DC-DC Converter Gate Driver Preventing MOSFET Self Turn-On
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Solution Overview
Problem
Non-insulated DC-DC converters experience self turn-on phenomena due to erroneous turn-on of low side MOSFETs, leading to reduced power efficiency, especially in systems with small power capacity where applying a negative voltage between the gate and source of the low side MOSFET is not feasible, and existing solutions like adding a capacitor reduce positive voltage during the ON period, increasing conduction loss.
Innovation Solution
A DC-DC converter design that includes a gate driver with a capacitor for generating negative voltage and specific switching elements to apply negative voltage between the gate and source of the low side MOSFET during the OFF period, preventing self turn-on and maintaining positive voltage during the ON period, thus reducing conduction loss and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor is added to the gate driver to apply negative voltage between gate and source of the low side MOSFET, then self turn-on is prevented, but the positive voltage during ON period is reduced causing increased conduction loss
Solution Approach 1:
The gate driver circuit is segmented into multiple switching elements (first through fifth switching elements) that independently control different aspects of gate voltage. The first and third switching elements control the positive voltage application, while the second, fourth, and fifth switching elements control the negative voltage generation and application. This segmentation allows simultaneous achievement of self turn-on prevention and conduction loss reduction by precisely controlling when negative voltage is applied only during OFF periods.
Solution Approach 2:
The gate driver applies negative voltage periodically only during the OFF period of the low side MOSFET through controlled switching. The switching elements are timed to generate negative voltage during dead time or OFF periods, and stop generating negative voltage during ON periods. This periodic action prevents self turn-on during critical moments while maintaining full positive voltage during conduction periods, thereby reducing conduction loss.
2Reliability
If a negative voltage is applied between gate and source of the low side MOSFET using a DC voltage source, then self turn-on is prevented, but the system becomes inapplicable to small power capacity converters
Solution Approach 1:
The gate driver circuit generates its own negative voltage internally using the fifth switching element and capacitor connected to the gate driving DC power source, eliminating the need for an external negative voltage source. This self-service approach makes the circuit adaptable to small power capacity systems where external voltage sources are impractical, while still achieving effective self turn-on prevention.
Solution Approach 2:
The circuit dynamically changes the voltage parameter at the gate terminal by switching between positive voltage (during ON period) and negative voltage (during OFF period). The fifth switching element controls the connection to the capacitor, enabling parameter change from 0V to negative voltage only when needed. This dynamic parameter change achieves self turn-on prevention while maintaining compatibility with small power capacity converters.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents self turn-on without increasing conduction loss, thereby enhancing power efficiency in DC-DC converters, particularly in systems with small power capacity.
Implementation Method 1
a capacitor for generating negative voltage
Data Source
AI summary
A DC-DC converter in which self turn-on can be prevented and can improve power efficiency. In a non-insulated DC-DC converter, self turn-on is prevented by applying a negative voltage between a gate and a source of a low side MOSFET by the use of a capacitor for generating negative voltage when the low side MOSFET is in an OFF state. Also, when the low side MOSFET is in an ON state due to the capacitor for generating negative voltage, a positive voltage applied between the gate and the source of the low side MOSFET does not drop from a voltage of a gate driving DC power source that is supplied from a gate power input terminal. Therefore, the power efficiency is improved.