DC Powering Rane Rap Units 电路图.pdf

DC Power-1 Introduction This note explains how to operate Rane units designed for remote AC operation from DC powerwhether batteries, DC- DC converters or DC power supplies. The techniques shown do not require any unit modification. All wiring is external to the unit. There are techniques that do require unit modifica- tion, but these are better left explained by our Technical Service personnel. 1991 Rane Corporation RaneNote 133 DC Powering Rane RAP (Remote AC Power) Units Voltage however, a summary of progress did appear in the AES journal3. Much was learned, and Rane decided to continue the pursuit of a separate remote power supply standard of its own. Participation in the AES committee demonstrated that using AC remote power was, overall, superior to DC power. Rane took this to heart and nicknamed their revised line of products RAP, an acronym for Remote AC Power. All units equipped with black DC jacks were redesigned with red AC jacks, and a remote power supply was shipped with each unit. Gone was DC, and gone was the optionnow remote power was required4. But Murphy likes to play her little jokes. Now we find ourselves once again explaining how to run Rane products from DC. Life is never dull. DC Powering RAP Units It came at us from several directions: Disney wanted to run Rane units from the 24 volt batteries used to power their magnificent floats. Consultants and contractors needed ways to comply with emergency paging requirements dictating that certain audio equipment run from batteries upon AC power failure. Car installers started calling about modifying units for competition auto installations. Requests came in for retrofit- ting Rane units for the upgrade RV market and even execu- tive jets. A Southwest police department wanted to install FPE 13 parametric equalizers into police cars to improve intelligibility of reception. There was even a sightseeing outfit installing Rane products into tour buses for use by their guides. Mark Wentling from E&E Exports (Los Angeles) gets the credit for elegantly solving the puzzle of how to DC power units designed for remote AC use. Mark worked for years as an audio design engineer (MXR, Music Man, Fender, to name a few) before getting into the export business. One day he looked at our voltage doubler circuit and mused that maybe if we were to add just two diodes (soon to become known as the DC diodes) it should be possible to power all Rane RAP units from DC. Amazing. He was right. It took over a year to add the DC diodes to all the units5. This is a long time, but Rane knew that once the re-engineer- ing was complete the actual cost of the diodes was small enough to warrant adding them to every RAP unit. As suspected, a grateful few benefited immensely. Minimum DC Voltage All Rane RAP units operate from an 18 VAC remote transformer equipped with a center tap. This powers a dual output DC voltage doubler found in each unit. The voltage doubler steps up the low AC voltage (necessary for world- wide safety agency compliance and exemption) to high enough levels to allow each units positive and negative voltage regulators to operate. These voltage regulators put out the industry standard levels of 15 VDC (see the DC-DC Converter section for an exception). This voltage runs all the internal circuitry and indicators. These regulators require an absolute minimum of 17 VDC to operate. In a typical RAP product the voltage doubler circuits create at least 20 VDC. Even with a 10% low AC mains line (normal pro audio design-limits) this guarantees regulator operation. Taking the 17 VDC number and allowing an additional one volt drop across the added DC diodes brings us to a minimum required DC input of 18 VDC to guarantee normal operation. Maximum DC Current Every RAP unit has the maximum required AC current silk-screened under the RJ12 modular POWER jack and also listed on its Data Sheet. The DC current equals one-third (1/3) the AC current. (See the VC 18 Voltage Converter Data Sheet for a listing of these DC currents.) The DC current is much less than the AC current for two reasons: DC eliminates the diode AC-to-DC conversion factor and the inefficient voltage doublers. These two combine for a factor of about three. Connector Wiring Rane uses RJ12 modular jacks wired per Figure 1. The details and history of this jack appear in Rane Note 1214. There