-cycle application device including the DC power-supply device. The DC power-supply device includes a rectifier circuit, a reactor connected to an input or an output side of the rectifier circuit, a first capacitor and a second capacitor serially connected between output terminals to a load, a charging unit that selectively charges one or both of the first capacitor and the second capacitor, and further includes a control unit that controls the charging unit so that voltage unbalance between the first capacitor and the second capacitor is suppressed.