Download Hypex UCD Cell Spec v1.4

Hypex Electronics
“Universal Class D” UCD 150W IP Cell
Features
UCD is a class D amplifier circuit designed to unite
price, performance and versatility requirements at a
point not seen before in the field of audio power amplifiers. A new control/feedback system is used to obtain low output impedance and low distortion, with all
active components in the signal path operating in onoff mode (i.e. without linear amplification), insuring
maximum sonic transparency. The all-discrete construction of the circuit results in very high quality.
1.
•
Ultrahigh-Fidelity Sound
•
Extremely Low Output Impedance
•
Large, Load-Independent Bandwidth
•
Low Noise and Distortion
•
All-Discrete Construction
•
Fully Passive Signal path / No Analog
Amplification.
•
Differential Input
•
Pop-Free Stop Mode
•
Short-Circuit Detection
Applications
•
•
Home Theatre Systems
Active Loudspeakers
•
Miniature Component Systems
Block Diagram
In+
In-
Control
Circuit
Switch
Driver
Out
Switch
Driver
Hypex Electronics, Ulgersmaweg 137-D, 9731 BR Groningen, The Netherlands.
Contact: Jan-Peter van Amerongen, Tel:+31·50·5246993, Fax:+31·50·5254591, e-mail: [email protected]
Hypex Electronics
2.
Specifications
2.1. Absolute Maximum Ratings
Property
Power supply voltage
Output current
Symbol
VDD-VSS
IO
Continuous output
power
PO,C
Limit
120
6
Unit
V
A
(rms)
W
120
Conditions/Notes
Tamb=40ºC
2.2. Performance specifications
Normal Operating Conditions: Vdd-Vss=90V. Measurement Bandwidth=20kHz
Property
Rated output power
Symbol
Pr
Distortion and noise
Signal-to-noise ratio
DC offset
Frequency Response
Power Bandwidth
Output impedance
THD+
N
SNR
VDC
BW
PBW
ZO
Idle losses
Efficiency
Gain
Input impedance
P0
η
AV
Zi
Common-Mode Rejection
Power supply ripple
rejection
Idle switching rate
Frequency modulation
CMRR
Min
110
150
165
160
-
Typ
0.015
Max
0.03
Unit
W
W
W
W
%
Conditions/Notes
ZL=8Ω, THD<1%
ZL=6Ω, THD<1%
ZL=6Ω, THD=10%
ZL=4Ω, THD<1%
10W, 20Hz-20kHz
120
-50m
92
4.0
1.7k
9.5k
125
0-50k
20-30k
0.02
0.03
0.07
1.8
93
4.55
1.8k
10k
30
+50m
0.03
0.04
0.08
2
5.0
1.9k
10.5k
dB
V
Hz
Hz
Ω
Ω
Ω
W
%
V/V
Ω
Unwtd
70
-
PSRR
60
fSW,0
fSW
420k
+0/-3dB (3Ω<ZL<∞)
-3dB
DC-1kHz
10kHz
20kHz
Power stage and coil only
100W, 6Ω
Inverting input
Noninverting input
dB
440k
460k
≈fSW,0·(1-M)4
dB
Hz
M=Modulation Index. -1<M<1
2.3. Construction Technology
Preferred construction is FR4 two-layer board material with 35µ (1oz/ft2) copper. All SMDs are mounted
on the bottom side for wave soldering.
2.4. Dimensions (one mono-channel cell)
Width: 50mm
Depth: 60mm
Height: 40mm (includes PCB and lead-outs)
Distance between pin 6 of JP1 and pin 1 of JP2: 10.2mm
Hypex Electronics, Ulgersmaweg 137-D, 9731 BR Groningen, The Netherlands.
Contact: Jan-Peter van Amerongen, Tel:+31·50·5246993, Fax:+31·50·5254591, e-mail: [email protected]
Hypex Electronics
3.
Connections
The demonstration boards have two male JST XH connectors for mating with JQ counterparts for PCB
mounting or female XH cable connectors (see www.jst.com).
3.1. JP1: Power and Control
Pin
1
Name
/ENA
2
3
4
5
6
VDR
+VB
GND
-VB
/ERR
Description
Enable line. Pull to GND to operate amplifier. Should be driven by an open collector output. This line floats to
+VB in mute position (47kΩ). Allow 1s between power-up and driving /ENA for pop-free operation.
Supply for MOS gate drivers. Internally regulated to -VB+10V. Connect to GND or to -VB+15V.
Positive power supply rail. Nominally +45V.
Ground. Power supply ground in case a star grounding scheme is employed.
