Switching Driver EMI Reduction via Auxiliary Switch Control
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Solution Overview
Problem
Switching drivers in class-D power amplifiers generate EMI effects and power ripple due to leakage currents and parasitic diode activation during dead-time, which affect output signals and increase electromagnetic interference.
Innovation Solution
The proposed switching driver incorporates high-side and low-side auxiliary switches, controlled by drivers that adjust their turn-on and turn-off velocities based on output end voltage slopes, reducing EMI and power ripple by managing the cut-off velocities of these auxiliary switches during dead-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the high-side switch and low-side switch are turned off during dead-time to avoid leakage current, then the risk of leakage current is reduced, but the output end voltage changes rapidly causing EMI effect and power ripple
Solution Approach 1:
The patent introduces an auxiliary switch as an intermediary component connected in parallel with the main switch. During dead-time, when the main switch is turned off, the auxiliary switch remains on to provide a continuous current path for the inductive load, preventing rapid voltage changes at the output end. This intermediary component resolves the contradiction by maintaining circuit continuity without allowing leakage current through the main switch.
Solution Approach 2:
The patent divides the switching function into two independent parts: the main switch for normal power switching operations and the auxiliary switch for dead-time current path management. This segmentation allows each switch to be optimized for its specific function - the main switch for efficient power transfer and the auxiliary switch for EMI reduction during dead-time periods.
2Stability of the object's composition
If the auxiliary switch cut-off velocity is increased to reduce power ripple, then the voltage stability is improved, but the switching speed requirements and complexity increase
Solution Approach 1:
The patent employs a feedback mechanism where the control circuit monitors the output end voltage and dynamically adjusts the auxiliary switch cut-off timing. When voltage ripple is detected, the feedback signal modifies the cut-off velocity of the auxiliary switch to suppress the ripple. This feedback-based approach achieves voltage stability without requiring overly complex switching control, as the system self-regulates based on actual output conditions.
Data Source
AI summary
A switching driver capable of reducing EMI effect and power ripple is disclosed. When the switching driver wants to increase the voltage of an output end, a non-overlapping signal generator controls a low-side driver to quickly turn off a low-side switch, and detects an ascending slope of the voltage of the output end to control a cut-off velocity of a low-side auxiliary switch. When the switching driver wants to decrease the voltage of the output end, the non-overlapping signal generator controls a high-side driver to quickly turn off a high-side switch, and detects a descending slope of the voltage of the output end to control a cut-off velocity of a high-side auxiliary switch. As the descending slope becomes higher, the cut-off velocity of the high-side auxiliary switch becomes slower. Accordingly, the switching driver can reduce EMI effect and power ripple operating in a dead-time.