RU2321164C1 - Voltage commutator with current overload protection - Google Patents

Abstract

FIELD: electronic engineering, possible use for commutating constant current power circuits in non-contact commutating devices, load controllers and electronic time relays.

SUBSTANCE: known voltage commutator contains current sensor, electronic switch, load block, first and second relay elements, mono-stable multi-vibrator, AND element, trigger, OR element, indicator, voltage set-point generator and operational amplifier. Introduced to the device are following components: third and fourth relay element, temperature sensor, second mono-stable multi-vibrator and galvanic decoupling unit. First and second relay elements through OR circuit or first mono-stable multi-vibrator switch the trigger and disable the electronic switch in case of current overload both in transient and stable modes. The third relay element switches the electronic key off in case of load termination. The fourth relay element, connected to output of temperature sensor, switches the electronic key on in case of its overheating.

EFFECT: expanded functional capabilities, increased reliability due to reduced power consumption, protection of overheating, responsive management of modes of operation of voltage commutator.

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Description

The invention relates to the field of electronic technology and can be used in switched power supplies and for switching power DC power circuits with protection against overcurrent and overheating of the electronic key in contactless switching devices (BKU), load controllers and electronic timers.

Known voltage switch with overcurrent protection [1], containing a series-connected current sensor, an electronic switch and a load unit, the first and second relay elements, a waiting multivibrator (single vibrator), the element And, the trigger and the element OR.

The disadvantages of this device are the limited functionality and scope, the inability to control the current state of the load current, the temperature of the electronic switch, the absence of an indication of incorrect operation of the voltage switch: load break, over current mode, disconnection of the load unit when the electronic switch is overheated.

The closest technical solution to the proposed device is a voltage switch with overcurrent protection described in patent RU 2258302 [2], containing a series-connected current sensor, an electronic switch, a load unit, a reference resistor, a transistor and a limiting resistor, the first and second relay elements, one-shot, AND element, trigger and OR element, indicator, voltage regulator and operational amplifier.

The disadvantages of the proposed device are also the limitation of functionality and scope, in addition, low reliability due to high power consumption, as a current sensor, an electronic switch, a reference resistor, a transistor and a current limiting resistor connected in series with the load have a large resistance in the electronic key saturation mode; the lack of protection of the switch from overheating, the inability to control the current state of the load current, the temperature of the electronic key and open circuit of the switch load block.

The objective of the invention is to expand the functionality, scope and increase the reliability of the voltage switch by reducing power consumption, operational control of the load current, switch temperature and open circuit in the load circuit, as well as the introduction of protection of the switch from overheating of the electronic key.

To solve this problem, a voltage switch with protection against overcurrent, containing a current sensor, an electronic switch, a load unit, the first and second relay elements, a single vibrator, an And element, a trigger, an OR element, an indicator, a voltage adjuster, and an operational amplifier ( a current sensor, an electronic switch and a load unit are connected in series and connected to a switching voltage source), an additional third and fourth relay elements are introduced, a temperature sensor, which is a two-terminal device consisting of a cross Neutral transistor VT1 pnp or npn type and three series-connected resistors R1-R3, moreover, the first terminal of the resistor R1 is connected to the positive bus of the second voltage source E, the second terminal of the resistor R1 is connected to the first terminal of the resistor R2 , the output of the temperature sensor and the emitter of the transistor VT1, the base of which is connected to the connection point of the resistors R1, R2, and the collector is connected to the negative bus of the second power supply source E and the second output of the resistor R3, the second one-shot and galvanic isolation node, input s whose inputs are on / off switch voltage, and an output connected to a first input of AND gate and input of the second monostable multivibrator. The output of the second one-shot is connected to the R-input of the trigger, the output of which is connected to the second input of the element And, and the third input of the element And is connected to the output of the fourth relay element, while the output of the element And is connected to the input of the electronic key. The inputs of the operational amplifier are connected to the current sensor, and the output is connected to the output of the switch, on which a voltage proportional to the load current is generated, as well as to the first inputs of the first, second and third relay elements, the second inputs of which are respectively connected to the first, second and third outputs of the master voltage, the fourth output of which is connected to the first input of the fourth relay element, the second input of which is connected to the output of the temperature sensor and the output of the switch, on which the voltage is formed proportional to the temperature of the electronic key, and the outputs of the first, second and third relay elements are connected to the inputs of the OR element, the output of which is connected to the input of the first one-shot, its output is connected to the S-input of the trigger, the input of the display unit is connected to the output of the third relay element and the input element OR.

