Totem-Pole PFC Current Detection Without Transformer Isolation
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Solution Overview
Problem
Existing power conversion devices with totem pole type power factor correction circuits face complexity and increased costs due to the need for current transformers to detect current alternations, which output positive and negative signals that cannot be directly used by control ICs, requiring insulation and additional circuitry.
Innovation Solution
A power conversion device configuration using a first and second current detector in series with a coil, semiconductor switches, diodes, and a smoothing capacitor, where the control circuit performs pulse width modulation based on current detection results and polarity detection, allowing direct input to the control circuit without the need for insulation and reducing harmonic wave noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a current transformer is used to detect current alternations, then current detection is achieved, but the circuit becomes complicated and cost increases
Solution Approach 1:
The patent replaces the expensive current transformer with simple, inexpensive current detectors (resistors) that can be easily integrated into the circuit. These detectors are basic components with no moving parts or complex construction, dramatically reducing both cost and circuit complexity while maintaining the ability to detect current alternations for PWM control
Solution Approach 2:
The patent extracts the essential function of current detection from the complex current transformer and implements it through simple resistive detectors in series with the coil. This separation allows the detection function to be performed by basic components without requiring the insulation and complex signal conditioning circuitry of a current transformer
2Difficulty of detecting and measuring
If a current transformer is used to detect current alternations, then current detection is achieved, but cost increases
Solution Approach 1:
The patent replaces the expensive current transformer with simple, inexpensive current detectors (resistors) that can be easily integrated into the circuit. These detectors are basic components with no moving parts or complex construction, dramatically reducing both cost and circuit complexity while maintaining the ability to detect current alternations for PWM control
3Ease of operation
If current alternation detection is converted to GND reference signal, then control IC compatibility is achieved, but insulation is required
Solution Approach 1:
The patent connects the current detectors in series with the coil so that their output signals are naturally referenced to the same potential as the control IC (GND). This equipotential connection eliminates the need for insulation or potential reference conversion, allowing direct compatibility with the control IC while maintaining ease of operation
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 configuration simplifies the control circuit, reduces costs by eliminating the need for expensive current transformers, and ensures efficient power conversion with minimal harmonic wave noise by controlling the current to be sinusoidal with the same phase as the AC voltage.
Implementation Method 1
A first current detector and a second current detector are provided. A coil has a first end connected to a first terminal of the power supply AC through the first and second current detectors connected in series
Implementation Method 2
A first semiconductor switch has a source terminal connected to a second end of the coil. A second semiconductor switch has a drain terminal connected to the second end of the coil. A first diode has a cathode connected to a drain terminal of the first semiconductor switch and an anode connected to a second power supply terminal
Implementation Method 3
A smoothing capacitor is connected in parallel with the first and second diodes
Data Source
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AI summary
A power conversion device includes first and second current detectors. A coil is connected a first power terminal through the first and second current detectors. A first switch has a source terminal connected to the coil and a second semiconductor switch has a drain terminal connected to the coil. A first diode is connected between a drain terminal of the first semiconductor switch and a second power supply terminal. A second diode is connected between a source terminal of the second semiconductor switch and the second power terminal. A capacitor is connected in parallel with the first and second diodes. A control circuit is configured to turn the first and second semiconductor switches on or off based on current detections of the first and second current detectors.