脉宽调制器电路图及应用介绍(PWM circuit)
A pulse width modulator (PWM) is a device that may be used as an efficient light dimmer or DC motor speed controller.
The circuit described here is for a general purpose device that can control DC devices which draw up to a few amps of
current. The circuit may be used in either 12 or 24 Volt systems with only a few minor wiring changes.
This device has been used to control the brightness of an automotive tail lamp and as a motor speed control for small DC
fans of the type used in computer power supplies.
PWM控制器可以用于灯光亮度调节及直流电机的速度控制。本电路可以为通用设备提供几安培的驱动能力。电路稍作调整后可以方便的用于12或24V供电。这个装置可以控制汽车尾灯的亮度，及电脑电源直流风扇速度控制器。 
Parts 零件清单
U1: LM324N quad op-amp
U2: 78L12 12 volt regulator
Q1: IRF521 N channel MOSFET
D1: 1N4004 silicon diode
LED1 Red LED
C1: 0.01uF ceramic disc capacitor, 25V
C2-C5: 0.1uF ceramic disk capacitor, 50V
R1-R4: 100K 1/4W resistor
R5: 47K 1/4W resistor
R6-R7: 3.3K 1/4W resistor
R8: 2.7K 1/4W resistor
R9: 470 ohm 1/4W resistor
VR1: 10K linear potentiometer
F1: 3 Amp, 28V DC fast blow fuse
S1: toggle switch, 5 Amps