Bridgeless PFC Current Sensing Circuit with Transformer Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bridgeless boost PFC circuits face challenges in efficiently sensing currents through switches and inductors, particularly in medium and large power applications, due to common mode noise and complex circuit configurations.
Innovation Solution
A bridgeless power factor correction circuit system with a current sensing circuit utilizing current transformers (CTs) to accurately sense currents flowing through switches and inductors, featuring a simpler configuration and lower cost, capable of handling stronger anti-interference and higher power requirements, and employing a controlling method that senses currents during both switch on and off states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional bridgeless boost PFC circuits are used, then the circuit can operate with reduced diode conducting loss, but the current sensing becomes complex and susceptible to common mode noise
Solution Approach 1:
The patent segments the current sensing function by using separate current transformers for different current paths (inductor current and switch current), allowing independent sensing of each current component. This segmentation simplifies the overall sensing circuit design while maintaining accuracy in the bridgeless boost PFC topology.
Solution Approach 2:
The patent introduces current transformers as intermediary devices to sense currents without direct electrical connection to the high-voltage switching nodes. This intermediary approach isolates the sensing circuit from common mode noise while accurately measuring the currents flowing through the inductor and switches.
2Loss of energy
If bridgeless boost topology is adopted, then efficiency increases due to reduced diode losses, but current sensing accuracy deteriorates due to common mode noise
Solution Approach 1:
Current transformers serve as intermediary devices that magnetically couple the sensing circuit to the current-carrying conductors without direct electrical connection. This magnetic coupling provides galvanic isolation, blocking common mode noise from reaching the sensing circuit while accurately reproducing the current waveform for measurement.
Solution Approach 2:
The patent replaces direct electrical connection-based current sensing with magnetic field-based sensing using current transformers. This substitution eliminates the direct electrical path that introduces common mode noise, relying instead on electromagnetic induction to sense currents with high accuracy and noise immunity.
3Device complexity
If simple current sensing methods are used, then circuit configuration is simpler, but sensing precision is insufficient for high power applications
Solution Approach 1:
The patent replaces simple resistive sensing or direct voltage measurement methods with current transformer-based magnetic sensing. This substitution provides galvanic isolation and high-precision current measurement capability suitable for high power applications, while the transformer coupling maintains relatively simple circuit integration.
Solution Approach 2:
Current transformers act as intermediary devices that provide both electrical isolation and precise current measurement. The magnetic coupling mechanism allows accurate current signal transmission to the control circuit while blocking high-voltage transients and common mode noise, achieving both simplicity and precision.
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 solution enables accurate and efficient current sensing with simpler circuit configurations, reduced costs, and enhanced anti-interference capabilities, suitable for applications requiring higher power and precise current signal sampling without the need for additional control circuits.
Implementation Method 1
a first current transformer (CT) for sensing a first current flowing through the bidirectional switch coupled to the bidirectional switch in series, which having a primary side winding coupled to the bidirectional switch and a first and a second secondary side windings
Data Source
AI summary
The configurations of a bridgeless PFC circuit system and a controlling method thereof are provided. The proposed system includes a bridgeless PFC circuit including a first bridge arm having a first and a second terminals and a first middle point, a second bridge arm having a first and a second terminals and a second middle point, and a bidirectional switch coupled between the first middle point and the second middle point, and an inductor coupled between the first middle point and an AC power source coupled to the second middle point, and a current sensing circuit including a first current transformer sensing a first current flowing through the bidirectional switch, which having a primary side winding coupled to the bidirectional switch and a first and a second secondary side windings, and a switching device coupled to the two secondary side windings.