Switching Power Supply Transistor Gate Delay Circuit
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Solution Overview
Problem
Existing switching power supply devices face high switching losses due to recovery currents in MOS transistors, and previous solutions either incur conduction losses or increase costs with additional components like freewheeling diodes and multiple MOS transistors.
Innovation Solution
A switching power supply device design featuring a high withstand voltage transistor and a low withstand voltage transistor in series, where the low withstand voltage transistor performs switching operations, minimizing recovery currents by utilizing built-in diodes without external freewheeling diodes, and employing delay circuits to control gate potential variations at different speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If two MOS transistors and a freewheeling diode having high withstand voltage are provided, then recovery current is prevented, but costs become high
Solution Approach 1:
The patent enables the MOS transistor to serve itself by utilizing its built-in parasitic diode for backflow prevention. This self-service approach eliminates the need for external backflow prevention diodes and reduces the number of high-voltage components required, thereby lowering overall system cost while maintaining effective recovery current prevention.
Solution Approach 2:
The MOS transistor is designed to perform multiple functions: switching operation, backflow prevention, and freewheeling current path provision. By making the MOS transistor multi-functional through proper configuration of its parasitic diode, the patent eliminates the need for separate dedicated components, reducing component count and overall system cost.
2Speed
If the potential of the control electrode varies rapidly, then switching speed is improved, but misfiring occurs due to voltage variation affecting the control electrode
Solution Approach 1:
The patent applies preliminary action by pre-charging the control electrode to a voltage higher than the threshold voltage before the switching operation begins. This preliminary voltage preparation ensures that when the switching signal is applied, the MOS transistor switches rapidly without experiencing misfiring due to voltage variations, as the control electrode is already in a stable high-voltage state ready for immediate switching.
Data Source
AI summary
A highly efficient and low-cost switching power supply device includes a high withstand voltage transistor and a low withstand voltage transistor. When current flows from a second node to a first node, the high withstand voltage transistor turns on and the low withstand voltage transistor turns off, causing current to flow through a built-in diode of the low withstand voltage transistor. Since current does not flow through the parasitic diode of the high withstand voltage transistor, the recovery current is reduced. Furthermore, since a first delay circuit including resistors and a diode is connected to the gate electrode of the high withstand voltage transistor, and a second delay circuit including resistors and a diode is connected to the gate electrode of the low withstand voltage transistor, precise adjustment of the switching speed during switching operation is possible, and losses are reduced.