Application Note: Transient Voltage Suppressors (TVS Diode) Applications Overview Transient Threats - What are Transients? 100% 90% Current (I) % Voltage Transients are defined as short duration surges of electrical energy and are the result of the sudden release of energy previously stored or induced by other means, such as heavy inductive loads or lightning. In electrical or electronic circuits, this energy can be released in a predictable manner via controlled switching actions, or randomly induced into a circuit from external sources. VOLTAGE CURRENT 25kV 20kA 10 µs 1ms 30n 60n tr = 0.7 to 1.0ns Switching 500ms Figure 2: ESD Test Waveform The exponential rise time of lightning is in the range 1.2µsec to 10µsec (essentially 10% to 90%) and the duration is in the range of 50µsec to 1000µsec (50% of peak values). ESD on the other hand, is a much shorter duration event. The rise time has been characterized at less than 1.0ns. The overall duration is approximately 100ns. Why are Transients of Increasing Concern? Component miniaturization has resulted in increased sensitivity to electrical stresses. Microprocessors for example, have structures and conductive paths which are unable to handle high currents from ESD transients. Such components operate at very low voltages, so voltage disturbances must be controlled to prevent device interruption and latent or catastrophic failures. RISE-TIME DURATION 600V 500A 50µs EMP 1kV 10A 20ns 1ms ESD 15kV 30A <1ns 100ns Table 1: Examples of transient sources and magnitude Sensitive microprocessors are prevelant today in a wide range of devices. Everything from home appliances, such as dishwashers, to industrial controls and even toys use microprocessors to improve functionality and efficiency. Characteristics of Transient Voltage Spikes Transient voltage spikes generally exhibit a “double exponential” wave, as shown below for lightning and ESD. Most vehicles now also employ multiple electronic systems to control the engine, climate, braking and, in some cases, steering, traction and safety systems. lpp lpp/2 t1 Many of the sub- or supporting components (such as electric motors or accessories) within appliances and automobiles present transient threats to the entire system. t t2 Careful circuit design should not only factor environmental scenarios but also the potential effects of these related components. Table 2 below shows the vulnerability of various component technologies. Figure 1: Lightning Transient Waveform Littelfuse.com I60 10% Repeatable transients are frequently caused by the operation of motors, generators, or the switching of reactive circuit components. Random transients, on the other hand, are often caused by Lightning and Electrostatic Discharge (ESD). Lightning and ESD generally occur unpredictably, and may require elaborate monitoring to be accurately measured, especially if induced at the circuit board level. Numerous electronics standards groups have analyzed transient voltage occurrences using accepted monitoring or testing methods. The key characteristics of several transients are shown in the table below. Lighting I30 1 © 2015 Littelfuse, Inc. Outdoor LED Lighting Vulnerability (volts) VMOS 30-1800 MOSFET 100-200 GaAsFET 100-300 EPROM 100 JFET 140-7000 CMOS 250-3000 Schottky Diodes 300-2500 Bipolar Transistors 380-7000 SCR 680-1000 In a cloud-to-ground strike (as shown at right) the transientgenerating effect is far greater. This diagram shows a typical current waveform for induced lightning disturbances. 100 90 50 10 O1 TIME t t1 t2 Inductive Load Switchinge The switching of inductive loads generates high energy transients which increase in magnitude with increasingly heavy loads. When the inductive load is switched off, the collapsing magnetic field is converted into electrical energy which takes the form of a double exponential transient. Depending on the source, these transients can be as large as hundreds of volts and hundreds of Amps, with duration times of 400 milliseconds. TVS Diode Transient Voltage Scenarios Electrostatic Discharge (ESD)e Electrostatic discharge is characterized by very fast rise times and very high peak voltages and currents. This energy is the result of an imbalance of positive and negative charges between objects. Typical sources of inductive transients include: ESD that is generated by everyday activities can far surpass the vulnerability threshold of standard semiconductor technologies. Following are a few examples: • Generator• Motor • Relay• Transformer • Walking across a carpet: 35kV @ RH = 20%;1.5kV @ RH = 65% These examples are common in electrical and electronic systems. Because the sizes of the loads vary according to the application, the wave shape, duration, peak current and peak voltage are all variables which exist in real world transients. Once these variables can be approximated, a suitable suppressor technology can be selected. • Walking across a vinyl floor: 12kV @ RH = 20%;250V @ RH = 65% • Worker at a bench: 6kV @ RH = 20%;100V @ RH = 65% • Vinyl envelopes: 7kV @ RH = 20%;600V @ RH = 65% The diagram at right shows a transient which is the result of stored energy within the alternator of an automobile charging system. • Poly bag picked up from desk: 20kV @ RH = 20%;1.2kV @ RH = 65% Lightning Induced Transientse Even though a direct