SPS80 r3 800W AC/DC Switching power supply for audio

Transcription

1 800W AC/DC Switching power supply for audio Description coldamp SPS80(r3) is an AC/DC switching power supply designed specifically to operate high power audio amplifiers, (for example, 2xBP4078 Class-D modules at full power) from mains up to a continuous power above 800W The reduction of size and weight as compared to a linear power supply + toroidal transformer is huge: around 650g versus 5.5Kg at the same power level. The outputs are regulated but at the same time have a high capacitance reservoir (6600uF per rail uf at input bus), allowing for a very estable output even at heavy loading and music peaks above 1200 watts. It includes an auxiliary isolated ±12V supply and a nonisolated, temperature controlled, output for fan use. Features Symmetric (nominal ±58V) regulated output**, min. 7A Auxiliary, isolated output: ±12V 250mA Fine-adjust of output, within 2 ranges (±38 to ±53V and ±48 to ±61V) Selectable input range ( VAC / VAC) for worldwide use via wire connection. Relay bypassed inrush limiter, soft start, fuse protected mains input. EMI filter at input and output chokes. Temperature controlled FAN output with external temperature sensor input Overcurrent protection, latched for 2 seconds with red LED indicator Startup circuit overtemperature protection. Screw terminals for mains input, faston for main outputs, 100mil std. header for aux. output LED indicator at main output. Size and weight: Dimensions: 179.5x149x41mm Weight: 650 g aprox Operating conditions Parameter Min Typ Max Units Mains input voltage* VAC Mains input frequency 50/60 Hz Mains fuse rating (fast blow) 6.3 A Output voltage** ±38V ±58V ±61V V Continuous output current per rail 30m 7 A Continuous output power W Aux. output voltage ±12 V Continuous auxiliary output current (each rail) ma Fan output voltage (temperature controlled) V Fan max. current consumption 120 ma Switching frequency 85 KHz * Selectable in two ranges by means of external wire connection ( VAC and VAC). ** Adjustable by means of a jumper and fine adjust potentiometer, in two ranges (±38 to ±53V and ±48 to ±61V) Other output voltages, even single-output, available at request. There is a special version, SPS80HV, with ±60 to ±85V outputs. 1

2 WARNING: This product operates at mains voltage and has accessible live parts. It is intended to be assembled INSIDE finished equipment only and must never be exposed to inadvertent touch, that could lead to severe injury or death. This product is Class I and MUST BE EARTHED. Chassis must be connected to mains earth and use an approved mains cable, connected to a earthed mains plug. Observe extreme care during installation and NEVER touch any part of the board while it is connected to mains. Lethal voltages above 320V can be present. Once disconnected, allow at least 5 minutes so all capacitors get fully discharged and no dangerous voltages are present at any point of the circuit. In order to meet the max. 41mm height required for 1U racks, the PCB bottom is kept open so, if the chassis where the PSU is installed is metallic, an insulating plastic layer must be placed between the bottom of the PCB and the chassis (but not below the PSU frame to avoid ruining the thermal contact). This is the only way to keep proper creepage for safety. If the chassis free height is below 45mm, it is mandatory to place an insulating sheet between the cover and the input bus capacitors. Replace input fuse with same type and rating only (6.3A) Always use a double-circuit input switch to disconnect both live and neutral input lines. A filtered / switched / fused IEC mains inlet is recommended, rated at least at 6A (10A in VAC mains countries) Coldamp declines any responsibility for damages caused to persons or other equipment when any of the above rules hasn t been strictly followed. 2

3 Basic connection In order to connect the SPS80 power supply, only the mains input (with Earth) and output connections are required. Input voltage is fed via a couple of screw terminals plus a screw for the earth connection, as shown in the figure 1. A filtered/fused/switched IEC mains inlet is recommended for AC input. Current rating should be at least 6A for VAC countries or 10A for VAC countries. (see selecting mains operating voltage section) (Remove the earth screw washer when connecting the wire with a terminal). Fig. 1: Mains input connections WARNING: Lethal voltages are present at some points of this product. Avoid direct contact with any part of the supply during operation / installation, and also within 5 minutes after the supply has been unplugged from mains in order to fully discharge the storage capacitors. Output is taken from the faston at the opposite side of the board. There are 2 of them for each rail (+VCC=positive rail, -VSS=negative rail) and 4 for GND. Note that output GND is electrically isolated from mains and Earth. Fig. 2: Main output connections A minimum loading (25-30mA per rail) may be required for the supply to operate quietly. Connecting a BP4078 module is enough to provide this load. Auxiliary supplies The SPS80 (r2) power supply has two onboard auxiliary outputs, with common ground (isolated from main output GND) and regulated at ±12V (250mA max per rail) This output can be very convenient for powering circuits such as controls, crossovers, active preamplifiers, thermal managers, etc. It can be used to power BP4078 modulators or driver as well, in order to reduce the power dissipated by them in no signal conditions. (see BP4078 appnotes). Please note that these supplies may require a minimum load (10mA) in order to regulate correctly. Any op-amp, or even a LED will be enough. -12V +12V Aux GND Fig. 3: Auxiliary ±12V output 3

