Self-Biasing Ideal Diode Circuit for High-Voltage NMOS Rectification
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Solution Overview
Problem
Existing ideal diode circuits face challenges in using low-voltage control circuitry for high-voltage AC rectification, leading to increased size, cost, and power consumption due to the need for special high-voltage handling and continuous charge pump operation.
Innovation Solution
An ideal diode circuit using a low-loss switch with a novel boost circuit that generates a gate voltage higher than the anode voltage without continuous switching, allowing low-voltage control circuitry independent of earth ground, reducing power dissipation and size, and enabling efficient operation across various AC voltages and frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional high-voltage control circuitry is used for high-voltage AC rectification, then the circuit can handle high voltages, but the size and cost of the control circuitry increases
Solution Approach 1:
The patent introduces a floating charge pump circuit as an intermediary mechanism that generates a boosted voltage reference floating above the rectified voltage. This floating reference acts as a mediator, allowing low-voltage control circuitry to indirectly control high-voltage switching without being directly exposed to high voltage stresses, thus reducing control circuitry complexity while maintaining high-voltage handling capability
Solution Approach 2:
The patent transitions from earth-grounded voltage references to floating voltage references that move with the rectified voltage level. By changing the reference dimension from fixed ground to floating potential, the control circuitry operates at low voltage differentials while still controlling high-voltage switches, effectively decoupling control voltage requirements from power voltage levels
2Ease of operation
If a charge pump is used to generate boosted voltage for NMOS gate control, then the NMOS transistor can be properly controlled, but the charge pump consumes continuous power
Solution Approach 1:
The patent implements a periodic self-biasing mechanism where the charge pump operates only during specific phases of the rectified voltage cycle. The circuit uses the natural oscillation of the rectified voltage to periodically charge the floating reference capacitor, eliminating the need for continuous charge pump operation while maintaining adequate gate voltage for NMOS control throughout the cycle
Solution Approach 2:
The floating charge pump circuit is designed to automatically regulate its own operation based on the rectified voltage level. The circuit self-adjusts the charging frequency and duration of the floating reference capacitor based on the instantaneous voltage conditions, eliminating external control and reducing overall power consumption while maintaining proper NMOS gate drive
3Reliability
If the charge pump runs continuously to maintain boosted voltage, then the NMOS transistor remains properly driven, but power consumption increases
Solution Approach 1:
The patent replaces continuous charge pump operation with periodic charging events synchronized to the rectified voltage waveform. The floating reference capacitor is charged only when needed during voltage transitions, reducing energy loss while maintaining stable NMOS drive through the natural energy storage and release characteristics of the capacitor
Solution Approach 2:
The circuit recovers energy from the rectified voltage waveform itself, using the voltage swings during normal operation to recharge the floating reference capacitor. This energy recovery mechanism eliminates waste of the inherent voltage oscillations and reduces the burden on the charge pump, thereby reducing overall power consumption while maintaining drive stability
Data Source
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AI summary
An ideal diode circuit is described which uses an NMOS transistor as a low-loss ideal diode. The control circuit for the transistor is referenced to the anode voltage and not to ground, so the control circuitry may be low voltage circuitry, even if the input voltage is very high, referenced to earth ground. A capacitor is clamped to about 10-20V, referenced to the anode voltage. The clamped voltage powers a differential amplifier for the detecting if the anode voltage is greater than the cathode voltage. The capacitor is charged to the clamped voltage during normal operation of the ideal diode by controlling the conductivity of a second transistor coupled between the cathode and the capacitor, enabling the circuit to be used with a wide range of frequencies and voltages. All voltages applied to the differential amplifier are equal to or less than the clamped voltage.