Negative power supply rail. Nominally –45V.
Error output. This line is pulled down to –VB when an overcurrent in either power MOSFET is detected. External control circuitry should respond by releasing /ENA for one second. Response time of this external circuit must be below 50µs.
3.2. JP2: Audio I/O
Pin
1
2
3,4,5
6,7,8
4.
Name
IN+
INGND
OUT
Description
Noninverting audio input
Inverting audio input
Output ground
Speaker output
Typical Performance Graphs
Measurement condi tions: Test lead set as in section 5.1. Unregulated power supply of +/-45V
with 2x4700µF storage. Load impedance=6Ω.
4.1. Frequency Response at ∞, 6 and 3Ω
+10
+8
+6
+4
+2
d
B
+0
-2
-4
-6
-8
-10
20
50
100
200
500
1k
2k
5k
10k
20k
Hz
50k 100k
Frequency response is a 1st order low-pass characteristic with a corner frequency of 50kHz and is
independent of load. All “fully digital” amplifiers and most analog class D amplifiers exhibit a frequency
response which can deviate by as much as 10dB from the nominal-load response under common load
conditions.
Hypex Electronics, Ulgersmaweg 137-D, 9731 BR Groningen, The Netherlands.
Contact: Jan-Peter van Amerongen, Tel:+31·50·5246993, Fax:+31·50·5254591, e-mail: [email protected]
Hypex Electronics
4.2. Output Impedance
100
50
20
10
5
2
O
h
1
m
500m
s
200m
100m
50m
20m
10m
20
50
100
200
500
1k
2k
5k
10k
20k
50k 100k
Hz
The upper trace shows the output impedance of the output filter, input (=switching node) shorted to
ground. This is typical of the output impedance found on “fully digital” amplifiers and on analog class D’s
without post-filter feedback. Clearly visible are the parallel resonant frequency and the DC resistance of
the coil. The bottom trace is the output impedance of the same circuit, but with the amplifier operating. It
is very evident that the feedback loop has full control over the output, with the resonant peak completely
gone and the DC resistance lowered. The rise with frequency corresponds with an inductance of 560nH,
much lower than the inductances commonly inserted at the output of linear amplifiers to decouple capacitive loads.
4.3. THD versus Power at 1kHz
1
0.5
0.2
0.1
0.05
%
0.02
0.01
0.005
0.002
0.001
1m
2m
5m 10m 20m
Measurement filter=AES17 (20kHz).
50m 100m
500m 1
2
5
10
20
50
W
Hypex Electronics, Ulgersmaweg 137-D, 9731 BR Groningen, The Netherlands.
Contact: Jan-Peter van Amerongen, Tel:+31·50·5246993, Fax:+31·50·5254591, e-mail: [email protected]
100 200
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4.4. THD versus Frequency at 1, 30, 70 and 100W
1
0.5
0.2
0.1
0.05
100W
%
0.02
70W
0.01
30W
1W
0.005
0.002
0.001
20
50
100
200
500
1k
2k
5k
10k
20k
Hz
Measurement filter=30kHz. THD is essentially independent of frequency. Minor thermal modulation is evident at lower frequencies.
4.5. Alternative Modulator Settings
The unusual flexibility of UCD allows different optimizations of the modulator/control circuit. Shown below
is a plot of the same circuit board, where only the passive control network is modified. One setting offers
best THD at moderate power levels (typical listening levels) and mild clipping behaviour, whereas the other
setting yields better linearity up to full rated power.
1
0.5
0.2
0.1
0.05
%
0.02
0.01
0.005
0.002
0.001
1m
2m
5m 10m 20m
50m 100m
500m
1
2
5
10
20
W
Hypex Electronics, Ulgersmaweg 137-D, 9731 BR Groningen, The Netherlands.
Contact: Jan-Peter van Amerongen, Tel:+31·50·5246993, Fax:+31·50·5254591, e-mail: [email protected]
50
100
Hypex Electronics
4.6. Noise Floor FFT
+0
-20
-40
-60
d
B
r
-80
-100
A
-120
-140
-160
-180
0
2k
4k
6k
8k
10k
12k
14k
16k
18k
20k
Hz
Shown is a 16k point FFT (at 44.1kHz) of the noise floor of an UCD module (inputs shorted) with
0dB=100W. At a noise gain of 1+ AV=5.55 this noise level corresponds to an input voltage noise of
20nV/√Hz at the comparator input. Indeed, only the input pair contributes to noise – even the 1/f noise
corner is visible.
5.
