| 摘要 |
An electronic speed controller for a radio controlled model has conversion circuitry to derive a dc signal having a level that is proportional to the information pulse width of the radio control signal, but which is insensitive to changes in the frame rate thereof. This dc signal level is compared with a reference triangular wave to obtain a digital control signal having a duty cycle proportional to the information pulse width. This signal is used to gate battery voltage to the motor, thereby to control its speed. In one embodiment, the battery voltage is supplied to the motor via a power transistor. A switching regulator connected between the motor battery and the base of the power transistor provides sufficient base current to drive that transistor into saturation regardless of the motor battery voltage, and with the base current responsive to the Vbe of that transistor. The regulator is gated on by the digital control signal. In another embodiment, battery voltage is supplied to the motor via a power transistor bridge. One or the other pair of bridge transistors is turned on by the digital control signal, which in this embodiment is a three-level signal having a polarity dependent on whether the information pulse width is above or below a certain mid-range value. The gating circuitry provides constant base drive current to the pair of bridge transistors that is turned on.
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