NMOS Switching Circuit for Reverse Protection Without Auxiliary Power
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Solution Overview
Problem
P-channel MOSFETs are expensive and have limited performance and variety, restricting the development of PMOS input and output switches, which are typically used as reverse protection switches in electronic circuits.
Innovation Solution
A switching circuit configuration that includes a charging sub-circuit, a switching sub-circuit with NMOS switches, and a functional sub-circuit with a high operating voltage node, allowing for simple driving and control of NMOS switches without the need for additional auxiliary power supplies, enabling efficient input and output switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If P-channel MOSFETs are used as reverse protection switches, then ease of operation is improved, but cost increases and device variety is limited
Solution Approach 1:
The patent replaces expensive P-channel MOSFETs with cheaper N-channel MOSFETs in a push-pull configuration. The NMOS switches are controlled by charging/discharging their gate capacitances through diodes and capacitors, creating a cost-effective alternative that maintains the reverse protection function while reducing component cost and increasing device variety options.
2Device complexity
If N-channel MOSFETs are used instead of P-channel MOSFETs, then cost decreases and device variety increases, but driving complexity increases
Solution Approach 1:
The patent implements self-service driving for NMOS switches using the circuit's own power supply voltage. The charging sub-circuit charges the gate capacitance of NMOS switches through diodes during specific phases, and the switches turn off automatically when the gate capacitance discharges. This eliminates the need for external auxiliary power supplies or complex control circuits, making the NMOS driving as simple as PMOS driving while reducing cost.
Solution Approach 2:
The patent uses preliminary action by pre-charging the gate capacitance of NMOS switches before they need to conduct. The charging sub-circuit charges the gates of NMOS switches in advance during non-conduction phases, ensuring they are ready to turn on immediately when needed, thus simplifying the overall control mechanism.
3Ease of operation
If auxiliary power supplies are added to drive NMOS switches, then ease of operation improves, but device complexity increases
Solution Approach 1:
The patent makes the power supply serve multiple functions: it provides both the main operating voltage and the driving voltage for NMOS gates. The charging sub-circuit uses the existing power supply voltage to charge capacitor, which in turn charges the gate of NMOS switches. This multi-functionality eliminates the need for separate auxiliary power supplies, maintaining ease of operation while reducing circuit complexity.
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 provides a cost-effective and efficient switching mechanism for electronic circuits by utilizing a simple circuit structure to drive NMOS switches, addressing the limitations of P-channel MOSFETs and enabling effective input and output switching with reduced complexity and cost.
Implementation Method 1
the switching circuit may further comprise a first capacitor, one end of the first capacitor being connected to that one of the first end and second end of the switching sub-circuit which is connected to the functional sub-circuit
Implementation Method 2
the charging sub-circuit comprises a first diode, a second diode and a second capacitor, wherein the anode of the first diode is connected, as the second input end of the charging sub-circuit, to the input power supply
Data Source
Figure 1~2a
Figure 2b~3a
Figure 3b
AI summary
Embodiments of the present invention provide a switching circuit. The circuit comprises: a charging sub-circuit, which has a first input end and an output end; a switching sub-circuit, which has a first end, a second end, and a control end, wherein the control end of the switching sub-circuit is connected to the output end of the charging sub-circuit; and a function sub-circuit, which is connected to the first end or the second end of the switching sub-circuit, and has a first node, wherein an operating voltage of the first node is higher than an input voltage of an input power supply, the switching sub-circuit comprises one or more NMOS switches, and the first input end of the charging sub-circuit is connected to the first node.