Power Supply Switch Circuit Using Low-Breakdown MOS Transistors
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Solution Overview
Problem
Conventional power supply switch circuits for semiconductor integrated circuits require high-breakdown-voltage MOS transistors, leading to increased costs and the need for special through-current preventing circuits to manage parasitic diode currents when switching between 3.3 V and 1.8 V power supply voltages.
Innovation Solution
A power supply switch circuit utilizing low-breakdown-voltage MOS transistors, with PMOS and NMOS transistors connected through switch control circuits that manage voltage levels to prevent unwanted currents, eliminating the need for a special through-current preventing circuit by ensuring the transistors operate within a 1.8 V breakdown voltage condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-breakdown-voltage MOS transistors are used to handle 3.3 V power supply switching, then the power supply switch circuit can operate at higher voltage levels, but the manufacturing cost increases due to higher process costs
Solution Approach 1:
The patent changes the voltage parameter constraints by using low-breakdown-voltage MOS transistors (1.8 V) instead of high-breakdown-voltage transistors (3.3 V). This is achieved by introducing voltage level conversion circuits that translate control signals to appropriate voltage levels for each transistor, allowing the system to switch between 3.3 V and 1.8 V power supplies while keeping transistor breakdown voltage requirements low, thereby reducing manufacturing costs
2Adaptability or versatility
If high-breakdown-voltage MOS transistors are used, then the circuit can switch between 3.3 V and 1.8 V power supplies, but additional through-current preventing circuitry is required to manage parasitic diode currents
Solution Approach 1:
The patent extracts and eliminates the need for separate through-current preventing circuits by carefully designing the control logic and voltage level conversion such that the parasitic diode currents are naturally prevented. The control circuits are designed to ensure proper turn-off sequencing and voltage level management, which inherently prevents through-current flow without requiring additional dedicated preventing circuitry
Solution Approach 2:
The patent introduces voltage level conversion circuits as intermediaries between the control logic and the power supply switch transistors. These level shifters translate control signals to the appropriate voltage levels for each transistor (1.8 V or 3.3 V), enabling proper control of low-breakdown-voltage transistors while switching between different power supply voltages, thereby simplifying the overall circuit architecture
3Ease of manufacture
If low-breakdown-voltage MOS transistors are used, then manufacturing cost is reduced, but the transistors cannot directly handle 3.3 V power supply switching
Solution Approach 1:
The patent introduces voltage level conversion circuits as intermediaries that translate control signals to the appropriate voltage levels for each transistor. These level shifters enable the control logic to properly drive low-breakdown-voltage MOS transistors (1.8 V) even when switching between 3.3 V and 1.8 V power supplies, effectively bridging the voltage gap without requiring the transistors to have high breakdown voltage
Data Source
AI summary
In order to provide a power supply switch circuit using only low-breakdown voltage transistors and eliminate the need for a special through-current preventing circuit, the switch control circuits output a signal ranging from a ground voltage level to a second power supply voltage level when a first power supply voltage (0 V/3.3 V) is in off-state and a second power supply voltage (0 V/1.8 V) is in on-state, and a signal ranging from the second power supply voltage level to a first power supply voltage level when the first and second power supply voltages are in on-state, thereby allowing a PMOS transistor and an NMOS transistor to turn on or off.