Switching Power Supply Communication via Feedback Loop
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Solution Overview
Problem
Existing switching power supply systems require additional devices for communication between the primary and secondary sides of the transformer, increasing costs and complexity, and are limited by the working mode of the primary controller, which can be affected by oscillations caused by the secondary diode and parasitic capacitance.
Innovation Solution
A control method and circuit that uses a secondary MOS to generate a switching pulse signal in the Reset Time of an on/off cycle, coupling the signal through the transformer to the primary controller, allowing communication without extra devices and avoiding oscillations, thus enabling communication between the secondary and primary sides without additional hardware or mode limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If optical coupler or communication chip is added to realize communication between primary and secondary sides, then communication function is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing feedback loop FB serve dual purposes: both voltage feedback and communication signal transmission. The secondary controller utilizes the feedback loop to send communication signals to the primary controller without requiring separate communication channels, thereby eliminating the need for optical couplers or communication chips while maintaining communication functionality.
Solution Approach 2:
The system uses its own existing feedback mechanism to accomplish communication tasks. The feedback loop, which already exists for voltage regulation, is repurposed to carry communication signals, allowing the system to serve its communication needs through self-resource utilization rather than external additions.
2Device complexity
If communication is implemented in dead time using secondary diode oscillation, then no additional devices are required, but oscillation between inductor and parasitic capacitance interferes with signal detection
Solution Approach 1:
The patent extracts the communication signal generation from the problematic dead time period and relocates it to the Reset Time. By using the secondary MOS tube to generate signals during Reset Time instead of relying on secondary diode oscillation in dead time, the harmful oscillations between inductor and parasitic capacitance are eliminated while maintaining the ability to transmit communication signals through the feedback loop.
Solution Approach 2:
The patent changes the timing parameter for communication signal generation from dead time to Reset Time. This parameter change transforms the working conditions, allowing the secondary MOS tube to operate in a state that produces clean, detectable signals without the harmful oscillations that occur during dead time when the secondary diode is involved.
3Loss of information
If primary controller works in DCM mode to enable dead time communication, then communication is possible, but working mode flexibility is reduced
Solution Approach 1:
The patent performs preliminary action by generating communication signals during Reset Time before the dead time period. This advance signal generation during the Reset Time allows the primary controller to receive and process communication signals without needing to operate in DCM mode, thereby maintaining CCM mode operation and preserving working mode flexibility while still enabling communication.
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
This solution simplifies the power supply system by eliminating the need for extra communication devices, supports the secondary controller working in CCM mode, and allows clear detection of communication signals without oscillations, enhancing system reliability and efficiency.
Implementation Method 1
through an auxiliary winding of the transformer, coupling transiently varied signals of the voltage drop to a pin FB of the primary controller
Data Source
AI summary
Disclosed are a control method and a control circuit for a switching power supply, said switching power supply comprises a secondary side controller and a secondary side MOS transistor connected between a load and a secondary side winding of a transformer. The present invention is used for detecting a working state of the secondary side winding of a transformer and a type of a communication signal transmitted by a load, and for generating a switching pulse signal VG in a Reset Time interval of an on/off cycle according to the type of the communication signal; the primary side controller detects a variation amplitude of the transiently varied signal of the voltage drop at the pin feedback (FB) in the Reset Time interval; if the variation amplitude of the transiently varied signal is greater than a pre-set value ΔVref, the primary side controller judges that the signal is a communication signal, and records the communication signal.