Switch Circuit Control for Load Current Reduction in DCM
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Solution Overview
Problem
Switch circuits, such as BUCK circuits, face challenges in reducing load current as they transition from continuous conduction mode (CCM) to discontinuous conduction mode (DCM) due to fixed switching cycles, preventing further reduction of duty ratio and load current.
Innovation Solution
A control circuit that acquires and compares the time between the falling edge of a turn-on signal of the second switch transistor and the rising edge of the first switch transistor's turn-on signal in the next duty cycle, adjusting the cycle of the first switch transistor's turn-on signal to a second fixed time when the first time is less than the first fixed time, and adjusting the sum of second time and first fixed time to achieve spread spectrum when the first time is more than the first fixed time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching cycle of the first switch transistor is fixed to achieve constant frequency operation, then the switch circuit operates stably in CCM, but the duty ratio cannot be further decreased when transitioning to DCM, preventing further reduction of load current
Solution Approach 1:
The patent applies dynamics by making the switching cycle of the first switch transistor variable rather than fixed. The control circuit dynamically adjusts the switching cycle based on the conduction state of the second switch transistor, transitioning from a fixed cycle in CCM to a variable cycle in DCM. This allows the duty ratio to continue decreasing in DCM mode, enabling further load current reduction while maintaining stable operation through adaptive cycle adjustment.
2Productivity
If the switching cycle is extended to reduce duty ratio in DCM, then load current can be reduced further, but the switch circuit may incorrectly operate in CCM or experience improper spread spectrum activation
Solution Approach 1:
The patent implements feedback by using the conduction state of the second switch transistor as a control signal to adjust the switching cycle of the first switch transistor. The control circuit detects whether the second transistor is conducting and uses this information to determine the appropriate switching cycle, ensuring the circuit maintains proper DCM operation and prevents incorrect CCM operation or improper spread spectrum activation while achieving further load current reduction.
Data Source
AI summary
The present invention provides a control method and a control circuit for a switch circuit and a corresponding switch circuit device. The control circuit comprises: an acquiring module, configured to acquire first time; a comparing module, connected with the acquiring module and configured to compare first time with first fixed time; and an adjusting module, connected with the comparing module. The adjusting module adjusts a cycle of a turn-on signal of a first switch transistor to second fixed time when the first time is less than the first fixed time. The adjusting module adjusts the sum of second time and the first fixed time to the second fixed time to achieve spread spectrum when the first time is more than the first fixed time. The control circuit for the switch circuit provided by the present invention is used for controlling the switch circuit for spread spectrum.