Power Voltage Selection Device Latch-Up Prevention
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Solution Overview
Problem
Conventional power voltage selection devices experience latch-up issues due to parasitic transistors turning on, leading to increased current flow and power consumption, especially when there is a delay in the power-up sequence of multiple power voltages.
Innovation Solution
A power voltage selection device with a body voltage control unit that ensures one of the power voltages has a higher voltage level than the other, preventing latch-up by controlling the supply to the body of the PMOS transistors, using additional PMOS and NMOS transistors to manage voltage differences and prevent parasitic transistor activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple power voltages are supplied to electronic devices with different voltage levels, then the electronic devices can operate with various power sources (AC adapter or battery), but latch-up occurs due to parasitic transistors turning on when there is a delay in the power-up sequence, leading to increased current flow and power consumption
Solution Approach 1:
The body voltage control unit performs preliminary action by controlling the body voltage of PMOS transistors before the power-up sequence completes. It ensures that the body voltage is properly established and maintained at the correct voltage level before the power selection switching occurs, preventing parasitic transistor activation during voltage transitions.
Solution Approach 2:
The body voltage control unit acts as an intermediary between the multiple power voltage sources and the PMOS transistors. It mediates the voltage differences by controlling the body terminal voltage, ensuring that the voltage difference between source and body does not exceed the threshold that would activate parasitic transistors, thus preventing latch-up while allowing multiple power sources to be used.
2Reliability
If the body voltage is not properly controlled during power-up sequence delays, then parasitic transistors turn on causing latch-up, but adding body voltage control circuitry increases device complexity
Solution Approach 1:
The body voltage control unit is designed to work with multiple power voltage sources universally. It can control the body voltage regardless of which power source (AC adapter or battery) is being used, making the latch-up prevention mechanism applicable to all power supply scenarios without requiring separate control circuits for each power source.
Solution Approach 2:
The body voltage control unit dynamically adjusts the body voltage parameter based on the power-up sequence and the active power source. By changing the body voltage parameter appropriately during different stages of power-up and depending on which power source is active, the circuit prevents latch-up without requiring overly complex control logic.
3Speed
If parasitic transistors are allowed to turn on during voltage transitions, then the circuit responds quickly to power changes, but this causes increased power consumption and heat generation due to latch-up
Solution Approach 1:
The body voltage control unit applies preliminary anti-action by preventing the conditions that lead to latch-up before they can occur. It controls the body voltage to ensure that the voltage difference between source and body remains below the threshold for parasitic transistor activation, thereby preventing the harmful latch-up effect while still allowing rapid power switching.
Data Source
AI summary
A power voltage selection device includes a first power voltage and a second power voltage; a power selection unit having a first PMOS transistor and a second PMOS transistor, wherein the first power voltage is supplied to a source of the first PMOS transistor, a gate of the first PMOS transistor receives a first enable signal, the second power voltage is supplied to a source of the second PMOS transistor, a gate of the second PMOS transistor receives a second enable signal, and a body of the first PMOS transistor is coupled to a body of the second PMOS transistor; an output unit having a common node to which a drain of the first PMOS transistor and a drain of the second PMOS transistor are commonly coupled; and a body voltage control unit controlling to supply one of the first power voltage and the second power voltage to the bodies of the first PMOS transistor and the second PMOS transistor, wherein the one has a higher voltage level than the other.