Boost Converter Startup Control for Short-Circuit Detection
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Solution Overview
Problem
Conventional boost converters face issues with surge currents during power-up, which can damage electronic components, and require additional detection pins and result in power loss, reducing system efficiency.
Innovation Solution
A switching power supply with a bus protection switch and a diode configuration that performs short-circuit detection without additional pins, using a buck converter to gradually increase output voltage during startup, eliminating the need for bus detection resistors and differential sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bus sensing resistor and differential sampling pins are used for short-circuit detection, then short-circuit protection is achieved, but the device complexity increases and power loss occurs
Solution Approach 1:
The patent extracts the short-circuit detection function from the traditional bus sensing resistor and differential sampling approach, relocating it to the bootstrap capacitor voltage monitoring mechanism. This eliminates the need for separate detection pins and resistors, reducing device complexity while maintaining protection capability.
Solution Approach 2:
The bootstrap capacitor serves multiple functions: it provides gate drive voltage for the high-side switch and simultaneously acts as the detection element for short-circuit protection. By monitoring its voltage, the system achieves both operational control and safety detection without additional components.
2Reliability
If a bus sensing resistor is used for short-circuit detection, then short-circuit protection is achieved, but power loss increases
Solution Approach 1:
The patent removes the bus sensing resistor from the circuit, eliminating the source of continuous power loss. Short-circuit detection is achieved instead by monitoring the bootstrap capacitor voltage, which does not introduce significant power loss during normal operation.
3Speed
If the output voltage rises quickly during startup, then power-up speed is improved, but surge current increases causing component damage
Solution Approach 1:
The patent implements preliminary short-circuit detection by monitoring the bootstrap capacitor voltage before full power operation begins. This allows the system to detect faults early in the startup sequence, preventing surge currents from damaging components while still enabling relatively fast power-up.
Solution Approach 2:
The system uses feedback from the bootstrap capacitor voltage to control the startup sequence. When the voltage indicates a short-circuit condition, the system prevents full power operation, thereby avoiding surge currents while maintaining fast startup under normal conditions.
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
Reduces power loss and improves system efficiency by eliminating the need for extra chip pins and allowing a gradual rise in output voltage, enhancing operational safety.
Implementation Method 1
a first diode DPL, a cathode of the first diode DPL is connected to a common node between the bus protection switch Q1 and the boost converter 21, and an anode of the first diode DPL is connected to a ground terminal
Implementation Method 2
an inductor L, the inductor L is coupled to the input terminal of the switching power supply 20
Data Source
Figure 1~3
Figure 4~6
AI summary
The present disclosure provides a switching power supply. The operating states of the bus protection switch is controlled to generate a low current, which charges the output capacitor during the short-circuit detection phase. A short-circuit fault of the switching power supply can be identified by monitoring whether the output voltage rises to a predetermined value. Unlike conventional methods, this approach eliminates the need for bus detection resistors and differential sampling, thereby reducing the number of required chip pins and simplifying chip design. Additionally, during the soft-start phase, the power-on duration is extended and the peak of charging current to the output capacitor is reduced, allowing the output voltage to rise gradually, thereby slowing the ramp rate of the output voltage, enabling the output voltage to reach the input voltage, reducing power loss, improving system efficiency, and enhancing operational safety.