Switching Voltage Regulator Input Sensing via Level Shifting Resistors
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Solution Overview
Problem
Conventional switching voltage regulators require complex and costly external circuitry to accurately sense input current and voltage, which increases complexity and cost, and may exceed the maximum voltage ratings of the controller.
Innovation Solution
Incorporating a low ohmic shunt resistor in series with the input power rail and high ohmic level shifting resistors connected to sense pins, allowing the controller to sense input current and voltage internally without external amplifiers, by shifting the voltage across the shunt resistor to a level within the controller's voltage ratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external amplifier and high-side shunt resistor are used to sense input current, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the sensing function from external circuitry and integrates it into the controller's internal sense pins. The shunt resistor remains external but its sensing function is coupled to internal circuitry through level-shifting resistors, eliminating the need for external amplifiers and high-side current sensors.
Solution Approach 2:
The level-shifting resistors act as intermediaries between the shunt resistor and the controller's sense pins. They transfer the current sensing information while adapting the voltage level to match the controller's input requirements, enabling accurate sensing without external amplification.
2Measurement precision
If voltage divider is used to sense input voltage, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The level-shifting resistors serve dual functions: they enable current sensing by providing a voltage drop proportional to shunt current, and simultaneously enable voltage sensing by providing a reference path for the input voltage measurement through the same sense pin infrastructure.
Solution Approach 2:
The patent merges current sensing and voltage sensing functions into a unified circuit topology using the same shunt resistor and level-shifting resistors for both measurements, eliminating the need for separate voltage divider circuitry.
3Measurement precision
If direct sensing of input current and voltage is implemented, then measurement precision is improved, but the controller voltage rating is exceeded
Solution Approach 1:
The level-shifting resistors serve as voltage-level intermediaries, scaling down the high input voltage and shunt voltage to safe levels that match the controller's sense pin voltage ratings while preserving the proportional relationship needed for accurate measurement.
Solution Approach 2:
The circuit transforms the voltage parameters through the level-shifting resistors, changing the voltage level from potentially dangerous high voltages to safe low voltages suitable for the controller's internal circuitry, while maintaining the measurement accuracy through proportional relationships.
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 minimizes regulator complexity and cost by enabling internal sensing of input current and voltage, maintaining accuracy while avoiding voltage rating exceedance, with minimal power loss and efficient operation.
Implementation Method 1
sense the input current of the regulator as a function of the voltage across the shunt resistor
Implementation Method 2
shifting the voltage across the shunt resistor to a level within the controller's voltage ratings
Data Source
AI summary
A voltage regulator includes a power stage configured to produce an output voltage from an input voltage at an input voltage terminal, a shunt resistor connected in series between the input voltage terminal and the power stage, a first level shifting resistor connected in series between a first terminal of the shunt resistor and a first sense pin of the controller, and a second level shifting resistor connected in series between a second terminal of the shunt resistor and a second sense pin of the controller. The input current of the regulator is sensed as a function of the voltage across the shunt resistor, as shifted down by the level shifting resistors and measured across the sense pins. The input voltage of the regulator is sensed as a function of the current flowing through either one of the level shifting resistors, as measured at one of the sense pins.