A1000SMPS

A1000SMPS 1KW SMPS for Audio Amplifiers

The A1000SMPS Switched Mode Power Supply (SMPS) is specially designed to be used for Audio
Amplifiers, both Linear Amplifiers such as class AB Amplifiers or Switched Amplifiers such as Class D or Class T.
A1000SMPS use Soft-Switched Half-Bridge Converter Topology. Due to the topology used, the A1000SMPS has very
low EMI noise, lower losses and is more compact than a similar power rating linear power supply or SMPS with
similar output power rating. The A1000SMPS has a regulated main symmetrical output voltage, which powers the
Audio Amplifier Power stage, and an auxiliary symmetrical regulated output voltage, useful for small signal stages,
protection and monitoring within the amplifier system. The default output voltage ranges from ±45V to ±60V, for
the main output voltage and ±12V or ±15V for the auxiliary output voltage. On request, other output voltage
values can be provided, ranging from ±25V to ±150V, regulated and adjustable within ±15% limits. The A1000SMPS,
it is suitable to be used with most of the Amplifiers from the market, not just with the Connexelectronic ones.
A1000SMPS Features:
 High Frequency soft-switched Half-Bridge Converter Topology for high efficiency, up to 90% and low EMI.
 230V AC and 120V AC models available.
 1000W Continuous Output Power, 1200W Peak Output Power, 1600W Short-Time Peak Power.
 Adjustable regulated output voltage ranges from ±45V to ±60V for the stock version, other output voltage
values can be provided, with output voltage ranging from ±25V to ±150V, adjustable within ±15%.
 Differential Auxiliary Voltage available, with voltage choice in range of ±12V to ±15V at 500mA.
 Excellent voltage balance between positive and negative rail, the voltage difference is below 2V if one rail
is unloaded and other is fully loaded, useful feature for class D Amplifiers which suffer from bus pumping.
 Complete protection set, Under-voltage, Overvoltage, Over-current, and Over-temperature Protection.
 Burst-Mode operation at low load or no-load for high efficiency.
 On-board Soft Start for smooth turns ON without current peaks or breaker tripping.
 Compact size 200x120x44mm lightweight 900 grams for the heatslug version, 1Kg for the heatsink version.

Fig.1 A1000SMPS picture

Page 1
 A1000SMPS

A1000SMPS Description: The current for the audio amplifiers producers, both in HI-FI or Pro-
Audio field, is to use a hard-switching unregulated SMPS or at most a Quasi-Resonant unregulated SMPS. The main
reason behind this is the cost, which is much lower for such power supplies than for a regulated one; another
reason is for easier synchronization of the power supply switching frequency with the half of the amplifier
switching frequency to avoid beating. In some cases, is either not possible, or unnecessary. The A1000SMPS has
regulated output voltage, both the main voltages and the auxiliary voltages, making this power supply suitable to
be used both with Class AB amplifiers, or with Class D or Class T amplifiers, which usually have lower Power Supply
Rejection Ratio than the Class AB amplifiers, especially if Audiophile Sound Quality is required. Unlike many other
amplifiers which are using SMPS, since this Power Supply has regulated output voltage, providing a constant
output voltage, from zero load to full load, this translates in cleaner sound, without peaks and drops, without hard
clipping and distortions and true, real deep bass, transparent and clean medium and high frequencies.
The topology used for the A1000SMPS is Soft-Switched Half-Bridge Converter Topology. It was chosen due
to its many advantages compared with all other topologies. Among the advantages, we consider that the most
important are superior efficiency, up to 90.9% lower EMI and noise, compact size, low weight and reasonable
complexity. An important aspect which must be considered when the A1000SMPS is powered ON, the initial
current drawn from the mains is few times higher than the average operating current. The reason for this is that
the filter capacitors are completely discharged, and act as a short circuit for a brief period. The current is higher as
the capacitors capacity and voltage is higher, and is proportional with the capacitor stored energy (CU²/2). To
prevent harmful effects which this high value inrush current might have to the Power Supply components, two
thermistors were used to limit the inrush current to a lower value than the mains fuse can trip or might damage
any components from the Amplifier Power Supply. These thermistors are passive components which has the
property to decrease its resistance when the temperature increases. It has higher electrical resistance at low
temperature, thus reducing the inrush current, and when the current which passes through, will heat-up the
thermistor, the resistance will decrease, and the dissipated power will be reduces. Once the A1000SMPS has
started up, a relay will bypass the thermistors, reducing the power dissipated to zero, for better reliability and
lower operating temperature. Note that there is no need to use any other external power soft-start circuit when
the A1000SMPS is powered from standard mains supply voltage of 110 or 220V AC.
The A1000SMPS features a soft-start characteristic, which allows progressive charge of the output filter
capacitors, with a controlled charging current, without tripping over-current protection. When chosing the working
voltage of the capacitors, need to consider that this voltage must be higher than the maximum output voltage
which can be set on A1000SMPS. The default value o these capacitors are 6800uF at 63V or 10000uF at 63V for the
±45V to ±60V SMPS version. These capacitors have enough capacitance for most stringent applications, adding
extra capacitors is not necessary or recommended, because if the capacitance is too high, the over-current
protection might trip during power ON. Although the soft-switching characteristic allows the A1000SMPS to run
cooler than similar power hard-switched SMPS’s, over-temperature protection option was added. This consists of a
circuit which monitors the temperature of the primary MOS-FET’s and disables the power supply when the
operating temperature reach 90˚C. If the over-temperature protection is needed, a small thermal switch can be
mounted on the heat sink or heatslug, which will monitor the temperature of the main switching transistors, and
will disable the A1000SMPS operation when the temperature reach the threshold of 90˚C, switching ON the
A1000SMPS automatically when the temperature has dropped below 80˚C. In all this time, the mains power is still
present on the A1000SMPS board, but the control circuit is disabled. The green LED which monitors the voltage
presence will be OFF, although the mains power is still present on the board. This implies that care should be taken
to not touch anything during the over-temperature disabled state, and at least 5 minutes after the mains power
was completely disconnected to prevent any electric shock hazard.
The A1000SMPS features an over-current protection, with 2 preset tripping levels. First level trips the
current limit, at about 120% of the nominal output current, and then the second level disables the A1000SMPS
when the output current exceeds 160% for more than 100ms. In this way, the maximum continuous power and
maximum peak power can be kept within 120% and 160% limits. When the output current exceeds the nominal
current, the small orange LED will be ON, indicating that an over-current condition occurred, and measures must
be taken to reduce the current draw to a safe value, since the over-current protection limits the primary peak
current and if there is a short-circuit present on the output, the current on the secondary side will increase to
dangerous values when the output voltage will decrease, trying to keep the output power constant, not just the
voltage or the current.

