Bridge Rectifier Transient Voltage Protection
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Solution Overview
Problem
Existing rectifier circuits in electrical devices often require partial assembly and testing before high-voltage isolation testing, as transient protection devices are susceptible to damage during this process, leading to inefficiencies in manufacturing.
Innovation Solution
A battery charging device configuration with metal-oxide varistors connected in parallel with specific diodes of a full-wave rectifier, along with capacitors, allows for surge protection without direct connection to chassis ground, enabling full assembly and testing without damaging the surge suppression components during high-voltage isolation testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transient protection devices (MOVs) are connected in parallel with diodes of a bridge rectifier for surge protection, then the rectifier diodes are protected from excessive voltage, but the MOVs are susceptible to damage during high-voltage isolation testing
Solution Approach 1:
The patent extracts the transient protection function from the traditional chassis-ground-connected configuration and relocates it to be connected in parallel with specific diodes (D3 and D4) of the bridge rectifier. This extraction allows the MOVs to protect against surges while being isolated from the high-voltage stress of isolation testing that affects chassis-ground connections.
Solution Approach 2:
The patent introduces capacitors as intermediary components connected between the MOV connection points and chassis ground. These capacitors act as mediators that provide a path for high-voltage isolation testing without directly exposing the MOVs to damaging voltage levels, thereby protecting the MOVs while maintaining testing capability.
2Productivity
If transient protection devices are installed before high-voltage isolation testing, then surge protection is provided during operation, but the devices cannot be fully assembled and tested before final testing
Solution Approach 1:
The patent enables preliminary assembly of the complete device including MOVs before high-voltage isolation testing. The specific connection configuration allows the device to be fully assembled with transient protection in place, and then undergo complete testing including isolation testing, without requiring disassembly or reconfiguration.
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 protects the rectifier diodes from excessive voltage and improves manufacturing efficiency by allowing the device to be fully assembled and tested without damaging the surge suppression components, ensuring compliance with lightning and industrial surge tests.
Implementation Method 1
a first metal-oxide varistor (first MOV) connected in parallel with the third diode, and a second metal-oxide varistor (second MOV) connected in parallel with the fourth diode
Implementation Method 2
The capacitor is a first capacitor arranged to electrically couple the anodes of the third diode and the fourth diode to a chassis ground of the device
Data Source
Figure 1
Figure 2
AI summary
A battery charging device (10) for charging a battery with power drawn via a wall plug (20) includes a full-wave rectifier (30) of four diodes, two first metal-oxide varistors (MOVs), and a capacitor. The two MOVs are connected in parallel with the lower diodes of the bridge. The capacitor is arranged to electrically couple the anodes of the lower diode to a chassis ground (54) of the device (10). This configuration allows for isolation voltage (hi-pot) testing to be performed with the MOVs in place.