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Author Topic: How much ripple is acceptable from a switcher? Eric Robinson Jedi Master Film Handler Posts: 538 From: Santa Rosa, CA Registered: Jan 2005 posted 08-08-2006 05:25 PM                     Due to a complaint about short bulb life in a particular projector, I decided to measure the DC output of the switching power supply for any AC ripple. The switcher is a Strong - 6280005 3000 to 5000 watt When the bulb is running the DC power is 25VDC Using a scope I measured the power out at 2.5 VAC peak to peak This seems like an awfully high value for AC. Did I perform the measurement correctly by measuring the voltage output right at the switchers terminals while the bulb was running? Should I perhaps use a DVM set to AC to measure AC ripple?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 08-08-2006 07:58 PM                     quote: Eric Robinson Using a scope I measured the power out at 2.5 VAC peak to peak At what frequency was this ripple? Normally with any type of swtcher the ripple is so high of frequency >35khz as to be invisible to the lamp itself. This hf ripple is one of the main advantages of switchers. Your 2.5 volt level is ery low too. One can also control the inrush current alot better than on a brute force boat anchor type rectifier. In a strong switcher it is impossible to get any LF ripple through just by the nature of its design. I would check for possible excessive inrush current(unlikley though) and for at least 1200 cfm exhaust at the stack with the doors shut and the dowser open assuming a 3kw lamp. Mark  |  IP: Logged Eric Robinson Jedi Master Film Handler Posts: 538 From: Santa Rosa, CA Registered: Jan 2005 posted 08-09-2006 12:51 AM                     I knew I should have measured the frequency. The cfms measure about 600 and I think it is a 3K bulb. I'll never get more cfms though, this is the nature of this business. I am curious about the method for measuring inrush current though. Perhaps you could point me to some resources to learn about the inrush current spec for xenon bulbs and the measurement technique.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 08-09-2006 01:07 AM                     Isn't the 628000 series the old black "large Suitcase" switcher?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 08-09-2006 08:17 AM                     Thats not enough air flow for a 3K... only about half enough. Check with your lamp manufacturer to find out his maximum allowable inrush spec. Note that you need a peak and hold DC amprobe or a storage oscilloscope and standard current shunt to measure it across... Mark  |  IP: Logged

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