Power supply arrangement for resistive-inductive loads

Abstract

Power supply arrangement for a resistive-inductive load (L) in a DC circuit - with a ground connection (M) for connection to a ground of the DC circuit, - with a first connection (1) for connection to a pole (UBAT) positive with respect to ground of a DC voltage source of the DC circuit, - with a second connection (2) for the resistive-inductive load (L), - with a first controllable switching element (T1) between the first terminal (1) and the second terminal (2) and - with a free-running branch between the second terminal (2) and the ground terminal (M), - wherein the freewheeling branch has a freewheeling diode (D1) and a second controllable switching element (T2) connected in series, with a control terminal whose control terminal is connected to the first terminal (1) via a means (D2, C1, R1) for control, - wherein, by means of the means (D2, C1, R1) for control, at least in undisturbed normal operation, the second controllable switching element (T2) can be controlled to close if, during or after a switch-off of the first controllable switching element (T1), the potential at the second terminal (2) has dropped below the potential at ground, and - wherein, by means of the means (D2, C1, R1) for control, the second controllable switching element (T2) can be controlled to open in the event of an interruption of the connection of the freewheeling branch to ground. characterized in that, - that the means (D2, C1, R1) for controlling a Zener diode (D2) includes, - that the Zener diode (D2) is arranged opposite to the forward direction between the first terminal (1) and the control terminal of the second controllable switching element (T2), and - that the breakdown voltage of the Zener diode (D2) ◯ is less than the voltage that results between the first terminal (1) and the second terminal (2) when or after the first controllable switching element (T1) is switched off and / or ◯ greater than the voltage that results from an interruption of the connection of the freewheel branch to ground (M) between the first terminal (1) and the second terminal (2).

Description

[0001] The invention relates to a power supply arrangement for a resistive-inductive load in a DC circuit, wherein the power supply arrangement is equipped with a ground terminal for connection to a ground of the DC circuit, with a first terminal for connection to a positive terminal of a DC voltage source of the DC circuit, with a second terminal for the resistive-inductive load, with a first controllable switching element between the first terminal and the second terminal, and with a freewheeling branch between the second terminal and the ground terminal. The freewheeling branch comprises, in series, a freewheeling diode and a second controllable switching element with a control terminal, the control terminal of which is connected to the first terminal via a control means.

[0002] Such a power supply arrangement for an inductive load in a DC circuit is known from document EP 1 227 562 A1. The second controllable switching element of the power supply arrangement is controlled such that it is conductive when the power supply arrangement is connected to the DC voltage source with the correct polarity and is non-conductive (i.e., blocked) when the power supply arrangement is connected to the DC voltage source with reverse polarity. Blocking the second controllable switching element when connected to the DC voltage source with reverse polarity ensures, for example, that electronics controlling the first controllable switching element are protected from damage due to reverse polarity.

[0003] If, on the other hand, the power supply arrangement is connected to the DC voltage source with the correct polarity, the second controllable switching element is conductive and allows current to flow through the freewheeling branch when the first controllable switching element is switched off.

[0004] The second controllable switching element provides effective protection against reverse polarity connection of the power supply assembly to a DC voltage source.

[0005] In the prior art arrangement, the means for controlling the second controllable switching element comprises an ohmic resistor. This resistor connects the control electrode, i.e., the gate of the field-effect transistor designated as the second controllable switching element, to the first terminal of the power supply assembly. A Zener diode is connected in reverse bias in parallel with the gate-drain path of the field-effect transistor. The ohmic resistor and the Zener diode divide the voltage between the first and second terminals of the power supply assembly. The resulting voltage at the control electrode (gate) of the second controllable switching element causes the second controllable switching element to conduct as soon as the power supply assembly is connected to the DC voltage source with the correct polarity.

[0006] An unwanted current flow from the power supply assembly through the inductive load to ground can occur if the connection between the freewheeling branch and the DC network ground is interrupted. This can happen, for example, if the connection between the source and ground terminals within the power supply assembly is broken, or if the connection between the ground terminal of the power supply assembly and the ground of the DC circuit is broken outside the power supply assembly. In such a case, a so-called ground dip can occur, meaning a positive voltage drop occurs between the ground terminal of the power supply assembly and the ground of the DC circuit. The potential at the ground terminal is higher than the potential at the ground of the DC circuit. Therefore, the potential at ground is lower than the potential at the ground terminal, which explains the name for the effect of ground dip.

