Current Balanced Push-Pull Inverter Snubber Circuit Design
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Solution Overview
Problem
Inverter circuits, particularly center tap push-pull type, face efficiency issues due to continuous current flow in discharge resistors caused by potential differences between snubber capacitors and power supplies, leading to high losses and inefficient operation, as well as excessive surge voltages from leakage inductance, which burden the snubber circuit.
Innovation Solution
The inverter circuit design includes two switching elements with snubber circuits featuring series-connected snubber capacitors and diodes, and discharge resistors that allow only half of the surplus charge to be discharged, minimizing heat generation and surge voltage, using a current balanced push-pull type configuration to reduce current flow and eliminate excessive surge voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a discharge resistor is provided in a center tap push-pull type inverter circuit to discharge the snubber capacitor, then the snubber capacitor can be discharged, but a current flows continuously in the discharge resistor due to the large potential difference between the snubber capacitor and power supply, causing large losses and poor efficiency
Solution Approach 1:
The snubber capacitor is divided into two series-connected capacitors (first snubber capacitor and second snubber capacitor). This segmentation allows the voltage to be distributed across both capacitors, reducing the potential difference across each individual capacitor and thereby reducing the continuous discharge current and associated losses.
Solution Approach 2:
A diode is introduced as an intermediary component in the discharge path. The diode allows discharge current to flow only when the snubber capacitor voltage exceeds the power supply voltage by a certain margin, blocking the continuous discharge current that would otherwise flow due to the large potential difference, thus reducing losses while maintaining surge suppression capability.
2Object-affected harmful factors
If a snubber circuit is provided to clamp surge voltage generated by leakage inductance, then surge voltage is suppressed, but the burden upon the snubber circuit becomes heavy due to excessively great induced voltage from leakage inductance in center tap push-pull configuration
Solution Approach 1:
The snubber capacitor is segmented into two series-connected capacitors, which distributes the voltage stress across both capacitors rather than concentrating it on a single capacitor. This reduces the burden on each individual capacitor and the overall snubber circuit while maintaining effective surge voltage clamping.
3Object-affected harmful factors
If a typical snubber circuit with snubber resistor is used to attenuate surge voltage oscillation, then surge voltage is suppressed, but efficiency deteriorates due to heat generation in the snubber resistor
Solution Approach 1:
The invention replaces the traditional snubber resistor (which continuously dissipates energy as heat) with a discharge resistor that only operates intermittently to discharge the snubber capacitor when needed. This substitution eliminates continuous heat generation while maintaining surge suppression capability, significantly improving efficiency.
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 ensures high efficiency by minimizing losses in discharge resistors and reducing surge voltages applied to switching elements, maintaining low current flow and preventing excessive voltage clamping, thus enhancing overall circuit performance.
Implementation Method 1
a snubber capacitor and a snubber resistor for damping which attenuates surge voltage oscillation are connected in series
Implementation Method 2
the charge for charging and discharging the snubber capacitor is converted to heat by the snubber resistor
Implementation Method 3
when a switching element is turned OFF, a surge voltage is applied to that switching element due to the operation of leakage inductance between the primary side and the secondary side of a transformer
Data Source
AI summary
This current balanced push-pull type inverter circuit includes first and second switching elements, and an output transformer which includes a first primary winding and a second primary winding connected in series between said first and second switching elements, and also includes a secondary winding for obtaining an output voltage. This inverter circuit also includes a first voltage supply capacitor, a second voltage supply capacitor, and a control unit. A first snubber circuit, in which a first free wheel diode and first and second snubber capacitors are connected in series, is connected in inverse parallel to the first switching element. A first discharge resistor is connected between the first snubber capacitor and a first power supply capacitor, and a second discharge resistor is connected between the second snubber capacitor and a third power supply capacitor. And a second snubber circuit and discharge resistors are connected to the second switching element as well, in a similar manner.