参数资料
型号: AN1042
厂商: ON SEMICONDUCTOR
英文描述: High Fidelity Switching Audio Amplifiers Using TMOS Power MOSFETs
中文描述: 高保真开关音频放大器使用的TMOS功率MOSFET
文件页数: 4/12页
文件大小: 108K
代理商: AN1042
AN1042/D
http://onsemi.com
4
+
R5
R4
Audio
Input
Figure 6. Duty Cycle Controller
+
U1D
(Comparator)
Variable
Duty Cycle
Output
R7
R6
U2C
C3
From Current
Limit
C4
R8
From Output
Current
Compensation
+
U1B
C2
R2
R1
C1
R3
120 kHz
+5
–5
+2
–2
The
±
2 volt triangle is applied to the non–inverting input
of U1D. The error voltage normally varies over this same
range. As it does so, the output of U1D is a square wave at
120 kHz whose duty cycle varies from 0% to 100%. The
error voltage will exceed normal limits if the amplifier
should clip. In that case, the output drive waveform will
lock up at either +5 or –5 volts. If not corrected, the ac
coupling of the drive signal would cause a loss of drive to
the final amplifiers and associated severe distortion.
To prevent loss of drive, the drive waveform duty cycle
must be restricted to the range of 5% to 95%. This is
accomplished by the circuit of Figure 7. The 120 kHz square
Figure 7. Schematic of Duty Cycle Limiter and Output Driver
Drive to
Switches
R13
R14
Q1
Q2
R12
C5
C6
–5
+
U1C
(Comparator)
R9
Variable
Duty
Cycle
+5 V
–5 V
U4A
U4B
U3A
R
Q
U3B
R
Q
R10
R11
A
B
A
B
–5 V
120 kHz
+5 V
+5 V
–5 V
+2 V
–2 V
+5 V
–5 V
+5 V
–5 V
250 ns
250 ns
120 kHz
Input
High Limit
5%
Low Limit
95%
Integrator
Output
U1B
Variable
Duty Cycle
U1D Output
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