[introduction] this applied note introduced how to realize SPST of type of acceptance of a blame, segregation (short-hilted broadsword / sheet casts) bipolar mains switch, this switch can be used at generation to be as high as the twinkling of 200A and 75V to change. This switch can be used at checking power source and power source IC. This switch is designed to test fast circuit only, can guide in the implementation inside tens of accept seconds connect and pass time.

This applied note introduced how to realize SPST of type of acceptance of a blame, segregation (short-hilted broadsword / sheet casts) bipolar mains switch, this switch can be used at generation to be as high as the twinkling of 200A and 75V to change. This switch can be used at checking power source and power source IC. This switch is designed to test fast circuit only, can guide in the implementation inside tens of accept seconds connect and pass time.

Introduce

Testing circuit of common power source, especially when power source IC, a common problem is the switch of the big electricity that need can arise twinkling to change and processing needs and voltage pulse. This kind of switch must can receive all sorts of circuit develop to attack repeatedly, specific depend on the type of the power source that be measured and its application.

Below certain circumstance, can use commerce to check laden; otherwise, be necessary to develop a kind of unique test setting. If a side of switch receives power source repeatedly common power source, and power source also is a system fitly common power source, install a design very simple. If do not have, need a design to define switch driver oneself, this may be very complex. An enough and general switch can carry out breakdown of transient state of most power source the test will be very useful. The norms overview of this kind of switch should include the biggest voltage and voltaic rating, and the great majority on the market is at present intermediate the test demand of power source.

Switch should have the voltaic capacity that exceeds 100A, can bear at least the open circuit voltage of 75V. It must be bipolar, flow with Yuzai and maintain voltage, because a few tests can produce ringing electricity, and circuit of a few power source can arise bipolar output. Guide connect and close speed to should be inside second of a few accept, so that observe the response of fast circuit. The series connection resistor of switch must low. Series connection inductance also must very low, this means physical measure small and voltaic way is shorter. Finally but it is important least of all to be not is, switch must electric segregation, and have low-down output allow to terrestrial electricity — if want,insert switch circuit and not screwy its function or answer, this is a major attribute.

Circuit explains

Graph the 1 switch that showed the most item in satisfying afore-mentioned wish list. It uses side to be less than the implementation of digital isolator coupler of 1pF to side capacitance. Its total transmission defer is 80ns, output rise time is 40ns about. Twinkling of the 75V that outputs class to comprise De Sen MOSFET to be able to handle either polarity by two low R, 200A changes.

Switch component (two output MOSFET is used turn over series connection to join) have inductance of resistor of 7m Ω series connection and 25nH series connection. Below ON condition, it is appropriative two polarity electric current (include 0 hand in more) linear resistor, won’t introduce harmonic accordingly lack fidelity, appropriative metal contact.

Graph 1. This circuit makes can 5V logistic signal will control a blame special (segregation) mains switch (Q1 – Q2) , this switch can handle 75A pulse when 200V.

Laden to absorbing the low resistance that is more than 50A electric current, switch rise time (the definition is ON transient state) basically decide by series connection inductance. To limits of inferior electric current, rise time under 40ns, decay time (involve transient state) basically concern with laden impedance.

Circuit is kept apart (switch) the power source of side is galvanic cell of a group of 3V lithium coin of 3 series connection (battery of lithium of CR2025 manganese dioxide) . To the switch rate of thousands of hertz, type of this kind of cell is nominal practicable 170mAh should support use a many month continuously. To normal testboard application, if maintain permanent link, battery life should be controlled in 3 months.

The input comes for 0V 5V number signal, its ask exclusively is to rise to be less than 20ns with decay time, width of the smallest pulse (ON or OFF) for 50ns. When guiding electrify shedding is less than 18A, switch can hold ON or OFF position till the cows come home.

In the graph 1 in, IC1 and IC2 form detector of a brim, the basis inputs the symbol of edge, bring to bear on to side of T1 simple either narrow pulse. Across is very low still. Accordingly, t1 pulse polarity depends on bring to bear on the inputs signal edge polarity of circuit. The sub join of T1 is in inphase and logistic bumper (input output) on, this bumper by driver of MOSFET of power of double passageway low margin (IC3) half composition. This bumper expression is bistable circuit (trigger) , this circuit answers T1 primary end pulse and setting, answer negative pulse restoration. Next, bistable circuit output is circuit input (bring to bear on to input signal to the number of brim detector) carbon.

Two driver of the other in part of IC3 and IC4 are shunt-wound join. Their input is received repeatedly bistable output, their output paralell connection joins, the effect of field of power of grid De Sen of two low R manages drive (IRFB3077) . Two MOSFET join with opposing series connection kind, leakage pole joins exterior switch power source joins, two grid join together, two power source join together. The paralell connection of 3 driver raised the switch rate of power MOSFET, because the each part of IC2-IC3 can provide the electricity of peak value grid of 4A, 3 person come 12A. MOSFET source extremely the negative pole that receives batteries repeatedly.

