Switching Power Supply Transistor Bridge Control
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Solution Overview
Problem
Switching power supplies, particularly those used in high-fidelity amplifiers, experience significant heating due to parasitic capacitance and 'hard-switching' phenomena, which limits their efficiency and lifespan.
Innovation Solution
A control unit dynamically alters the switching order of the midpoints between high and low values over time, introducing time offsets and varying dead times between transistor switches to optimize energy exchange and reduce heating, while maintaining balanced current flow through the transformer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed inductance is connected in series with the transformer primary to enable periodic energy exchange between parasitic capacitors and inductance, then simultaneous conduction is avoided, but excessive local heating remains
Solution Approach 1:
The patent applies dynamics by making the dead time variable rather than fixed. The control unit adjusts the dead time between switching operations of transistors in the same branch based on real-time operating conditions, allowing the system to adapt to varying energy exchange requirements and reduce localized heating while maintaining reliable operation.
Solution Approach 2:
The patent changes the parameter of dead time from a constant value to a variable parameter that can be adjusted dynamically. By modifying the dead time duration according to operating conditions, the system optimizes energy exchange between parasitic capacitors and inductance, reducing excessive heating while preventing simultaneous conduction.
2Reliability
If dead time is introduced between switching of transistors in the same branch to prevent simultaneous conduction, then reliability improves, but heating remains very high during frequent energy variations
Solution Approach 1:
The control unit dynamically adjusts the dead time duration based on the specific operating conditions and energy exchange requirements. This dynamic adjustment allows the system to maintain reliable operation by preventing simultaneous conduction while optimizing the energy transfer process to minimize heating during frequent energy variations.
Solution Approach 2:
The system employs feedback mechanisms where the control unit monitors operating conditions and adjusts dead time accordingly. This feedback loop ensures that dead time is optimized for each operating state, preventing simultaneous conduction while minimizing excessive heating during rapid energy transitions.
3Reliability
If dead time is applied to limit hard-switching phenomena, then transistor reliability improves, but energy dissipation increases due to frequent charging and discharging of parasitic capacitances
Solution Approach 1:
The patent changes the dead time parameter from fixed to variable, allowing optimization of the trade-off between reliability and energy loss. By adjusting dead time based on operating conditions, the system maintains transistor reliability while minimizing energy dissipation from parasitic capacitance charging and discharging.
Solution Approach 2:
This principle is not directly applicable to this patent as it deals with electrical switching rather than material porosity.
4Ease of operation
If the switching power supply operates with fixed switching parameters, then control simplicity is maintained, but heating becomes excessive during audio amplifier applications with rapid energy variations
Solution Approach 1:
The control unit introduces dynamic adjustment of switching parameters, specifically variable dead time, while maintaining overall system simplicity. This dynamic control allows the system to adapt to rapid energy variations in audio amplifier applications, reducing excessive heating without significantly complicating the control architecture.
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 approach reduces localized heating, enhances thermal distribution between branches, and optimizes the switching power supply's performance by minimizing voltage stress and optimizing current flow, leading to improved efficiency and extended lifespan.
Implementation Method 1
The transistors used in the switching arms of the switching power supply intrinsically comprise a parasitic capacitance between the drain and the source of each transistor
Implementation Method 2
an inductance connected in series with the winding of the primary of the transformer in order to enable a periodic exchange of energy between the parasitic capacitors of the transistors and this inductance
Data Source
AI summary
A switching power supply is provided which includes an input for an input current at an input voltage, a controlled transistor bridge having two branches each with two transistors, the two branches being connected in parallel to the input terminals, a transformer having a primary connected between the midpoints of the two branches formed between the transistors of each branch, an output for an output current connected to the terminals of a secondary circuit of the transformer, and a control unit for the transistors to alternately switch each of the midpoints between high and low values with a time offset between the switching times of the midpoint values. The control unit is also capable of ensuring that the time order for switching of the midpoints between the high and low values thereof varies over the course of time.