Application notes
5.1. Minimal Test Connection
Performance and EMC measurements can be carried out with cable connections directly made to the module. Refer to 5.2 for proper connections for listening tests. Sonic performance using this minimal test connection will be compromised.
To AP test set generator out
(low-Z output setting)
1
3
2
To AP analyzer input
1
3
2
Test load
ININ+
GND
GND
GND
OUT
OUT
OUT
ENA
VDR
VB+
GND
VBERR
To PSU
2x2200u (if not included on PSU)
Hypex Electronics, Ulgersmaweg 137-D, 9731 BR Groningen, The Netherlands.
Contact: Jan-Peter van Amerongen, Tel:+31·50·5246993, Fax:+31·50·5254591, e-mail: [email protected]
Hypex Electronics
5.2. Preferred audio connections
RB
RA
RA ’
AV
R
A V,TOT =A V ·(2· A +1)
RB
RB
RA
AV
A V,TOT =A·(
V
RA
+1)
RB
The traditional “star ground” concept, while offering a solution to LF ground loops, has been proven to be
unworkable in environments where high-frequency performance is also an issue. This is the case with applications containg digital and switching power circuits, and with all applications when irradiation sensitivity is
concerned. The physical loops that are inevitably created when a signal and its return follow different paths,
are radiating and receiving antennae for (electro-) magnetic fields. These HF problems are readily solved by
using an unbroken ground plane, but this again potentially have the problems addressed by star-grounding.
For this reason, the UCD cell is equipped with differential inputs. These are used either to receive the input signal with reference to the local ground of the preamplifier circuit (right), or to build a fully balanced
input in “instrumentation amplifier” fashion (left).
Even if the input is unbalanced, the balanced circuit shown left offers a significant sonic improvement over
the unbalanced buffer/preamp circuit. Suitable op-amps are, depending on budgetary and sonic requirements, OPA627, OPAx134 and TL07x, as well as many discrete preamplifier circuits, provided they have a
low output impedance.
5.3. EMC and AM Tuner Compatibility
Even without shielding the circuit, together with its board lay-out, meets most common legal radiation limits (including EN55013/CISPR13, FCC part 15 class B) by a generous margin. In a properly designed application UCD will not interfere with FM radio reception. In audio systems comprising an AM tuner, interference-free reception requires the use of multiple fixed switching frequencies.
Under normal condition, switching frequency is set by the control loop characteristics and is variable with
modulation. The switching frequency automatically synchronises to a reference clock mixed with the input
signal. The frequency can then be chosen such that no harmonics are near the tuning frequency or its mirror. In practice, two frequency settings suffice.
While the audio performance in frequency-locked mode is more than sufficient for AM radio, the amplifier
is best left unlocked in other conditions.
5.4. Mutual Interference
Frequently with the application of unsynchronised class D amplifiers, interference from one channel into
another is a concern. The effect shows up as whistles (tones) corresponding to the frequency difference of
the channels involved, and harmonics thereof. In the design of UCD, special care has been taken to avoid
these problems. First and foremost, radiation and conducted interference are kept to a minimum by onboard measures. Secondly, the input stage supports a differential input that is very insensitive to HF noise.
Below is a compound noise FFT of all six channels of an application board using the demonstration modules
shown on the front page. This board does not contain any specific EMC measures. Nearly no disturbance
component exceeds the –120dB limit. In any real application this means the disturbances are well below the
noise floor.
Hypex Electronics, Ulgersmaweg 137-D, 9731 BR Groningen, The Netherlands.
Contact: Jan-Peter van Amerongen, Tel:+31·50·5246993, Fax:+31·50·5254591, e-mail: [email protected]
Hypex Electronics
+0
-20
-40
-60
d
B -80
r
-100
-120
-140
-160
-180
0
2k
4k
6k
8k
10k
12k
14k
16k
18k
20k
Hz
5.5. Adapted Versions
This data sheet outlines the properties of a specific prototype implementation. Being a discrete circuit UCD
can be customised to suit specific customer requirements. This is readily done during the industrialisation
phase of the application. Relatively minor circuit modifications are:
• Lower power versions at reduced cost
• Added clock input for AM mode sync
• Cost optimisation by using more tightly specified passives
• Higher audio performance through better gate drive parts
• Different sonic preference (selected passive components)
Major redesigns open up a wider range of options. This includes high-power versions (200W…1kW), fullbridge versions for single supply operation and higher power, and IC integration.
Hypex Electronics, Ulgersmaweg 137-D, 9731 BR Groningen, The Netherlands.
Contact: Jan-Peter van Amerongen, Tel:+31·50·5246993, Fax:+31·50·5254591, e-mail: [email protected]