| This paper focus on the Class-D audio amplifier applied to portable electronics and introduces a concrete solution according to the technology trends and customer's requirement。Meanwhile, it also verifies its feasibility by simulation and the actual test data. The key technical solutions are included as below:1. PWM modulator with Filter-less output architecture, which can minimize quiescent power dissipation, save system cost, board space, and simplify the design of system2. The BTL output driver applied to bias the output DC voltage differential at two sides of load to OV, which can thoroughly solve not only the pop noise resulted from the sudden change of VBIAS, such as impact noise during powering on and off, but also various noises in normal operation. The isolation coupling capacitor which is necessary when driven by half-bridge can also be removed. With the same supply voltage, the BTL signal output range is 2 times of Half-bridge amplifier due to the load with differential drive. With the same supply voltage, it is capable of providing 4 times of maximum output power than Half-bridge amplifier, therefore, achieve larger output power even the IC is working at low voltage.3. Full differential amplifier with common-mode feedback circuit can provide high CMRR (Common Mode Rejection Ratio) and improve the capability of anti-interference and suppressing common-mode signal. Moreover, even operating with a single power supply, the extremely high PSRR (Power Supply Rejection Ratio) can be achieved to reduce the impact to amplifier due to system noise.4. New feedback circuit and full differential amplifier applied to the 2nd order integrator to process the PWM signal, which greatly improves the THD+N.5. Employing various protection circuits including soft start, OCP (Over Current Protection), OTP (Over Temperature Protection), shoot-through protection, UVLO (Under-voltage Lockout) and LEB (Leading Edge Blanking), protects the IC from all risks. |
PDF Full Text Request