Three-Level Active PFC Circuit for Power-On Overvoltage Buffering
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Solution Overview
Problem
Household electrical appliances using three-phase power face safety issues due to overvoltage damage, which can lead to device failure and even fires, especially when power devices in rectifier circuits are short-circuited.
Innovation Solution
A three-phase power conversion circuit with a three-level active Power Factor Correction (PFC) unit and power-on units that include controllable switch modules. The control unit manages the switching of these modules to buffer devices during power-on, preventing overvoltage damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three-phase power is applied to household electrical appliances, then power supply safety is improved, but overvoltage damage can occur when power devices are short-circuited, leading to device failure or fires
Solution Approach 1:
The control unit delays the turn-on signal of the main power switch for a predetermined time period after power input is detected. This preliminary delay action allows the circuit to initialize safely before full power is applied, preventing overvoltage damage to the electrolytic capacitor and other components during power-on transient states
Solution Approach 2:
The circuit incorporates an RC circuit (resistor-capacitor combination) connected in parallel with the electrolytic capacitor. This cushioning circuit absorbs voltage spikes and limits inrush current during power-on, protecting the capacitor from overvoltage damage without requiring more expensive high-voltage-rated capacitors
2Ease of manufacture
If the withstand voltage of electrolytic capacitor is limited to 450V, then cost is reduced, but the capacitor cannot withstand the 620V direct current bus voltage, resulting in overvoltage damage
Solution Approach 1:
An RC circuit is introduced as an intermediary protective element between the high-voltage DC bus and the electrolytic capacitor. The resistor limits inrush current while the capacitor in the RC circuit absorbs voltage spikes, enabling the use of lower-voltage-rated (450V) electrolytic capacitors in a 620V system without compromising reliability
Solution Approach 2:
The control unit implements a delayed turn-on strategy where the main power switch is activated only after a predetermined time period following power input detection. This preliminary delay prevents the capacitor from being subjected to full bus voltage during the transient power-on state, allowing the use of lower-voltage-rated capacitors
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 improves the operational safety of the circuit, prevents device damage from overvoltage, and prolongs the service life of the household electrical appliance.
Implementation Method 1
at least two power-on units arranged corresponding to three-phase input terminals of the three-level active PFC unit, each of the at least two power-on units including a first controllable switch module and a second controllable switch module connected in parallel
Data Source
AI summary
Provided are a three-phase power conversion circuit for a household electrical appliance, a household electrical appliance, and a power-on control method for a household electrical appliance. The three-phase power conversion circuit includes a three-level active PFC unit, at least two power-on units, and a control unit. The three-phase power, subsequent to being converted by the three-level active PFC unit, obtains a first DC power and a second DC power to supply power to corresponding loads. The power-on unit is arranged at input terminals of the three-level active PFC unit to buffer a device in the three-level active PFC unit when the three-level active PFC unit is powered on. A first controllable switch module and a second controllable switch module in the power-on unit and the three-level active PFC unit are controlled by the control unit to complete buffering.