strike is clearly destructive, transients induced by lightning are not the result of a direct strike. T V T1 90% VS 10% VB V = 25V to 125V t T1 = 5ms to 10ms S A similar transient can VB = 14V R = 0.5Ω to 4Ω T= 40ms to 400ms also be caused by other DC motors in a vehicle. For example, DC motors power amenities such as power locks, seats and windows. These various applications of a DC motor can produce transients that are just as harmful to the sensitive electronic components as transients created in the external environment. When a lightning strike occurs, the event creates a magnetic field which can induce transients of large magnitude in nearby electrical cables. A cloud-to-cloud strike will effect not only overhead cables, but also buried cables. Even a strike 1 mile distant (1.6km) can generate 70 volts in electrical cables. Littelfuse.com PERCENT OF PEAK VALUE Device Type Application Note: Transient Voltage Suppressors (TVS Diode) Applications Overview 2 © 2015 Littelfuse, Inc. Outdoor LED Lighting Application Note: Transient Voltage Suppressors (TVS Diode) Applications Overview TVS Diode Device Typical Applications DC Supply Protection DC Load Protection DC Supply Protection DC Supply Protection Circuit Circuit DC Supply Protection Breaker DC Load Protection Breaker + Options + DC input AC input + DC Load Protection DC Load Protection DC Supply Protection DC Load Protection R R Options Circuit Breaker R Options DC input Rectifier Network DC input TVS TVS TVS To Load TVS TVS TVS DC output DC output LoadTVS TVS Load Load Load - DC motor DC motor - DC motor DC motor Operational Amplifier Operational Amplifier Operational Amplifier Operational Amplifier Protection +I C + TVS DC Input TVS - R- To Load Load + DC output DC output TVS DC Input - TVS To Load A.C. Supply Protection A.C. Supply Protection Elector-Magnetic Interference Limiting EMI Limiting A.C. Supply Protection EMI Limiting EMI Limiting + Supply A.C. Protection +EMI Limiting DC Input R To Load TVS Rectifier Network TVS AC input DC input Load TVS + AC input Load AC Supply Protection DC Input + AC input Load Circuit Breaker Options Rectifier TVS Rectifier Network Network TVS RL +I I +TVS C RL - OR RL Operational Amplifier + - OR - + + - OR - C (A) TVS (A)TVS (B) RL - OR - C TVS TVS TVS (B) (A) (B) I + TVS (A) (B) Combined MOV Varistor and TVS Diode Protection Scenarios MOV + TVS Combination: MOV + Choke + TVS Combination: 24VDC Choke Inductor MOV TVS MOV GND MOV Varistor High Energy Withstand Littelfuse.com TVS Diode Low Clamping Voltage Capacitor Choke MOV Varistor V33ZA70PX Special low voltage 20mm diameter MOV [email protected]/20µs (1 time) 3 TVS TVS Diode SMBJ28A/SMBJ30A SMCJ28A/SMCJ30A © 2015 Littelfuse, Inc. AC Outdoor LED Lighting Application Note: Transient Voltage Suppressors (TVS Diode) Applications Overview Telecom DC/DC Protection Circuit Telecom DC/DC Protection 48VDC AC 220V AC/DC Nano Fuse 461 Series Power Fuse 30A - 50A LVSP Fuse TVS Diode SMCJ or AK3 Series DC/DC AK6 TVS Diode For 48vdc Lightning Protection: TVS Diode: AK6-66CL Lightning Fuse: LVSP15-R Power fuse: TLS035L/456020 For 5vdc Lightning Protection: Fuse: 461 Series TVS:AK3-7.5CL, 5.0SMDJ Circuit Protection of 24VDC with high surge capability Circuit Protection of 24VDC with High Surge Capatbility Outside World Primary Protection: AK10-030 TVS Diode SMDJ28A TVS for PWM (Pulse Width Modulate TVS Diode driver protection Fuse 0451001 Cx Cx 400VDC Fuse Secondary TVS 0451001 CM Choke Cy NM Choke PWM Shield Ground TVS for PWM (Pulse Width Modulated) Power Over EthernetEthernet (PoE) ProtectionPoE protection Power Over driver protection Pulse Width Modulated (PWM) Driver Protection 400VDC TVS +Vin Secondary -Vin TVS Diode SMBJ58A PWM Driver and Feedback Control Vout Ethernet and PD controller PWM Littelfuse.com PSE Power Sourcing Equipment 4 © 2015 Littelfuse, Inc. Outdoor LED Lighting Application Note: Transient Voltage Suppressors (TVS Diode) Applications Overview LED Driver LED Driver Protection BR1 MB6S 600 V L L1 1.2 mH L2 1.2 mH CONTROL R3 3.3 kΩ D1 DFL5160-7 D C5 1 μF 16 V FP C4 1 μF 16 V R3 2.2 Ω 1% R4 3.3 kΩ S C3 C1 100 nF 33 nF 500 V 630 V L3 3 EE10 330 μH 1 C2 68 nF 250 V VR2 SMAJ350A RTN D2 DFLS1200-7 R5 85 - 135 RV1 VAC 140 VAC N R1 3.3 kΩ LinkSwitch-PL BP U1 LNK458KG C6 10 nF 50 V F1 5A C7 22 μF 50 V VR1 1N4756A 47 V 35 V, 130 mA RS485 Interface protection PI-6539-051411 RS485 Interface Protection TVS FUSE 3 2 1 VDD5V CHOKE 0461.600 8 GDT SL1421A090 7 6 5 FUSE 0461.600 VCC RO B RE A DE GND DI 1 RXD 2 SEN 3 4 TXD TVS SMBJ6.0CA RS232 interface protection with high surge requiremen VDD5V RS232 Interface Protection with High Surge Requirement FUSE RS232 TX 04611.25ER GDT SL1411A075SM TVS SMDJ15CA TVS SMDJ15CA GDT SL1411A075SM TVS SMDJ15CA PGND PGND GDT SL1411A075SM TVS SMDJ15CA 1 6 2 7 3 8 4 9 5 FUSE RS232RX 04611.25ER GDT SL1411A075SM TVS SMDJ15CA RS232GND GDT SL1411A075SM FUSE 04611.25ER TVS SMDJ15CA Littelfuse.com 5 GDT SL1411A075SM © 2015 Littelfuse, Inc. Outdoor LED Lighting Application Note: Transient Voltage Suppressors (TVS Diode) Applications Overview Inverter / VFD protection in IGBT Module Inverter / VFD protection inProtection IGBT Module TVS Diode AK3-430 L1 L2 L3 IGBT Gate Protection IGBT Gate Motor protection IGBT Rg TVS Diode SMBJ16CA Rge Littelfuse.com 6 © 2015 Littelfuse, Inc.