DC/DC Converter Inductor Current Sensing via Parasitic DCR
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Solution Overview
Problem
Existing DC/DC converters face inefficiencies in current sensing due to power loss in current sense resistors and potential damage to controllers from high output voltages during current sensing, particularly when using DCR resistance for current detection.
Innovation Solution
A DC/DC converter design incorporating a switch, inductor with parasitic DCR, two voltage dividers, and a controller, where a capacitor measures current by sensing voltage across it, with carefully selected resistor ratios to match time constants and reduce voltage feedback to the controller, allowing for safe and efficient current sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensing resistor is used to sense the current through the inductor, then the current feedback signal can be obtained, but power loss occurs on the current sense resistor
Solution Approach 1:
The patent extracts the current sensing function from a separate current sense resistor and utilizes the inductor's inherent parasitic DCR resistance instead. This eliminates the need for an additional sensing resistor, thereby removing the associated power loss while maintaining current sensing capability through the existing DCR element.
Solution Approach 2:
The inductor's parasitic DCR resistance, which is an unavoidable parasitic element, is repurposed to serve the dual function of inductance and current sensing. By making the DCR serve the sensing function, the system eliminates the need for a separate sensing resistor and its associated power loss.
2Loss of energy
If the inductor series resistance (DCR) is used as the current-sensing element with a resistor and capacitor network, then power loss is reduced, but high output voltage may damage the controller
Solution Approach 1:
The patent introduces a voltage divider network as an intermediary between the high-voltage current sensing node and the controller input. This voltage divider scales down the high voltage signal to a safe level for the controller while preserving the proportional relationship needed for accurate current sensing, thus protecting the controller from voltage damage.
Solution Approach 2:
The patent transforms the voltage level parameter of the sensing signal through the voltage divider network. By changing the voltage parameter from high (potentially damaging) to low (safe for controller), the system maintains sensing accuracy while eliminating the harmful high voltage effect on the controller.
3Measurement precision
If the resistor and capacitor network is coupled in parallel with the inductor for current sensing, then the current can be determined by sensing voltage across the capacitor, but the voltage feedback to the controller increases
Solution Approach 1:
The voltage divider acts as an intermediary that scales down the voltage feedback signal before it reaches the controller. This allows the system to maintain accurate current measurement capability while reducing the voltage feedback level to a safe and efficient range for the controller.
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 design enhances inductor current sensing capability, reduces power loss, and extends the range of output voltages while keeping the voltage feedback at a safe, low level, thereby protecting the controller and improving overall efficiency.
Implementation Method 1
A capacitor is coupled between the first voltage divider and the second voltage divider to measure the current through the inductor by sensing a voltage across the capacitor
Implementation Method 2
The current through the inductor can be determined by sensing the voltage across the capacitor
Implementation Method 3
The first voltage divider is coupled to the output node for generating a divided voltage of the output voltage
Implementation Method 4
The inductor having a parasitic direct current resistance is used for coupling the switch to an output node
Data Source
AI summary
A DC/DC converter for converting an input voltage to an output voltage comprises a switch, an inductor, two voltage dividers, a capacitor, and a controller. The switch coupled to the input voltage. The inductor having a parasitic direct current resistance is used for coupling the switch to an output node of the DC/DC converter so as to generate the output voltage at the output node. The first voltage divider is coupled to the output node for generating a divided voltage of the output voltage. The second voltage divider is coupled to the switch and ground. The capacitor coupled to the first voltage divider and the second divider to measure the current through the inductor by sensing a voltage across the capacitor. The controller coupled to the first switch for enabling and disenabling it so as to discontinuously providing power from the input voltage to the inductor.