[0007] Document DE 198 17 792 A1 discloses a circuit arrangement with the aforementioned features. Unlike the circuit arrangement known from document EP 1 227 562 A1, this arrangement uses an integrated circuit as its control means. This integrated circuit, at least during undisturbed normal operation, controls the second controllable switching element to close when, during or after the first controllable switching element is switched off, the potential at the second terminal has dropped below the potential at ground. Furthermore, if the connection of the freewheeling branch to ground is interrupted, the second controllable switching element is controlled to open by this same control means.

[0008] Further state of the art is known from the documents WO 02 / 071 429 A1 and DE 10 2004 032 721 A1 as well as the Wikipedia article “Comparator (Analog Technology)”, edited on 14.09.2010, 21:25 UTC, accessed on 08.04.2025, 08:21 UTC).

[0009] Document WO 02 / 071 429 A1 discloses an electrical circuit for preventing an arc across an electrical contact when the contact opens. The circuit includes a timer that forces a delayed increase in the contact voltage compared to the open contact. To provide an electrical circuit for preventing an arc across an electrical contact that is highly likely to prevent arcing when the switching contact opens, the circuit further includes a transistor connected in parallel with the switching contact. This transistor comprises, for example, a power MOSFET operated in source configuration, or a Darlington transistor formed by two bipolar transistors or by a bipolar transistor and a field-effect transistor.

[0010] Document DE 10 2004 032 721 A1 discloses a device or method for controlling an inductor with a control circuit and a first and second extinguishing device, wherein the control circuit controls a switching means that establishes or interrupts a current flow to the inductor, wherein when the current flow to the inductor is interrupted, the control circuit first operates the first extinguishing device, and after a free-running extinguishing time which is not less than a minimum time, operates the second extinguishing device, wherein the first and second extinguishing devices extinguish a current induced in the inductor and the second extinguishing device extinguishes the induced current faster than the first extinguishing device.

[0011] The Wikipedia article reveals how comparators are structured, function, and can be used.

[0012] The invention is therefore based on the problem of improving a power supply arrangement mentioned at the outset in such a way that a current flow is prevented in the event of an interruption of the connection of the freewheeling branch to the ground of the DC network.

[0013] This problem is solved according to the invention by the fact that the means for controlling the switching element comprises a Zener diode which is arranged opposite to the forward direction between the first terminal and the control terminal of the second controllable switching element. The breakdown voltage of the Zener diode is - less than the voltage that results between the first terminal and the second terminal when or after the first controllable switching element is switched off, and / or - greater than the voltage that results from an interruption of the connection of the freewheel branch to ground between the first terminal and the second terminal.

[0014] In contrast to the prior art, the means for controlling the second controllable switching element is now designed to ensure that, in the event of a ground fault, the second controllable switching element is activated to open. It is particularly advantageous if the means for controlling the second controllable switching element only activates it to close when, after the first controllable switching element has been switched off, a current flow through the load is to be directed via the freewheeling circuit in order to protect the load.

[0015] The control terminal of the second controllable switching element can be connected via a resistor to a node between the freewheeling diode and the second controllable switching element. Advantageously, the second controllable switching element is a field-effect transistor.

[0016] The control circuitry can include a capacitor connected in parallel with the Zener diode. This capacitor can accelerate the switching on of the second controllable switching element after the switching off of the first, provided the second controllable switching element is a field-effect transistor.

[0017] The means of control can include a threshold switch which, depending on the voltage between the first terminal and the second terminal, connects the control terminal of the second controllable switching element to a control voltage.

[0018] The invention is explained in more detail below with reference to the accompanying drawing. It shows: Fig. 1 a simplified circuit diagram of a power supply arrangement according to the invention.

[0019] The one in Fig.The power supply arrangement S shown in Figure 1 has a first connection 1 to a positive terminal UBAT of a DC voltage source (not shown) and a second connection 2 to a resistive-inductive load L. Within the power supply arrangement S, the first connection 1 and the second connection 2 are connected via a first controllable switching element T1. The first controllable switching element T1 is controlled by an electronic circuit E, which is not described further. This electronic circuit E is connected to the first connection 1 for its own power supply. The electronic circuit E is also connected to a ground connection M of the power supply arrangement S.

