RU2542952C2 - Voltage switch with overcurrent protection - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is referred to electronic engineering and may be used in power supply sources with overcurrent protection, mainly in spacecraft control systems. The electronic key connected to the common point of the switch and load unit and a relay element with hysteresis are controlled by means of the first and second AND elements by switching on and off power supply to the load unit. In case of current overload, power is disconnected from load unit.

EFFECT: decreased weight and dimensions The voltage switch with overcurrent protection comprises an electronic switch with MOS structure, which supplies power to the load unit.

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Description

The present invention relates to the field of electronic technology and can be used in switched power supplies with overcurrent protection, mainly in control systems of spacecraft.

Known voltage switch with overcurrent protection [1], containing an electronic switch, first and second relay elements, current sensor, trigger, load unit, operational amplifier, voltage adjuster, transistor.

A disadvantage of the known device is its complexity and the use of a current sensor (shunt). When switching high currents, considerable power is allocated to the shunt, which leads to an increase in the mass and dimensions of the voltage switch due to the installation of a metal element that removes heat from the shunt, designed to remove heat of high power.

The closest technical solution to the proposed device is a voltage switch with overcurrent protection, described in [2]. The known voltage switch contains a series-connected current sensor, an electronic switch and a load unit, as well as a relay element, a trigger.

и при сопротивлении датчика тока (шунта) $$r_{ш}=4\text{ мОм}$$

тепловыделение шунта составит 10 Вт. Для отвода такого тепла от шунта требуется значительный по массе и габаритам металлический элемент, что увеличивает массу и габариты коммутатора напряжения.A disadvantage of the known device is that it uses a current sensor to implement its main function. When switching large currents in the chains of their flow, significant interference occurs. To obtain a reliable level of operation of the relay element, it is necessary that the level of the useful signal exceeds the level of the interference signal. This requires increasing the ohmic resistance of the current sensor, and this leads to a significant increase in the dissipated power on it and, as a consequence, to an increase in mass and dimensions. For reliable operation of the relay element that turns off the switch when an overload current occurs, the value of the useful input signal of the relay element should be at the level of 100-300 mV. So when switching current $$I_H=\mathrm{fifty}\mathrm{BUT}$$

and with the resistance of the current sensor (shunt) $$r_w=\mathrm{four}\text{mOhm}$$

the heat shunt will be 10 watts. To remove such heat from the shunt, a metal element of considerable weight and dimensions is required, which increases the mass and dimensions of the voltage switch.

The objective of the invention is to reduce the mass and dimensions of the voltage switch. This task is achieved in that the voltage switch with overcurrent protection, contains an input bus, a first element And, a relay element with hysteresis, the inverse output of which is connected to the first input of the first element And, and an electronic switch and a load block connected in series, while the electronic switch is made in the form of an electronic key with a MOS structure, and a second element And and an electronic key are added to the voltage switch, the signal input of which is connected to a common point of the load unit and the electronic of the crown switch, the output of the electronic key is connected to the input of the relay element with hysteresis, the inverse output of which is connected to the first input of the second element And, the second input of which is connected to the input bus and the second input of the first element And, the output of the second element And is connected to the control input of the electronic key, the output of the first element And is connected to the control input of the electronic switch.

Figure 1 shows a block diagram of a voltage switch with overcurrent protection. In this diagram: 1 - input bus, 2 - first I element, 3 - electronic switch, 4 - load block, 5 - second I element, 6 - electronic key, 7 - relay element with hysteresis.

The input bus 1 is connected to the second inputs of the first 2 and second 5 AND elements, the first inputs of which are connected to the inverse output of the relay element with hysteresis 7. The electronic switch 3 and the load unit 4 are connected in series, while their common point is connected to the signal input of the electronic key 6 the output of which is connected to the input of the relay element with hysteresis 7. The output of the first element And 2 is connected to the control input of the electronic switch 3, the output of the second element And 5 is connected to the control input of the electronic key 6.

The voltage switch with overcurrent protection operates as follows. As an electronic switch 3, an electronic key (transistor) with a MOS structure is used. A feature of such an element is the ability to switch large currents, while switching different currents, the ohmic resistance of an open element (transistor) is practically independent of the current value and amounts to a small amount (units of mOhm). In this case, the voltage drop across the open (switched on) element will linearly depend on the value of the switched current.

