Power Source Controlling IC for AC-DC Converter Protection
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Solution Overview
Problem
Conventional AC-DC converters with power factor improving circuits (PFC) require multiple integrated circuits and external parts, increasing cost and complexity, and lack protection functions against abnormal states such as overvoltage, short circuits, and overpower conditions, which hinders miniaturization and efficient operation.
Innovation Solution
A power source controlling semiconductor integrated circuit that includes a control circuit, voltage generating circuit, pull-up section, and voltage comparing circuits to manage the current through a voltage converting transformer, enabling protection functions like stopping operation upon detecting abnormal states without increasing the number of parts, and using a single photocoupler for feedback and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a power factor improving circuit (PFC) is added to raise the power factor of the AC-DC converter, then the power factor is improved, but the number of integrated circuits and external parts increases, leading to increased cost and device complexity
Solution Approach 1:
The patent combines the PFC control circuit and the switching power source control circuit into a single semiconductor integrated circuit. The control circuit includes a PFC control section that generates a PFC control signal to control the PFC switching element, and a switching power source control section that generates a switching control signal based on feedback voltage. This integration eliminates the need for separate PFC control ICs and reduces external components, thereby improving the power factor while reducing device complexity and cost.
2Reliability
If protection functions are added to protect against abnormal states (overvoltage, short circuit, overpower), then the reliability is improved, but the number of parts and device complexity increases
Solution Approach 1:
The patent integrates multiple protection functions into the single semiconductor integrated circuit. The control circuit includes a feedback voltage detection section that detects the feedback voltage and compares it with a reference voltage to determine abnormal states. When the feedback voltage exceeds the reference voltage (indicating overvoltage, short circuit, or overpower conditions), the control circuit stops outputting the switching control signal, thereby protecting the system. This integration provides comprehensive protection without requiring additional separate protection circuits or components.
Solution Approach 2:
The protection function operates autonomously within the control circuit. The feedback voltage detection section continuously monitors the feedback voltage and automatically compares it with the reference voltage. When an abnormal state is detected, the control circuit automatically stops the switching control signal output without requiring external intervention or additional protection components. This self-service mechanism provides reliable protection while minimizing device complexity.
3Manufacturing precision
If the photocoupler is used for feedback control, then the insulated DC power source device achieves proper voltage regulation, but the photocoupler does not effectively function at startup when no alternating currents are induced in the auxiliary winding
Solution Approach 1:
The patent applies preliminary action by providing a startup circuit that generates a startup signal to initialize the control circuit before normal operation begins. The startup circuit detects when the feedback voltage is below a predetermined threshold (indicating startup conditions) and generates a startup signal that sets the control circuit to a predetermined initial state. This preliminary initialization ensures that the control circuit is properly configured before the photocoupler begins its feedback function, preventing malfunctions during startup while maintaining proper voltage regulation 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 allows for compact DC power source devices with improved power factor switching control and protection against abnormal states, preventing malfunctions during startup and enabling miniaturization by reducing the number of components.
Implementation Method 1
a voltage converting transformer having a primary side winding to which the voltage rectified by the diode bridge circuit is input
Implementation Method 2
a first external terminal to which a detected voltage from a secondary side of the transformer is fed back through a photocoupler
Data Source
AI summary
A power source controlling IC controlling a current flown through the primary side winding of a transformer is provided with an external terminal to which a detected voltage from the secondary side is fed back through a photocoupler; a control circuit generating and outputting a control signal of a switching element controlling the current according to an input voltage; a voltage generating circuit generating an internal reference voltage based on the input voltage; a pull-up section connected to the terminal to pull up the potential of the terminal to the internal reference voltage to give a bias voltage to a light receiving element of the photocoupler; and a voltage comparing circuit comparing the voltage of the external terminal and a predetermined reference voltage, wherein the control circuit stops outputting the control signal based on the output of the first voltage comparing circuit when detecting an abnormality.