Switchable Current Source Circuit with Precharged Gate Storage
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Solution Overview
Problem
Existing current switch circuits face challenges with slow turn-on times when the ratio between input and output transistors is large, stability issues in high-speed operations, and high power consumption, particularly due to the limitations of small reference currents and increased circuit area.
Innovation Solution
A switching circuit with a reference voltage input device, gate voltage charge storage, and a feedback loop that uses a comparator to control the reference voltage, allowing for a large reference current to be used for a short time, and includes a pull up and pull down current source to maintain the sense current equal to the reference current, enabling efficient precharge and discharge modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a large reference current is used for fast switching, then switching speed is improved, but power consumption increases
Solution Approach 1:
The gate voltage charge storage arrangement is precharged to a voltage higher than needed for normal operation before the switching event. This preliminary action stores energy in advance, allowing the output transistor to switch on rapidly without requiring a continuously large reference current, thus achieving fast switching while reducing overall power consumption.
Solution Approach 2:
The reference current is applied periodically rather than continuously - it is switched on briefly to precharge the gate voltage storage arrangement, then switched off during normal operation. This periodic application of current achieves fast switching capability while dramatically reducing average power consumption compared to continuously applying a large reference current.
2Use of energy by moving object
If a small reference current is used to reduce power consumption, then power consumption is improved, but switching speed deteriorates
Solution Approach 1:
The gate voltage charge storage arrangement is precharged to a voltage higher than needed for normal operation before the switching event. This preliminary action stores energy in advance, allowing the output transistor to switch on rapidly without requiring a continuously large reference current, thus achieving fast switching while reducing overall power consumption.
3Measurement precision
If the ratio between input and output transistors is increased to improve current scaling, then current accuracy is improved, but turn-on time increases
Solution Approach 1:
The gate voltage charge storage arrangement is precharged to a voltage higher than needed for normal operation before the switching event. This preliminary action stores energy in advance, allowing the output transistor to switch on rapidly without requiring a continuously large reference current, thus achieving fast switching while reducing overall power consumption.
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 achieves fast and accurate current switching with reduced power consumption and smaller circuit area, ensuring the output current is a scaled version of the reference current, while being insensitive to process and temperature variations.
Implementation Method 1
a comparator, which depending on the sign of a difference between the reference current and the sense current, controls the charging or discharging of the reference voltage charge storage device
Implementation Method 2
a gate voltage charge storage arrangement for storing a precharge voltage derived from the reference voltage
Implementation Method 3
a feedback loop for controlling the reference voltage stored on the reference voltage charge storage device to maintain the sense current equal to the reference current
Data Source
Figure 1
Figure 2
Figure 3(a)~3(c)
AI summary
a switchable current source in which a reference voltage value to be used in driving the gate of an output transistor is sampled and stored. The reference voltage is derived using a reference current source which feeds a current sensing transistor. The current sensing transistor is turned off when the output transistor is turned off, so that the reference current source then does not consume power. A large reference current Iref can then be used for a short time.