Choke Current Timing in DC-DC Converters for Sensorless Control
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Solution Overview
Problem
Conventional zero current detection (ZCD) methods in active voltage converters require immediate reaction to zero crossings, placing high demands on control units and lacking closed-loop control, leading to computational challenges and hardware limitations.
Innovation Solution
A method that determines parameters characterizing current or voltage by measuring durations between zero crossings and vertices of the choke current, allowing for indirect control and reducing the need for direct zero crossing reactions, enabling plausibility checks and error corrections, and using simpler microcontrollers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional zero current detection (ZCD) method is used to detect zero crossing of current immediately, then control response speed is improved, but control unit computational burden increases and no time remains for plausibility check and error correction
Solution Approach 1:
The patent applies preliminary action by measuring the duration of the triangular choke current waveform in advance and using this pre-measured duration to calculate the average current. This eliminates the need for immediate computational response at zero crossing points, as the control unit already has the duration value stored and ready for calculation, thereby reducing real-time computational burden while maintaining fast response.
2Volume of moving object
If high switching frequencies are used to minimize installation size of passive components, then power density is improved, but control complexity and computational requirements increase
Solution Approach 1:
The patent applies self-service by utilizing the inherent triangular waveform characteristics of the choke current to automatically determine the average current through simple duration measurement and calculation. The system uses its own internal timing resources and the natural waveform properties rather than requiring complex external sensing or computation, thereby simplifying control complexity even at high switching frequencies.
3Productivity
If direct reaction to zero crossing is implemented, then control dynamics are improved, but no time remains for plausibility check and error correction of ZCD signal
Solution Approach 1:
The patent introduces an intermediary approach by using the duration measurement of the triangular waveform as a mediator between the physical zero crossing events and the control decisions. Instead of directly reacting to zero crossings, the system measures the overall duration and derives control information from this intermediate parameter, which allows time for validation and error checking while maintaining control effectiveness.
4Loss of energy
If conventional ZCD method is used, then zero voltage switching (ZVS) control is achieved, but switching frequency is not controllable and open-loop control is required
Solution Approach 1:
The patent implements feedback by calculating the average choke current from the measured duration and using this calculated average current as feedback to control the switching frequency and duty cycle. This closed-loop feedback mechanism enables controllable switching frequency while maintaining zero voltage switching, as the controller can adjust operating parameters based on the real-time average current information derived from duration measurements.
Data Source
AI summary
Method (100) for ascertaining a parameter (I_avg, I_N, I_P, V_c), wherein the parameter (I_avg, I_N, I_P, V_c) characterizes a current or a voltage in a circuit arrangement (200). The circuit arrangement (200) comprises an inductor (L) through which an alternating choke current (I_L) flows. The method comprises the steps of: ascertaining (120) at least one duration (TN1) between two zero crossings (N_−, N_+) of the choke current (I_L), or a duration (TNE1) between a zero crossing (N_−, N_+) and a vertex (E_−, E_+) of the choke current (I_L); ascertaining (130) the parameter (I_avg, I_N, I_P, V_c) as a function of the ascertained duration (TN1, TNE1).