Back-to-Back Power Switch Gate Offset 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, necessitating a solution for zero-current turn-on operation.
Innovation Solution
A power switch controller with an amplifier and offset generator that applies an offset voltage higher than the source voltage to the gate terminal of the back-to-back power switch, allowing zero-current turn-on and maintaining stable on-resistance, using a one-stage amplifier buffer and current mirrors to manage the offset voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current sources are used to turn on the back-to-back power switch, then the power switch can be turned on, but non-zero current flows through the switch during turn-on, which interferes with IDDQ testing
Solution Approach 1:
The offset generator pre-charges the gate capacitor to a voltage level above the threshold voltage before the actual turn-on signal is applied. This preliminary action ensures that when the turn-on signal arrives, the switch transitions with minimal additional current, enabling zero-current turn-on operation that does not interfere with IDDQ testing
Solution Approach 2:
An offset voltage is introduced as an intermediary between the control signal and the power switch gate. This offset voltage, generated by the offset generator circuit, bridges the gap between the threshold voltage requirement and the zero-current turn-on requirement, allowing the switch to turn on without drawing measurement-interfering current
2Stability of the object's composition
If a simple voltage controller is used, then the device complexity is low, but the on-resistance varies with temperature and process variations
Solution Approach 1:
The amplifier is configured with its second input coupled to its output, creating a feedback loop that continuously monitors and stabilizes the gate voltage. This feedback mechanism compensates for temperature and process variations, maintaining stable on-resistance despite environmental changes, while the one-stage amplifier design keeps the overall complexity manageable
3Adaptability or versatility
If conventional relays or analog switches are used, then bidirectional signal flow is achieved, but mechanical components or intrinsic diodes prevent true bidirectional operation
Solution Approach 1:
The gate-to-source voltage is dynamically adjusted using an offset voltage that can be modulated based on the desired signal direction. By changing the voltage parameter beyond the threshold voltage, the controller enables both power MOSFETs to conduct simultaneously in either direction, achieving true bidirectional signal flow without the blocking effects of intrinsic diodes
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 temperature and process variations, thereby enhancing the effectiveness of defect detection and reducing power consumption.
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
an amplifier having a supply terminal configured to receive a supply voltage, an output configured to be coupled to a gate terminal of the back-to-back power switch, a first input configured to be coupled a source terminal of the back-to-back power switch, and a second input coupled to the output of the amplifier
Data Source
AI summary
In an embodiment, a power switch controller for driving a back-to-back power switch includes: an amplifier having a supply terminal configured to receive a supply voltage, an output configured to be coupled to a gate terminal of the back-to-back power switch, a first input configured to be coupled a source terminal of the back-to-back power switch, and a second input coupled to the output of the amplifier. 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.