BLDC Power Supply Circuit Using Phase Current for DC Sensing
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Solution Overview
Problem
Current power supply control circuits for BLDC motors require shunt resistors to measure DC current consumption, leading to additional power consumption, heat dissipation, and complex circuitry, which hinders performance and increases PCB occupation.
Innovation Solution
A power supply control circuit that calculates DC current consumption based on phase current signals without using shunt resistors in the DC link, employing a shunt resistor for low-side phase current sensing, amplification, offset correction, and low-pass filtering to obtain the DC current consumption, and an alternative method using three shunt resistors for each phase with summation and filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shunt resistors are used to measure DC current consumption, then current measurement is achieved, but power consumption increases and heat dissipation occurs
Solution Approach 1:
The patent extracts the DC current measurement function from the traditional shunt resistor method and implements it through software calculation based on phase current signals. This removes the physical shunt resistor from the DC link, eliminating its power consumption and heat dissipation while preserving the measurement capability through mathematical computation of the relationship between phase currents and DC current.
Solution Approach 2:
The patent replaces the physical/mechanical measurement system (shunt resistor with voltage measurement) with a computational/electronic system. Instead of using a physical component to measure DC current directly, the system uses microcontroller-based calculation algorithms that process phase current signals to derive DC current consumption, thereby eliminating the need for power-dissipating physical measurement components.
2Measurement precision
If shunt resistors are used to measure DC current consumption, then current measurement is achieved, but heat dissipation increases
Solution Approach 1:
The patent removes the shunt resistor from the DC link circuit, extracting the measurement function and implementing it through software calculation. This eliminates the source of heat dissipation (the shunt resistor's I²R losses) while maintaining measurement accuracy through computational methods that calculate DC current from phase current signals.
Solution Approach 2:
The patent substitutes the thermal-generating physical measurement system with a computational system. The microcontroller calculates DC current consumption by processing phase current signals through algorithms, replacing the shunt resistor's physical measurement mechanism with mathematical computation, thereby eliminating heat generation associated with the physical resistor.
3Measurement precision
If additional shunt resistors are added to measure DC current, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing phase current measurement system multi-functional. The same phase current signals that are already being measured for motor control purposes are also used to calculate DC current consumption. This eliminates the need for separate DC current measurement circuitry, reducing device complexity while maintaining measurement capability through dual-use of existing measurement infrastructure.
Solution Approach 2:
The patent merges the DC current measurement function with the existing phase current measurement system. Instead of adding separate measurement circuits, the solution combines multiple measurement functions into a unified approach where phase current signals serve both motor control and DC current monitoring purposes, thereby reducing overall circuit complexity.
4Measurement precision
If shunt resistors are used in the DC link, then DC current measurement is achieved, but PCB occupation area increases
Solution Approach 1:
The patent extracts the DC current measurement function from the physical DC link circuit and relocates it to the computational domain. By removing the shunt resistor from the PCB circuit layout, the solution eliminates the space required for the resistor component, its mounting area, and associated high-current trace routing, thereby reducing PCB occupation area while preserving measurement capability through software-based calculation.
Solution Approach 2:
The patent substitutes the physical measurement infrastructure with a computational approach. The microcontroller-based calculation system requires minimal PCB space compared to the physical shunt resistor assembly, eliminating the need for large current-carrying traces and component mounting areas, thus significantly reducing overall PCB occupation area.
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 eliminates the need for shunt resistors, reducing power consumption, heat dissipation, and PCB space, while providing precise DC current measurements for improved motor control and overcurrent protection without introducing errors or acoustic noise.
Implementation Method 1
a shunt resistor Rshunt for phase current sensing having a voltage Vshunt that corresponds to a total phase current signal Ishunt of the three phase BLDC motor across the shunt resistor Rshunt
Implementation Method 2
an amplifier to amplify the voltage Vshunt
Implementation Method 3
an output voltage VO obtained from a low pass filter applied to the amplified voltage Vshunt from the amplifier
Data Source
AI summary
A power supply control circuit of a three-phase brushless DC (BLDC) motor is provided. The control circuit includes means for calculating the DC current consumption IS based on a phase current signal Ishunt of the BLDC motor, the means including a shunt resistor Rshunt, an amplifier and a low pass filter. The amplifier is configured to amplify a measured voltage Vshunt that corresponds to the current Ishunt across the resistor Rshunt and perform an offset correction. The low pass filter is configured to provide a filtered voltage VO of the voltage Vshunt. The DC current IS is calculated based on the voltage VO.