The drawing shows a block diagram of a voltage switch with overcurrent protection.

In the drawing: 1, 2 - voltage switch on / off inputs, 3 - current sensor, 4 - electronic switch, 5 - load block, 6 - trigger, 7 - OR element, 8 - first one-shot, 9 - I element, 10 - the first relay element, 11 - the second relay element, 12 - the third relay element, 13 - the fourth relay element, 14 - the operational amplifier, 15 - voltage regulator, 16 - display unit, 17 - the second one-shot, 18 - galvanic isolation unit, 19 - temperature sensor, 20 - switch output, the voltage at which is proportional to the load current, 21 - switch output, on the voltage on which is proportional to the temperature of the electronic key.

The drawing shows the simplest execution of the elements of the flowchart. At the same time, the elements of the proposal may have unprincipled differences. So, the galvanic isolation node 18 can be performed using either an optoelectronic element or a transformer. A non-inductive low-resistance resistor with a resistance of 1 mOhm was used as a load current sensor 3. The voltage regulator 15 is a voltage regulator, for example, a potentiometer.

The power supply voltage U _p is the energy source for the load unit 5, its rated voltage depends on the type of equipment in which the proposed device is used, and can be, for example, 27, 60, 130 V.

The second voltage source E serves to power the elements of the device, the voltage regulator 15 and the temperature sensor 19. Its voltage is determined by the type of elements used and can be, for example, 9 V.

The on / off inputs of the voltage switch 1, 2 are connected to the inputs of the galvanic isolation unit 18, the output of which is connected to the first input of the And 9 element and the input of the second one-shot 17, the output of which is connected to the R-input of the trigger 6, the output of which is connected to the second input of the And element 9, the third input of which is connected to the output of the fourth relay element 13, and the output of the element And 9 is connected to the input of the electronic key 4, the inputs of the operational amplifier 14 are connected to the current sensor 3, and the output of the operational amplifier 14 is connected to the output of the comm tator 20 and with the first inputs of the relay elements 10, 11, 12, the second inputs of which are connected respectively to the first, second and third outputs of the voltage regulator 15, the fourth output of which is connected to the first input of the fourth relay element 13, the second input of which is connected to the output of the temperature sensor 19, the output of the switch 21, and the outputs of the relay elements 10, 11, 12 are connected to the inputs of the element OR 7, the output of which is connected to the input of the first one-shot 8, and its output is connected to the S-input of the trigger 6, the input of the display unit 16 is connected to the course of the third relay element 12.

The voltage switch with overcurrent protection operates as follows.

According to the signal supplied to the on / off inputs 1, 2 of the voltage switch, the galvanic isolation unit 18 generates a positive signal received at the first input of the And 9 element, and at the same time launches the second one-shot 17, which switches the trigger 6 to the state when the output is formed a positive signal arriving at the second input of the And 9 element, and if the temperature of the electronic key 4 is less than the critical temperature at which the electronic key and the switch are turned off, then at the third input of the And 9 element the output of the fourth relay element 13 also receives a signal "logical 1", which allows the element And 9 to turn on the electronic key 4.

An electronic switch 4 connects the load unit 5 and the current sensor 3 to a power supply source U _p .

Depending on the load parameters, the current I ₁ in the transient process, the duration of the transient process, the current I ₂ in steady state, the minimum possible switching current I ₃ and the temperature of the electronic key, the threshold values of h ₁ and the current delay t _{1 of the} first relay element 10 are determined , the threshold value of h ₂ and the current delay t _{2 of the} second relay element 11, the threshold value of h _{3 of the} third relay element 12, the threshold value of h _{4 of the} fourth relay element 13.