Page 2
 A1000SMPS

The main output voltage can be adjusted within ±15% limits or more, depending on the version. To adjust
the output voltage, on the upper right side of the pcb is a small potentiometer, R46 between one of the primary
electrolytic capacitors and the small heat sink of the secondary auxiliary voltage. This potentiometer is multi-turns
potentiometer, allowing precise voltage set. The auxiliary output voltage is fixed, and can have one of these values:
±5V, ±12V or ±15V. The default auxiliary voltage is set to ±12V. For most applications, this is the most used voltage,
and that’s why was chosen.
To be able to deliver the nominal output power, the A1000SMPS must be equipped with a heat sink which
allows easy removal of the excess heat produced by the power devices, the primary side switches and the
secondary side diodes. The A1000SMPS comes with a heatsink, heatslug or no heat sink at all, depending on user’s
choice. The heatsink version uses a low thermal resistance heatsink, with about 2˚C/W thermal resistance, which is
suitable for most of the applications, where the A1000SMPS is used to power audio amplifiers. The heatslug
version uses a heatslug, which is a rectangular piece of aluminum on which the power semiconductors are
mounted and which serves as heat transfer between the power devices and a bigger heatsink which can be the
housing or enclosure wall or a custom made heatsink. The no-heat sinkversion must be used with a custom heat
sink, and the reason why the smps can be purchased without heat sink is that in some cases the user has its own
heatsink which is more suitable to a particular application than the existing heat sink or heatslug. In any case, the
A1000SMPS should never be used without a proper heat sink, or just with the heatslug, because this will lead to
excessive temperature and possible damage to the power devices. Also, for the no-heat sink version, all the power
devices must be electrical isolated from the heatsink with special insulating material, which will be provided at
purchasing the non-heatsink A1000SMPS version. The A1000SMPS must be installed in an enclosure which will
prevent accidental access to any part of the board, since it carries dangerous high voltages and potentially lethal if
a direct contact is made between any non-isolated part of the board and human body.
Warning:
Before you proceed with installation, make sure you have read this warning
A1000SMPS: The A1000SMPS is powered from the mains voltage and the primary side of the
SMPS has hazardous voltages up to 340V DC and up to 500V AC. This voltage levels are present
on the top and bottom of the board, and during installation and operation should never touch
any part of the SMPS while it is connected to the mains and at least 5 minutes after complete disconnect from
mains. If any adjustment or reconnection needs to be done, disconnect the unit from the mains and allow all
capacitors to discharge for at least 5 minutes before handling it. Any ignorance of this warning will be made on
user’s responsibility, and can lead to serious injuries and possible death by electrocution if is handled improperly.
This product has no serviceable parts other than the on-board mains fuse. In case of blown fuse, only replace
the fuse with the same type and rating. Do not attempt to change any other component from the A1000SMPS. A
safety clearance of at least 6mm must be kept between the board and the case, or any conductive part of the
amplifier. The heat transfer between the heatsinks and ambient must not be obstructed for proper operation.
A1000SMPS characteristics:
Parameters Minimum Nominal Maximum Peak time lim. Option 1 Option 2 Option 3

