Ideal Diode Control Circuit With Fast Reverse Recovery
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Solution Overview
Problem
Low power applications face challenges with supply headroom issues and excessive power dissipation due to the forward voltage drop of diodes, and Schottky diodes are not available in most semiconductor processes, necessitating a circuit that functions as an ideal diode with fast forward and reverse recovery.
Innovation Solution
A circuit comprising a P-channel transistor and amplifiers that dynamically bias the transistor gate to act as an ideal diode, ensuring fast forward and reverse recovery with low voltage headroom, utilizing CMOS technology and parasitic diodes to minimize recovery times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a diode is used in low power applications, then the forward voltage drop causes supply headroom issues and excessive power dissipation, but replacing it with a transistor requires complex control circuitry to achieve ideal diode functionality
Solution Approach 1:
The patent employs feedback mechanisms where the output voltage is monitored and fed back to control the gate voltage of the transistor. This feedback loop dynamically adjusts the transistor's conduction state to maintain ideal diode behavior, resolving the contradiction between reducing power loss and maintaining simple circuit operation.
Solution Approach 2:
The circuit uses the voltage across the transistor itself to generate the gate control voltage through internal amplifier circuits. This self-service approach eliminates the need for external complex control circuitry, allowing the transistor to automatically regulate its own operation while minimizing power dissipation.
2Loss of energy
If a Schottky diode is used to reduce forward voltage drop, then power dissipation is reduced, but Schottky diodes are not available in most semiconductor processes
Solution Approach 1:
The patent changes the operating parameters of a standard MOS transistor by dynamically controlling its gate voltage based on the voltage across it. This parameter change allows the transistor to operate in a regime that mimics Schottky diode behavior with lower forward voltage drop, achieving the same power dissipation reduction without requiring specialized Schottky process technology.
Solution Approach 2:
The circuit copies the functional behavior of a Schottky diode using a standard MOS transistor and control circuitry. By replicating the ideal diode characteristics through active control, the patent achieves Schottky-like performance in processes where Schottky diodes are not available.
3Loss of energy
If a transistor is used to act as an ideal diode, then forward voltage drop is reduced, but achieving fast forward and reverse recovery requires complex control circuitry
Solution Approach 1:
The control circuitry prepares the gate voltage in advance based on the instantaneous voltage across the transistor. This preliminary action ensures that the transistor is already in the optimal conduction state before current needs to flow, enabling fast forward recovery without requiring complex real-time control mechanisms.
Solution Approach 2:
The patent employs dynamic control where the gate voltage continuously adapts to the instantaneous voltage across the transistor. This dynamic adjustment allows the transistor to rapidly transition between conduction and blocking states, achieving fast forward and reverse recovery while maintaining simple circuit architecture.
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 described circuit achieves low power, low voltage operation with quick forward and reverse recovery times, reducing power loss and voltage headroom concerns, suitable for low power applications like portable devices.
Implementation Method 1
a first amplifier connected to receive the input voltage at a first input and the output voltage at a second input and to provide a first signal that dynamically biases a gate of the first P-channel transistor as a function of the voltage across the first P-channel transistor
Implementation Method 2
a second amplifier connected to receive the input voltage at a first input and the output voltage at a second input and to provide a second signal that acts to turn off the gate of the first P-channel transistor responsive to the input voltage being less than the output voltage
Data Source
AI summary
In described examples of a circuit that operates as a low-power ideal diode, and an IC chip that contains the ideal diode circuit, the circuit includes: a first P-channel transistor connected to receive an input voltage on a first terminal and to provide an output voltage on a second terminal; a first amplifier connected to receive the input voltage and the output voltage and to provide a first signal that dynamically biases a gate of the first P-channel transistor as a function of the voltage across the first P-channel transistor; and a second amplifier connected to receive the input voltage and the output voltage and to provide a second signal that acts to turn off the gate of the first P-channel transistor responsive to the input voltage being less than the output voltage.