Inductive Current Sensing for Constant Peak Current in DC-DC Converters
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Solution Overview
Problem
Existing constant peak current circuits in DC-DC conversion apparatuses fail to maintain a constant peak value of inductor current when input voltages vary, leading to significant differences in peak current output due to propagation delays and input voltage-dependent offset currents.
Innovation Solution
An inductive current sensor with a sampling unit, voltage-voltage conversion unit, and input compensation unit is employed to generate a sensing voltage inversely proportional to the inductor current, with an input voltage compensation unit adjusting the initial voltage level to reduce propagation delay times, ensuring a constant peak current regardless of input voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional constant peak current circuit is used, then the circuit can operate with simple structure, but the peak value of inductor current varies significantly with different input voltages
Solution Approach 1:
The patent applies preliminary action by pre-charging the sampling capacitor to the input voltage level before the sensing operation begins. This is achieved through a pre-charge transistor that connects the sampling capacitor to the input voltage source during an initialization phase. By preparing the capacitor with the correct initial voltage corresponding to the input voltage level, the circuit eliminates the need for complex dynamic adjustment mechanisms during the actual current sensing operation, thus maintaining peak current consistency across different input voltages without significantly increasing overall circuit complexity.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the initial voltage level of the sampling capacitor based on the input voltage. The pre-charge transistor gate is controlled to enable charging when the input voltage exceeds a threshold, automatically adapting the capacitor's initial voltage to match the input voltage conditions. This parameter adjustment allows the sensing circuit to maintain accurate peak current detection across varying input voltages (e.g., 1.6V to 3.6V) without requiring complete circuit redesign for each voltage condition.
2Loss of time
If the sampling capacitor is not pre-charged to input voltage level, then the circuit operation is simpler, but the propagation delay increases and peak current varies with input voltage
Solution Approach 1:
The patent implements preliminary action by charging the sampling capacitor to the input voltage level before the current sensing operation begins. A pre-charge transistor is controlled by a gate signal that activates when the input voltage exceeds a threshold, ensuring the capacitor is properly initialized before measurement. This preliminary charging action significantly reduces the propagation delay during the actual sensing operation, as the capacitor starts from the correct voltage level rather than requiring gradual charging during the measurement phase.
Solution Approach 2:
The patent applies preliminary anti-action by preemptively counteracting the voltage difference that would otherwise cause propagation delay. By pre-charging the sampling capacitor to match the input voltage level, the circuit eliminates the voltage differential that would slow down the sensing operation. This anticipatory measure prevents the delay problem before it occurs, allowing the sensing circuit to respond immediately when the inductor current reaches the peak value, regardless of the input voltage level.
Data Source
AI summary
An inductive current sensor is used for a constant peak current circuit of a DC-DC conversion apparatus and has a sampling unit, a voltage-voltage conversion unit and an input voltage compensation unit. The sampling unit is used to receive a feedback voltage and an input voltage and generate a sampling voltage proportional to the feedback voltage accordingly, and the feedback voltage is related and inversely proportional to an inductor current by the DC-DC conversion apparatus. The voltage-voltage conversion unit is electrically connected to the sampling unit to receive the sampling voltage and the input voltage, and generate a sensing voltage inversely proportional to the sampling voltage accordingly. The input voltage compensation unit is electrically connected to the voltage-voltage conversion unit for receiving the input voltage to provide an initial voltage level of the sensing voltage, and the initial voltage level is proportional to the input voltage.