RU2502169C1 - Device for protection of electronic instruments against high peak voltages in on-board network of transport vehicle - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention proposes a scheme using an electronic switch on the basis of a transistor that is in-series connected to a break of a positive power bus and operates in a Closed/Open mode depending on the transport vehicle (TV) mains voltage value and has short activation/deactivation time in comparison to pulse duration; therefore, it manages to cut out short high-voltage pulses with duration of at least less than 1 microsecond. At overvoltage values the instrument is powered from the capacitance, and when normal value (nominal for this transport vehicle) of voltage is reached, the switch is set back to Closed mode, and the protected electronic instrument starts its operation again from a transport vehicle power source.

EFFECT: improving reliability.

4 cl, 3 dwg

Description

The invention can be used in electrical engineering, in particular in devices for protecting electrical devices from high peak network voltages. The present invention relates to electrical engineering and, in particular, to devices for protecting electronic devices from high and peak voltage values in the vehicle's on-board network (hereinafter - TS).

In the on-board network of vehicles, for example, snowmobiles, motorcycles, scooters and other vehicles, due to the imperfection of the standard voltage regulator, the voltage amplitude values in the on-board network can regularly reach high values up to 200 V, so-called regular high overvoltages or (which is the same thing) voltage surges, which are visible on the voltage diagram of a real sample of the on-board snowmobile network shown in Figure 1. With the division price along the Y axis = 10 V, along the X axis the division price is 25 mc, for a pulse duration of 250 μs at engine speeds of 1500 s ^-1 emissions outside 60 V are visible. At high speeds, the amplitude is even larger (the solid horizontal line corresponds to zero the voltage value in the network is “0” V). These voltage surges, coming to the power input of a radio electronic device, can disable semiconductor devices and microcircuits or cause malfunctions of individual electronic devices installed on a vehicle, which for this reason need protection. On such separate electronic devices can be installed additional protecting devices.

State of the art

Known invention RU 2017254 (priority from 04.15.1992, IPC 5 H01H 85/30, H02H 3/08) "Controlled electrical fuse", which increase the reliability and selectivity of the fuse during short circuit in the protected AC circuit by shunting the fuse insert with a triac, the control electrode of which is connected to the increased potential of the rated voltage of the ferroresonant circuit connected in parallel to the protected load. The disadvantage of this device is that it has a fuse, which must be replaced after the protection is activated. And the electronics only compensates for the spread in the parameters of the fuse-links and “surely causes the fuse-link to burn out” when “short circuit is detected in the protected circuit”.

Another invention RU 2145759 (priority 12.02.1998, IPC 7 Н02Н 9/04, G01R 19/165) "Device for surge protection in a constant voltage power supply network" contains two voltage limiters connected in series and opposite each other and connected between conductors, through which the supply voltage to the electronic device. The device contains an LED circuit and a fused jumper, which forms a safety chain with the first voltage limiter, which allows providing an indication of the failure of the voltage limiter, which increases the reliability of electronic devices, indicates the presence or absence of mains voltage and signals a malfunction of the protection device. The disadvantage of this device is that the protection is built on the principle of absorption of pulse energy and an indication of the failure of the protection device. In the case of the passage of a powerful pulse, the energy of which is more than the limiters can absorb, the protection device will fail, the alarm will go off. If the protection device is not restored in time (it takes time), then the next impulse can damage the device. If the overvoltage pulses follow regularly, as in Figure 1 (alternating time 25 ms), then during such a time it is impossible to respond to this situation and prevent the failure of the device. Also, the disadvantage is that the absorption of powerful pulses leads to an increase in the linear dimensions of the voltage limiters and the need for heat dissipation during absorption.

A device is known according to US patent US 7075765 (issued July 11, 2006, application 2004/0174648 dated April 23, 2003, IPC 6 Н02Н 3/00 (20060101)), which proposes a circuit for limiting the current in the power circuit due to branching using thyristors in branches of the circuit, while the power is supplied by switching between the branches of the network depending on the current value, which is measured by the measuring device and supplied to the shunt device (thyristor), which has a high resistance at a normal current value, and whose resistance becomes low, when Yes, the current value exceeds the limit for this network. Because thyristors are connected in parallel with the power supply, heat is released to them when the protection is triggered, and additional heat removal is required, which leads to an increase in the size of this device, in addition to the fact that for reusable fuses, the recovery time takes from tenths to several seconds, and during this time the device is in the off state. If the pulses of high peak voltages follow regularly, as in Figure 1, then the fuse heats up, it opens the power circuit, and as a result, the device does not work.

Disclosure of the invention.

To overcome the aforementioned disadvantages of the known devices, the claimed technical solution is proposed, however, it is not possible to select any of the above-known known technical solutions as the closest analogue.

