Active Diode Circuit for AC/DC Power Conversion
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Solution Overview
Problem
The diode rectifier bridge in power conversion circuits experiences high temperature rises and complex structures due to low efficiency, leading to increased volume and potential plastic degradation in power adapters and chargers.
Innovation Solution
An active diode circuit with a logic unit, constant current source, and switch transistors is introduced to monitor and control the conduction state of parasitic body diodes, reducing conduction losses and incorporating PFC inductors for efficient rectification and power correction, replacing traditional diode rectifier bridges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a diode rectifier bridge is used for AC-DC conversion, then the circuit structure is simple, but the conversion efficiency is low and temperature rise is high
Solution Approach 1:
The patent changes the operating parameters of the rectifier by using synchronous switching of MOSFETs instead of passive diode conduction. The active switching devices operate in their optimal conduction region, reducing on-resistance and conduction losses compared to standard diode rectification, thereby improving conversion efficiency while maintaining manageable circuit complexity
Solution Approach 2:
The patent replaces the passive mechanical-diode rectification system with an active electronic switching system using MOSFETs controlled by PWM signals. This substitution enables more efficient energy transfer and reduced thermal losses through controlled switching operations rather than relying on diode forward voltage drops
2Device complexity
If a diode rectifier bridge is used, then the circuit is simple, but the temperature rise causes plastic shell degradation
Solution Approach 1:
By changing from passive diode conduction to active MOSFET switching, the patent reduces conduction losses and associated heat generation. The active switching devices can be controlled to minimize on-state resistance and switching losses, directly addressing the temperature rise issue that threatens plastic enclosure integrity
Solution Approach 2:
The patent converts the previously harmful heat generation from diode conduction losses into a controlled parameter through active switching. By using synchronous rectification with MOSFETs, the system transforms the thermal management problem into a controllable electrical parameter, reducing heat generation at its source rather than merely managing the thermal consequences
3Use of energy by moving object
If bridgeless PFC with dual inductors is used, then power factor is improved, but system volume increases
Solution Approach 1:
The patent merges the PFC inductor function with the existing input filter inductor, eliminating the need for separate PFC inductors. This consolidation achieves power factor correction while avoiding the volume increase that would result from adding dual inductors to the system
Solution Approach 2:
The patent makes the input filter inductor serve multiple functions: both as an EMI filter component and as the PFC inductor. This multi-functionality approach achieves power factor correction without requiring additional volume for dedicated PFC magnetic components
4Measurement precision
If more discrete devices are used in control circuit, then PFC control is more precise, but device complexity increases
Solution Approach 1:
The patent designs a controller that integrates multiple functions into a single device: PWM generation, body diode state detection, synchronous rectification control, and PFC control. This multi-functional approach achieves precise control without increasing device complexity through multiple discrete components
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
This solution reduces temperature rises, simplifies the PFC circuit, improves power density, and enhances efficiency in AC/DC power conversion by utilizing active diode circuits with low conduction loss characteristics.
Implementation Method 1
the constant current source is configured to provide a constant current for the power interface when a voltage input from the drain interface of the active diode circuit charges an external energy storage capacitor through the power interface
Implementation Method 2
monitor whether a parasitic body diode of the first switch transistor is in conduction state, that is, whether a voltage difference between a source electrode and a drain electrode of the first switch transistor is greater than a conducting voltage of the body diode
Implementation Method 3
a differential mode inductor of the common-differential mode inductor is configured for energy storage of a PFC circuit
Implementation Method 4
a common mode inductor of the common-differential mode inductor is configured to eliminate common-mode noise
Data Source
Figure 1~2
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Figure 5~6
AI summary
The present application relates to the field of electronic technology and provides an active diode circuit and an AC/DC power conversion circuit, including a power interface, a drain interface, a control interface, a source interface, a logic unit, a constant current source, and a first switch transistor. A first terminal of the constant current source is connected to the drain interface of the active diode circuit, a second terminal and a third terminal of the constant current source are both connected to the power interface, and a fourth terminal of the constant current source is connected to the logic unit; a first input terminal of the logic unit is connected to the fourth terminal of the constant current source, a second input terminal of the logic unit is connected to the control interface, and an output terminal of the logic unit is connected to a gate electrode of the first switch transistor; and the drain electrode of the first switch transistor is connected to the drain interface of the active diode circuit, and the source electrode of the first switch transistor is connected to the source interface of the active diode circuit. The present application solves the problems of the diode temperature rise of the rectifier bridge and the complex structure of the PFC circuit.