Start-up Circuit Discharges EMI Filter Voltage for Power Saving
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Solution Overview
Problem
Traditional switching mode power supplies face challenges in power saving, particularly at light-load and no-load conditions due to the fixed power loss and standby power consumption caused by bleeding resistors in EMI filters, which are inefficient and wasteful.
Innovation Solution
A start-up circuit is introduced that includes a detection circuit to generate a sample signal, a sample circuit to produce a reset signal for discharging the EMI filter, and a delay circuit to manage the discharging signal, allowing for the controlled discharge of stored voltage in X-capacitors when the power source is shut down, thereby reducing standby power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bleeding resistor is placed across the X-capacitors of the EMI filter to discharge stored energy and prevent electric shock, then safety is improved, but standby power consumption increases due to fixed power loss
Solution Approach 1:
The patent applies the dynamics principle by making the bleeding resistor's resistance value variable rather than fixed. The resistor changes its resistance dynamically based on the operating state: at high voltage it has low resistance to discharge stored energy quickly for safety, and at low voltage it has high resistance to minimize standby power consumption. This dynamic adjustment resolves the contradiction between safety and energy efficiency.
Solution Approach 2:
The patent implements parameter changes by varying the resistance value of the bleeding resistor according to the voltage level. The resistor transitions between different resistance states based on voltage thresholds, allowing the system to optimize both safety (at high voltage) and power saving (at low voltage). This parameter variation enables the system to adapt to different operating conditions and resolve the technical contradiction.
2Reliability
If a fixed resistance bleeding resistor is used to discharge EMI filter voltage, then safety is ensured, but power saving performance deteriorates at light-load and no-load conditions
Solution Approach 1:
The patent uses dynamics by implementing a variable resistance bleeding resistor that adjusts its resistance based on voltage levels and operating conditions. At high voltage, the resistor provides low resistance for rapid discharge to ensure safety. At low voltage and no-load conditions, it switches to high resistance to minimize power loss. This dynamic behavior resolves the contradiction between safety requirements and energy efficiency.
Solution Approach 2:
The patent applies parameter changes by varying the resistance value of the bleeding resistor according to different operating states. The resistance parameter is adjusted based on voltage thresholds and load conditions, enabling the system to maintain safety at high voltage while minimizing power loss at low voltage and no-load conditions. This parameter adaptation resolves the technical contradiction.
3Reliability
If the bleeding resistor continuously discharges the X-capacitors to maintain safety, then electric shock prevention is improved, but standby power consumption increases
Solution Approach 1:
The patent applies periodic action by implementing a control mechanism that activates the bleeding resistor only when necessary. The resistor is turned on periodically or conditionally based on voltage detection, rather than operating continuously. This periodic activation maintains electric shock prevention while significantly reducing standby power consumption compared to continuous discharge operation.
Solution Approach 2:
The patent uses dynamics by making the bleeding resistor's operation conditional rather than continuous. The resistor dynamically switches between active and inactive states based on voltage levels and safety requirements. This dynamic control enables the system to maintain electric shock prevention only when needed, thereby reducing standby power consumption while preserving safety.
Data Source
AI summary
A start-up circuit to discharge EMI filter is developed for power saving. It includes a detection circuit detecting a power source for generating a sample signal. A sample circuit is coupled to the detection circuit for generating a reset signal in response to the sample signal. The reset signal is utilized for discharging a stored voltage of the EMI filter.