PWM Controller Dual-Function Pin for Temperature and AC Line Detection
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Solution Overview
Problem
Conventional PWM controllers require a larger pin count and package size to integrate over-temperature and AC line brownout protection functions, leading to increased costs and board area, due to limited pin count.
Innovation Solution
A PWM controller design that utilizes a dual-function pin to detect temperature and AC line voltage, incorporating current sources, switches, sample-and-hold circuits, and detection circuits to provide both over-temperature and AC line brownout protection using a single pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate pins are used for temperature detection and AC line detection, then detection accuracy is improved, but pin count and package size increase
Solution Approach 1:
The patent makes the first detection pin perform multiple functions by time-division multiplexing. During the first time period, the pin detects temperature through the negative temperature coefficient resistor. During the second time period, the pin detects AC line voltage through the voltage division circuit. This allows one pin to replace what would traditionally require two separate pins, reducing package size while maintaining detection accuracy for both parameters
Solution Approach 2:
The patent implements periodic switching between temperature detection and AC line detection functions. The control circuit alternates between activating the temperature detection path (first switch closed, second switch open) and the AC line detection path (first switch open, second switch closed) in different time periods. This periodic action allows the single pin to accurately capture both temperature and AC line voltage information without interference, resolving the contradiction between using one pin versus two pins
2Device complexity
If a single pin is used for both temperature and AC line detection, then pin count is reduced, but detection reliability may deteriorate
Solution Approach 1:
The patent segments the detection process into distinct time periods and functional paths. The detection circuit is divided into a temperature detection path (with first switch and negative temperature coefficient resistor) and an AC line detection path (with second switch and voltage division resistors). By segmenting both the circuit paths and time periods, the patent ensures that each detection function has its own dedicated circuit elements, preventing signal interference and maintaining detection reliability even though a single pin is shared
Solution Approach 2:
The patent prepares both detection paths in advance with dedicated switches and circuit elements. Before each detection phase, the corresponding switch is closed to connect the appropriate sensing circuit to the pin. This preliminary preparation ensures that when detection is needed, the correct circuit is already connected and ready, avoiding any reliability issues that might arise from rapid switching or improper circuit configuration
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
Enables the detection of temperature and AC line voltage, as well as providing protection against over-temperature and brownout conditions, within a smaller pin count and package size, reducing costs and board area while maintaining effective protection.
Implementation Method 1
a negative-temperature-coefficient resistor 333, having one end coupled to the common contact and another end coupled to the dual-function pin
Data Source
AI summary
A PWM controller detecting temperature and AC line via a single pin and a power converter using the PWM controller, the PWM controller comprising: an output pin for providing a PWM signal; and a dual-function pin for receiving a temperature signal when the PWM signal is at a high level, and for receiving an AC line signal when the PWM signal is at a low level.