170W Class D Amplifier schematic diagram

Description: The combination of the LM4651 driver IC and the LM4652 power MOSFET Class D power amplifier IC provides a high-efficiency amplifier solution, suitable for self-powered speakers, subwoofers, and quality car boosters. The LM4651 is a fully integrated conventional pulse width modulator (PWM) driver, containing undervoltage, short circuit, overmodulation, and thermal shutdown protection circuitry. The IC features a standby function that shuts down the pulse width modulation, minimizing supply current. The LM4652 is a fully integrated H-bridge Power MOSFET IC in a TO220 power package. The IC has a built-in temperature sensor to alert the LM4651 when the die temperature exceeds the threshold limit. Used together, the LM4651 and LM4652 form a simple, compact, efficient, high-quality power audio amplifier solution complete with protection, normally seen only in Class AB amplifiers. The maximum efficiency of this circuit is 85% at 125W with a standby attenuation greater than 100dB. The total harmonic distortion (THD) at 10W, 4 ohms, 10 - 500Hz is a maximum of 0.3%. The supply voltage cannot exceed ±22V. For optimal performance, a suitable preamplifier is required. With the addition of a preamplifier, the gain of the power stage can be significantly reduced to improve performance. The gain should be set to 10 V/V, allowing for low gain on the Class D stage while maintaining a total system gain sufficient for line-level sources. The input filter used does not noticeably increase THD performance but helps maintain a flat frequency response as the Q of the output filter changes with load impedance. It is advised not to attempt building this amplifier as a first project, as Class D high-power amplifiers are complex and costly, and a small error during assembly can lead to significant damage to the power IC or other expensive components.

The LM4651 and LM4652 combination represents a sophisticated solution for high-efficiency audio amplification, particularly in applications requiring compactness and reliability. The LM4651 serves as the driver, utilizing pulse width modulation to control the output signal effectively. Its integrated protection features, including undervoltage lockout and thermal shutdown, ensure safe operation under various conditions, preventing damage to the circuit.

The LM4652, functioning as the power stage, is designed in an H-bridge configuration, allowing for efficient power delivery to the load. The TO220 packaging facilitates effective heat dissipation, essential for maintaining performance during extended use. The built-in temperature sensor enhances reliability by providing real-time monitoring of the IC temperature, enabling proactive management of thermal conditions.

This amplifier design achieves a remarkable efficiency of 85% at a power output of 125W, making it suitable for high-performance audio applications. The low total harmonic distortion of 0.3% at 10W output indicates minimal signal degradation, preserving audio fidelity. The maximum supply voltage limitation of ±22V ensures compatibility with a wide range of power supply configurations while maintaining safety margins.

Incorporating a preamplifier into the circuit allows for optimized gain settings, reducing the gain of the power stage to 10 V/V. This adjustment enhances overall system performance, especially in scenarios involving line-level audio sources. Additionally, the input filter plays a crucial role in maintaining frequency response integrity, accommodating variations in load impedance without adversely affecting THD performance.

Due to the intricacies involved in building Class D amplifiers, it is recommended that individuals undertake this project only after gaining sufficient experience with electronic assembly and troubleshooting. The potential for damage to components underscores the necessity for careful construction and adherence to design specifications.The combination of the LM4651 driver IC and the LM4652 power MOSFET Class D power amplifier IC provides a high efficiency amplifier solution, suitable for self-powered speakers, subwoofers and quality car boosters. The LM 4651 is a fully integrated conventional pulse width modulator (PWM) driver, containing undervoltage, short circuit, overmodulat

ion, and thermal shutdown protection circuitry. The IC features a standby function which shuts down the pulse width modulation, minimizing supply current. The LM 4652 is a fully integrated H-bridge Power Mosfet IC in a TO220 power package. The IC has a built in temperature sensor to alert the LM4651 when the die temperature exceeds the threshold limit.

Used together, the LM4651 and LM4652 form a simple, compact, efficient, high quality power audio amplifier solution complete with protection, normally seen only in Class AB amplifiers. The maximum efficiency of this circuit is 85% at 125W with a standby attenuation greater than 100dB. The THD at 10W, 4 ohms, 10 - 500Hz is max. 0. 3%. The supply voltage can not exceed ± 22V. For the best performance a suitable preamplifier is required. With the addition of a preamplifier the gain of the power stage can be greatly reduced to improve performance.

The gain should be set to 10 V/V allowing for low gain on the Class D stage with a total system gain high enough to be a complete solution for line level sources. The input filter used here does not noticeably increase THD performance but will help to maintain a flat frequency response as the Q of the output filter changes with load impedance.

Do not attempt to build this amplifier as your first project! Class D high power amplifiers are expensive, difficult to build and a very small error during assembly can lead to total devastation of the power IC or other costly components.