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2. 发明公开

EP1014566A2 Dual mode class D amplifier 审中-公开
标题翻译：双模D类放大器
公开(公告)号：EP1014566A2
公开(公告)日：2000-06-28
申请号：EP99403240.7
申请日：1999-12-21
申请人： Intersil Corporation
发明人： Hoyt, David , Begley, Patrick , Hernandez, Arecio , Pullen, Stuart , Stranc, Jeffrey
IPC分类号： H03F3/217 , H03F1/02
CPC分类号： H04B15/04 , H03F1/0261 , H03F3/2171
摘要： Pulse width modulated (« Class D ») amplifiers and controllers switching in the 50khz to 2 MHz range generate harmonics which interfere with AM radio reception. This has precluded wide spread acceptance of class D amplifiers in products with an AM radio. The amplifiers described here use a modified modulation technique when operating with an AM radio to avoid generating harmonics at the receiver selected frequency or its intermediate (IF) frequency. One embodiment switches the mode of operation to a class AB amplifier when an AM signal is amplified.
The AM/FM switch 10 sets the mode of operation. The AM mode detector block, 1, generates a logic signal depending on the switch. If AM-compatibility mode is engaged, then the amplifier operates as a class AB amplifier. The AM logic signal is applied to the two transmission gates, 4, so that the class AB amplifier is connected directly to the gates of the MOSFETS. Meanwhile, the inverted AM signal tri-states both gate drivers. Sensing the voltage drop across the two resistors, Rel and Re2, provides current limit protection. When AM-compatibility mode is not engaged, the amplifier operates as a class D amplifier. The two transmission gates are open disconnecting the class AB from the gates. The inverted AM signal enables both gate drivers.
摘要翻译：脉冲宽度调制（«Class D»）放大器和控制器在50khz到2 MHz范围内切换会产生干扰AM无线电接收的谐波。这阻止了AM收音机产品中D类放大器的广泛接受。这里描述的放大器在与AM无线电一起工作时使用改进的调制技术，以避免在接收器选择的频率或其中间频率（IF）产生谐波。一个实施例在AM信号被放大时将操作模式切换到AB类放大器。 AM / FM开关10设定操作模式。 AM模式检测器块1根据开关产生逻辑信号。如果使用AM兼容模式，则放大器作为AB类放大器工作。 AM逻辑信号被施加到两个传输门4，使得AB类放大器直接连接到MOSFET的栅极。同时，反相的AM信号使两个栅极驱动器三态。感测两个电阻Rel和Re2上的电压降可提供电流限制保护。当不兼容AM兼容模式时，放大器作为D类放大器工作。两个传输门打开，将AB类从门上断开。反相的AM信号使两个门驱动器。

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