Bipolar Active Clamp Switch for Leakage Inductance Recycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing switch mode power supplies face challenges in efficiently recycling leakage inductance losses, particularly due to the high cost and complexity associated with active clamp circuits that require high side drivers, which are expensive and increase the overall cost of off-line active clamp flyback technology.
Innovation Solution
The use of a bipolar junction transistor configured as a bipolar clamp switch, which leverages its storage charge properties to maintain conductivity and function as an active clamp without the need for a high side driver, allowing for efficient recycling of leakage inductance losses and reducing costs by eliminating the requirement for expensive high voltage IC technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If active clamp circuits are made with N-type MOSFET switch devices and include a high side driver, then leakage inductance losses can be recycled, but the cost and complexity of the power supply increases significantly
Solution Approach 1:
The patent extracts and eliminates the high side driver circuit from the active clamp configuration by using a bipolar transistor's inherent storage charge properties to perform the clamping function without requiring external driver circuitry, thereby reducing complexity while maintaining energy recycling capability
Solution Approach 2:
The bipolar transistor serves itself by utilizing its own storage charge properties to maintain conductivity and perform the active clamp function without requiring an external high side driver, making the system self-sufficient and reducing overall circuit complexity
2Loss of energy
If high side drivers are used in active clamp circuits, then leakage inductance can be recycled, but the cost of the power supply increases due to expensive high voltage IC technology
Solution Approach 1:
The patent replaces expensive high voltage IC technology with a simpler bipolar transistor configuration that uses readily available components, significantly reducing manufacturing cost while maintaining the energy recycling function through the transistor's natural charge storage behavior
3Loss of energy
If N-type MOSFET switch devices are used in active clamp circuits, then leakage inductance losses can be recycled, but the overall cost increases compared to bipolar devices
Solution Approach 1:
The patent changes the device type parameter from N-type MOSFET to bipolar transistor, utilizing the bipolar device's different operational characteristics (specifically its storage charge properties) to achieve the same energy recycling function at lower component cost
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 approach enables efficient recycling of leakage inductance losses, reduces electromagnetic interference, and lowers the peak drain voltage, resulting in a more cost-effective and efficient power supply solution for switch mode power supplies, particularly in applications like smartphones and routers.
Implementation Method 1
a collector-base junction of a bipolar junction transistor including a base, an emitter and a collector is forward biased at a start of a secondary stroke of a switched mode power supply enabling current to flow from the collector to the base
Implementation Method 2
current flowing through the bipolar junction transistor is enabled to reverse an electrical charge stored in the bipolar junction transistor when energy associated with leakage inductance in a transformer is transferred to a capacitor thereby keeping the bipolar junction transistor conductive
Data Source
AI summary
A switch mode power supply can include a bipolar device (e.g., bipolar junction transistor) connected in series with a capacitor and operable as a bipolar clamp switch where the bipolar device can be turned on by forward biasing a collector-base junction. The capacitor connected in association with the bipolar device can keep the bipolar clamp switch conductive for a limited time based on energy obtained from a transformer primary winding and stored in the capacitor when the base-collector junction bias is reversed. Storage charge properties of the bipolar clamp switch can be used to keep it conductive and working as an active clamp without requiring a high driver circuit.