PFC DC/AC/DC Converter with Switchable Threshold Current
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Solution Overview
Problem
Conventional power supply apparatuses require two separate insulation type DC/DC converters, leading to increased component count, cost, and space usage due to the need for a transformer, which is costly and inefficient, especially when the input voltage is low.
Innovation Solution
A power supply apparatus with a single insulation type DC/DC converter that uses a switchable threshold current to optimize the on-time of the second switching transistor, reducing power loss and component size by adjusting the threshold current based on intermediate voltage levels, allowing the second switching transistor to operate efficiently in both standby and normal states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two separate insulation type DC/DC converters are used, then the power supply can operate in both standby and normal states, but the component count, cost, and space usage increase
Solution Approach 1:
The patent merges the functionality of two separate DC/DC converters into a single converter by combining the standby switch and main power supply switch into one switching element. This single converter uses a transformer with multiple windings to provide both standby power (through auxiliary winding) and main power conversion (through primary and secondary windings), thereby reducing component count while maintaining dual-state operation capability
Solution Approach 2:
The single DC/DC converter is designed to perform multiple functions: it provides power conversion for normal operation mode and standby mode simultaneously. The transformer configuration enables the converter to deliver power to different output circuits depending on the switching state, making the converter universal for both operational states without requiring separate dedicated converters
2Reliability
If a transformer is included in the DC/DC converter, then insulation and power conversion are achieved, but cost and size increase
Solution Approach 1:
The patent implements a nested transformer structure where the auxiliary winding for standby power is embedded within the same transformer core as the main power windings. The transformer is configured with primary, secondary, and auxiliary windings sharing a common magnetic core, allowing the standby power pathway to be nested within the main power conversion structure, thereby reducing overall transformer size and eliminating the need for separate transformers
3Device complexity
If the threshold current is fixed, then the control is simple, but power loss increases when input voltage is low
Solution Approach 1:
The patent implements dynamic threshold current adjustment where the threshold current value changes based on the input voltage level. When input voltage is low, the threshold current is reduced to minimize power loss in the switching transistor. This dynamic adaptation allows the converter to optimize efficiency across varying input conditions while maintaining stable operation, with the control circuit automatically adjusting the threshold based on voltage sensing
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 power loss and component size, lowering costs and space requirements while maintaining efficient operation across varying voltage states, achieving a more economical and compact power supply solution.
Implementation Method 1
a rectifier circuit configured to full-wave rectify AC voltage
Implementation Method 2
a power factor correction circuit including a non-insulation type DC/DC converter configured to receive an output voltage of the rectifier circuit, and to generate a DC intermediate voltage, and configured to operate such that the phase of the input current matches the phase of the AC voltage thus rectified
Implementation Method 3
an insulation type DC/DC converter configured to receive the intermediate voltage, and to convert the level of the intermediate voltage thus received
Data Source
AI summary
A second control circuit is configured to switch a pulse signal to a level which turns off a second switching transistor when a coil current that flows through a primary winding reaches a predetermined threshold current. The second control circuit is configured to start a switching operation when a power supply for an electronic device is turned on, to set the threshold current to a first value when an intermediate voltage is higher than a predetermined level, and to set the threshold current to a second value that is lower than the first value when the intermediate voltage is lower than a predetermined level. A first control circuit is configured to start a switching operation upon receiving an instruction from a microcontroller to start operating.