Ecler-MPA4_400-pwr-sm维修电路原理图.pdf
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1、 MPA4-400 SERVICE MANUAL 1000100100POWER10OFFONCHANNEL 4VOL5CLIPSPCHANNEL 1CHANNEL 35SP5CLIPCHANNEL 2CLIPSP5400MULTICHANNELPOWER AMPLIFIERMPTHERMALSPCLIPLECREA4-VOLVOLVOLMAINS INPUTGNDXLR CONNECTIONS: PIN 1 - GROUND, PIN 2 - PHASE, PIN 3 - NON PHASEIN 2LINK CH 1LINK CH 2IN 4BRIDGE IN 3BRIDGEOFFONIN
2、3+IN 4GND LINKSTEREOBRIDGEIN 1+IN 2ONIN 4CHANNEL 4HP FILTEROFFONOFFIN 2BRIDGE IN 1STEREOCHANNEL 2LP FILTERIN 1IN 3LINK CH 1CHANNEL 3IN 1IN 3IN 1+IN 2CHANNEL 1CH 2 -CH 2 +MINIMUM LOAD: 4 OHM STEREO, 8 OHM BRIDGEFOR BRIDGED OUTPUT USE RED POSTS ONLY.OUTPUTBRIDGEDCH 3 -CH 4 -CH 4 +CH 3 +BRIDGEDCH 1 -CH
3、 1 +RadioFans.CN 收音机爱 好者资料库SERVICE MANUAL MPA4-400 INDEX - BLOCK DIAGRAM - FUNCTIONING DESCRIPTION - SCHEMATICS Power amplifier Inputs Power Supply + Outs Leds + potentiometers - COMPONENTS LOCATION SCHEMA Power amplifier Power Supply + Inputs + Outs Leds + potentiometers - TESTING AND QUALITY CONTR
4、OL - TECHNICAL CHARACTERISTICS - WIRING DIAGRAM - CONFIGURATION DIAGRAM - MECHANICAL DIAGRAM - PACKING DIAGRAM RadioFans.CN 收音机爱 好者资料库52-0017-0100 EP14-02.doc 1 of 2 The amplifying stage basic structure is actually the one commonly used until now, this is, a push-pull mounted A-B class amplifier, us
5、ing 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 than 3. The amplifiers feedback runs through a resistor and a capacitor associated to the OpAmps non-invert
6、ing 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-source junction, keeping them on their conduction knee. On the other hand, they carry out the OpAmps output vo
7、ltage 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 current sources output, which passes through the BF-transistors load resistors. The bias current stability agai
8、nst 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 consequence, if the temperature rises, the reference voltage decreases, thus the gate-source voltage also does, and
9、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 impedance as constant as possible, no matter which load is connected to the stages output, or which signal fre
10、quency 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 the output to signal ground when the DC level is enough to get the diac triggered. To prevent this from happening whi
11、le carrying audio signal (sine-wave, music), the diacs reference voltage is taken from a filter formed by resistor R161 and capacitor C123. The protection circuitry supervises at any time the power consumed by the MOSFETS. The circuitry basically consists on two sections: MOSFETs drain current (Id)
12、monitoring and drain-source voltage (Vds) monitoring. When the drain current exceeds a certain limiting value, a transistor (called control-transistor) becomes conducting, together with an auxiliary circuitry (helper), formed by a transistor (which is the same type as the control-transistor) and a 8
13、2V Zener diode. This value determines the point where the auxillary circuitry starts to run. The helper-transistors base-emitter junction curve is used to obtain a non-linear variation on the MOSFETS gate-source voltage control, and thus on their drain current. author: Queralt date: 020927 project:
14、EP14-02 product: MPA4-400 ECLER approved: num: 52.0017 version: 01.00 title: FUNCTIONING DESCRIPTION52-0017-0100 EP14-02.doc 2 of 2 Moreover, as the helper-transistors base-emitter current is temperature-dependent, the controlling circuitry (basically the control-transistor) compensates the safe ope
15、ration area (SOA) drift due to temperature. 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 adequately in order to maintain the MOSFET
16、s power consumption as close as possible to its SOA. Moreover, the amplifier also includes 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 ar
17、e used to be rectified and sent to an optocupler (led-resistor) which modifies its impedance 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 inpu
18、t signal level decreases until the system becomes stable. Also a dual-function temperature 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.
19、The circuitry is formed by LM35D-type IC, which acts like a thermal probe, an amplifier, 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 shunt
20、ing a 22 resistance to the BF-type transistors load resistors. This way, the output signal 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 whol
21、e system reaches again a voltage-stable situation. Due to this, hearing annoying transients 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 Tri
22、gger-Schmitt trigging level is reached, and the amplifier starts functioning. C=47F resets 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. PARTS LIST: PRINTED CIRCUIT 11.0956.03.01
23、CodeDescriptionReferenceFCXCD1220022pC101FCXCD41000100nC102FCXCD41000100nC103FCCE25010010u/50C104FCCE25047047u/50C105FCXCD1680068pC106FCXCD1680068pC107FCCE35047047u/100C108FCCE35047047u/100C109FCCE25010010u/50C110FCXCD41000100nC111FCXCD1150015pC112FCXCD41000100nC113FCCE25010010u/50C114FCXCD44700470n
24、C115FCXCD44700470nC116FCXCD1150015pC117FCXCD1150015pC118FCCDK52200C220n/100VC119FCCDK52200C220n/100VC120FCXCD26800680pC121FCXCD26800680pC122FCCDK20010C1u/63VC123FCXCD4010010nC124FCXCD4010010nC125FCCDH71100C100n/400VC126FCCDH71047C47n/400VC127FCXCD41000100nC128FCXCD41000100nC129FCXCD41000100nC130FCCE
25、25010010u/50C131FCXCD44700470nC132FCCE25010010u/50C133FCCE10000047u/16C134FCXCD44700470nC135FCCE25047047u/50C136FCCE25047047u/50C137FCCE25010010u/50C138FCCE154700470u/25C139FCXCD1220022pC140FCXCD41000100nC141FCXCD41000100nC142FCCE25010010u/50C143FCCE25047047u/50C144FCXCD1680068pC145FCXCD1680068pC146
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