Rectifier Clamp Circuit for Lower-Voltage Smoothing Capacitors
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Solution Overview
Problem
Existing AC/DC converters face challenges in downsizing and cost reduction due to the need for high-voltage electrolytic capacitors, which are necessary to handle √2 times the AC input voltage, especially in converters without power factor correction.
Innovation Solution
A rectifier circuit with a bridge circuit and a voltage clamp circuit that includes a clamp transistor and smoothing capacitor, connected in series between the bridge circuit output and a common ground line with the DC/DC converter, allowing for reduced voltage requirements on the smoothing capacitor and enabling the use of smaller components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-voltage electrolytic capacitor is used to handle √2 times the AC input voltage, then the rectifier circuit can operate reliably, but the size and cost of the AC/DC converter increase
Solution Approach 1:
The patent divides the voltage handling function into two parts: the bridge circuit handles the AC input voltage, while the clamp transistor and smoothing capacitor handle only the ripple voltage. This segmentation allows the smoothing capacitor to operate at a lower voltage level, reducing its size while maintaining overall system reliability.
Solution Approach 2:
The clamp transistor acts as an intermediary element between the bridge circuit output and the smoothing capacitor. It controls the voltage applied to the capacitor, allowing the capacitor to see a reduced voltage waveform and thereby reducing its required capacitance and voltage rating.
2Reliability
If a high-voltage electrolytic capacitor is used to handle √2 times the AC input voltage, then the rectifier circuit can operate reliably, but the cost of the AC/DC converter increases
Solution Approach 1:
The patent segments the voltage handling function so that the smoothing capacitor only needs to handle ripple voltage rather than the full rectified voltage. This segmentation reduces the capacitor's voltage rating requirement, leading to lower component cost while maintaining reliable operation through the added clamp transistor control.
Solution Approach 2:
The patent changes the voltage parameter applied to the smoothing capacitor by introducing the clamp transistor. The capacitor voltage is changed from √2×VAC (conventional) to a reduced level with lower peak voltage, allowing the use of lower-voltage, lower-cost capacitors while maintaining system reliability through active voltage control.
3Adaptability or versatility
If separate ground lines are used for the rectifier circuit and DC/DC converter, then each circuit can be independently designed, but the component count and circuit complexity increase
Solution Approach 1:
The patent merges the ground lines of the rectifier circuit and DC/DC converter into a common ground. This consolidation reduces the number of ground connections and simplifies the overall circuit layout while maintaining proper reference potentials for both circuits, thereby reducing complexity without sacrificing design flexibility.
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 reduces the size and cost of the AC/DC converter by allowing the use of smaller electrolytic capacitors and simplifies the DC/DC converter drive circuit, reducing common mode noise and component count.
Implementation Method 1
a bridge circuit that rectifies an AC voltage
Implementation Method 2
a voltage clamp circuit that includes a clamp transistor and a smoothing capacitor sequentially connected in series between an output terminal of the bridge circuit and a ground line and is structured to control on and off of the clamp transistor according to an output voltage of the bridge circuit
Implementation Method 3
a voltage clamp circuit that includes a clamp transistor and a smoothing capacitor sequentially connected in series
Data Source
AI summary
In a rectifier circuit, a bridge circuit rectifies an AC voltage. A voltage clamp circuit includes a clamp transistor, and a smoothing capacitor sequentially connected in series between an output terminal of the bridge circuit and a ground line, and controls on and off of the clamp transistor according to an output voltage of the bridge circuit. A DC/DC converter at a subsequent stage is connected in parallel with the smoothing capacitor.