на открытом электронном коммутаторе 3 можно представить в видеIn general, the voltage drop $$U_{\mathrm{TO}}$$

on the open electronic switch 3 can be represented as

$$U_{\mathrm{TO}}=r_{\mathrm{TO}}{I}_N\text{(one)}$$

- коммутируемый ток нагрузки, $$r_{К}$$

- сопротивление электронного коммутатора 3 в открытом (включенном) состоянии.Where $$I_N$$

- switched load current, $$r_{\mathrm{TO}}$$

- the resistance of the electronic switch 3 in the open (on) state.

We will assume that the electronic switch 3 is in the open (on) state if a positive signal U ₂ from the output of the first element And 2 (U ₂ = 1) is supplied to its control input, and in the closed (off) state if U ₂ = 0. We also believe that in the initial state the signal at the inverse output of the relay element with hysteresis 7 U ₇ = 1. In this case, when the signal on the input bus 1 U _BX = 1, the electronic switch 3 is in the open (on) state, when U _BX = 0, the electronic switch 3 is in the closed (off) state. As follows from the structural diagram of figure 1, the electronic key 6 operates synchronously with the electronic switch 3 (the electronic key 6 is open if the signal from the output of the second element And 5 U ₅ = 1, the electronic key 6 is closed if the signal U ₅ = 0, and it output signal U ₆ = 0).

Let the response level of the relay element with hysteresis 7 is chosen equal to U _P. This means that when the voltage drops on the switch 3 U _К = U _П , the relay element will trigger with hysteresis 7 (the hysteresis of the relay element 7 is chosen equal to U _П ). The output signal of the relay element 7 U ₇ = 0 and the output signals of the first 2 and second 5 elements And will be equal to U ₂ = 0 and U ₅ = 0, respectively. These signals turn off the electronic switch 3 and the electronic key 6. The electronic switch 3 removes voltage from the load unit 4.

The voltage U _P is selected from the condition of the specified current I _N , at which it is necessary to disconnect the voltage from the load unit 4, and the known resistance of the electronic switch 3 r _K in accordance with (1). If, for example, r _K = 4 mOhm and the tripping current I _N = 50 A, then U _P is chosen equal to 0.2 V. If the load current I _N exceeds 50 A, then the electronic switch 3 will disconnect the voltage from the load unit 4. When disconnecting power from the load unit also turns off the electronic switch 6, which removes the input voltage from the relay element with hysteresis 7 (U ₆ = 0), which allows the relay element 7 to be in the off state.

Compared with the known voltage switch [2], the present invention has smaller mass and dimensions due to the removal of requirements for heat removal from the current sensor, which is absent in the proposed circuit. In a known circuit, when using a current sensor with r _w = 4 mOhm at a current of 50A, a power of 10 W is dissipated.

To remove heat of 10 W, a metal exhaust surface of 2 dm ² is required. With a permissible overheating at the current sensor at 30 ° C compared to the ambient temperature, a heat sink with a heat sink surface of 100 × 200 mm will be required. When using an aluminum plate with a thickness of 5 mm as a heat sink, the heat sink mass will be 250 g, which is a significant value for one switch. When using electronic switches in control systems, for example, spacecraft, the additional mass is a significant drawback.

The proposed set of features in the solutions considered by the authors was not found to solve the problem and does not follow explicitly from the prior art, which allows us to conclude that the technical solution meets the criteria of "novelty" and "inventive step". As elements for implementing the device, logical elements And, for example, of the 564 series, standard relay elements, electronic switches with a MOS structure, for example, type 2P7161 B, electronic keys of the 564 series can be used.

Literature

1. RF patent No. 2258302, cl. H03K 08/17, 2005

2. RF patent No. 2208291, cl. H03K 08/17, 2003

Claims (1)

A voltage switch with overcurrent protection, comprising an input bus, a first element And, a relay element with hysteresis, the inverse output of which is connected to the first input of the first element And, and an electronic switch and a load unit connected in series, characterized in that the electronic switch is made in in the form of an electronic key with a MOS structure, and, in addition, a second element And and an electronic key are added to the voltage switch, the signal input of which is connected to a common point of the load unit and the electronic of the second switch, the output of the electronic key is connected to the input of the relay element with hysteresis, the inverse output of which is connected to the first input of the second element And, the second input of which is connected to the input bus and the second input of the first element And, the output of the second element And is connected to the control output of the electronic key, the output of the first element And is connected to the control input of the electronic switch.