DC-DC Converter Mode Switching for Light-Load Efficiency
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Solution Overview
Problem
Existing DC-DC converters face challenges in accurately detecting light load states without using expensive ICs and in improving efficiency during long no-load states.
Innovation Solution
The DC-DC converter employs a control circuit with multiple control modes, including first intermittent control based on input current, hybrid control combining pulse width and intermittent control, and second intermittent control based on output voltage, allowing for efficient operation across varying load states without requiring high-cost current detection ICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse width control is used in light load state, then output voltage can be controlled, but pulse width becomes very narrow making accurate current detection difficult
Solution Approach 1:
The patent dynamically switches between different control modes (PWM mode and intermittent control mode) based on the detected load state. When the load is light and pulse width becomes very narrow, the system transitions to intermittent control mode where the switching element is operated intermittently rather than continuously, maintaining adequate pulse widths for accurate detection while still achieving light load operation.
Solution Approach 2:
The system changes the control parameter from continuous pulse width modulation to intermittent operation timing. By detecting the load state and switching control modes, the system adjusts the operational parameters of the switching element to maintain detectable pulse widths even in light load conditions, avoiding the need for expensive high-precision detection circuits.
2Productivity
If intermittent control based on input current is used, then light load detection is achieved, but additional current detection circuitry is required
Solution Approach 1:
The control circuit is designed to perform multiple functions: it detects the load state, determines when to switch between PWM and intermittent control modes, and controls the switching element operation. By integrating these functions into a single control circuit that can operate in different modes, the patent avoids adding separate dedicated current detection circuits while still achieving accurate light load detection and control.
3Loss of energy
If DC-DC converter operates in no-load state for long periods, then power saving is needed, but efficiency must be maintained
Solution Approach 1:
In intermittent control mode, the switching element is operated periodically rather than continuously during light load and no-load states. The control circuit intermittently activates the switching element to maintain output voltage while significantly reducing power consumption compared to continuous operation, thereby improving efficiency during extended no-load periods while maintaining system reliability.
Data Source
AI summary
A control circuit includes a first mode for thinning out pulses of a drive signal according to an input current, a hybrid mode combining pulse width control that controls a pulse width of the drive signal and intermittent control that thins out pulses of the drive signal, and a second mode for thinning out the pulses according to an output voltage. The control circuit selects the second mode when a duty ratio of the drive signal is a predetermined threshold or less, selects the hybrid mode when the duty ratio of the drive signal exceeds the predetermined threshold and the input voltage is a predetermined specified value or more, and selects the first mode when the duty ratio of the drive signal exceeds the predetermined threshold and the input voltage is less than the predetermined specified value.