Zero Standby SMPS Using Secondary Wakeup and Startup Transistor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switching mode power supplies (SMPS) experience significant standby power consumption even when devices are not in use, leading to energy waste and environmental concerns, as they continuously draw power, necessitating a reduction in standby energy consumption.
Innovation Solution
The implementation of a system that automatically detects load conditions, shuts down most circuits in the primary side control IC during no-load conditions, and uses a secondary side control IC to maintain an extremely low switching frequency, along with a power transistor as a startup current amplifier, allowing for a large resistor to reduce startup power consumption, achieving zero standby power while maintaining dynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is reduced in light load or no load conditions, then switching loss of power transistor is reduced and power conversion efficiency is increased, but the system cannot maintain good dynamic performance when load changes
Solution Approach 1:
The patent implements dynamic switching frequency adjustment where the controller automatically modifies the switching frequency based on real-time load conditions. During light load or no load conditions, the switching frequency is reduced to minimize switching losses and improve efficiency. When load changes are detected, the frequency is increased to maintain good dynamic performance. This dynamic adaptation resolves the contradiction between energy loss reduction and reliability maintenance.
Solution Approach 2:
The patent changes the switching frequency parameter according to load conditions to optimize both efficiency and dynamic performance. By adjusting this critical parameter dynamically, the system achieves low switching loss during light load while maintaining responsiveness during load transitions, effectively resolving the technical contradiction.
2Reliability
If auxiliary power supplies continuously draw power as long as the product is plugged in, then the power supply is always ready to operate, but significant standby energy waste occurs
Solution Approach 1:
The patent implements periodic monitoring instead of continuous operation. The controller periodically checks load conditions and system state, entering a low-power standby mode when no load is detected. This periodic action maintains the system's ability to detect and respond to load changes while dramatically reducing standby energy consumption, resolving the contradiction between operational readiness and energy waste.
Solution Approach 2:
The system uses secondary side control to monitor output voltage and automatically trigger primary side control IC to wake up when needed. This self-service mechanism ensures the system remains ready to operate without continuous power draw from auxiliary supplies, as the monitoring and activation are triggered only when necessary.
3Speed
If a small resistor is used for startup current, then startup speed is faster, but power consumption of startup resistor is higher
Solution Approach 1:
The patent introduces a power transistor as an intermediary component between the startup resistor and the control circuit. This transistor amplifies the startup current, allowing the use of a larger resistor value (which consumes less power) while still achieving fast startup performance. The transistor acts as a current amplifier that overcomes the limitation of using a high-value, low-power-consumption resistor, thus resolving the contradiction between startup speed and resistor power consumption.
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 effectively reduces standby power consumption to zero, meeting the International Electrotechnical Commission's definition of less than 5 mW, while ensuring good dynamic performance and accurate output voltage control within ±5%, addressing the urgent need for ultra-low standby power in consumer electronics.
Implementation Method 1
a transformer having a primary winding for coupling to an input power source, a secondary winding for providing an output of the SMPS
Implementation Method 2
an auxiliary winding... an awakening signal is induced in the auxiliary winding
Implementation Method 3
a power transistor coupled to the primary winding... controlling the power switch in response to a feedback voltage signal
Implementation Method 4
a resistor coupled between the input power source and a control terminal of the power transistor for triggering a primary current flow through the power transistor for providing startup power
Data Source
AI summary
A switching mode power supply (SMPS) includes a power transistor coupled to the primary winding of transformer and a resistor coupled between the input power source and a control terminal of the power transistor for triggering a primary current flow through the power transistor for providing startup power. A primary side control circuit is configured to regulate the output of the SMPS. A secondary side control circuit is coupled to the secondary winding and being configured to provide a first electrical signal to the secondary winding when an output voltage of the SMPS is less than a first reference voltage, whereupon an awakening signal is induced in the auxiliary winding and causes the primary side control circuit to provide a turn-on signal to the power transistor. The primary side control circuit is configured to enter a standby mode or a normal operating mode in response to the awakening signal.