Load-Selective Input Voltage Sensor for AC-DC Power Converters
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Solution Overview
Problem
Off-line power converters face challenges in measuring input voltage efficiently at light loads, leading to significant power consumption and potential damage from high voltages, as existing methods require continuous sensing to prevent damage, which is inefficient and costly.
Innovation Solution
A load-selective input voltage sensor is implemented, which enables voltage sensing only during specific periods, using a high voltage transistor to control current flow and a current mirror to represent the input voltage, reducing power consumption by limiting sensing to when necessary, and optionally using a switching voltage or discharging stray capacitance to prevent false readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous voltage sensing is implemented to prevent damage from high voltages, then reliability is improved, but power consumption increases significantly at light loads
Solution Approach 1:
The patent implements periodic voltage sensing by enabling the sensing circuit only during specific switching periods when the power converter operates at light load conditions. A load detection circuit monitors the operating state and activates the voltage sensing function only when needed, rather than continuously. This periodic activation significantly reduces power consumption at light loads while maintaining adequate protection through periodic monitoring of the input voltage.
Solution Approach 2:
The patent dynamically adjusts the voltage sensing operation based on the load conditions of the power converter. The sensing circuit is enabled or disabled according to the actual operating state, transitioning between active and inactive states. This dynamic control optimizes the balance between reliability (voltage protection) and power consumption by adapting the sensing activity to the current operational requirements.
2Measurement precision
If a potential divider is used to measure input voltage, then measurement precision is improved, but the number of components and device complexity increase
Solution Approach 1:
The patent extracts the voltage sensing function from a separate potential divider circuit and integrates it into the existing current mirror circuitry of the power converter. By utilizing the current mirror that already exists for other control functions, the patent eliminates the need for additional potential divider components, thereby reducing device complexity while maintaining measurement precision through the same voltage sampling mechanism.
Solution Approach 2:
The patent makes the current mirror circuit serve multiple functions: it continues to perform its original current copying function while simultaneously being used for voltage sensing. The same circuit elements that mirror currents are also used to sample and measure the input voltage, achieving multi-functionality that reduces the overall number of components needed in the system.
3Use of energy by moving object
If a small sensing current is used to reduce power consumption, then power usage is improved, but measurement precision deteriorates due to noise interference
Solution Approach 1:
The patent introduces an intermediary approach by using the existing voltage nodes and circuit structures within the power converter as mediation points for sensing. Rather than introducing a separate sensing path that would require additional current, the patent leverages the natural voltage points already present in the circuit, allowing measurement without requiring extra sensing current that could be affected by noise.
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 approach reduces power consumption and minimizes the risk of damage from excessive input voltage, especially at light loads, by selectively sensing the input voltage only when required, thereby enhancing the efficiency and reliability of power converters.
Implementation Method 1
a current that flows through a potential divider is representative of an input voltage to the power converter
Implementation Method 2
a current mirror to represent the input voltage
Data Source
AI summary
An ac-dc power converter controller includes a switch driver circuit coupled to generate a drive signal to control switching of a power switch to control a transfer of energy from an input of the power converter to an output of the power converter. An input sense circuit is coupled to receive an input sense signal representative of the input of a power converter. A sense enable circuit is coupled to generate a sense enable signal in response to the drive signal. The sense enable signal is coupled to control the input sense circuit to sense the input sense signal for an extended duration of time after the power switch turns OFF.