The values of h ₁ , h ₂ , h ₃ , h _{4 are} determined by the formulas:

Where:

I ₁ - current in the transition process;

I ₂ - current, in steady state;

I ₃ - minimal possible switching current;

R _W - resistance of the current sensor 3;

To _y is the gain of the operational amplifier 14;

E is the voltage of the second power supply source, which serves to power the elements of the device and temperature sensor 19;

R ₁ , R ₂ , R ₃ - the resistance of the resistors R1, R2, R3 of the temperature sensor 19;

T _cvd is the temperature coefficient of one pn junction of a silicon transistor;

T _cr ° C is the critical temperature at which the electronic key 4 is turned off;

T ° C - ambient temperature.

Using the voltage adjuster 15 form the voltage corresponding to the thresholds of operation h ₁ -h ₄ relay elements.

Consider the state of the electronic key 4, if at the moment of switching on the load current I _n lies within I ₃ <I _n <I ₁ .

In this case, the voltage at the output of the operational amplifier 14 is less than the operation thresholds h ₁ , h _{2 of the} relay elements 10, 11 and more than the operation threshold h _{3 of the} third relay element 12. Since the output voltage of the operational amplifier 14 is supplied to the non-inverting inputs of the first and second relay elements 10 , 11 and to the inverting input of the third relay element 12, they are not turned on, and the electronic key 4 remains closed after it is turned on.

If at the moment of switching on the current I _n > I ₁ , then the voltage at the output of the operational amplifier 14 will exceed the threshold value h ₁ and the first relay element 10 will turn on, while the output signal "logical 1" is input to the element OR 7, which starts the first one-shot 8, the output signal of which at the S-input translates the trigger 6 to the state when the signal "logical 0" is generated at its output, which through the And 9 element turns off the electronic key 4.

If during operation an increase in the load current I _n to a value of I ₂ occurs, then the second relay element 11 is turned on, the output signal of which through the OR element 7 starts the first one-shot 8 and turns it off at the S-input of trigger 6, as a result of which the electronic key 4.

If, at the time of switching on or during operation, the load current I _n decreases and I ₃ ≤0.1I _{n n} or the load block 5 breaks, the voltage at the output of the operational amplifier 14 will become lower than the threshold value h ₃ , and in case of a break load block 5 - may be zero. Since the voltage of the response threshold h ₃ supplied to the non-inverting input of the third relay element 12 becomes greater than the voltage from the output of the operational amplifier 14, in this case the third relay element 12 is turned on, which through the element OR 7, the first one-shot 8, the trigger 6 and the element And 9 turns off the electronic key 4.

If during operation of the voltage switch the ambient temperature rises or the load current I _n increases to a value, for example, 0.8I ₁ , at which the first relay element 10 does not trip yet, then in this case the saturation resistance of the electronic switch 4 increases, which leads to I’ll warm it up.

The temperature sensor 19 is a two-terminal device made on a silicon transistor pnp or npn type and three series-connected resistors R1, R2, R3.

In the formula (4), the first expression

sets the value of the output voltage at the output of the switch 21 and the output of the temperature sensor 19, proportional to the ambient temperature T ° C.

In the formula (4), the expression

determines the change in voltage at the output of the temperature sensor 19 when the operating temperature changes by 1 ° C.

, например, равное 9, и учитывая, что Т_cvd≈2,3 мВ/град, получим, что при нагревании электронного ключа на 1°С, напряжение на выходе датчика температуры 19 уменьшается на 10 мВ.Choosing a relationship

, for example, equal to 9, and taking into account that T _cvd ≈2.3 mV / deg, we get that when the electronic switch is heated by 1 ° C, the voltage at the output of the temperature sensor 19 decreases by 10 mV.

Such a circuit of the temperature sensor 19 can improve the accuracy of the fourth relay element 13.

Suppose that during the operation of the voltage switch, its temperature increases, and the voltage from the temperature sensor 19 reaches a threshold value h _{4 of the} fourth relay element 13. In this case, the fourth relay element 13 generates a "logical 0" signal at the output that goes to the input of the And 9 element and turns off the electronic key 4. The temperature of the electronic key 4 and the temperature sensor 19 decreases, the voltage at the output of the temperature sensor increases and becomes greater than the threshold h ₄ . With this value of h _{4, the} fourth relay element 13 switches and a positive voltage is generated at its output, which turns on the electronic switch 4. This mode of operation of the fourth relay element 13 will continue until the cause of the temperature rise of the electronic switch is eliminated.

