Keywords: automotive audio power amplifier
Circuit principle: as shown in Figure audio power amplifier circuit, IC1 LM358 dual operational amplifier composed of a preamplifier, half of it operating in the inverted state of the left channel, the right channel and the other half in the state of operating in the same phase, pre amplification of the amplifier is equal to 1, except that the signal is inverted in the outer channel where the sound, it also provides an integrated circuit TDA2030 power amplifiers IC2 and IC3 input bias. In order to enable the power amplifier output, the DC voltage is slowly increased, and the "Kara" sound generated instantaneously generated in the power supply is eliminated. Introducing the "Kara" sound circuit R6, C5, and power supply in the circuit. When passing, the voltage on the C5 is slowly increased, and the output is not generated "" sound. The diode VD2 is used for the power discharge capacitor C5 fast discharge, and the regulator tube VD1 is used for the DC voltage of the power amplifier output, and thus the fluctuation of the power supply circuit does not affect the quality of the audio play. Another feature of this circuit can operate in a normal single-channel state, such as listening to language programs, in which case the power consumption is reduced, and the lower limit frequency of the amplified signal is improved. At the same time, the speaker BL3 and the filter are disconnected by the switch SA1, and the speakers BL1, BL2 are connected by capacitors C16, C17, and reduce signals below 100 Hz to 150 Hz. BL1, BL2 speakers are also connected by R17, C14, and R18, C15, signals above 300 Hz frequencies. Audio power amplifier parameters are as follows: (1) the playback frequency (-3dB level) is rated in the range of 25 ~ 22000HZ; effective power (2) stereo channels of 5.5W × 2; (3) low power channel is active 22W; (4) rated input voltage 0.25V; (5) harmonic coefficient at the rated input voltage of 0.12%; (6) the voltage amplification factor of 26dB; (7) quiescent current of 120mA ~ 150mA; (8) for the supply voltage 11.7 ~ 14.4V. A maximum of one feature of the audio amplifier is turned on its way, which is turned on by means of two electromagnetic relays K1 and K2 in the "K" plus the two terminals of the relay when the power supply through the capacitor C22, and C23 and coupled later on, the capacitor is charged via the diode VD3 series with the relay winding turns, thus reducing the consumption current flowing through the relay windings, the power amplifier improves temperature conditions.
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Component selection and installation of: self-inductance L1, the use of the output transformer core portable radio, a full bobbin winding enameled wire with 1.0mm ~ 1.2mm. Inductance L2, L3 is a hollow core coil, and a cross section of about 1 mm 2 is 100 turns with a cross section of about 1 mm 2 in a wooden pattern in a diameter of 50 mm. The first is to determine the adjustment of the power amplifier quiescent current of the amplifier does not exceed 150 ~ 200mA. The relays K1, K2 are not applied, and the contacts K1.1, K2.1 are short-circuited by a short route. When the fuse fu1 is connected, the static current is measured. For the relays K1, K2 plus voltage (removed K1.1, K2.1 short route), turn on the voltage circuit, K1.1, K2.1 contact closed. The switch SA1 is shown in the illustrated position, adds a music signal in the luminous side of the amplifier, and selects the volume R17, R18 to balance the volume between the low frequency and the medium high frequency network. Adjusting R11, R12 can change the amplification factor of the amplifier, and adjusting C5 can change the growth time of the amplifier output DC voltage.
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