Surge Protection Circuit for Bridge Rectifier with Peak Voltage Charging
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Solution Overview
Problem
Existing surge protection circuits for circuits with bridge rectifier and power factor correction (PFC) modules are inefficient and require high-quality components, as they often charge and discharge capacitors with every half-cycle of the mains supply, leading to reduced capacitor lifetime and increased costs.
Innovation Solution
A surge protection circuit using a capacitor charged to a peak voltage during normal operation and discharged only during surge events, employing diodes and a discharge means like a Zener diode and resistor to manage energy dissipation only during surges, allowing for the use of lower quality components and extending capacitor lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor is used in prior art surge protection circuits, then surge protection is provided, but the capacitor is charged and discharged with every half-cycle of mains supply, reducing its lifetime and requiring high-quality components
Solution Approach 1:
The patent applies periodic action by using the natural half-cycle rectification of the mains supply to charge the capacitor only during specific periods (when the supply voltage is higher than the capacitor voltage), rather than continuous charging. The discharge occurs only during surge events, creating a periodic charge-discharge pattern that extends capacitor life and allows use of lower quality components.
Solution Approach 2:
The capacitor serves a dual function: it acts as both a surge protection element and a voltage reference that automatically charges itself during normal operation when the mains voltage exceeds the capacitor voltage. This self-charging mechanism eliminates the need for external charging circuits and reduces component stress.
2Reliability
If discharge means is always connected to the capacitor, then the capacitor can discharge during surge events, but the capacitor is continuously discharged during normal operation, reducing efficiency
Solution Approach 1:
The discharge means is made dynamic through the use of a discharge switch (such as a thyristor or TRIAC) that remains non-conductive during normal operation and only becomes conductive when triggered by a surge event. This dynamic switching ensures the capacitor is protected during surges while minimizing energy loss during normal operation.
Solution Approach 2:
The circuit incorporates feedback through voltage detection across the capacitor that triggers the discharge switch only when the voltage exceeds a predetermined threshold indicating a surge event. This feedback mechanism ensures discharge occurs only when necessary, preventing continuous energy dissipation during normal 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 solution provides robust and economical surge protection by minimizing component stress during normal operation, extending capacitor life, and effectively managing surge events in circuits without a direct current path to the output capacitor.
Implementation Method 1
a capacitor (C2) which is charged by a surge event
Implementation Method 2
discharge means...configured to discharge the capacitor when the voltage across the capacitor is in excess of the peak value of the maximum supply voltage
Data Source
Figure 1~3
Figure 4a~4b
Figure 4c~4d
AI summary
A surge protection circuit for a circuit comprising a rectification module (433). The surge protection circuit comprising a first diode (420), a second diode (422), a capacitor (424; 524; 624) and discharge means (426). The anode of the first diode (420) is connected to a first input of the rectification module (433), and the anode of the second diode (422) is connected to a second input of the rectification module (433). The cathode of the first and second diodes (420, 422) are both connected to the first plate of the capacitor (424; 524; 624). The second plate of the capacitor (424; 524; 624) is connected to the negative output of the rectification module (433). The capacitor (424; 524; 624) is configured such that it is consistently charged to substantially the peak value of a supply voltage during normal operation between surge events. The discharge means (426) is connected to the first plate of the capacitor (424; 524; 624) and is configured to discharge the capacitor (424; 524; 624) when the voltage across the capacitor (424; 524; 624) is in excess of the peak of the maximum value of the normal supply voltage and not discharge the capacitor when the voltage across the capacitor is not in excess of the peak of the maximum value of the normal supply voltage.