Back-to-Back Power Switch Gate Control for Zero-Current Turn-On
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Solution Overview
Problem
Conventional back-to-back power switches require non-zero current to turn on, which can interfere with current measurements during IDDQ testing and other applications, and are not effective in maintaining stable turn-on potential across temperature and process variations.
Innovation Solution
A power switch controller that uses a one-stage amplifier buffer to drive the gates of the back-to-back power switch, generating an offset voltage higher than the source terminal voltage to maintain zero current turn-on and stable on-resistance, comprising a current mirror, transistors, and an offset generator to manage the gate-source voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current sources are used to turn on power MOSFETs, then the power switch can be activated, but non-zero current flows through the switch which interferes with IDDQ testing
Solution Approach 1:
The patent inverts the conventional approach by using a amplifier buffer to generate an offset voltage that actively counteracts the turn-on current. Instead of allowing current to flow and then controlling it, the invention pre-establishes a voltage offset that prevents current flow from occurring in the first place during testing conditions
Solution Approach 2:
The patent changes the voltage parameter at the gate terminal by introducing an offset voltage generated by the amplifier buffer. This parameter change (adding V_OFFSET) modifies the gate-source voltage relationship to achieve zero current turn-on condition, transforming the switching behavior to be compatible with IDDQ testing requirements
2Reliability
If simple voltage control is used to turn on power MOSFETs, then the circuit is simple, but the turn-on potential is not stable across temperature and process variations
Solution Approach 1:
The amplifier buffer provides feedback control by continuously monitoring the voltage difference between its inputs and adjusting the output accordingly. This feedback mechanism ensures that the offset voltage remains stable despite temperature and process variations, maintaining consistent turn-on characteristics without requiring complex external control circuits
Solution Approach 2:
The amplifier buffer acts as an intermediary between the simple voltage control input and the power MOSFET gates. It translates the control voltage into a stable offset voltage that compensates for environmental variations, providing a middle layer that enhances reliability while keeping the overall control structure relatively simple
3Reliability
If back-to-back power MOSFETs are used without offset voltage, then the switch operates bidirectionally, but the on-resistance varies with temperature and process
Solution Approach 1:
The patent changes the electrical parameter (voltage) applied to the power MOSFET gates by introducing a controlled offset voltage. This parameter modification stabilizes the on-resistance by compensating for temperature and process variations, ensuring consistent performance across different operating conditions while managing 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
Enables zero-current turn-on of back-to-back power switches, minimizing interference in IDDQ testing and maintaining consistent performance across temperatures and process variations, with adjustable current consumption and reduced on-resistance.
Implementation Method 1
the amplifier is configured to generate an output voltage at the output of the amplifier, the output voltage being an offset voltage higher than a voltage at the first input of the amplifier
Implementation Method 2
comprising a current mirror, transistors, and an offset generator to manage the gate-source voltage
Implementation Method 3
a second transistor having a gate coupled to the first input of the amplifier, and a current path coupled between the current path of the first transistor and the current mirror
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
In an embodiment, a power switch controller (204) for driving a back-to-back power switch (102) includes: an amplifier (206) having a supply terminal configured to receive a supply voltage (Vcc), an output configured to be coupled to a gate terminal (G) of the back-to-back power switch (102), a first input configured to be coupled a source terminal (S) of the back-to-back power switch (102), and a second input coupled to the output of the amplifier (206). The amplifier is configured to generate an output voltage at the output of the amplifier, the output voltage being an offset voltage higher than a voltage at the first input of the amplifier (206).