AC Leakage Current Reduction Circuit for Solid-State Switches
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Solution Overview
Problem
Solid-state AC switches experience undesirable leakage currents due to parasitic capacitances that charge and discharge during AC waveform half-cycles, even when the switching devices are turned Off, leading to current flow and potential device damage.
Innovation Solution
A leakage reduction circuit is introduced that applies a positive bias voltage across the controlled terminals of solid-state switching devices when they are Off, maintaining a minimum voltage and preventing the discharge of parasitic capacitances, thereby reducing leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid-state switching devices are turned Off to block AC power distribution, then power blocking capability is improved, but leakage current increases due to parasitic capacitance discharge
Solution Approach 1:
The leakage reduction circuit applies a bias voltage in advance to counteract the discharge of parasitic capacitances. By maintaining a voltage differential across the SSSDs before the AC waveform reaches zero-crossing, the circuit prevents the formation of leakage current spikes that would otherwise occur during the Off state.
Solution Approach 2:
The invention changes the voltage parameter across the controlled terminals of the SSSDs by introducing a bias voltage. This parameter change maintains a minimum voltage differential even when the SSSDs are Off, thereby altering the electrical conditions that cause parasitic capacitance discharge and reducing leakage current.
2Use of energy by moving object
If parasitic capacitances are allowed to charge during AC half-cycles, then energy storage occurs, but discharge during zero-crossing causes leakage current
Solution Approach 1:
The invention converts the harmful discharge of parasitic capacitances into a beneficial effect by using the leakage reduction circuit to control the discharge process. The bias voltage manages the energy release from parasitic capacitances in a controlled manner, preventing harmful leakage current spikes while allowing the natural charge/discharge cycle to occur.
3Object-generated harmful factors
If a bias voltage is applied across controlled terminals of SSSDs, then leakage current is reduced, but additional circuit complexity is introduced
Solution Approach 1:
The leakage reduction circuit acts as an intermediary between the AC power source and the SSSDs. It introduces a bias voltage through additional circuit elements (such as voltage sources, resistors, or capacitors) that mediate the electrical conditions across the SSSD controlled terminals, reducing leakage current while adding controlled complexity to achieve the desired performance.
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 effectively minimizes leakage current spikes from approximately twenty milliamps to less than five milliamps, ensuring reliable operation and preventing potential device damage by maintaining a minimum voltage across the controlled terminals.
Implementation Method 1
This is a result of parasitic capacitances associated with each SSSD that charge/discharge during the half-cycles of the AC waveform. For example, the junction capacitance associated with the SSSDs allow energy to be stored during a half-cycle of the AC waveform
Data Source
AI summary
A solid-state power distribution system having a first solid-state switching device (SSSD) and a second solid-state switching device (SSSD) for distributing power from an AC power source to a load includes a leakage current reduction circuit for reducing leakage current generated by the SSSDs when Off. When the first and second SSSDs are Off, the leakage current reduction circuit provides a positive bias voltage across controlled terminals of the first SSSD and a negative bias voltage across controlled terminals of the second SSSD.