Bridge Circuit Current Detection Without Sense Resistor
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Solution Overview
Problem
Existing motor drivers consume unnecessary power and increase costs due to the need for a sense resistor for current detection, which also increases the number of parts in electronic apparatuses.
Innovation Solution
A circuit device with a bridge circuit, detection circuit, and control circuit that compares the on-current and on-resistance of transistors to control switching periods without a sense resistor, incorporating temperature compensation to maintain accurate switching despite temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sense resistor is provided for current detection, then current monitoring is achieved, but power consumption increases and the number of parts increases
Solution Approach 1:
The patent extracts the current detection function from the external sense resistor and relocates it to the internal transistor on-resistance. By using the on-resistance of transistors Q1-Q4 that are already present in the bridge circuit, the patent eliminates the need for a separate sense resistor, thereby reducing power consumption while maintaining current detection capability through voltage measurement across these internal resistances.
Solution Approach 2:
The patent makes the transistor on-resistance serve multiple functions: it acts as both the switching element resistance necessary for motor control and as the sensing element for current detection. This multi-functionality eliminates the need for dedicated sense resistors, reducing both power consumption and part count while achieving accurate current monitoring through the existing transistor structures.
2Measurement precision
If a sense resistor is provided for current detection, then current monitoring is achieved, but the number of parts increases
Solution Approach 1:
The patent extracts the current detection function from the external sense resistor and relocates it to the internal transistor on-resistance. By using the on-resistance of transistors Q1-Q4 that are already present in the bridge circuit, the patent eliminates the need for a separate sense resistor, thereby reducing power consumption while maintaining current detection capability through voltage measurement across these internal resistances.
Solution Approach 2:
The patent makes the transistor on-resistance serve multiple functions: it acts as both the switching element resistance necessary for motor control and as the sensing element for current detection. This multi-functionality eliminates the need for dedicated sense resistors, reducing both power consumption and part count while achieving accurate current monitoring through the existing transistor structures.
3Loss of energy
If transistor on-resistance is used for detection, then power consumption and part count are reduced, but temperature characteristics affect detection accuracy
Solution Approach 1:
The patent compensates for temperature-induced changes in transistor on-resistance by dynamically adjusting the reference voltage Vref based on detected temperature. As temperature increases and causes on-resistance to increase (affecting detection accuracy), the system modifies the reference voltage parameter to maintain accurate current detection thresholds, thereby preserving measurement precision despite temperature variations.
Solution Approach 2:
The patent implements a feedback mechanism where temperature is continuously monitored and used to adjust the reference voltage for current detection. This closed-loop approach ensures that temperature-induced variations in transistor on-resistance are compensated in real-time, maintaining detection accuracy while using the power-efficient internal resistance sensing method.
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 configuration reduces power consumption and part count by eliminating the sense resistor, while maintaining accurate motor control and overheating protection through temperature compensation.
Implementation Method 1
a detection circuit configured to compare a reference voltage and a detection voltage set using an on-current and an on-resistance of at least one of the high-side transistor and the low-side transistor
Implementation Method 2
the reference voltage may have a second temperature characteristic that compensates for a first temperature characteristic of the detection voltage, and the detection circuit may compare the detection voltage and the reference voltage having the second temperature characteristic
Data Source
AI summary
Provided is a circuit device in which reduction of power consumption, reduction of the number of parts, and the like can be realized by eliminating the need for a sense resistor. The circuit device includes a bridge circuit, and a control circuit configured to compare a reference voltage VR and a detection voltage V2 (V1) set using the on-current and the on-resistance of at least one of a low-side transistor and a high-side transistor, output a detection result, control switching on and off of transistors in the bridge circuit, and perform switching from a charge period to a decay period.