is a distinguishing factor to note about this wiring. Even though it is not obvious why this configuration was adopted (it has to do with accidental telephone hook-up), the wiring is symmetrical. Although unintentional, this produced the very favorable byproduct of the plug not being polarized when used for DC voltages. When wiring-up or buying cable, it is not necessary to worry about pin numbers, or beginning from right or left, or whether it uses twisted or straight flat cable. Just remember: negative voltage goes to the center two pins, positive to the next outer pair, and the common goes to the two outside pins. Two parallel conductors for each connection are standard. This reduces wiring impedance and doubles current capacity. Rane uses and recommends 26 AWG size wire (two parallel 26 AWG wires are rated at 1.5 amps). Also observe the following: Use only 6-wire cable and modular connectors for all interconnection. Common 4-wire cable and connectors will not work. Do not substitute 4-wire for 6-wire cable and connectors. RadioFans.CN 收音机爱 好者资料库 DC Power-3 Figure 2. Battery Wiring for RAP units Figure 4. DC Power Supply Wiring Figure 1. RJ 12 Modular Jack & Plug Wiring Battery Operation Figure 2 shows the correct wiring for battery operation. Note this requires two batteries wired in series to create the necessary bipolar input voltage. One is not enough. If only one battery is available, see the next section on DC-DC Converters. Also note the batteries must be rated 24 V. The more common 12 V batteries do not provide enough input voltage to operate the regulators. If the regulators do not operate, the units noise performance is apt to be unaccept- able. The unit will work, but it will not work properly. Sometimes you are lucky and can get away with it, but not too often. We have seen enough noisy 12 VDC installations to make us recommend 24 V batteries only. DC-DC Converter Operation Powering RAP units from only one battery requires a DC- DC converter. Figure 3 shows the typical arrangement. What is not common are the output voltage levels of 18 VDC. These satisfy our previously discussed minimum for regulator operation. Unfortunately the more commonly found 15 VDC converters should not be used. Again, maybe you will be lucky and not have noise problems, but dont bet on it. Higher output voltage converters may also be used, but should not exceed 24 VDC. Greater than this begins to tax the regulators maximum power limit. Caveat: The PE 17 is an exception. The PE 17 uses internal 17 VDC regulators, and requires at least a 20 V DC-DC converter. Beware. Remember to observe the maximum DC current require- ments when buying the converter. DC Power Supply Operation A DC power supply is an alternative to using batteries or DC-DC converters. Figure 4 diagrams the hook-up required. As shown, wire a dual power supply (or two single supplies) in series to produce a bipolar output voltage. Setting each supply for 18 volts results in a single 18 VDC source. This arrangement is popular for emergency use where many RAP units run from one large DC power supply operated by a master AC mains UPS source. Figure 3. DC-DC Converter Wiring DC Power-4 Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5098 TEL (425)355-6000 FAX (425)347-7757 WEB 06008 5-99 References 1. D. Bohn, Rane Note 118: Remote Power System, (Rane Corporation, 1987). Although out of print, interested parties may obtain photocopies upon request. 2. D. Bohn, “Remote Power Supply Standards: A Proposal,” S&VC, Vol. 5, pp. 70-78, Nov.15, 1987). 3. “Summary of Progress Before Dissolution of AES Work- ing Group on Power Supply Interfacing,” J. Audio Eng. Soc. (News of the Standards Committee), Vol. 39, pp. 275- 276 (Apr 1991). 4. D. Bohn, Rane Note 121: RAPRemote AC Power: An Idea Long Overdue, (Rane Corporation, 1989). 5. The PS 1, RPS 4 and SM 82 RAP units do not have DC diodes. On the PS 1 and the RPS 4 it was felt they would never be needed, and on the SM 82 the addition proved too difficult. 6. Richard Clark & David Navone, “Isolation,” AUTOSOUND 2000 TECH BRIEFS, June/July 1992, pp. 149-153. Subscriptions and individual copies available from Autosound 2000 Tech Briefs, 2563 Eric Lane, Suite D, Burlington, NC 27215, (910) 570-0341. Very highly recommended reference series for anyone involved in automotive sound installation. These guys are the gurus no one knows more.