Switching Control Circuit for Capacitor Discharge in Power Supplies
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In insulated power supply circuits, when the AC voltage is interrupted, the control circuit that operates using the auxiliary coil voltage cannot function, leading to potential electric shocks during maintenance due to accumulated charge in capacitors.
Innovation Solution
A switching control circuit that includes a control circuit to output control signals for managing the transistor's switching control, utilizing a first drive circuit for normal operation and a second drive circuit to control the transistor's on-resistance for discharging the capacitor when the input voltage is interrupted, ensuring safe discharge of the capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control circuit operates using the auxiliary coil voltage, then the power supply circuit can function during normal operation, but when the AC voltage is interrupted and the auxiliary coil voltage drops, the control circuit cannot operate and the capacitor cannot be discharged
Solution Approach 1:
The patent introduces a detection circuit as an intermediary that monitors the AC voltage status and capacitor charge state independently of the control circuit's operational status. This detection circuit can detect the need for discharge even when the control circuit is non-operational due to auxiliary coil voltage drop, thereby mediating between the power supply system and the discharge mechanism to eliminate the harmful electric shock risk.
Solution Approach 2:
The system is designed to automatically detect and initiate capacitor discharge when AC voltage interruption is detected, without requiring manual intervention or control circuit operation. The discharge control circuit autonomously activates based on detection signals, enabling the system to service itself by eliminating the hazardous charge condition even when the main control circuit is incapacitated.
2Device complexity
If a single drive circuit is used for transistor control, then the device complexity is reduced, but the system cannot differentiate between normal operation and AC interruption to perform appropriate discharge control
Solution Approach 1:
The patent segments the drive circuit into two distinct circuits: a first drive circuit for normal switching control during AC power supply, and a second drive circuit for discharge control when AC voltage is interrupted. This segmentation allows each circuit to be optimized for its specific function and enables the system to adapt to different operational conditions by switching between the two circuits based on detection signals.
Solution Approach 2:
The system dynamically switches between the first drive circuit and the second drive circuit based on the operational status detected by the detection circuit. When AC voltage is supplied, the first drive circuit controls the transistor for normal power conversion; when AC voltage is interrupted, the second drive circuit takes over to control the transistor for capacitor discharge, providing dynamic adaptability to changing conditions.
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
The solution allows for safe and appropriate discharge of capacitors when the input voltage is interrupted, preventing electric shocks during maintenance and ensuring the power supply circuit operates effectively.
Implementation Method 1
a transformer including a primary coil provided on a primary side thereof, a secondary coil provided on a secondary side thereof, and an auxiliary coil, the primary coil being configured to have a voltage of the first capacitor applied thereto
Implementation Method 2
a first capacitor configured to smooth an input voltage of the power supply circuit
Implementation Method 3
a second capacitor configured to have a voltage from the auxiliary coil applied thereto
Data Source
AI summary
A power supply circuit having a first capacitor, a transformer including a primary coil having a voltage of the first capacitor applied thereto, a secondary coil and an auxiliary coil, a second capacitor having a voltage from the auxiliary coil applied thereto, a transistor controlling an inductor current flowing through the primary coil, a control circuit outputting a first control signal when supply of the input voltage is unstopped, or is stopped yet a voltage of the second capacitor reaches a first level, and outputting a second control signal thereafter when the voltage of the second capacitor further reaches a second level, a first drive circuit outputting a first drive signal for switching control of the transistor in response to the first control signal, and a second drive circuit outputting a second drive signal for controlling on-resistance of the transistor to discharge the first capacitor, in response to the second control signal.