Ecler-MPA4_150-pwr-sm维修电路原理图.pdf
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1、 MPA4-150 SERVICE MANUAL CLIP40123SP CLIP64CLIPSP601098712397101823CHANNEL 15CHANNEL 25SP64SP CLIP64201098701310987CHANNEL 35CHANNEL 45POWER4- 150AMPPOWER AMPLIFIERMULTICHANNELONOFFCEEL RVOLVOLVOLVOLTHRadioFans.CN 收音机爱 好者资料库SERVICE MANUAL MPA4-150 INDEX - BLOCK DIAGRAM - SCHEMATICS - COMPONENTS LOCA
2、TION 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52-0006-0101 EP05-99 angls.doc 1 of 2 The amplifying stage basic structure is actually the one commonly used until now, this is, a push-p
3、ull 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 than 3. The amplifiers feedback runs through a resistor and a capacitor
4、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 mosfets gate-source junction, keeping them on their conduction knee. On the other hand,
5、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 current sources output, which passes through the BF-transistors load resisto
6、rs. 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 consequence, if the temperature rises, the reference voltage decreases, thus the
7、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 impedance as constant as possible, no matter which load is connected to the
8、 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 the output to signal ground when the DC level is enough to get the diac triggered.
9、 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 time the power consumed by the MOSFETS. The circuitry basically consists on two secti
10、ons: 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 to BFs load resisitor, reduring the gate-source voltage, and also reducing Id. If th
11、e 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 MOSFETs power consumption as close as possible to its S
12、OA. author: J. Colominesdate: 050401 project: EP05-99 product: MPA4-150 ECLER approved: num: 52.0006 version: 01.01 title: FUNCTIONING DESCRIPTION52-0006-0101 EP05-99 angls.doc 2 of 2 Moreover, the amplifier also includes an ANTICLIP system. When the amplifier reaches its clipping level, the OpAmp b
13、ecomes 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 impedance as a function of those peaks amplitude. The resulting impedance is part of a
14、 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 temperature control circuitry is provided: - Temperature-depending control of the cooling
15、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 amplifier, thermal probe level comparator and a 7805-type voltage regulator. The amplifier
16、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 signal of the amplifier is effectively cutted off. The STAND-BY circuit. This circuit
17、 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 transients and noises during start up through the loudspeakers is avoided. This delay is
18、 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 resets or discharges when the unit is turned off. During a short period of time, a BC
19、817-type transistor acts like a switch, connecting two 75 parallel resistors to C=47/50V. author:Queraltdate:000719approved:num:52.0006version:01.00FUNCTIONING DESCRIPTIONtitle:EP05-99The amplifying stage basic structure is actually the one commonly used until now, thisis, a push-pull mounted A-B cl
20、ass amplifier, using P-type (IRFP9240) and N-type(IRFP240) mosfets.The systems controlling core is a NE5534 OpAmp, which is internally compensated inorder to obtain an amplifying gain ratio equal or greater than 3. The amplifiersfeedback runs through a resistor and a capacitor associated to the OpAm
21、ps non-inverting input.Transistors BF871 and BF872 are common-base configured, becoming actually acurrent source structure. They accomplish a dual function: on one hand, they polarisethe mosfets gate-source junction, keeping them on their conduction knee. On the otherhand, they carry out the OpAmps
22、output voltage variations, referred to signal ground.The polarisation current adjustment is fixed by a 2k5 trimming potentiometer connectedto the BF transistors base. This current is added to the current sources output, whichpasses through the BF-transistors load resistors. The bias current stabilit
23、y againsttemperature is fixed through the BD437 transistors. Their temperature- dependent baseemitter voltage curve is used to alter adequately the current sources reference voltage.As a consequence, if the temperature rises, the reference voltage decreases, thus thegate-source voltage also does, an
24、d finally the bias current also decreases.The Zobel network, formed by a resistor-inductor-capacitor group, and which is locatedat the amplifiers output, intends to keep the amplifiers load impedance as constant aspossible, no matter which load is connected to the stages output, or which signalfrequ
25、ency 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 diactriggered. To prevent this from happening while ca
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