Uninterruptible Power Supply Buck-Boost Circuit Topology
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Solution Overview
Problem
Conventional uninterruptible power supplies (UPS) face challenges in efficiently generating output DC voltages during both line and backup modes of operation, particularly in using high-voltage devices for buck-boost circuits, which lead to increased losses and costs, and may limit frequency operation.
Innovation Solution
A rectifier/boost converter circuit configuration that allows the use of lower voltage devices for buck-boost transistors by repositioning the buck-boost transistor between the diode and negative boost transistor, enabling the use of lower voltage IGBTs or MOSFETs, and employing controlled switches in series to derive negative DC voltage from a backup source during backup mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage devices are used for buck-boost transistors in conventional UPS, then the UPS can generate output DC voltages in both line and backup modes, but this leads to increased losses, increased costs, and limited frequency operation
Solution Approach 1:
The circuit is segmented into two distinct operational modes: line mode using a first buck-boost circuit with first buck-boost transistors, and backup mode using a second buck-boost circuit with second buck-boost transistors. This segmentation allows each circuit to be optimized for its specific voltage requirements, with the second circuit using lower-voltage devices appropriate for battery voltage levels.
Solution Approach 2:
The system dynamically switches between two different circuit configurations based on operational mode. A controller selectively activates the first buck-boost circuit during line mode and the second buck-boost circuit during backup mode, allowing the circuit topology and device voltage ratings to adapt to the specific operational requirements.
2Adaptability or versatility
If high-voltage devices are used for buck-boost transistors, then the UPS can operate in both line and backup modes, but this increases device costs
Solution Approach 1:
The UPS is divided into two separate buck-boost circuits, each designed with appropriate voltage-rated devices for its specific operating conditions. The first circuit handles line voltage input, while the second circuit handles battery voltage input, allowing each to use cost-effective devices matched to their voltage requirements.
Solution Approach 2:
The system changes operational parameters by switching between two distinct circuit configurations. During line mode, the first circuit with high-voltage devices is activated; during backup mode, the second circuit with lower-voltage, lower-cost devices is activated, optimizing cost while maintaining dual-mode capability.
3Reliability
If high-voltage devices are used for buck-boost transistors, then the UPS can provide regulated power output, but this limits frequency operation
Solution Approach 1:
The system dynamically selects the appropriate buck-boost circuit based on operational mode, enabling higher frequency operation in backup mode where the second circuit with lower-voltage devices is used. This dynamic adaptation allows the UPS to achieve better frequency performance when operating from battery power.
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 reduces voltage stress on transistors, allowing for efficient power factor correction and AC output generation while minimizing losses and costs, and enabling higher frequency operations.
Implementation Method 1
a rectifier/boost converter circuit that transforms an input voltage to an output voltage
Implementation Method 2
in a backup mode of operation, negative DC voltages are derived from the backup voltage source using a current path from the backup voltage source through at least two controlled switches coupled in series
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
At least one aspect is directed to an uninterruptible power supply that includes a first input to receive a first input voltage from a first voltage source, a second input to receive a second input voltage from a second voltage source, and a boost circuit coupled to the first input and the second input. The boost circuit is configured to provide a positive output DC voltage and a negative output DC voltage derived from at least one of the first input voltage and the second input voltage. The uninterruptible power supply is configured such that in a back-up mode of operation, the negative output DC voltage is derived from the second input voltage using a circuit that includes at least two controlled switches coupled in series.