Isolated Switch Drive Circuit with Single-Transformer Power Transfer
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Solution Overview
Problem
Existing galvanically isolated switch drive circuits face challenges with high propagation delays and power efficiency due to large transformer sizes and leakage inductances, especially at low or high duty cycles, and require additional power supplies across isolation barriers, increasing complexity and cost.
Innovation Solution
A galvanically isolated switch drive circuit using a single magnetic coupling device with a compact transformer structure for both signal and power transfer, minimizing the volt-second product and being insensitive to transformer leakage inductances, with a control circuit capable of independent operation on the floating side and optional fault regulation, and employing a clock recovery circuit and synchronous finite state machine for robust control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional galvanically isolated switch drive circuits use large transformers for power transfer, then power transfer capability is improved, but propagation delay increases and transformer size increases
Solution Approach 1:
The patent segments the transformer operation into distinct phases: a first phase for signal transfer only (with power switch open) and a second phase for power transfer (with power switch closed). This temporal segmentation allows the transformer to be optimized for signal fidelity during the first phase while enabling power transfer during the second phase, thereby reducing propagation delay without sacrificing power transfer capability.
Solution Approach 2:
The control circuit performs preliminary action by opening the power switch before signal transfer and closing it after signal transfer completes. This preliminary configuration ensures that signal transfer occurs without the burden of power transfer requirements, minimizing propagation delay, while subsequent closure of the power switch enables the necessary power transfer to the floating side.
2Power
If traditional galvanically isolated switch drive circuits use large transformers, then power transfer is improved, but device complexity and cost increase
Solution Approach 1:
The transformer is designed to serve multiple functions: signal transfer, power transfer, and floating side power supply. By utilizing the same transformer and its secondary winding for both signal and power transfer operations, and by using the rectified power from the secondary winding to supply the floating side control circuit, the patent eliminates the need for separate power supply circuits and reduces overall device complexity while maintaining full power transfer capability.
Solution Approach 2:
The patent merges the signal transfer function and power transfer function into a single transformer structure. The primary winding handles both control signals and power input, while the secondary winding provides both isolated output signals and power to the floating side. This consolidation reduces the number of components, simplifies the circuit architecture, and lowers cost while achieving both signal isolation and power transfer.
3Power
If galvanically isolated switch drive circuits use additional power supplies across isolation barriers, then power availability is improved, but device complexity increases
Solution Approach 1:
The floating side control circuit serves itself by obtaining its operating power from the rectified output of the transformer's secondary winding. The same transformer that provides galvanic isolation and signal transfer also generates the power supply voltage for the floating side through rectification of the transferred power. This self-service approach eliminates the need for external power supplies on the floating side, reducing device complexity while ensuring adequate power availability.
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 achieves low-latency and high-efficiency signal transfer with reduced propagation delay, compact transformer integration, and independent floating side control, suitable for a wide range of switching frequencies including low frequencies and static operations, while maintaining power efficiency and reducing design complexity.
Implementation Method 1
The magnetic coupling device receives control signals from a primary side and delivers control signals to a floating side
Implementation Method 2
The magnetic coupling device receives control signals from a primary side and delivers control signals to a floating side
Data Source
AI summary
Switch drive circuits include galvanically isolated switch circuits with power transfer from the switch driver input side to the switch side. A switch drive circuit uses a single transformer to transfer control signals to a secondary side for control of the switch along with power to a secondary side circuit to drive the switch in response to the control signals. By detecting the control signal first before drawing current, the effects of leakage inductance in the transformer are reduced.