Switching Converter Dead-Time Reduction via Mode Detection
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Solution Overview
Problem
Switching converters face efficiency reduction due to dead-time and reverse-recovery issues, which occur when power switches are not properly timed, leading to short circuits and unwanted power dissipation.
Innovation Solution
A switching converter design that includes a mode detector and controller to identify operational modes of power switches, allowing the second power switch to be biased during a predetermined period when the first power switch is in saturation mode, thereby reducing dead-time and preventing reverse-recovery by ensuring the second power switch turns on before the switching node reaches a voltage that would forward bias its body diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead-time is introduced between switch on times to prevent short circuits, then reliability is improved, but efficiency deteriorates due to power loss during dead-time
Solution Approach 1:
The patent applies preliminary action by pre-biasing the second power switch with a predetermined voltage during the first period (when the first power switch is in linear mode) so that the second power switch is already in a state ready for conduction before the dead-time expires. This allows the second power switch to turn on immediately when needed during the second period (when the first power switch is in saturation mode), eliminating the traditional dead-time gap and preventing power loss while maintaining short circuit protection.
2Loss of energy
If power switches are switched off immediately to reduce dead-time, then efficiency is improved, but reverse-recovery issues occur causing unwanted power dissipation
Solution Approach 1:
The patent applies preliminary action by pre-biasing the second power switch during the first period before the switching node voltage reaches levels that would forward bias the body diode. This ensures that when the second power switch turns on during the second period, it does so in a controlled manner without causing reverse-recovery effects, thereby reducing power dissipation while avoiding harmful reverse-recovery phenomena.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the bias voltage applied to the second power switch based on the operating mode detected during the first period. The controller modifies the gate voltage parameter of the second power switch to optimize its conduction state, enabling it to turn on smoothly during the second period without triggering reverse-recovery in the body diode, thus eliminating unwanted power dissipation.
3Reliability
If dead-time is extended to ensure proper switch timing, then reliability is improved, but productivity deteriorates due to reduced switching frequency capability
Solution Approach 1:
The patent applies preliminary action by pre-biasing the second power switch during the first period, which allows the switching converter to operate with minimal or zero dead-time. This enables the system to achieve higher switching frequencies (improving productivity) while maintaining reliable switch timing through the mode detector and controller that coordinate the switching transitions based on the operational mode, thus resolving the contradiction between reliability and productivity.
Data Source
AI summary
A switching converter with reduced dead-time and without reverse-recovery is disclosed. The switching converter includes a first power switch coupled to a second power switch, a mode detector and a controller. The mode detector is adapted to detect a mode of operation of the first power switch and the second power switch, and to identify a first period during which the first power switch is turned on and operates in a linear mode while the second power switch is turned off. The controller is adapted to bias the second power switch with a predetermined voltage during the first period to turn on the second power switch during a second period. In the second period the first power switch is operating in a saturation mode.