DC-DC Converter Control Circuit for ACF and LLC Mode Adaptation
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Solution Overview
Problem
Conventional DC-DC converters require dedicated control devices for ACF and LLC resonant half bridge converters, limiting their application to a single operating mode and leading to unstable operation in light or heavy load situations.
Innovation Solution
A single control circuit capable of selectively controlling LLC resonant half bridge and ACF converters, featuring a mode selection section, soft start section, PWM comparison section, clock generation section, and latch section, which adapt to ACF or LLC operating modes by generating appropriate signals and frequencies to stabilize output voltage across varying loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dedicated control devices are used for ACF and LLC resonant half bridge converters, then each converter can be controlled in its specific operating mode, but the system requires multiple control devices and cannot adapt to varying load conditions
Solution Approach 1:
The control circuit is designed to perform multiple functions by selectively operating in different modes (ACF mode or LLC resonant half bridge mode) based on load conditions. The circuit includes mode selection logic that determines which operating mode to use, allowing a single control device to replace multiple dedicated control devices while maintaining the ability to control both converter types effectively.
2Reliability
If PWM control is used for ACF converter, then output voltage can be stabilized under heavy load, but the converter becomes unstable under light load conditions
Solution Approach 1:
The control circuit dynamically switches between operating modes based on load conditions. Under heavy load conditions, the circuit operates in ACF mode with PWM control for stable output voltage. Under light load conditions, it transitions to LLC resonant half bridge mode which provides better stability. The mode selection section continuously monitors load conditions and dynamically adjusts the operating mode to maintain optimal performance across all load ranges.
3Reliability
If PFM control is used for LLC resonant half bridge converter, then the converter operates efficiently at light load, but becomes unstable under heavy load conditions
Solution Approach 1:
The control circuit dynamically switches between operating modes based on load conditions. Under light load conditions, the circuit operates in LLC resonant half bridge mode with PFM control for efficient operation. Under heavy load conditions, it transitions to ACF mode with PWM control for stable output voltage. The mode selection section continuously monitors load conditions and dynamically adjusts the operating mode to maintain optimal performance across all load ranges.
Data Source
AI summary
A control circuit of a DC-DC converter is provided. A mode selection section selects an Active Clamp Forward (ACF) or a Logic Link Control (LLC) mode. A soft start section generates a soft start signal in the ACF and LLC modes. A PWM comparison section compares a current detection signal with a feedback signal, a feedback reference signal and the soft start signal in the ACF mode, and generates a PWM signal based on a comparison result. A selection section selects the PWM signal of the PWM comparison section in the ACF mode. A clock generation section generates a clock signal having a fixed frequency in the ACF mode, and generates a clock signal having a frequency based on an operating current and the soft start signal in the LLC mode. A latch section maintains the PWM signal in response to the clock signal in the ACF mode and maintains the clock signal in the LLC mode.