Low Power Ideal Diode Circuit Using Dynamic Gate Biasing
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Solution Overview
Problem
In low power applications, traditional diodes can cause supply headroom issues and excessive power dissipation due to their forward voltage drop, and Schottky diodes are not available in all semiconductor processes, necessitating an alternative solution for fast forward and reverse recovery.
Innovation Solution
A circuit using a p-channel transistor with dynamic gate biasing and amplifiers to control the transistor's operation as an ideal diode, enabling low power, low voltage, and fast recovery in both forward and reverse directions, implemented in CMOS technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a traditional diode is used, then the circuit provides simple diode functionality, but the forward voltage drop causes supply headroom issues and excessive power dissipation
Solution Approach 1:
The patent changes the operating parameters of the transistor by dynamically adjusting the gate voltage based on the voltage across the transistor. This dynamic parameter adjustment allows the transistor to operate as an ideal diode with minimal voltage drop, resolving the contradiction between low power dissipation and simple circuit operation.
Solution Approach 2:
The patent employs feedback mechanisms where the voltage across the transistor is continuously monitored and used to adjust the gate voltage. This feedback loop enables the transistor to maintain optimal operating conditions, achieving low power dissipation while maintaining diode functionality without excessive circuit complexity.
2Loss of energy
If a Schottky diode is used, then the forward voltage drop is reduced, but Schottky diodes are unavailable in many semiconductor processes
Solution Approach 1:
The patent uses parameter changes by dynamically adjusting the gate voltage of the transistor to achieve low forward voltage drop characteristics similar to Schottky diodes. This approach maintains the manufacturing advantage of using standard CMOS processes while achieving the desired low voltage drop performance.
Solution Approach 2:
The patent copies the functional characteristics of a Schottky diode using a transistor with dynamic gate control. By replicating the low voltage drop behavior through control circuitry rather than using actual Schottky diode structures, the invention achieves Schottky-like performance in processes where Schottky diodes are unavailable.
3Reliability
If a single transistor is used to replace the diode, then the circuit achieves ideal diode characteristics, but the gate voltage control complexity increases
Solution Approach 1:
The patent uses feedback to automatically control the gate voltage based on the voltage across the transistor. This feedback mechanism maintains ideal diode characteristics by ensuring the transistor operates in the appropriate region, while the automatic control reduces the perceived complexity compared to manual or complex control schemes.
Solution Approach 2:
The transistor's gate voltage is self-adjusted based on the voltage across the device itself. This self-service mechanism allows the transistor to maintain ideal diode characteristics without requiring external complex control circuitry, as the device automatically regulates its own operating point.
4Speed
If fast recovery is achieved, then the circuit responds quickly to voltage changes, but the circuit complexity and power consumption increase
Solution Approach 1:
The feedback mechanism detects voltage changes across the transistor and rapidly adjusts the gate voltage in response. This fast feedback loop enables quick forward and reverse recovery speeds while maintaining low power consumption, as the control is event-driven rather than continuously active.
Solution Approach 2:
The control circuit operates periodically based on voltage transitions rather than continuously. This periodic action achieves fast recovery speeds by responding only when necessary, reducing unnecessary power consumption associated with continuous control mechanisms.
Data Source
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AI summary
In described examples of a circuit (100) that operates as a low-power ideal diode, the circuit (100) includes a p-channel transistor (102) connected to receive an input voltage (VIN) on a first terminal and to provide an output voltage (VOUT) on a second terminal, a first amplifier (106) connected to receive the input voltage and the output voltage and to provide a first signal that dynamically biases a gate of the p-channel transistor (102) as a function of the voltage across the p-channel transistor, and a second amplifier (104) connected to receive the input voltage and the output voltage and to provide a second signal that operates to turn off the gate of the p-channel transistor (102) responsive to the input voltage (VIN) being less than the output voltage (VOUT).