The input of MAX5048 allows to realize brim detector easily logically, MAX5054 S (use as power transistor driver) power comsumption of inferior static state prolonged battery life. Accordingly, in low end (control and segregation, IC1 and IC2) with high end (power source driver, IC3 and IC4) include likeness but different IC driver.

Graph the 2 equivalent circuit that showed mains switch, include main parasitism component. Like circuit of all power source, the capability of permanent power processing of switch depends on offerred radiator. But, because include radiator to be able to increase parasitism to output capacitance greatly, because this should be designed,do not include radiator. Regard processing as the compensation when 200A pulse, pulse width must be restricted for 8ms, switch occupies sky comparing to must be restricted for the biggest 0.5% . Change to 80A twinkling, pulse does not suffer enclose limitation, because this can last longer (be as long as 50ms) , but 80A transient occupies sky comparing to should not exceed 3% .

Graph 2. This is circuit of a mains switch, with the graph 1 circuit comparatives, but include main parasitism element.

Below room temperature switch does not have clamp when inductance, graph 1 circuit repeats the energy in pulse to absorb ability to be 280mJ in individual blame, or in the biggest occupy sky comparing to fall for the circumstance of 200% for 1mJ/ pulse.

Coupling transformer design uses at the capacitance between the smallest size and winding: Primary coil circles, sub two v/LIT all over the ground, twine in ferrite of Fair-Rite 2643000801 7.5mm X 7.5mm on magnetism bead. Transformer structure still installs switch load and switch control circuit between the biggest allow voltage difference. Open electromagnetism line when use general when insulation system, it can bear easily 1kV, if electrical wiring is used,upright fluorine dragon or similar high quality, high especially electric tigidity insulating material is isolated from, can bear exceed 1kV. To taller voltage segregation, still should examine all and other side that encloses a design.

The; that the ferrite magnetism core of T1 must be considered as electric conduction because this, must not allow it to contact the two side of switching equipment at the same time. This switch does not have interlocking protection, before because this is in,be being used must the state of battery of lithium of test and verify. Did not include circuit in order to assure the condition of the switch when electrify (ON or OFF) . Accordingly, before any other power source that opening a setting, must open the power source of switching equipment. Because switch condition enforces by the first changeover that brings to bear on to be carried in the input, because this is before the others electrify to the setting, switch should be opened circularly at least and shut.

Test result

In the graph 3 – 5 in, coping weaveform is digital input, bottom weaveform is the pulse of 25 μ S that observes on load of sex of 5 Ω block, receive 50V power source through opening conjunction. Because weaveform is the tension that produces on resistor of short film of extremely low inductance, accordingly they are close to weaveform of switch electric current very much. Graph the appearance of approximate 3A pulse of 200 rushs too in its and rise time (60ns comes 80ns) the respect gets the influence of inductance of the parasitism in method of tall electric current and capacitance. Graph the 4 rise time that showed this pulse and guide a graph of transmission defer; 5 showed decay time is mixed involve transmission delay. Graph 6 – the 8 identical weaveform that showed 5 Ω load and 10A pulse, use job of same 50V power source. The 30ns that the rise time that arises from this is close to MOSFET more comes rise time of 40ns inherent switch, suffer enclose and the limitation of source pole inductance.

Graph 3. From the graph 1 in, answer control signal (5) pulse of 2 μ S (1) appear on the load that establishs ties by 0.25 Ω resistor and 50V power source.

Graph 4. The rise time that the graph shows 3 times and guide a transmission defer, with 40ns/cm scanning rate is examined.

Graph 5. The decay time that the graph shows 3 times and involve transmission delay, scanning rate is 40ns/cm.

Graph 6. From the graph 1 in, answer control signal (5) pulse of 2 μ S (1) appear on the load that establishs ties by 5 Ω resistor and 50V power source.

Graph 7. The rise time that the graph shows 6 times and guide a transmission defer, with 40ns/cm scanning rate is examined.

Graph 8. The decay time that the graph shows 6 times and involve transmission delay, scanning rate is 40ns/cm.

Summary

This applied notes says palpability simplifies the SPST that power source checks is bipolar the design of mains switch. This switch can bear the big electricity that during switch twinkling changes, produces and voltage pulse, can use at checking the great majority on the market intermediate power source. It can handle the 75V of two kinds of polarity, 200A twinkling changes; it came true inside tens of accept seconds open and shut time; it has resistor of low series connection and; of inductance of low-down series connection it uses electric segregation, output is very low to ground capacitance.

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