100W Class D Amplifier for Car Audio

In the circuit of Figure 2, the audio signal is coupled to the input of the dual D flip-flop CD4013 (IC1) through a 470nF capacitor. After being processed by the internal circuit of CD4013, two signals with opposite polarities containing audio components are output from the Q and Q terminals. After the two signals with opposite polarities are power-amplified by the high-speed MOSFET drive circuit TC4426, the high-power MOSFET tube IRFP140 is driven to work in the switching state. The audio signal is output to the speaker through the coupling of T2, driving the speaker to make sound.

The circuit in Figure 2 can work normally when connected to a speaker with an impedance of 4 to 16Ω, with an efficiency higher than 76%. Due to the presence of output transformer T2, the output sound has a tube-like flavor.

The high-speed MOSFET drive circuit TC4426 can work stably in the power supply range of 4.5V to 18V. Its output drive current is as high as 1.5A, and the output impedance is only 7Ω (the internal circuit is shown in Figure 3). Therefore, it is an ideal device for driving MOSFET power amplifier tubes. Since the circuit is relatively simple, it is very suitable for audio enthusiasts to make it themselves, so the parameters of each component are given below for imitation.

The output tube uses MOSFET field effect tube IRFP140 (100V, 30A, 150W). VD1 and VD2 use high-speed Schottky diode MBR150. If MBR150 is not available, it can be replaced with other diodes of the same type. T1 uses high-strength enameled wire with a diameter of 1mm to double-wind 8 turns on a 3C85 core with a diameter of 25mm. T2 primary uses high-strength enameled wire with a diameter of 1mm to wind 6 turns on a 3C85 core with a diameter of 25mm, and then uses high-strength enameled wire with a diameter of 0.8mm to wind 21 turns on the core as the secondary.

L1 is made of 0.8mm diameter high-strength enameled wire, which is wound 64 turns on the T-157-2 ferrite core. L2 is made of 0.8mm diameter high-strength enameled wire, which is wound 64 turns on the T-130-2 ferrite core.

If the amplifier has noise interference during operation, a 47nF capacitor can be installed between the voltage input terminals of CD4013 and TC4426 (close to the pins).

The resistors are all five-color ring metallized resistors, the resistor of the MOSFET output tube control electrode is a 2.2Ω, 2W metal film resistor, the three 470nF capacitors are WIMA capacitors, and the remaining capacitors are ordinary capacitors.