UPS Battery Mode Control for Active PFC Hold-Up Time
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Active PFC switching power supplies in UPS systems face issues where the hold-up time is not adequately maintained during AC power source termination, leading to premature shutdown due to bulk capacitor voltage dropping below the low threshold voltage, preventing emergency power supply during the defined hold-up time.
Innovation Solution
A controlling method for the battery mode of the UPS that monitors AC power source termination and switches to battery mode, converting DC power to a square wave with ON and OFF times alternately configured to ensure each OFF time is equal to or less than the hold-up time, maintaining the bulk capacitor voltage above the low threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UPS outputs a square wave with OFF time longer than the hold-up time, then the inverter can operate with standard switching patterns, but the bulk capacitor voltage drops below the low threshold voltage causing the active PFC switching power supply to shut down
Solution Approach 1:
The inverter outputs a square wave with multiple ON times and OFF times alternately configured within each half-period, creating periodic action patterns that ensure each OFF time does not exceed the hold-up time capability of the active PFC switching power supply, thereby maintaining bulk capacitor voltage above the low threshold
Solution Approach 2:
The controller dynamically adjusts the switching pattern of the inverter based on the hold-up time characteristics of the connected active PFC load, configuring at least two ON times and two OFF times within each half-period to adapt to the specific hold-up time requirements of the load
2Reliability
If the OFF time between adjacent pulses is reduced to be equal to or less than the hold-up time, then the bulk capacitor voltage is maintained above the low threshold, but the inverter switching complexity increases
Solution Approach 1:
Each half-period of the square wave is segmented into at least two ON times and two OFF times, dividing the continuous switching operation into discrete segments that collectively ensure the OFF time constraint is met while maintaining power supply reliability
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 method ensures continuous emergency power supply to the active PFC switching power supply during the hold-up time by maintaining the bulk capacitor voltage above the low threshold, thereby preventing shutdown and ensuring orderly system operation.
Implementation Method 1
The bulk capacitor (CBULK) is connected to an output of the PFC circuit, so the bulk capacitor (CBULK) is charged by the DC power from the PFC circuit. The bulk capacitor (CBULK) discharges a short term DC power for the DC to DC converter (32).
Implementation Method 2
the inverter (41) converts the DC power of the battery set (44) to a square wave
Data Source
AI summary
A controlling method of a battery mode of a UPS for an active PFC power supply has the following acts of monitoring the AC power source and determining whether the AC power source is terminated or not, wherein if a determining result is positive, the controlling method proceeds to next act, and switching to the battery mode and converting a DC power source of a battery to a square wave. The square wave has a period, and each half of the period is alternately constituted by at least two ON times and at least two OFF times, and each of the at least two OFF times is equal to or less than a hold-up time of the active PFC load having a hold-up time circuit. Therefore, the voltage of the bulk capacitor of the active PFC power supply under a discharge condition is not lower than the low threshold voltage, since the OFF time of the square wave signal will be kept equal to or less than the hold-up time.