Buck Switch Protection Circuit for High-Frequency DC-DC Converters
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Solution Overview
Problem
The increasing switching frequency in DC-DC converters leads to switching loss and overheating, reducing power efficiency and necessitating a lightweight and compact design.
Innovation Solution
A protection circuit is introduced for the DC-DC converter, comprising a first and second protection capacitor, a protection inductor, and a protection diode, which reduces voltage stress on the buck switch by supplying a protection voltage between the nodes, thereby minimizing switching loss without additional on-off control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switching frequency of the DC-DC converter is increased to reduce weight and size, then the converter becomes more compact, but the switching loss increases and power efficiency reduces
Solution Approach 1:
A protection circuit is introduced as an intermediary component between the input voltage source and the buck switch. This circuit includes a protection capacitor connected in parallel with the buck switch and a protection diode connected in series with the buck switch. The protection circuit mediates the voltage stress on the buck switch by providing an alternative current path through the protection diode and capacitor, thereby reducing the voltage spike and switching loss without requiring changes to the main switching frequency
Solution Approach 2:
The protection capacitor is pre-charged to a voltage level that cushions the voltage stress on the buck switch before switching occurs. When the buck switch turns off, the protection capacitor provides a pre-established voltage buffer that prevents excessive voltage spikes, and the protection diode conducts to discharge this capacitor through a controlled path, thereby cushioning the impact before it can cause damage or excessive loss
2Weight of moving object
If the switching frequency is increased to achieve lightweight design, then the converter weight reduces, but the converter overheats due to increased switching loss
Solution Approach 1:
The protection circuit acts as a thermal management intermediary by reducing switching loss through the protection diode and capacitor combination. This intermediary structure provides a controlled discharge path that limits the energy dissipated as heat during switching transitions, thereby managing temperature without affecting the high switching frequency operation that enables lightweight design
Solution Approach 2:
The protection circuit converts the harmful effect of voltage spikes and switching loss into a beneficial controlled discharge mechanism. The protection diode, which would normally be a source of forward voltage drop, is utilized to provide a controlled current path that dissipates energy in a manageable way, transforming the potential harm of high-frequency switching into a beneficial thermal management solution
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
This solution allows for reduced switching loss, enabling higher switching frequencies and a lightweight, compact DC-DC converter design.
Implementation Method 1
a first protection capacitor C P1 connected between the first node N 1 and a second node N 2, and a second protection capacitor C P2 connected between a third node N 3 and ground
Implementation Method 2
a protection inductor L P connected between the second node N 2 and the third node N 3
Implementation Method 3
a protection diode D P connected between the first node N 1 and the third node N 3
Data Source
Figure 1
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AI summary
A protection circuit according to the present disclosure is for a direct current (DC)-DC converter including a buck switch connected between a voltage input terminal and a first node, the buck switch being controlled by a switching cycle and a duty cycle of a switching signal; a buck inductor connected between the first node and a voltage output terminal; a buck capacitor connected between the voltage output terminal and a ground; and a buck diode connected between a second node and the ground. The protection circuit is connected to the first node, the second node and the ground. When the buck switch is switched between an On state and an OFF state according to the switching signal, the protection circuit is configured to supply a protection voltage between the first node and the ground so that voltage stress of the buck switch is smaller than an input voltage supplied between the voltage input terminal and the ground.