The introduction of the voltage switch node galvanic isolation 18 and the second voltage source E expands the functionality of the claimed device, since the load unit 5 can be connected to both positive and negative bus voltage source U _p .

Consider the process of determining the actual parameters of the voltage switch and determine the values of currents I ₁ , I ₂ at which the electronic switch 4 is turned off.

In a real voltage switch, the current I ₁ represents the switch overload current both in the transient process and in the steady state, and its value is (3-4) I _n .

The turn-off delay t1 of the electronic key 4 at a current of I ₁ is (0.1-0.5) ms. The current I ₁ represents a short circuit current and its value is (6-8) I _n .

In this case, the turn-off delay t _{2 of the} electronic key 4 is several times less than t ₁ and is equal to (20-40) μs. Current I ₃ = 0.1I _n .

The switch-off temperature of the electronic key is 4 T _cr ° C during its overheating is in the range from 110 to 120 ° C. Based on the accepted definitions of I ₁ , I ₂ , I ₃ , t ₁ , t ₂ , T _cr ° C and their values, you can compile a table that determines the nature of the failure of the voltage switch.

Table Item Number The output signal of the operational amplifier U _y , The output signal of the temperature sensor U _dt Controlled parameter Indicator Status Nature of the fault one 2 3 four 5 one U _y <h ₁ I ₁ - overload current 0 I ₁ <(3-4) I _n normal Work one 2 3 four 5 2 U _y <h ₂ I ₂ - current K3 0 I ₂ <(6-8) I _n normal Work 3 U _y > h ₃ I ₃ - minimum 0 I ₃ > 0.1 I _n , load current normal Work four U _dt > h ₄ T _cr ° C 0 T ° C <T _cr ° C normal Work 5 U _y > h ₁ I ₁ ; t≥t ₁ one I ₁ ≥ (3-4) I _n overload on current 6 U _y > h ₂ I ₂ ; t≤t ₁ one I ₂ ≥ (6-8) I _n short circuit 7 U ₂ <h ₃ I ₃ one I ₃ ≤0,1I _n load break 8 U _dt t <h ₄ T _cr ° C 1; 0 T ° C≥T _cr ° C overheat

Let at the moment the switch is turned on, the voltage at the output of the operational amplifier 14 and the output of the switch 20 be greater than the response threshold h ₃ and less than the response thresholds h ₁ and h ₂ (positions 1-3 of the table). In this case, the load current is 0.1 I _n <I _n <I ₂ , the relay elements 10, 11, 12 remain off, the trigger 6 is in the "logical 1" state, the electronic key 4 remains on, and the display unit 16, implemented, for example, the LED will be in the off state (denote this state by “0”). Thus, the display determination unit 16 in the OFF state after formation signals according to positions 1-3 of the table indicates the correct setting of relay elements 10, 11, 12, respectively, defining a short-circuit allowable value I _2, minimum load current I _n overload current, current equal to 0.1I _n , and about the normal functioning of the switch.

Let the voltage at the output of the operational amplifier 14 be greater than the threshold value h _{1 of the} first relay element 10 at the moment of switching on the switch, but less than the threshold threshold h _{2 of the} second relay element 11 and the signal duration at the moment of switching on will be longer than the delay time t ₁ , then after the formation of signals according to position 5 of the table, the display unit 16 will be in the on state, since the first relay element 10 is activated, which, through the OR element 7, starts the one-shot 8 and translates the trigger 6 to the state when a “logical 0” signal is generated at its output, which, through the And 9 element, turns off the electronic key 4, disconnecting the load unit 5 from the power supply U _p .

Since the load current is I _n = 0, no voltage drop is created at the current sensor 3, and at the same time, the voltage U _y = 0 at the output of the operational amplifier 14 becomes lower than the threshold value h _{3 of the} third relay element 12. The third relay element also triggers the output signal puts the display unit 16 in the on state, indicating the absence of current in the load circuit according to position 7 of the table.

Suppose that at some point in time, for example, due to a failure, the load current is I _n > I ₂ , then after time t ₂ the second relay element 11 will turn on, which, through the OR element 7, the one-shot 8, the trigger 6, the And 9 element turns off electronic key 4, the third relay element 12 will turn on and with its output signal the indicator 16 will turn on, indicating the absence of current in the load circuit, according to position 6 of the table.

