Ecler-MPA4_150-pwr-sm 电路图 维修手册.pdf
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1、 MPA4-150 SERVICE MANUAL CLIP 4 0 1 2 3 SP CLIP 64 CLIPSP 6 010 9 8 7 1 2 3 9 7 10 1 82 3 CHANNEL 1 5 CHANNEL 2 5 SP 64 SP CLIP 64 2 010 9 8 7 0 1 3 10 9 8 7 CHANNEL 3 5 CHANNEL 4 5 POWER 4- 150AMP POWER AMPLIFIER MULTICHANNEL ON OFF CEEL R VOLVOLVOLVOL TH RadioFans.CN 收音机爱 好者资料库 SERVICE MANUAL MPA4
2、-150 INDEX - BLOCK DIAGRAM - SCHEMATICS - COMPONENTS LOCATION SCHEMA AND PART LIST - TESTING AND QUALITY CONTROL - TECHNICAL CHARACTERISTICS - WIRING DIAGRAM - MECHANICAL DIAGRAM - PACKING DIAGRAM RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 52-0006-0101 EP05-99 angls.doc 1 of 2 The amplifying st
3、age basic structure is actually the one commonly used until now, this is, a push-pull mounted A-B class amplifier, using P-type (IRFP9240) and N-type (IRFP240) mosfets. The systems controlling core is a NE5534 OpAmp, which is internally compensated in order to obtain an amplifying gain ratio equal o
4、r greater than 3. The amplifiers feedback runs through a resistor and a capacitor associated to the OpAmps non-inverting input. Transistors BF471 and BF472 are common-base configured, becoming actually a current source structure. They accomplish a dual function: on one hand, they polarise the mosfet
5、s gate-source junction, keeping them on their conduction knee. On the other hand, they carry out the OpAmps output voltage variations, referred to signal ground. The polarisation current adjustment is fixed by a 2k5 trimming potentiometer connected to the BF transistors base. This current is added t
6、o the current sources output, which passes through the BF-transistors load resistors. The bias current stability against temperature is fixed through the BD437 transistors. Their temperature- dependent base-emitter voltage curve is used to alter adequately the current sources reference voltage. As a
7、 consequence, if the temperature rises, the reference voltage decreases, thus the gate-source voltage also does, and finally the bias current also decreases. The Zobel network, formed by a resistor-inductor-capacitor group, and which is located at the amplifiers output, intends to keep the amplifier
8、s load impedance as constant as possible, no matter which load is connected to the stages output, or which signal frequency is to be amplified, in order to prevent an inverted-phase feedback signal. In order to avoid a DC offset on the output signal, a diac-triac tandem system is used, which shorts
9、the output to signal ground when the DC level is enough to get the diac triggered. To prevent this from happening while carrying audio signal (sine-wave, music), the diacs reference voltage is taken from a filter formed by resistor 33k2 and capacitor 1. The protection circuitry supervises at any tim
10、e the power consumed by the MOSFETS. The circuitry basically consists on two sections: MOSFETs drain current (Id) monitoring and drain- source voltage (Vds) monitoring. When Id exceeds a fixed values a control transistor in every branch starts to conduct like a switch, apliying a parallel resistor t
11、o BFs load resisitor, reduring the gate-source voltage, and also reducing Id. If the MOSFETs drain-source voltage (Vds) drops too low, a second circuitry actuates to alter the control-transistors triggering level, obtaining a SOA-like curve section and a current stage, which can be adjusted adequate
12、ly in order to maintain the MOSFETs power consumption as close as possible to its SOA. author: J. Colominesdate: 050401 project: EP05-99 product: MPA4-150 ECLER approved: num: 52.0006 version: 01.01 title: FUNCTIONING DESCRIPTION 52-0006-0101 EP05-99 angls.doc 2 of 2 Moreover, the amplifier also inc
13、ludes an ANTICLIP system. When the amplifier reaches its clipping level, the OpAmp becomes unable to keep the system under control, and as a consequence V peaks appear at its output (15V power supply). This peaks are used to be rectified and sent to an optocupler (led-resistor) which modifies its im
14、pedance as a function of those peaks amplitude. The resulting impedance is part of a voltage divider, together with the amplifiers input impedance. So, as the optocoupler increases its impedance, the amplifiers input signal level decreases until the system becomes stable. Also a dual-function temper
15、ature control circuitry is provided: - Temperature-depending control of the cooling fan speed, whose voltage supply is variable between 7 and 14 Vac. - Amplifier shutdown when temperature exceeds approximately 90C. The circuitry is formed by LM35D-type IC, which acts like a thermal probe, an amplifi
16、er, thermal probe level comparator and a 7805-type voltage regulator. The amplifier is responsible for the cooling fan speed control. The comparator triggers a relay, which cuts off the MOSFETs bias current by shunting a 22 resistance to the BF-type transistors load resistors. This way, the output s
17、ignal of the amplifier is effectively cutted off. The STAND-BY circuit. This circuit keeps the safety relay closed for about 10 seconds, thus the MOSFETs bias current is cutted off during this period, until the whole system reaches again a voltage-stable situation. Due to this, hearing annoying tran
18、sients and noises during start up through the loudspeakers is avoided. This delay is obtained by a RC-cell, where R=287K, and C=47F/50V. During start up, this RC-cells voltage smoothly rises until the 40106-type Trigger-Schmitt trigging level is reached, and the amplifier starts functioning. C=47F r
19、esets or discharges when the unit is turned off. During a short period of time, a BC817-type transistor acts like a switch, connecting two 75 parallel resistors to C=47/50V. author:Queraltdate:000719 approved: num:52.0006version:01.00 FUNCTIONING DESCRIPTION title: EP05-99 The amplifying stage basic
20、 structure is actually the one commonly used until now, this is, a push-pull mounted A-B class amplifier, using P-type (IRFP9240) and N-type (IRFP240) mosfets. The systems controlling core is a NE5534 OpAmp, which is internally compensated in order to obtain an amplifying gain ratio equal or greater
21、 than 3. The amplifiers feedback runs through a resistor and a capacitor associated to the OpAmps non- inverting input. Transistors BF871 and BF872 are common-base configured, becoming actually a current source structure. They accomplish a dual function: on one hand, they polarise the mosfets gate-s
22、ource junction, keeping them on their conduction knee. On the other hand, they carry out the OpAmps output voltage variations, referred to signal ground. The polarisation current adjustment is fixed by a 2k5 trimming potentiometer connected to the BF transistors base. This current is added to the cu
23、rrent sources output, which passes through the BF-transistors load resistors. The bias current stability against temperature is fixed through the BD437 transistors. Their temperature- dependent base emitter voltage curve is used to alter adequately the current sources reference voltage. As a consequ
24、ence, if the temperature rises, the reference voltage decreases, thus the gate-source voltage also does, and finally the bias current also decreases. The Zobel network, formed by a resistor-inductor-capacitor group, and which is located at the amplifiers output, intends to keep the amplifiers load i
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