4 Selecting mains operating voltage SPS80 power supply can operate from a broad range of AC input voltages (100 to 240VAC in two ranges, VAC and VAC). NOTE: This PSU is set up to work with VAC input by default when it is shipped. If your country mains voltage is between 100 and 125VAC, a wire must be connected from points A to B in the board (near the primary 200V capacitors). Note that the fuse rating must be increased to 10A for full power capability under these conditions. Selecting output voltage SPS80 r2 power supply can be easily configured for three different output voltages without soldering/desoldering any components. The factory setup is ±60V, although it can be easily changed to ±40 and ±50V by simply moving one jumper position. (For SPS80HV r2, available voltages are ±60, ±70 and ±85V). Figure 6 shows how to do it: Output voltage range selection Fine adjust potentiometer Fig. 6: Selection of output voltage. DON T change the voltage setting when the supply is on!! NOTE: At the lower output voltage settings, properly balanced load is recommended, or the positive & negative rails voltages may differ a little bit (<10% typically) if they are loaded with different currents: this typically happens with Class-D modules, that draw more current from the negative rail than from the positive rail. This is not usually a problem. Anyway, if the available output voltages are not adequate for your application, please contact us and we will try to help you. 4

5 Temperature controlled FAN output The SPS80 power supply has very high efficiency that makes cooling very easy. In amplifiers with several channels or when extreme operating conditions are feasible, forced cooling of the system may be recommendable. However, fan noise can be annoying specially in low level listening conditions, so it is desired that the speed of the fan is kept at a minimum if temperature is not high. SPS80 offers an easy way to implement a temperature-controlled-speed fan, needing only an external NTC resistor (such as the one integrated on BP4078 board). The board has a connector for that NTC and another connector for the 12V FAN output (max 120mA). Figure 4 shows where the two headers are located. FAN output NTC input Fig. 4: Fan output and NTC input Output voltage depends on the temperature measured, and the circuit is designed to be used with a nominal 20Kohm at 25ºC NTC (such as Murata NTSD1WB203FPB30, Digikey part. No ND). Fig. 5 shows a graph of the approximated output voltage as a function of temperature in this NTC. Fig. 5: Fan voltage versus temperature using the BP4078 NTC NOTE: If constant speed is desired, regardless of temperature, connect a resistor in place of the NTC. Output voltage is determined as: Vout=1.25( /Rset), so: Rset=47000/((Vout/1.25) 1)...where Rset (in ohms) is the resistor connected. For example, for approx. 12V output, connect a 5.6K resistor (0.25W is enough) in place of the NTC 5

6 Basic connection of 1 to 2 BP4078 modules (only power lines and speaker outputs are shown) Twist wires together 12V fan Join for VAC input range To speaker (channel L) + - Twist wires together Twist wires together Twist wires together Double circuit switch + - To speaker (channel R) IEC mains inlet NOTES to the figure: It is good to twist the three power lines together tightly to improve EMI behaviour and reduce coupled noise. The same applies to the speaker wires. For safety reasons, always connect earth and use an earthed plug and wire. Use double circuit on/off switch whenever possible. Take care that the thermistor used for fan control doesn t receive forced air directly, or it will become cooled and read an abnormally low temperature. For improved noise rejection, it is sometimes recommended to add a small HF choke in series with each supply rail (not with GND) near each module. Each SPS80 is supplied with 4 of these chokes. Layout guidelines: Although no noise problems have been found so far, it is always good to follow these guidelines at layout time: If space is not a problem, place the SPS80 PSU as far as possible from the modules, to minimize coupled noise. In any case, try to avoid that the primary switching section (near the bigger mosfets) of the SPS80r2 is near the modules input zone. Place the modules in a way so that the input section is opposed to the supply (as they are in the figure), so that the power connections are nearer the PSU. 6

7 Mechanical drawings (All dimensions are in mm) Important: Total height is 41mm max due to components. Use 6 M3 screws to fix the board to a chassis (inserting the screws from the bottom of the case) through the 6 marked holes, in order to provide enough cooling for continuous high power usage. Make sure that the holes of the chassis are scratchfree and the surface is totally flat, so there is good thermal contact. 7

8 Document History: Revision G (May, 30th 08) Mechanical drawings updated for new frame Revision F (March, 3rd 08) Updated safety section Revision E (February, 10th 08) Updated safety section Revision D (August, 30th 07) Updated photos Revision C (August, 29th 07) Mechanical drawings updated to r3 Revision B (August, 13th 07) Some figures updated Revision A (July, 07th 07) Copied from SPS80r2 datasheet and updated to reflect updates 8