The purpose of the claimed technical solution is to create a miniature device that protects individual electronic devices from high peak voltage values of the vehicle electrical system, leading to the failure of these electronic devices. Additionally, the proposed device allows, in the absence of a battery in the vehicle network, to avoid the need to use fuses and reusable fuses, to avoid interruptions in the operation of devices associated with the need to replace fuses or the recovery time of reusable fuses.

To overcome these shortcomings in the claimed protection device to reduce heat generation, a circuit is used using an electronic switch based on a transistor, while the electronic switch is connected sequentially to the positive power supply line break and operates in the “closed” / “open” mode depending on the voltage value in the network TS. The electronic switch is based on a transistor, which has a short on / off time compared to the pulse duration, so it manages to cut off short high-voltage pulses of a duration (for example, less than 1 μs).

The principle of operation of the claimed device is based (see FIG. 2 with a block diagram of the claimed device) on measuring the input voltage U _BX and switching the electronic switch to “closed” / “open” modes depending on the measured value. As an electronic key, bipolar or field effect transistors can be used. The voltage of the on-board network is supplied to the rectifier, then to the divider R1, R2, which is connected in parallel with the power supply and serves to coordinate the input voltage U _BX with a controlled stabilizer. If the input voltage is lower than the cut-off voltage, the key is in the “closed” mode, the capacitor C2 is charged, and the load R _H (the protected device) is supplied from the on-board network. If the input voltage exceeds the maximum safe value of the voltage of the electronic device (let's call it the cut-off voltage), then the switch is in the “open” mode and the load R _{H is} supplied from the capacitor C2. Due to this, the electronic device (s) connected to the output of the claimed device remain operational in the presence of high peak voltages. If the voltage of the on-board network exceeds the cut-off voltage for a long time, the device will switch to protection mode (the key is in the “open” mode) and will be in this state for an arbitrarily long time until the voltage of the on-board network becomes normal (nominal) for this vehicle, after which the key returns to the “closed” mode and the protected electronic device starts working again from the vehicle’s power source.

Description of drawings

The problem to be solved and the essence of the claimed technical solution can be explained using the following drawings.

Figure 1. Voltage plot in a real vehicle electrical system sample.

Figure 2. Block diagram of a device for protecting electronic devices from high peak voltages in the vehicle's on-board network.

Fig 3. Schematic diagram of the device for protecting electronic devices from high peak voltages in the vehicle electrical system.

The implementation of the invention.

The possibility of implementing the claimed device can be explained using a circuit diagram of a device for protecting electronic devices from high peak voltages in the vehicle's on-board network, shown in FIG. 3, operating from various types of current sources (direct and alternating). Depending on the value of the input voltage U _BX from the IP power supply, the electronic key switches to “closed” / “open” modes to ensure the normal operation of the electronic device. As an electronic key VT3 can be used bipolar or field effect transistors (for example, type BC 857). The voltage of the on-board network is supplied to the divider R1, R2, which is connected in parallel with the power supply and serves to coordinate the input voltage U _BX with a controlled stabilizer. If the input voltage is lower than the cut-off voltage, the key is in the “closed” mode, the capacitor C2 is charged and the load R _H (of the protected electronic device) is supplied from the on-board network. If the input voltage exceeds the cut-off voltage, then the switch is in the "open" mode and the load R _{H is} supplied by capacitor C2. Thus, the electronic device (s) connected to the output of the claimed device remain operational in the presence of high peak voltages. If the voltage of the on-board network exceeds the cut-off voltage for a long time (more than 0.5 s), the device will go into protection mode (the key is in the “open” mode) and will remain in this state for an arbitrarily long time until the voltage of the on-board network becomes normal (nominal) for this vehicle. Capacitor C1 serves to suppress high-frequency noise in the power supply, and its capacitance is in the range of 2.2-10 nF at a voltage of 250 V.

The nominal value of the capacitance C2 is chosen so that its voltage value on the capacitance satisfies the inequality condition:

Where:

u _otc. (b) is the cutoff voltage;

U _min. (B) - the minimum voltage at which the device remains operational;

I _sweat (A) is the current consumption of the device;

τ (C) is the maximum duration time of peak power pulses.

Transistors are selected with a minimum collector-emitter voltage in saturation Ukenas. - collector-emitter saturation voltage for a bipolar transistor and with a minimum value of drain-source resistance Rds (on) - channel resistance for the field-effect transistor in the “on” mode, which is required to reduce heat generation on the electronic key.

