Toshiba Review_In-depth understanding of photo relay TLP3547

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Toshiba Review_In-depth understanding of photo relay TLP3547 [Copy link]

  What is a photorelay? A photorelay is an electrically operated switch, which can be roughly divided into contact (mechanical) and non-contact (semiconductor) types. A photorelay is a semiconductor relay made of a MOSFET light-coupled LED, mainly used as a substitute for signal relays. Photorelays do not contain moving contacts, so they have longer-term reliability than mechanical relays.

• Using MOSFET as output device
• Mainly used to replace signal relays
• Can handle AC and DC loads
• Products with ION>1A are called large-capacity (current) photorelays

From the circuit structure diagram of the device, it can be seen that the photorelay does not contain contacts, but is composed of two back-to-back MOSFETs.

From this aspect, photorelays can improve the problems of mechanical relays such as contact gap sparks, contact sticking, and contact rebound.

How does the performance of photorelays compare with mechanical relays? Electrical Conditions

• Mechanical relays generally have low on-resistance, while photorelays have a range of products from high to low RON. Some high-capacitance photorelays have lower RON than mechanical relays.
• Unlike mechanical relays, leakage current will occur in photorelays when voltage is applied to the output side. For applications involving leakage, consider Toshiba's low leakage (pA series) products.

Switching Characteristics

• Mechanical relays generally require several milliseconds to switch the signal relay, and the contact bounce time needs to be considered. Toshiba's photorelay switching time is typically less than 1ms, and the high-speed photorelay switching time is typically as low as 0.01ms. No bounce time!

Parameter characteristics of TLP3547: [attach]382416 [/attach] 1>It should be noted that the reverse voltage VR of the LED is only 5V,

This shows that when the control signal of the LED may have a negative voltage, it must be ensured that the amplitude does not exceed VR. In order to protect the LED, there is a 1.5KΩ LED current limiting resistor on the back of the test board.

2>The Detector part of the table shows the current switching capability of the photorelay. It should be noted that the parameters in the table have three connection conditions A/B/C, and the corresponding currents are different.

And the current carrying capacity is negatively correlated with the device temperature. Derating is required when used in a high temperature environment. We connect this circuit through A for testing. The right picture mainly tests the delay time from the LED receiving power and turning on to the PIN5-PIN8 being turned on.

In order to be more intuitive, some test data are recorded in a table:

(Note: the delay time TON here refers to the time from the LED receiving power to the drain-source conduction)

The following are photos of the actual test: Wiring method When testing the on-resistance, the measurement range of the multimeter is limited, so there will be a large error, but it also shows that the internal resistance of TLP3547 is very small (50mΩ is written in the manual) The following is the test of the control end power supply and current consumption. Of course, the current consumption of TLP3547 is different at different supply voltages. Some of the content is referenced from the article of netizen qq335702318. Thank you very much!