Sunday, July 18, 2021

DIY Super Powerful Monoblock Car Amplifier Subwoofer - Class-D

DIY Monoblock Car Amplifier Subwoofer - Class-D
Hello, in this post, I will make a monoblock amplifier for subwoofer speakers that use a 12V power supply or battery, which I will later install in the car.

Class-D Subwoofer Amplifier

The following is a schematic of the amplifier block. there are several parts, namely the section for the dc to dc converter, from 12V it is increased to 45-75VDC CT voltage for the main supply of the amplifier, for the protection supply and 12V bias I also made from the secondary output of the transformer, so that it is isolated from the primary power supply voltage for supply ic opamp I use R Shunt + zener which is taken from the main supply. oh yes, for the amplifier, I use a class-d Halfbridge Dual feedback amplifier designed by Mr. Kartino S. For the totem, I use 2 TC4420, and use 4 mosfet. The mosfet that I will use later is 90n20, and I will use the amplifier later to handle speakers with an impedance of 1 ohm and even this amplifier can also be used for 1 ohm and below. for the subwoofer filter, I use the same as the one posted in the tda7294 subwoofer amplifier. For protection, I added a DC protector, an Over-current protector.

12V Class-D Subwoofer Amplifier

The following is the PCB layout that I have designed, the PCB size is 33.7x14.5cm, I made the size to fit the heatsink or cooler from the car amplifier that I have so that it looks like a car amplifier in general. I made a dual-layer PCB design, I will share the layout for free, you can click the link at end of the post. For dual layer PCB printing, I recommend JLCPCB because the price is sufficient and the work is fast, less than 2 weeks the PCB from JLCPCB has arrived at home. 

My primary elco uses a capacity of 6800uf voltage 25V and secondary Elco 1200uf 80V. The inductor for my filter uses an inductor rated at 8uH. I made 2 versions of the PWM, namely the TC4427 totem and the a1015 transistor. Friends, you can also download the PCB layout at the same link. PWM uses the TL494 IC and without using a pin header so it is directly soldered to the mainboard amplifier PCB. The trimpot on this PWM serves to regulate the secondary voltage output.

Next for the converter transformer, I use a green toroid with a diameter of 6.5cm. For the primary winding, I use 1.5mm wire for as many as 6 copies with a total of 6 turns. for the second part, I used 7 duplicate 1mm wires with 27 turns. and for the extra, I use a 1.5mm wire wrapped around as much as 10 turns.

For the fuse, you can adjust the capacity of the battery. my secondary diode uses a mur1560 diode, and 8 MOSFET transistors for the converter I use fdp054n10.

Next we test first whether the converter is working or not, install the fuse on the secondary output. then input the black 12V supply for the red min for the + and this small cable for the brake or remote voltage, for testing it can be jumped directly with the + voltage.

Then turn on the amplifier, if the Over Current led is active, set the trimpot to Over current, turn it to the right so it's not too sensitive.

 If the OCP is off then the protect led will light up for a while, and a small relay will activate. the sign is that the converter is working, and the red led near the speaker relay will also light up briefly and turn off, the led is for the protect indicator on the speaker. protect will work when the speaker is on or delayed, and if the speaker output is more than 3V DCO.

Next, we check the voltage at several points before installing the components, this is the op-amp supply voltage on the subwoofer filter, which is + - 30V and 15V to ground. if it does not come out can be checked on the Zener diode under the R shunt.

then this is the main supply voltage around 56V DC to Ground. This voltage can be set on the trimpot on the PWM board as I described earlier.

And this is the bias voltage and supply protector around 12V DC. if it does not come out the possibility of IC 7812 is damaged, for the TL071 opamp supply voltage on the amplifier section, the voltage reads 25V DC + - and to the ground is around 12VDC. if it doesn't come out it's possible that the Zener or rshunt is damaged. If the measurement point has been met, then we will install the IC before installing the CLass-D mosfet we check first whether the PWM amplifier is working or not, we can check using an oscilloscope, attach the probe to the low side MOSFET gate, and ground to the ground amplifier. Inject the input with the audio generator, then the gate will output a PWM signal with a freq according to the input freq. 

the amplifier driver is already working, then we turn it off first and install the MOSFET. MOSFET uses 4x 90N20 MOSFET.

 then we test again, attach the oscilloscope probe to the prefilter, and ground to the ground amplifier After that, turn it on again, now the PWM has come out, I set the freq at 160kHz, to set it, I can change the value of the resistor with the set freq label. If we hold the input, the duty will widen, this is a sign that the amplifier is working.

For more details check this youtube video: https://youtu.be/SbHpzabJLdM


Download:

Full schematic and PCB Layout Gerbe Files  Monoblock Subwoofer Car Amplifier Mainboard + PWM board









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