Main Output ±45V ±55V ±60V - ±25V - ±35V ±60V - ±80V ±80V - 100V
Voltage:
Aux. Output ±5V ±12V ±15V - ±5V - ±15V ±5V - ±15V ±5V - ±15V
Voltage:
Mains input 98V AC 110V AC 128V AC 134V AC 110V AC 110V AC 110V AC
voltage: 196V AC 220V AC 254V AC 272V AC 220V AC 220V AC 220V AC
Main Output 11A Continuous 9A Continuous 8A Continuous 12A 16A Continuous 7A Continuous 5.5AContinuous
Current: 14A Peak 12A Peak 11A Peak 15A 19A Peak 9A Peak 7A Peak
Aux. Output Nominal: 0.5 A Nominal: 0.5 A Nominal: 0.5 A Nominal: 0.5 A Nominal: 0.5 A Nominal: 0.5 A Nominal: 0.5 A
Current: Peak: 1.2A Peak: 1.2A Peak: 1.2A Peak: 1.2A Peak: 1.2A Peak: 1.2A Peak: 1.2A
No-Load Min: 4.2W Min: 4.4W Min: 4.6W - Min: 3.3W Min: 5.5W Min: 5.6W
power cons. Max: 4.9W Max: 5.3W Max: 5.7W Max: 3.7W Max: 6.2W Max: 6.7W
Efficiency at 110V: 87.8% 110V: 88.2 % 110V: 88.7 % 110V: 86.3 % 110V: 86.1 % 110V: 89.5 % 110V: 89.4 %
50% load 230V: 89.3% 230V: 89.9% 230V: 90.4% 230V: 88.4% 230V: 88.2% 230V: 90.9% 230V: 90.7%

Page 3
 A1000SMPS

The A1000SMPS dual voltage version, Auxiliary output can be used to supply power for other stages of the
amplifier, such as preamplifier, speaker protection, cross-over, etc. the A1000SMPS dual output version provide a
differential auxiliary output voltage in range of ±5 to ±15V, depending on the choice. The auxiliary output voltage
depends on the Output voltage of the linear regulator Integrated Circuit used for post regulation of the auxiliary
output voltage. The Auxiliary output voltage is already regulated, and further regulation is not necessary unless
lower voltage is required. The GND of the auxiliary output is isolated from the main output GND.
The A1000SMPS board size is 200x120mm and 40mm tall. It has 4 mounting holes at the corners of the
board, 4mm distance from the edge plus one more mounting hole between the transformer and secondary side
capacitors. This mounting hole is connected to the main output GND and should not be used if galvanic insulation
from between the main output GND and amplifier case is required, or must be insulated to prevent current loops.
The main output GND is already connected to the other mounting holes through a 10R resistor and 100nF
capacitors, C39 and R43 at the bottom right corner. The role of this simple circuit is to provide a coupling path
between main output GND and amplifier chassis without creating a high current Ground loop.

Fig.3 A1000SMPS board layout and size

Disclaimer:
The A1000SMPS shall be used according with the instructions provided in this document. The user should
NOT attempt to modify or change any of the parameters of this product, which can lead to malfunction. The
designer and manufacturer of the product, PCBstuff, and the official distributor, Connexelectronic, will not be
liable for any kind of loss or damage, including but not limited to incidental or consequential damages. Due to the
mains voltages of this board, the user should take all the caution measures needed when working with mains
voltages, should not touch any unisolated part of the board or connectors, or short-circuit any part of the board or
connectors. Any misusage will be made on user responsibility.
The designer and manufacturer PCBstuff reserve the right to make changes or modifications on the
product without notice. The A1000SMPS schematic and PCB design is PCBstuff proprietary and shall not be
distributed, copied or published without the PCBstuff written agreement. PCBstuff and Connexelectronic reserve
the right to offer limited support for the boards purchased directly from PCBstuff or Connexelectronic, and no
support at all for the similar boards which aren’t purchased directly from PCBstuff and Connexelectronic, or future
listed resellers, and from various reasons they look or pretend to be similar, exactly the same, or improved version
of the actual product. Purchasing the product means that you are aware and agree with all terms and conditions.
Page 4