Power Supply Bypass Switches With Series Impedance Current Sharing
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Solution Overview
Problem
Current power supply assemblies with parallel connected controllable semiconductor switches face issues with current sharing due to the negative temperature coefficient of resistance, leading to uneven current distribution and potential overheating.
Innovation Solution
A series impedance system is introduced to provide a balancing voltage drop for each semiconductor switch, compensating for current imbalances and maintaining current below a safe operating maximum by using series impedance members connected in series with each switch unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parallel connected controllable semiconductor switches are used in the by-pass switch system, then the power supply assembly can provide uninterrupted power supply with energy saving capability, but current sharing between the parallel switches becomes unbalanced due to negative temperature coefficient of resistance
Solution Approach 1:
The patent applies local quality by introducing individual series impedance members (resistors or inductors) connected in series with each controllable semiconductor switch. These local impedance elements create voltage drops that compensate for the uneven current distribution caused by the negative temperature coefficient of the switches, thereby balancing the current sharing locally at each switch while maintaining the overall uninterruptible power supply function.
2Productivity
If a controllable semiconductor switch with lower forward conduction voltage conducts more current, then the immediate current sharing improves, but the switch gets hotter and conducts even larger current share due to negative temperature coefficient of resistance
Solution Approach 1:
The patent applies preliminary anti-action by introducing series impedance members that create opposing voltage drops before the temperature-induced current imbalance becomes severe. The impedance members generate voltage drops proportional to the current through each switch, which counteracts the tendency of lower-voltage switches to draw excessive current and overheat, thereby preventing the positive feedback loop between temperature and current.
3Stability of the object's composition
If the series impedance system is introduced to balance current distribution, then current sharing between switches is improved, but the device complexity increases due to additional series impedance members
Solution Approach 1:
The patent applies parameter changes by carefully selecting the impedance values of the series impedance members to achieve optimal current balancing with minimal component values. By adjusting the impedance parameters (resistance or inductance values) to be small but sufficient for balancing, the patent achieves current distribution uniformity while minimizing the impact on overall system complexity and power 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
The series impedance system effectively balances current distribution among parallel connected switches, preventing overheating and ensuring predictable operation by maintaining current within safe limits.
Implementation Method 1
a series impedance system adapted to provide a balancing voltage drop for each of the parallel connected controllable semiconductor switches
Implementation Method 2
The balancing voltage drop automatically increases when a current through the controllable semiconductor switch increases
Implementation Method 3
Controllable semiconductor switches typically used in the by-pass switch systems are naturally commutated and have a negative temperature coefficient of resistance
Data Source
AI summary
A power supply assembly including a primary source connection, a secondary source connection, a load connection, a primary current supply route, a supply switch system, and a converter system. The supply switch system is electrically located in the primary current supply route, and adapted for disconnecting the primary source connection from the load connection, the supply switch system including a plurality of supply switch units connected in parallel, each of the supply switch units including a controllable semiconductor switch. The power supply assembly includes a series impedance system having at least one series impedance member, and adapted to provide a balancing voltage drop for each of the parallel connected supply switch units of the supply switch system, wherein the balancing voltage drop is in series with a corresponding supply switch unit.