Toshiba Photorelay Evaluation - AC Characteristics Test

tianshuihu

Toshiba Photorelay Evaluation - AC Characteristics Test [Copy link]

  We have previously evaluated the DC load characteristics of the photorelay TLP3547F. Today, let's take a look at its characteristics under AC load The test conditions are similar to the previous DC characteristic test (see the link below) Toshiba Photorelay Evaluation - DC Characteristics Test There are two main changes:

• The load power supply is changed from a DC power supply (power bank) to an AC signal source (50Ω output impedance)
• The load is changed to a 51Ω 3W power resistor

The updated schematic diagram is shown in the figure below Let's take a look at the waveform when the AC signal source frequency is 10Hz and the peak-to-peak value is 5V ch2: Optocoupler input drive signal (1Hz / 3.2V) ch1: AC signal source output signal ch4: Waveform between the two output pins of the photorelay It can be seen from the figure: When the optocoupler input is low level, the waveform at the output end of the photorelay is basically the same as the waveform of the AC signal source When the optocoupler input is high level, the photorelay is turned on quickly and the output waveform is almost "0"; the amplitude of the AC signal source output waveform becomes half of the original Next, let's look at the details. First, let's look at the situation when the photorelay TLP3547F is turned on. 378157 When I first saw this waveform, there were two "strange" things! First, after it was turned on, the amplitude at both ends of the load became half of the signal source - this is easy to understand, the series voltage divider. Second, after it was turned on, there was no "crossover distortion". But on second thought, there really shouldn't be any crossover distortion - MOS tubes are metal oxide semiconductor field effect transistors. Once the gate capacitance is fully charged (the internal potential reaches a certain threshold), the D and S poles of the MOS tube are equivalent to being turned on. At this time, no matter whether the current flows from the D pole to the S pole or vice versa, there is essentially no difference. It can be equivalent to a resistor with a very small resistance (i.e., the on-state internal resistance), so there will naturally be no crossover distortion. Just change the frequency of the AC signal source and see what happens 100Hz 1kHz 10kHz 100kHz It can be seen that signals from 10Hz to 100kHz can pass normally; the conduction time of the photorelay has no direct relationship with the frequency of the load signal source Under this test condition, the conduction time is about 4ms Next, let's take a look atthe situation when the photorelay TLP3547F is turned off 10Hz 100Hz 1kHz 10kHz 100kHz From the above pictures, we can see that the photorelayTLP3547F turns off much faster than it turns on, and the turn-off time is about 0.1ms (under this test condition). Conclusion: The performance of the photorelayTLP3547F in AC applications is similar to that in DC applications; In addition, the time required for the photorelayTLP3547F to turn on is significantly longer than its turn-off time, so it is necessary to pay attention to this in actual applications. So far, the evaluation of Toshiba photorelay[/size=4]TLP3547F is complete!