电子调光电路-----Electronic dimming circuit
电子调光电路
电子调光电路可以用来调节灯泡的亮度，以适应不同的照明要求。下图是电子调光电路。
这个电路是由可控整流电路和触发电路组成的可控硅调压电路。市电220v经二极管VD1～VD4组成的桥式整流后，加在可控硅VS的A、G两端的电压是一个正弦脉动电压。这个电压再由限流电阻R1降压后供给触发电路作为直流电源和同步电压。单结晶体管VT、电阻R4、电位器RP和电容c组成了张弛振荡器，在每半个周期内，当电容c上的充电电压达到单结晶体管的峰点电压时，单结晶体管由截止到导通，电容C就通过R2放电。这样在R2上输出一个脉冲，送到可控硅控制极G，触发可控硅导通，于是有电流流过电灯泡HL。可控硅导通后，在AG间的正向压降很小(约1V)，所以触发电路停止工作。电源电压过零点时，可控硅关断，待到下一个半周期开始，电容C又重新充电，重复上述过程。
调节电位器RP可以改变在每半个周期内可控硅导通时间的长短，从而控制供给灯泡HL的功率，也即调节灯泡的亮度,当电位器RP阻值调大时，电容C所需充电时间比较长才能使可控硅VS导通，可控硅的导通角就比较小，灯泡就暗；反之，当电位器RP阻值调小时，灯泡就亮。正常的情况下，调节电位器RP能使灯泡两端的电压在0～200V范围内变化，从而有效地控制了灯泡的亮度。
google translate:
Electronic dimming circuit can be used to adjust the brightness to suit different lighting requirements. The figure is the electronic dimming circuits.
This circuit is controlled rectifier circuit and the SCR trigger circuit voltage regulator circuit. 220v mains diode VD1 ~ VD4 formed by the bridge rectifier, the increase in SCR VS the A, G is a sinusoidal voltage across the pulse voltage. The voltage current-limiting resistor R1 by the following step-down DC power supply and trigger circuit as a synchronous voltage. Single-junction transistor VT, resistors R4, potentiometer and capacitor c RP relaxation oscillator formed in each half cycle, when the capacitor voltage charge c on the peak of single-junction transistor voltage, single-junction transistors by the deadline to conduction, capacitor C will discharge through R2. So that R2, on the output of a pulse sent to the SCR control very G, triggering SCR conduction, so a current flows through the bulb HL. SCR conduction, the forward voltage drop between the AG is small (about 1V), it triggers the circuit to stop working. Supply voltage zero-crossing point, the SCR off, until the time of starting the next half cycle, capacitor C charging again, repeat the process.
Adjustment potentiometer RP can be changed in each half period the length of SCR conduction to control the power supply lamp HL, ie, the brightness adjustment, when the potentiometer RP large transfer resistance, capacitance C required longer charging time can the VS SCR conduction, the conduction angle of SCR relatively small, light bulbs on the dark; the other hand, when the potentiometer resistance RP adjust the hour, the light bulb. Under normal circumstances, adjust potentiometer RP makes the voltage across the lamp in the range of 0 ~ 200V change, which effectively control the bulb's brightness.
This circuit is controlled rectifier circuit and the SCR trigger circuit voltage regulator circuit. 220v mains diode VD1 ~ VD4 formed by the bridge rectifier, the increase in SCR VS the A, G is a sinusoidal voltage across the pulse voltage. The voltage current-limiting resistor R1 by the following step-down DC power supply and trigger circuit as a synchronous voltage. Single-junction transistor VT, resistors R4, potentiometer and capacitor c RP relaxation oscillator formed in each half cycle, when the capacitor voltage charge c on the peak of single-junction transistor voltage, single-junction transistors by the deadline to conduction, capacitor C will discharge through R2. So that R2, on the output of a pulse sent to the SCR control very G, triggering SCR conduction, so a current flows through the bulb HL. SCR conduction, the forward voltage drop between the AG is small (about 1V), it triggers the circuit to stop working. Supply voltage zero-crossing point, the SCR off, until the time of starting the next half cycle, capacitor C charging again, repeat the process.
Adjustment potentiometer RP can be changed in each half period the length of SCR conduction to control the power supply lamp HL, ie, the brightness adjustment, when the potentiometer RP large transfer resistance, capacitance C required longer charging time can the VS SCR conduction, the conduction angle of SCR relatively small, light bulbs on the dark; the other hand, when the potentiometer resistance RP adjust the hour, the light bulb. Under normal circumstances, adjust potentiometer RP makes the voltage across the lamp in the range of 0 ~ 200V change, which effectively control the bulb's brightness.
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