Moreover, U _otc. - this is the value of the cut-off voltage equal to the input voltage, above which the electronic switch goes into the "open"mode; Umin - the minimum voltage value at which the connected device remains operational

Schematic diagram of a device for protecting electronic devices from high peak voltages in an on-board vehicle network operating from various types of current sources (direct and alternating) is shown in FIG. 3.

As a rectifier unit (1), a diode bridge can be used.

The divider (R1, R2) is connected in parallel with the power supply and is used to match the input voltage and the key management circuit. The values of the resistors R1, R2 are selected from the ratio:

As a controlled zener diode block (2), a TL431 with a control voltage of Vref = 2.5 V was used.

The choice of the values of the resistors R4, R5, R6 is determined by the characteristics of the transistor VT1, the cut-off voltage and the maximum current through the control zener diode. The nominal values of these resistors for use with VT1 can be, for example, the following, 1 kOhm, 30 kOhm and 1 kOhm, respectively. The value of R10 is determined by the recommendations of the manufacturer VT3 and does not significantly affect the operation of the device (the value can, for example, be of the order of 1 kOhm).

A polar or bipolar transistor is used as a key.

The device operates as follows. In accordance with the scheme in Fig. 3, the signal after the rectifier from the divider R1, R2 is fed to a controlled zener diode VD2 (TL 431), which provides a control signal to the transistor VT1, R5 is a current limiter of the zener diode, which has a maximum current of 100 mA, and R4 and R6 are resistors that provide the operating mode of the transistor VT1. As a transistor VT1, a bipolar transistor BC857 (pnp) can be used, which provides a bypass voltage to R7 and closes the power switch. IT is a stabilized current source, in our case IT with a current of 5 mA (any of the known ones can be used). When current flows through resistor R7, a voltage drop is created, which is necessary for the electronic key to fully open. The value of R8 can be, for example, 1 kOhm (according to the manufacturer’s recommendation, or it may be absent altogether or be of a different rating - this does not affect the performance).

When the voltage value of the on-board network U is less than the value of the cut-off voltage U _off. the electronic key is closed. At this time, the device is powered by the vehicle's on-board network and the C2 capacitor is charging. When the value of the mains voltage U is greater than the cut-off voltage U _off. the key opens. At this time, the device is powered by capacitance C2. As soon as the voltage value becomes less than U _OTC switch is closed and the process starts over again. T.O. at the cut-off voltage, the key switches from the “closed” / “open” mode and back, which protects the device from high peak voltages in the on-board network. The cutoff voltage value is selected from relation (3). U _p max - the maximum allowable operating voltage of the electronic device:

_Uotc ≤0.8 * Up max.

In our case, assuming that U max is 35-40 V, the cut-off voltage, respectively, will be 28-32 V.

Another condition for achieving the claimed technical result is the requirement for the values, Uke (collector-emitter) for bipolar and Usi (drain-source) for field-effect transistors, which should be greater than the maximum allowable pulse voltage of the vehicle electrical system. The circuit can be implemented on the basis of transistors of typical series, for example, the well-known series IRF 9640 (field) or BDX54C (bipolar), for which the value of Uси and Uкэ is greater than the maximum estimated value of the peak pulse voltage. Power supply of the load (protected device) due to this is carried out through the claimed device, which, being connected in front of it, allows to achieve the declared result - to protect the electronic device from overvoltages (high peak values) of the vehicle electrical system.

In addition to the independent implementation of the device according to the invention and connecting it in front of the protected electronic device, the device according to the invention can be made in one housing with the protected device (as part of the protected device), which will save the user from additional installation.

The possibility of implementing the claimed electronic device on the basis of the existing elemental base indicates compliance of the invention with the patentability requirement "industrial applicability".

Claims (4)

1. The device protects the electronic device from high peak voltage values of the on-board network, characterized in that it is connected in front of the protected electronic device and it includes a rectifier, capacitor C1, divider R1, R2 connected in parallel with the power source, electronic key unit with control unit with an electronic key, capacitance C2, while the electronic key block is connected in series with the current source and capacitance C2 so that when the input voltage is lower than the cut-off voltage, the electronic key is in In the “closed” state, when the input voltage reaches a value higher than the cut-off voltage, the key switches to the “open” state, and the electronic device starts to be powered from the capacitance C2, while the input voltage reaches the cut-off voltage again puts the electronic switch into the “closed” state, providing a working voltage for electronic device. 2. The device for protecting an electronic device from high peak voltage values of an on-board network according to claim 1, characterized in that a field effect transistor is used as an electronic switch. 3. The device for protecting an electronic device from high peak voltage values of an on-board network according to claim 1, characterized in that a bipolar transistor is used as an electronic switch. 4. The device protects the electronic device from high peak voltage values of the on-board network according to claim 1, characterized in that it is performed as part of a protected electronic device.

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