Overvoltage Protection Circuit Using Charge Pump and Error Amplifier
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Solution Overview
Problem
Conventional overvoltage protection circuits fail to stabilize output voltage effectively, especially when the external power supply voltage fluctuates, and may not function correctly under high input voltages, leading to potential damage to semiconductor integrated circuits.
Innovation Solution
An overvoltage protection circuit incorporating an N-channel MOSFET output transistor, a charge pump circuit to step up the input voltage, and an error amplifier to regulate the output voltage, with a controller to turn off the transistor when the input voltage exceeds a threshold, ensuring the output voltage remains stable and within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple switch element is used to turn OFF when input voltage exceeds threshold, then overvoltage protection is achieved, but output voltage fluctuates when external power supply voltage fluctuates below threshold
Solution Approach 1:
The patent implements a feedback mechanism where the error amplifier continuously monitors the output voltage and adjusts the gate voltage of the output transistor accordingly. The feedback voltage from the output terminal is compared with a reference voltage, and the difference (error voltage) controls the output transistor to maintain stable output voltage despite fluctuations in external power supply voltage.
Solution Approach 2:
The patent introduces an error amplifier and charge pump circuit as intermediary components between the input voltage source and the output transistor. These intermediary components process the voltage signals and provide controlled gate voltage to the output transistor, enabling precise output voltage regulation without directly exposing the transistor to raw input voltage fluctuations.
2Device complexity
If gate voltage is limited to source voltage level, then circuit simplicity is maintained, but input voltage cannot be taken out as output voltage
Solution Approach 1:
The patent changes the voltage parameter at the gate terminal of the output transistor by introducing a charge pump circuit. This circuit generates a gate voltage that can exceed the source voltage level, enabling the output transistor to properly regulate voltages where the input voltage is higher than the desired output voltage. This parameter change allows the circuit to handle a broader range of voltage conditions.
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 stabilizes the output voltage, prevents damage from high input voltages, and allows the output voltage to be maintained close to the input voltage, enhancing reliability and reducing the risk of surge voltage issues from poor external power supplies.
Implementation Method 1
a charge pump circuit which steps up the input voltage
Implementation Method 2
an error amplifier which receives a voltage stepped up by the charge pump circuit as a power supply, and outputs an error voltage of a feedback voltage corresponding to a voltage of an output terminal and a predetermined reference voltage to a gate of the output transistor
Data Source
AI summary
An input terminal is externally input with an input voltage. An output transistor of N-channel MOSFET is arranged between the input terminal and an output terminal. A charge pump circuit steps up the input voltage. An error amplifier receives a voltage stepped up by the charge pump circuit as a power supply, and outputs an error voltage of a feedback voltage corresponding to an output voltage of the output terminal and a predetermined reference voltage to a gate of the output transistor. A controller compares the input voltage with a predetermined threshold voltage, and forcibly turns OFF the output transistor when the input voltage is higher than the threshold voltage.