Voltage Converter With Segmented MOSFET and IGBT Stages
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Solution Overview
Problem
Switched-mode voltage converters face high switching losses due to the output capacitance of MOSFETs at low output currents and high switching losses with IGBTs at low currents, necessitating a solution that minimizes losses across a wide range of output currents and powers.
Innovation Solution
A voltage converter design incorporating both unipolar and bipolar transistors in parallel stages, with a control circuit that dynamically adjusts the output current distribution between the stages, utilizing MOSFETs for low currents and IGBTs for high currents to optimize power delivery and minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If MOSFETs are used in converter stages, then low on-resistance is achieved, but high output capacitance causes high switching losses at low output currents
Solution Approach 1:
The converter is divided into multiple converter stages, each capable of operating independently. The control circuit dynamically selects which stage(s) to activate based on the output current level, thereby segmenting the operational range to optimize performance at different current levels.
Solution Approach 2:
The converter stage configuration is made dynamic through the control circuit that adjusts the number of active converter stages based on the output current. This allows the system to transition between different operational modes (single stage vs. multiple stages) to minimize losses at varying current levels.
2Loss of energy
If IGBTs are used in converter stages, then high output currents are supported, but higher losses occur at low currents compared to MOSFETs
Solution Approach 1:
The converter uses multiple converter stages that can be selectively activated. At low output currents, only one stage is active, allowing the use of MOSFETs for low losses. At high output currents, additional stages are activated to share the current load, enabling the use of IGBTs which are better suited for high current applications.
Solution Approach 2:
The system changes the operational parameters by adjusting the number of active converter stages based on the output current level. This parameter change allows optimization of the transistor type selection (MOSFET vs. IGBT) according to the current demands, minimizing losses across the entire operating range.
3Power
If multiple converter stages are operated in parallel to supply high output currents, then high power delivery is achieved, but control complexity increases
Solution Approach 1:
The control circuit dynamically adjusts the number of active converter stages based on the output current requirements. This dynamic control allows the system to scale the complexity of the control circuit according to the power level, activating additional stages only when high output power is needed.
Solution Approach 2:
The control circuit changes operational parameters by adjusting the duty cycle and selecting which converter stages to activate. This parameter adjustment allows efficient control of multiple parallel stages without requiring complex control logic, as the control strategy adapts to the current power demands.
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 switching losses by leveraging the advantages of MOSFETs at low currents and IGBTs at high currents, enabling efficient power conversion across a broad range of output currents and powers.
Implementation Method 1
Each time the MOSFET is switched off, electric charge is stored in the output capacitance. When a voltage converter or a converter stage is operated in the CCM, a current through the inductive storage element does not decrease to zero. The output capacitance of a MOSFET implemented in a converter that is operated in CCM causes high switching losses during turn on due to the energy stored in the output capacitance.
Implementation Method 2
Each converter stage includes at least one inductive storage element and a switch which controls a current flow through the inductive storage element.
Data Source
AI summary
A voltage converter includes a first converter stage including a unipolar transistor coupled to a first inductive storage element, where the first converter stage is configured to provide a first output power signal including a first output current. Also, the voltage converter includes a second converter stage including a bipolar transistor coupled to a second inductive storage element, where the second converter stage is configured to provide a second output power including a second output current, and where a third output current is a sum of the first output current and the second output current. Additionally, the voltage converter includes a control circuit configured to control a power converter including the first output current and the second output current, where the first output current is higher than the second output current when the third output current has a first range of output current.