Input Voltage Evaluation Circuit for AC/DC Type Detection
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Solution Overview
Problem
Existing methods for evaluating the input voltage of power supplies are either inaccurate due to capacitive dividers or require costly and large components to handle overvoltages, and cannot reliably distinguish between direct and alternating voltages.
Innovation Solution
A circuit arrangement and method that uses a differential amplifier, rectifier units with compensation diodes, and a mixing unit to generate output signals from which the voltage type and value can be determined, allowing for accurate and cost-effective evaluation of input voltage by analyzing frequency and threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate measuring circuit using primary-side reference potential is used to continuously measure input voltage, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The input voltage measurement function is integrated into the existing control circuit that regulates the power supply output. The control circuit performs dual functions: regulating output voltage and measuring input voltage, eliminating the need for a separate dedicated measuring circuit.
Solution Approach 2:
The control circuit uses its own internal resources (processing unit, existing signal paths) to perform input voltage measurement, rather than requiring external dedicated measurement hardware. The system measures what it needs using its own capabilities.
2Object-affected harmful factors
If Y capacitors are used for electromagnetic compatibility, then EMC performance is improved, but measurement accuracy deteriorates due to capacitive voltage divider formation
Solution Approach 1:
The measurement function is extracted from the problematic path that includes Y capacitors. By measuring through the rectifier unit's output voltage rather than directly at the input, the measurement path is separated from the capacitive divider formed by Y capacitors, eliminating the measurement error while preserving EMC protection.
Solution Approach 2:
The rectifier unit's output voltage serves as an intermediary measurement point. Instead of measuring directly at the input (where Y capacitors cause errors), the system measures the rectified voltage which correlates with input voltage but is not affected by the capacitive divider.
3Reliability
If rectifier units are designed to withstand high overvoltage values, then reliability under surge conditions is improved, but component cost and space requirement increase
Solution Approach 1:
The control circuit monitors input voltage continuously and can detect surge conditions before they damage components. By providing early warning and enabling preventive actions (such as shutting down or protecting sensitive components), the system protects against overvoltage without requiring all components to be rated for extreme surges.
Solution Approach 2:
The control circuit uses feedback from the rectifier unit's output voltage to monitor input voltage conditions. This feedback mechanism allows the system to respond to overvoltage conditions intelligently, protecting components through control actions rather than requiring all components to be oversized for surge protection.
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 precise and robust determination of input voltage type and value, even under disturbances, using less expensive components and reducing the risk of component overload, thus improving measurement accuracy and safety.
Implementation Method 1
a differential amplifier which converts the input voltage into a useful signal
Implementation Method 2
a first rectifier unit, by means of which the useful signal is rectified
Data Source
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AI summary
The invention relates to a circuit arrangement from which an input voltage (Ue) of a power supply (SV) or a switched-mode power supply (SV) is evaluated – i.e., a value of the input voltage (Ue) of the power supply (SV) is determined, and a specific voltage type of the input voltage (Ue) is identified. For this purpose, the circuit arrangement (ME) is configured such that the input voltage (Ue) of the power supply (SV) drops across the input side of the circuit arrangement (ME). The circuit arrangement (ME) comprises at least one differential amplifier (DIF) for converting the input voltage (Ue) into a useful signal (NS), which is rectified by a first rectifier unit (GL1) arranged at an output of the differential amplifier (DIF). A first compensation diode (K1) is assigned to the first rectifier unit (GL1) such that a forward voltage of the first rectifier unit (GL1) is compensated.The circuit arrangement further comprises an inverter (INV) which generates an inverted signal (negNS) from the input signal (NS). The inverted signal (negNS) is rectified by a second rectifier unit (GL2) connected to an output of the inverter (INV). This second rectifier unit (GL2) is equipped with a second compensation diode (K2) to compensate for the forward voltage of the second rectifier unit (GL2). The circuit arrangement also includes a mixer unit (MS) which generates a first output signal (AS1) from the rectified input signal (NS) and the rectified, inverted signal (negNS). A second output signal (AS2) and, by means of an associated method, a voltage type of the input voltage (Ue) can be derived from this first output signal (AS1).