QR Flyback Overpower Protection Without Auxiliary Winding
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Solution Overview
Problem
Existing QR flyback converters rely on an auxiliary transformer winding for input voltage sensing and overpower protection, which increases circuit complexity, cost, and power dissipation due to the need for separate voltage regulators and inaccurate power control.
Innovation Solution
Eliminating the transformer auxiliary winding by using a voltage attenuator, filter, transistors, buffer, and sample-and-hold circuits to sense input voltage and current, and a current sense circuit to provide accurate overpower protection and control, eliminating the need for separate voltage regulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an auxiliary transformer winding is used for input voltage sensing and overpower protection, then voltage sensing and protection functions are provided, but circuit complexity increases
Solution Approach 1:
The patent combines the voltage sensing and overpower protection functions into the existing transformer windings and controller circuitry. The input voltage is sensed by dividing the voltage across the switch using a voltage division ratio, and the same controller that manages switch operation also performs overpower protection by comparing sensed voltage against threshold values. This eliminates the need for separate auxiliary windings and dedicated protection circuits.
Solution Approach 2:
The controller circuit is designed to perform multiple functions: it controls the switching operation of the power switch, senses the input voltage through the existing transformer windings, and provides overpower protection. By making the controller universal and multi-functional, the patent eliminates the need for separate dedicated circuits for each function, thereby reducing overall circuit complexity.
2Measurement precision
If an auxiliary transformer winding and separate voltage regulators are used, then voltage sensing is provided, but power dissipation increases
Solution Approach 1:
The patent merges the voltage sensing function with the existing power transformer windings. Instead of using a separate auxiliary winding that would require its own regulation circuitry, the sensing is performed by measuring the voltage across the main power switch and dividing it by a known ratio. This approach eliminates the power dissipation associated with separate voltage regulators while maintaining sensing accuracy.
Solution Approach 2:
The system uses its own existing components (the power switch and transformer windings) to perform the voltage sensing function. The controller utilizes the voltage already present across the switch during operation, dividing it by a known ratio to obtain the input voltage information. This self-service approach eliminates the need for external power-consuming sensing circuits.
3Measurement precision
If an auxiliary transformer winding is used, then voltage sensing is provided, but manufacturing cost increases
Solution Approach 1:
The patent combines the voltage sensing function with the existing power transformer and switch, eliminating the need for separate auxiliary windings. This reduces the bill of materials and simplifies the manufacturing process, as fewer components need to be procured, assembled, and tested.
Solution Approach 2:
The patent extracts the voltage sensing function from the traditional auxiliary winding architecture and implements it through software-based processing in the controller. By taking out the sensing function from hardware and implementing it through calculation (dividing the switch voltage by a known ratio), the patent reduces component count and manufacturing complexity.
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
Reduces circuit complexity, cost, and power dissipation while ensuring accurate overpower protection and efficient power control in QR flyback converters.
Implementation Method 1
a voltage attenuator circuit having an attenuator input and an attenuator output. The attenuator input is coupled to a switch terminal
Implementation Method 2
A filter circuit has a filter input and a filter output, wherein the filter input is coupled to the attenuator output
Implementation Method 3
A sample-and-hold (S/H) circuit has a sample input, a sample control terminal and a sample output. The S/H circuit is configured to provide at the sample output a minimum ringing voltage of a signal from the switch terminal
Implementation Method 4
A second transistor has third and fourth current terminals and a second control terminal. The second transistor is matched to the first transistor
Data Source
AI summary
Described embodiments include a protection circuit having a voltage attenuator circuit with an input coupled to a switch terminal. A filter circuit has a filter input coupled to the output of the attenuator. A first transistor has a first current terminal coupled to a power supply terminal, and a first control terminal coupled to the filter output. A second transistor, which is matched to the first transistor, has a third current terminal coupled to the first current terminal, a second control terminal coupled to the first control terminal, and a fourth current terminal coupled to a first voltage sense terminal. A buffer circuit has a buffer input coupled to the attenuator output. A S/H circuit has a sample input coupled to the buffer output, and a sample output providing a minimum ringing voltage of a signal from the switch terminal.