Series-Connected Bridge Switches Voltage Balancing
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Solution Overview
Problem
Existing high-power and high-voltage series-connected power devices face challenges in balanced static and dynamic voltage sharing due to parameter differences and gate signal delays, leading to inefficiencies in traditional snubber, gate control, and voltage clamping circuits, which result in increased losses and complexity.
Innovation Solution
A bridge circuit with series-connected switches and a control method that utilizes a voltage sensing circuit and control circuit to manage clamping capacitors during dead times, allowing freewheeling current to discharge capacitors without static resistance, reducing power loss and maintaining switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive snubber circuits are used to balance voltage of series-connected power devices, then voltage sharing is improved, but snubber loss increases and switching speed reduces
Solution Approach 1:
The patent introduces an auxiliary switch as an intermediary component connected in parallel with each series-connected power device. This auxiliary switch acts as a mediator that selectively connects or disconnects the snubber capacitor during different switching phases, enabling voltage balancing during dead time while preventing continuous energy dissipation through the snubber circuit.
Solution Approach 2:
The patent implements periodic voltage balancing by activating the auxiliary switch only during the dead time period of each switching cycle. This periodic action allows the snubber capacitor to charge during dead time and then discharge through the freewheeling diode in the next conduction phase, achieving voltage balancing without continuous energy loss.
2Reliability
If passive snubber circuits are used to balance voltage of series-connected power devices, then voltage sharing is improved, but device volume increases
Solution Approach 1:
The patent transforms the static snubber circuit into a dynamic configuration by introducing the auxiliary switch. The snubber capacitor is dynamically connected only when needed (during dead time) and disconnected during normal operation, reducing the overall circuit volume requirement while maintaining voltage balancing functionality.
3Reliability
If voltage clamping circuits with resistors are used to balance voltage, then voltage sharing is improved, but power loss increases
Solution Approach 1:
The patent converts the harmful effect of excess energy in the snubber capacitor into a beneficial voltage balancing mechanism. During dead time, the snubber capacitor charges to the voltage difference between series-connected devices. In the subsequent conduction phase, this charged capacitor discharges through the freewheeling diode, transferring energy back to the circuit and balancing voltages without continuous resistor dissipation.
Data Source
AI summary
A bridge circuit with series-connected switches and associated control method. The bridge circuit has a first bridge arm and a second bridge arm coupled to a common node, the first bridge arm has a plurality of series-connected first main switches, each first main switch is coupled in parallel with an auxiliary module, each first auxiliary module has a clamping capacitor and an auxiliary switch, the first bridge arm receives a first main switch signal to control the plurality of series-connected first main switches, the second bridge arm receives a second main switch signal, the control method is sensing voltages of the clamping capacitors in the first bridge arm, correspondingly generating voltage sensing signals, and turning on at least one auxiliary switch for a predetermined time during a dead time according to a sorting result of the voltage sensing signals.