Low Voltage DC-DC Converter Ramp Signal Gradient Control
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Solution Overview
Problem
Low voltage DC-DC converters in eco-friendly vehicles face issues with current control response characteristics in low load environments, leading to slower current control, switching losses, output ripple deterioration, and noise due to a unified gradient of the ramp signal used for PWM generation.
Innovation Solution
The solution involves an apparatus and method that adjust the gradient of the ramp signal used for PWM generation in low voltage DC-DC converters, sharpening it for current discontinuous modes and slowing its adjustment in current continuous modes by using a reference current receiver, a ramp signal generator, and a comparator to improve control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a unified gradient of ramp signal is used for PWM generation, then the device complexity is reduced, but the current control response characteristics deteriorate in low load environments
Solution Approach 1:
The patent implements dynamic adjustment of the ramp signal gradient by switching between two different gradients (first gradient for current discontinuous mode, second gradient for current continuous mode). This dynamic adaptation allows the system to optimize current control response characteristics for different operating conditions, resolving the contradiction between simplified structure and reliable control performance.
Solution Approach 2:
The patent changes the gradient parameter of the ramp signal based on the operating mode (current discontinuous or current continuous). By adjusting this key parameter according to load conditions, the system achieves improved current control response characteristics without significantly increasing device complexity, as the gradient switching can be implemented through control logic.
2Manufacturing precision
If a unified gradient of ramp signal is used, then the manufacturing precision is simplified, but the switching performance deteriorates causing switching losses
Solution Approach 1:
The system dynamically selects between two ramp signal gradients based on the current operating mode. In current discontinuous mode, the first gradient enables zero voltage switching (ZVS), eliminating switching losses. This dynamic adaptation resolves the contradiction by optimizing switching performance for each operating condition while maintaining manufacturing simplicity through a unified dual-gradient approach.
Solution Approach 2:
By changing the ramp signal gradient parameter according to operating mode, the system achieves zero voltage switching in low load conditions, thereby eliminating switching losses. This parameter adaptation allows the system to maintain high switching efficiency across different operating conditions without complicating the manufacturing process.
3Device complexity
If a unified gradient of ramp signal is used, then the device structure is simplified, but the output ripple increases
Solution Approach 1:
The patent implements dynamic gradient adjustment of the ramp signal based on operating mode. In current discontinuous mode, the first gradient provides finer control resolution that reduces output voltage ripple. This dynamic adaptation allows the system to maintain low output ripple across different operating conditions while keeping the control structure relatively simple through gradient switching logic.
4Ease of operation
If a unified gradient of ramp signal is used, then the system is easier to operate, but noise is generated in core components
Solution Approach 1:
The system dynamically adjusts the ramp signal gradient based on operating conditions. By using the first gradient in current discontinuous mode, the system achieves smoother current transitions that reduce noise in core components like transformers and inductors. This dynamic adaptation maintains ease of operation through automated mode-based gradient selection while eliminating noise issues.
Data Source
AI summary
An apparatus for controlling a low voltage direct current (DC)-DC converter (LDC) for an eco-friendly vehicle includes a reference current receiver for receiving a reference current, a ramp signal generator for generating a ramp signal by overlapping an input current of the LDC, and a DC offset and a sawtooth wave for adjusting a gradient of the ramp signal, and a comparator for generating a pulse width modulation (PWM) signal using the reference current received by the reference current receiver and the ramp signal generated by the ramp signal generator.