Non-synchronous Boost Converter Low-Voltage Load Disconnect
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Solution Overview
Problem
Conventional non-synchronous boost converters face inefficiency and high costs due to the use of high-voltage devices for load disconnection, which results in leakage current when shutdown, despite efforts to replace Schottky diodes with gate-controlled versions or insert high-voltage switches.
Innovation Solution
A non-synchronous boost converter design incorporating a low-voltage load disconnecting transistor with a clamping circuit and a current supply circuit, including a current mirror, to manage voltage and provide constant pre-charge and short circuit protection currents, ensuring efficient load disconnection without high-voltage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-voltage switch is inserted between the Schottky diode and the output voltage terminal for load disconnection, then the leakage current is prevented, but the cost increases and the on-resistance becomes greater causing poor efficiency
Solution Approach 1:
A low-voltage transistor is introduced as an intermediary component between the Schottky diode and output terminal. This transistor acts as a controlled switch that can disconnect the load without requiring a high-voltage device, thereby preventing leakage current while maintaining efficiency and reducing cost.
Solution Approach 2:
The invention changes the voltage parameter of the switching device from high-voltage to low-voltage. By using a low-voltage transistor with appropriate voltage rating (lower than the output voltage but sufficient for its operation), the system achieves load disconnection functionality without the drawbacks of high-voltage devices such as high cost and high on-resistance.
2Reliability
If a gate-controlled Schottky diode with LDMOS or JFET is used to turn off the diode for load disconnection, then leakage current is avoided, but the device complexity increases
Solution Approach 1:
The invention extracts the switching function from the Schottky diode itself and separates it into a dedicated low-voltage transistor. This allows the Schottky diode to maintain its simple structure and excellent forward voltage characteristics, while the load disconnection function is handled by a separate, simpler low-voltage transistor with basic gate control.
3Use of energy by moving object
If the converter is shutdown with input voltage still high, then power conversion stops, but leakage current flows through divider resistors to ground
Solution Approach 1:
The low-voltage transistor is positioned to disconnect the output terminal from the Schottky diode before the shutdown process completes. This preliminary disconnection action prevents the formation of the leakage current path through the divider resistors, ensuring that when the converter is shutdown, no significant leakage current flows even if the input voltage remains high.
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
The solution effectively disconnects the output voltage from the input voltage during shutdown, preventing leakage current and improving efficiency by using low-voltage components, while maintaining stable pre-charge and short circuit protection currents.
Implementation Method 1
a clamping circuit connected to the load disconnecting transistor to clamp the voltage between the gate and the source of the load disconnecting transistor
Implementation Method 2
a current supply circuit connected to the output voltage terminal to provide stable pre-charge current and short circuit protection current to the capacitor
Data Source
AI summary
A non-synchronous boost converter includes a low-voltage device connected between the input voltage terminal and the output voltage terminal of the converter. When the converter is shutdown, the low-voltage device disconnects the output voltage terminal and the input voltage terminal. Since it is a low-voltage device used in the converter for load disconnection, the efficiency of the converter is improved with lower cost.