Auxiliary-Winding Power Supply Control for Reliable Overvoltage Shutdown
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Solution Overview
Problem
Existing power supply control devices face challenges in effectively managing voltage overvoltage protection, particularly when the load increases, leading to potential failure in switching off the switching element due to excessive current flow through a dummy resistor, which can result in overvoltage protection voltage exceeding safe limits.
Innovation Solution
A power supply control device with a first control circuit that turns on a switch when a voltage exceeds a first reference voltage for a predetermined time, and a second control circuit that turns off the switching element when the voltage surpasses a second reference voltage, utilizing a transformer with primary, secondary, and auxiliary windings, and a capacitor, along with a resistor and switch in series between the power supply terminal and ground to manage voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large current is allowed to flow through the dummy resistor when voltage Vcc reaches 23V, then the voltage Vcc is dropped to prevent overvoltage, but the overvoltage protection function may fail and the switching element may not turn off reliably
Solution Approach 1:
The patent divides the overvoltage protection function into two separate control circuits: a first control circuit that manages the dummy resistor current based on a first reference voltage (23V), and a second control circuit that manages the switching element based on a second reference voltage (25V). This segmentation allows each circuit to operate independently with optimized parameters, preventing the conflict between dropping voltage and maintaining protection reliability.
Solution Approach 2:
The patent introduces a capacitor connected to the auxiliary winding as an intermediary energy storage element. This capacitor smooths the voltage fluctuations and provides a buffer between the switching element and the dummy resistor, allowing the system to manage overvoltage conditions more gracefully without requiring excessive current through the dummy resistor.
2Reliability
If the voltage Vcc is dropped by allowing current to flow through the dummy resistor, then overvoltage is prevented, but the switching element may fail to turn off due to excessive current
Solution Approach 1:
The patent separates the voltage dropping function (handled by the first control circuit and dummy resistor) from the switching control function (handled by the second control circuit). The first control circuit activates the dummy resistor when Vcc exceeds 23V to drop voltage, while the second control circuit independently monitors Vcc and turns off the switching element when it exceeds 25V, ensuring reliable switching control is not compromised by the current through the dummy resistor.
Solution Approach 2:
The patent changes the operational parameters by introducing two different reference voltages (23V for the dummy resistor control and 25V for the switching element control) and implementing time-based control logic. This allows the system to adjust its response based on the severity and duration of the overvoltage condition, preventing excessive current from affecting the switching element's ability to turn off.
3Reliability
If a dummy resistor is used to drop voltage Vcc, then overvoltage protection is achieved, but the system complexity increases and control precision is compromised
Solution Approach 1:
The patent implements a control system where two control circuits share common components such as the voltage detection mechanism and the auxiliary winding capacitor. The first and second control circuits both monitor the same Vcc voltage and can be integrated into a single control device, allowing them to perform multiple functions (voltage monitoring, dummy resistor control, and switching element control) without proportionally increasing overall system complexity.
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 effectively suppresses pseudo overvoltage influences and ensures reliable operation by dropping the voltage within controlled limits, reducing the risk of device failure and power consumption, while allowing for adjustable timing settings based on environmental conditions.
Implementation Method 1
A voltage Vcc of the power supply for driving such a power supply control device utilizes a voltage induced in auxiliary winding of a transformer by switching on and off of the switching element
Data Source
AI summary
A power supply control device that controls a switching element of a switching power supply apparatus which includes a transformer having a primary winding, a secondary winding, and an auxiliary winding, the switching element coupled to the primary winding, and a capacitor coupled to the auxiliary winding, includes: a power supply terminal coupled to one end of the capacitor; a switch and a resistor coupled in series between the power supply terminal and a ground; a first control circuit that controls the switch; and a second control circuit that controls the switching element, in which the first control circuit performs control to turn on the switch when a first voltage applied to the power supply terminal continuously exceeds a first reference voltage for a first time, and the second control circuit performs control to turn off the switching element when the first voltage exceeds a second reference voltage higher than the first reference voltage.