Switching Regulator Fast Startup Low Standby Power
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Solution Overview
Problem
Conventional flyback converters have long start-up times, which are undesirable in many applications, but reducing start-up time increases standby power utilization, making it challenging to achieve both fast start-up and low power consumption.
Innovation Solution
A switching regulator system with a charge pump and comparator circuitry that enables fast start-up by amplifying the base current of a power transistor, reducing the RC time constant while minimizing standby power consumption through strategic use of resistors and capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the resistance of resistor 104 is decreased to reduce the RC time constant and achieve fast start-up, then the start-up time is reduced, but the standby power utilization increases
Solution Approach 1:
The patent divides the start-up process into two distinct phases: an initial start-up phase using resistor 104 and capacitor 106 to provide initial base current, and a subsequent phase where the auxiliary winding takes over power supply. This segmentation allows optimized component values for each phase independently.
Solution Approach 2:
The patent uses the auxiliary winding to pre-charge capacitor 106 during normal operation before shutdown. This preliminary action ensures that when shutdown occurs, capacitor 106 already contains sufficient energy to provide the necessary base current for fast start-up without requiring a low-value resistor 104, thereby reducing standby power consumption.
2Use of energy by stationary object
If large values of resistance of resistor 104 and capacitance of capacitor 106 are used, then the standby power utilization is reduced, but the RC time constant increases resulting in long start-up time
Solution Approach 1:
Capacitor 106 is pre-charged by the auxiliary winding during normal operation before shutdown. This preliminary charging action stores sufficient energy in capacitor 106 to provide the necessary base current during start-up, allowing the use of large capacitor values for low standby power while maintaining fast start-up performance.
Solution Approach 2:
The auxiliary winding serves a dual function: it powers the switcher circuit during normal operation and simultaneously pre-charges capacitor 106 in preparation for shutdown. This self-service approach eliminates the need for external pre-charging circuits and reduces overall system complexity.
3Ease of operation
If capacitor 106 is used to supply base current during start-up, then the start-up process is enabled, but the RC time constant limits the speed of voltage rise at terminal VDD
Solution Approach 1:
Capacitor 106 is pre-charged to a high voltage level (e.g., 400V) by the auxiliary winding before shutdown. This preliminary action stores sufficient energy to rapidly charge terminal VDD during start-up, overcoming the RC time constant limitation and achieving fast voltage rise without requiring excessive current from resistor 104.
Solution Approach 2:
The patent changes the voltage parameter of capacitor 106 from a low voltage during normal operation to a high voltage (e.g., 400V) during shutdown preparation. This parameter change allows the capacitor to deliver a large charge quickly during start-up, effectively bypassing the RC time constant limitation of the resistor-capacitor combination.
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 system achieves fast start-up times and low standby power utilization by amplifying the base current, reducing the start-up time and power consumption, thus addressing the trade-off between start-up speed and power usage.
Implementation Method 1
A switching regulator system with a charge pump and comparator circuitry that enables fast start-up by amplifying the base current of a power transistor
Implementation Method 2
A switching regulator system with a charge pump and comparator circuitry
Implementation Method 3
Flyback converter 100 includes a transformer 102 that has primary, secondary, and auxiliary windings
Implementation Method 4
Capacitor 106 is used to start-up the flyback converter 100 by supplying enough current to the base terminal of transistor 110
Data Source
AI summary
A switching regulator having fast start-up time and low standby power is disclosed. In an exemplary embodiment, an apparatus includes a transistor that generates a charging current at a first current level from a base current received at a base terminal. The apparatus also includes a capacitor that charges in response to the charging current at the first current level to generate a voltage signal that increases at a first rate. The apparatus also includes a charge pump having an output coupled to the base terminal. The charge pump outputs a charge pump current when the voltage signal exceeds a first voltage level. The base current is increased by charge pump current to cause the transistor to generate the charging current at a second current level, and the capacitor charges in response to the charging current at the second current level to generate the voltage signal that increases at a second rate.