Power Supply Startup Circuit Dynamic Discharging Path
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Solution Overview
Problem
Conventional power supplies consume unnecessary power due to resistors used for discharging electromagnetic interference filters when not loaded, as they remain active even during normal operation.
Innovation Solution
A startup circuit that includes a first transistor, bias resistor, pull-down switch, voltage detector, and discharging path generator to detect AC input power status and provide a discharging path only when AC input is stopped, using a depletion mode transistor or junction field effect transistor, and components like comparators, watch-dog timers, and logic operation circuits to manage the discharging path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor is used to discharge the electromagnetic interference filter, then the filter can be discharged, but power is consumed continuously during normal operation
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a static resistor-based discharging system to a dynamic switch-controlled system. The switch is controlled by a detection circuit that monitors AC input status, enabling the discharging path to be dynamically activated only when needed (during startup or AC failure) and deactivated during normal operation, thereby eliminating continuous power consumption while maintaining reliable discharging functionality
Solution Approach 2:
The patent implements self-service through an automatic detection and control mechanism. The detection circuit automatically monitors the AC input status and controls the switch accordingly, eliminating the need for manual intervention or continuous power supply to maintain the discharging capability. The system serves itself by automatically activating the discharging path only when AC input is absent or during startup conditions
2Reliability
If a resistor is always connected for discharging, then the EMI filter is always discharged, but it causes main power consumption when not loaded
Solution Approach 1:
The patent applies preliminary action by preparing the discharging path in advance through a switch that can be quickly activated when needed. The detection circuit continuously monitors AC input status and preemptively activates the discharging path when AC failure is detected, ensuring immediate discharging capability without requiring a permanently connected resistor that would cause continuous power loss
Solution Approach 2:
The patent implements parameter changes by transitioning the discharging path resistance from a low-value state (when switch is closed during startup or AC failure) to a high-value state (when switch is open during normal operation). This dynamic parameter change allows the system to maintain effective discharging capability when needed while minimizing power loss 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 minimizes power loss by providing a discharging path for the electromagnetic interference filter only when AC input is stopped, thereby improving the efficiency of the power supply by avoiding unnecessary power consumption during normal operation.
Implementation Method 1
The voltage detector is coupled to the first transistor and the bias resistor and generates the detection result by detecting a voltage on the second end of the first transistor
Implementation Method 2
the first transistor is a depletion mode transistor or a junction field effect transistor
Data Source
AI summary
A power supply and its startup circuit are provided. The startup circuit includes a first transistor, a bias resistor, a pull-down switch, a voltage detector, and a discharging path generator. A first end of the first transistor receives alternating current (AC) input power. The bias resistor is serially coupled between a second end and a control end of the first transistor. The pull-down switch is turned on or turned off according to a detection result. The voltage detector generates the detection result by detecting a voltage on the second end of the first transistor. The discharging path generator provides a discharging path between the second end of the first transistor and a reference ground voltage according to the detection result.