Application Note AN-3003
Applications of Random Phase Crossing Triac Drivers
The MOC30XX family of random phase (non-zero crossing) triac drivers consist of an aluminum gallium arsenide infrared LED, optically coupled to a silicon detector chip. These two chips are assembled in a 6 pin DIP package, providing 7.5KVAC(PEAK) of insulation between the LED andthe output detector. These output detector chips are designed to drive triacs controlling loads on 115 and 220V AC power lines. The detector chip is a complex device which functions in the same manner as a small triac, generating the signals necessary to drive the gate of a larger triac such as Fairchild’s FKPF12N80. The MOC30XX triacs are capable of controlling larger power triacs with a minimumnumber of additional components. Table 1 lists the members of the MOC30XX random phase triac driver family. The family is divided by blocking voltage, VDM, and input LED trigger sensitivity, IFT. MOC3010/1/2 are rated at 250V, the MOC3020/1/2/3 are 400VAC, and the MOC3051/2 have a VDM of 600V. across the device. Once triggered into the on (conducting) state, the detector will remain there, even ifno current ﬂows through the LED, until the terminal current drops below the holding current (typically 100 µA) at which time the detector reverts to the off (non-conducting) state. The detector may be triggered into the on state by exceeding the forward blocking voltage, by voltage ramps across the detector at rates exceeding the static dv/dt rating, or by photons from the LED. The LED isguaranteed by the speciﬁcations to trigger the detector into the on state when the current passing through the LED is equal to, or greater than the IFT(max) speciﬁcation. For example the MOC3011M requires at least 10mA of LED current to guarantee turn-on. A similar device, the MOC3012M, has exactly the same characteristics except it requires only 5 mA to trigger. Since these devices look essentially likea small optically triggered triac, we have chosen to represent it as shown in Figure 1.
Basic Electrical Description
The AlGaAs LED has a nominal 1.3 V forward drop at 10 mA and a reverse breakdown voltage greater than 3 V. The maximum current to be passed through the LED is 60 mA. The detector has a minimum blocking voltage of 250 Vdc in either direction in the off state. In the on state,the detector will pass 100 mA in either direction with less than 3 V drop
Figure 1. Schematic Representation of an Optically Coupled Random Phase Triact Driver
Random Pase Triac Optocouplers Part Number MOC3010M
ANODE 1 6 MAIN TERM 5 *
IFT (ma) max 15 10 5 30 15 10 5 15 10
VTM (V) max 3 3 3 3 3 3 3 2.5 2.5
VDM (V) min 250 250 250 400 400 400 400 600 600
IH (µA) 100 100 100 100 100100 100 280 280
IDRM (nA) VISO max AC[PEAK] 100 100 100 100 100 100 100 100 100 7.5kV 7.5kV 7.5kV 7.5kV 7.5kV 7.5kV 7.5kV 7.5kV 7.5kV
MOC3011M MOC3012M MOC3020M MOC3021M MOC3022M MOC3023M MOC3051M MOC3052M
NC 3 *Do not connect
4 MAIN TERM
REV. 4.07 10/6/06
RLOAD VCC 10 mA 1 2 6 150 115 Vac R1 MOC3011M 4 VINWhen driving resistive loads, the circuit of Figure 2 may be used. Incandescent lamps and resistive heating elements are the two main classes of resistive loads for which 115 Vac is utilized. The main restriction is that the triac must be properly chosen to sustain the proper inrush loads. Incandescent lamps can sometimes draw a peak current known as “ﬂashover” which can be extremely high, andthe triac should be protected by a fuse or rated high enough to sustain this current.
Figure 2. Simple Triac Gating Circuit
Line Transients-Static dv/dt
Occasionally transient voltage disturbances on the ac line will exceed the static dv/dt rating of the MOC3011M. In this case, it is possible the MOC3011M and the associated triac will be triggered on. This is usually not a problem, except...
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