Offline Power Converter Multiplier for Terminal Reduction
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Solution Overview
Problem
Conventional power factor controllers for offline converters require additional input terminals to sense line voltage for on-time control and protection functions, increasing the cost of both the power factor controller chip and the circuit board.
Innovation Solution
The integration of a line sensing multiplier within the power factor controller that forms the product of the line voltage and the error signal without using an external sense signal, allowing for line voltage sensing through the duty cycle of the transistor drive signal, thereby eliminating the need for an additional input terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional input terminal is used to sense line voltage for on-time control and protection functions, then the power factor controller can implement voltage feed-forward and protection functions, but the cost of the power factor controller chip and circuit board increases
Solution Approach 1:
The patent combines the line voltage sensing function with the existing error signal terminal by using the duty cycle of the transistor drive signal as an indirect measure of line voltage. This merging eliminates the need for a separate line voltage sensing terminal while maintaining the protection and feed-forward functions that depend on line voltage information.
Solution Approach 2:
The system uses its own internal operating parameters (the duty cycle of the transistor drive signal) to infer line voltage conditions. By monitoring how the transistor is being controlled during normal operation, the controller can determine line voltage levels without requiring external sensing hardware, making the system self-sufficient for voltage sensing.
2Measurement precision
If an additional input terminal is used to sense line voltage, then accurate line voltage sensing can be achieved, but the manufacturing cost increases
Solution Approach 1:
The controller uses its own internal operating state (transistor duty cycle) to determine line voltage, eliminating the need for external sensing components. This self-service approach reduces component count and manufacturing cost while maintaining adequate measurement precision for protection and control functions.
Solution Approach 2:
The patent changes the sensing parameter from direct voltage measurement to indirect duty cycle measurement. By monitoring the duty cycle parameter that naturally varies with line voltage during normal operation, the system achieves sufficient measurement precision without requiring additional expensive sensing hardware.
3Device complexity
If the duty cycle of transistor drive signal is used to sense line voltage, then the terminal count is reduced, but the sensing method becomes more indirect
Solution Approach 1:
The duty cycle of the transistor drive signal serves as an intermediary parameter that correlates with line voltage. Instead of measuring line voltage directly, the system measures the duty cycle (which is already being generated for normal operation) and uses it as a proxy for line voltage sensing, simplifying the overall sensing architecture.
Data Source
AI summary
An integrated circuit power factor controller includes a feedback input terminal for receiving a feedback signal representative of an output voltage, a control terminal for receiving an error signal and adapted to be coupled to a compensation network, a drive terminal for providing a drive signal and adapted to be coupled to a transistor, and a pulse width modulator. The pulse width modulator is coupled to the feedback input terminal, the control terminal, and the drive terminal, and provides the drive signal having a duty cycle formed in response to the feedback signal. The pulse width modulator includes a line sensing multiplier having a first input for receiving the error signal, a second input for receiving the drive signal, and an output for providing a multiplied signal, and the pulse width modulator further provides the drive signal in response to the multiplied signal.