If during operation the electronic switch 4 heats up and its temperature rises above the temperature T _kr ° C, the fourth relay element 13 will turn on. Its output signal “logical 0” through the And 9 element switches off the electronic switch 4, and the load current I _n = 0, the voltage drop at the current sensor 3 will also become zero and the output voltage of the operational amplifier 14 will become less than the threshold value h _{3 of the} third relay element 12, which will turn on and turn on the display unit 16, position 8 of the table with its output signal.

After the electronic key 4 is turned off, its temperature decreases, the voltage at the output of the temperature sensor 19 becomes lower than the value of h ₃ , and the fourth relay element 13 is turned off, thereby turning on the electronic key 4, the third relay element 12 is turned off, including the display unit 16, according to position 4 of the table .

If the temperature of the electronic key 4 again rises to T _cr ° C, then the process of turning it off / on will repeat and will continue until the temperature is normalized.

The value of the operation thresholds h ₁ -h _{4 of the} relay elements 10-13 can be changed by the voltage adjuster 15 for each specific type of voltage switch depending on the load current I _n and the switch-off temperature of the electronic switch 4 when it is overheated, always preserving the specified margin of protection against overload and overheating .

Compared with the known voltage switch [2], the proposed device expands the functionality and scope, increases reliability by reducing power consumption, operational monitoring of the load current, electronic key temperature and open circuit in the load circuit, as well as introducing protection of the switch from overheating of the electronic key.

Thus, the introduction of the third and fourth relay elements, a temperature sensor, a second one-shot device and a galvanic isolation unit into the device, as well as the use of new functional connections, made it possible to carry out operational control of the current state of the load current, electronic key temperature, expanded the functionality and scope of the voltage switch .

As elements for the implementation of the device, AND, OR, one-shot logic elements, triggers of any series, standard relay elements, for example, 531CAZ series switches, electronic keys, operational amplifiers, for example, 1467 series, transistors, voltage regulators (potentiometers), can be used, LEDs

Information sources

1. Patent RU 2208291 C2, cl. H03K 17/08.

Voltage switch with overcurrent protection. Priority Date 07/11/2001

2. Patent RU 2258302 C2, cl. H03K 17/08.

Voltage switch with overcurrent protection. Priority Date 07/22/2003

Claims (1)

A voltage switch with overcurrent protection, comprising a current sensor, an electronic switch, a load unit, first and second relay elements, a single-shot device, an AND element, a trigger, an OR element, an indicator, a voltage regulator and an operational amplifier, while the current sensor is an electronic switch and the load unit are connected in series and connected to a switching voltage source, characterized in that the third and fourth relay elements, a temperature sensor, which is a two-terminal device and consisting of a belt pnp or npn transistor and three series-connected resistors, the first output of the first resistor connected to the positive bus of the second power supply source, the second output of the first resistor connected to the first output of the second resistor, the output of the temperature sensor and silicon emitter a transistor whose base is connected to the connection point of the second and third resistors, and the collector is connected to the negative bus of the second power source and the second terminal of the third resistor, the second one-shot the ator and the galvanic isolation node, the inputs of which are the on / off inputs of the voltage switch, and the output is connected to the first input of the And element, as well as the input of the second one-shot, the output of which is connected to the R-input of the trigger, the output of which is connected to the second input of the And element, and the third input of the And element is connected to the output of the fourth relay element, and the output of the And element is connected to the input of the electronic key, the inputs of the operational amplifier are connected to the current sensor, and the output is connected to the output of the switch, on which voltage proportional to the load current and with the first inputs of the first, second and third relay elements, the second inputs of which are connected respectively to the first, second and third outputs of the voltage regulator, the fourth output of which is connected to the first input of the fourth relay element, the second input of which is connected to the output of the temperature sensor and the output of the switch, on which a voltage is generated proportional to the temperature of the electronic switch, and the outputs of the first, second and third relay elements are connected s with the inputs of the OR element, the output of which is connected to the input of the first one-shot, and its output is connected to the S-input of the trigger, the input of the display unit is connected to the output of the third relay element and the input of the OR element.