Voltage Dropping Circuit Back Gate Variable Diode Prevents Backflow
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Solution Overview
Problem
In integrated circuits employing adaptive supply voltage (ASV) systems, the delayed supply of high-voltage power source voltage to low drop out circuits leads to backward current flow due to premature application of base voltage to the back gate terminal before high-voltage power source voltage is supplied, necessitating measures to prevent backflow and overcurrent.
Innovation Solution
A voltage dropping circuit with a back gate variable diode circuit, where a diode-connected transistor is used between the first node and the output stage transistor, allowing the first power source voltage to be applied to the back gate when it is higher and the second power source voltage to be applied when it is higher, effectively controlling the transistor's state based on voltage relationships to prevent backflow and overcurrent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low drop out circuit is used to generate back gate voltage in an ASV system, then the back gate voltage can be controlled to reduce transistor leak current, but backward current flows when base voltage is applied before high-voltage power source voltage is supplied
Solution Approach 1:
A diode-connected transistor is introduced as an intermediary component between the output terminal and the high-voltage power source terminal. This intermediary element allows normal operation current to pass while blocking backward current flow, resolving the conflict between enabling LDO functionality and preventing current backflow during power supply transitions.
Solution Approach 2:
The diode-connected transistor is configured to preemptively prevent backward current flow before it can occur during power supply sequence transitions. By establishing this protective mechanism in advance, the circuit avoids the harmful effect of current backflow while maintaining the ability to generate controlled back gate voltage for leak current reduction.
2Reliability
If a diode-connected transistor is added to prevent backflow, then current backflow is prevented, but the circuit complexity increases
Solution Approach 1:
The diode-connected transistor serves multiple functions simultaneously: it prevents backward current flow, allows forward current passage for normal LDO operation, and integrates seamlessly with the existing transistor structure. This multi-functionality achieves reliable backflow prevention without proportionally increasing circuit complexity.
Solution Approach 2:
The protective diode function is merged with the existing transistor structure by connecting the gate to the drain, creating a diode-connected transistor. This combination integrates the backflow prevention mechanism into the existing circuit architecture rather than adding a separate discrete component, thereby minimizing the increase in device 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 effectively prevents backward current flow and overcurrent during normal operation by dynamically controlling the back gate voltage, ensuring efficient power management and reduced power consumption in integrated circuits.
Implementation Method 1
a diode-connected transistor that is connected between the first node and the first terminal and configured to turn on or off in accordance with a magnitude relationship between the first power source voltage and the second power source voltage
Data Source
AI summary
A voltage dropping circuit generating a second power source voltage to output to a second node by dropping a first power source voltage supplied to a first node, includes: an output transistor having a first terminal to which the first power source voltage is supplied and a second terminal connected to the second node turns on or off according to a difference between the second power source voltage and a reference voltage; and a back gate variable diode circuit including a diode-connected transistor connected between the first node and the first terminal and to configured to turn on or off according to a voltage difference between the first and second power sources, wherein the first power source voltage is applied to the back gate of the diode-connected transistor when it is higher than the second power source voltage, and the second power source voltage is applied in other case.