[0020] The power supply arrangement S according to the invention has a freewheeling branch that connects the second terminal 2 to the ground terminal M. The ground terminal M is normally connected to the ground terminal of the DC voltage source, i.e., the ground of the DC voltage circuit to which the DC voltage source, the power supply arrangement 1 and the load L belong.

[0021] The freewheeling branch of the power supply arrangement S comprises, between the second terminal 2 and the ground terminal M, a reverse-biased diode D1, the anode of which is connected to the ground terminal M via a source-drain path of a field-effect transistor T2. The field-effect transistor T2 is also part of the freewheeling branch and is also referred to as the second controllable switching element of the power supply arrangement according to the invention.

[0022] The gate of field-effect transistor T2 is connected to the source of field-effect transistor T2 via a resistor R1. The gate of field-effect transistor T2 is also connected to the first terminal 1 via a parallel circuit consisting of a Zener diode D2 and a capacitor C1.

[0023] When the first field-effect transistor T1 is switched on in an undisturbed operation of the power supply arrangement S, the resistive-inductive load L is supplied via the power supply arrangement S. The current flows from the first terminal 1 through the field-effect transistor T1, the second terminal 2, the load L to the ground of the DC circuit.

[0024] When the first transistor T1 is switched off during normal operation, a negative potential relative to the ground of the DC circuit arises at the second terminal 2 due to the self-induction in the inductive component of the load L. This negative potential relative to the ground of the DC circuit at the second terminal 2 of the power supply arrangement S is naturally also lower than the positive potential at the first terminal 1 of the power supply arrangement S, which corresponds to the voltage at the positive terminal UBAT of the DC voltage source.

[0025] This in turn creates a voltage across Zener diode D2 that is greater than the Zener diode's breakdown voltage. This causes Zener diode D2 to conduct. This leads to a current flow and a voltage drop across the ohmic resistor R1, which causes the second field-effect transistor T2 to switch on. The freewheeling circuit is then open to the current driven by the resistive-inductive load L.

[0026] Due to various circumstances, the connection between the ground terminal M and the ground terminal of the DC voltage source can be interrupted. To prevent an unwanted current flow in such a case, the second transistor T2 ensures that current flow through the freewheeling branch is blocked. The voltage drop between the first terminal 1 and the second terminal 2 of the power supply assembly S is insufficient to cause a breakdown in the Zener diode D2. Consequently, there is also no sufficient current flow through the ohmic resistor R1 to cause the field-effect transistor T2 to switch on. In the event of a so-called ground drop, no current can flow from the power supply assembly S to the ground terminal of the DC voltage network. Reference symbol list S power supply arrangement L Consumers Electronics for controlling the first controllable switching element T1 first controllable switching element D1 Freewheeling diode T2 second controllable switching element D2 Zener diode C1 Capacitor R1 ohmic resistance 1. First connection of the power supply arrangement 2 second connection of the power supply arrangement M Ground connection of the power supply arrangement

Claims

[1] Power supply arrangement for a resistive-inductive load (L) in a DC circuit - with a ground connection (M) for connection to a ground of the DC circuit, - with a first connection (1) for connection to a pole (UBAT) positive with respect to ground of a DC voltage source of the DC circuit, - with a second connection (2) for the resistive-inductive load (L), - with a first controllable switching element (T1) between the first terminal (1) and the second terminal (2) and - with a free-running branch between the second terminal (2) and the ground terminal (M), - wherein the freewheeling branch has a freewheeling diode (D1) and a second controllable switching element (T2) connected in series, with a control terminal whose control terminal is connected to the first terminal (1) via a means (D2, C1, R1) for control, - wherein, by means of the means (D2, C1, R1) for control, at least in undisturbed normal operation, the second controllable switching element (T2) can be controlled to close if, during or after a switch-off of the first controllable switching element (T1), the potential at the second terminal (2) has dropped below the potential at ground, and - wherein, by means of the means (D2, C1, R1) for control, the second controllable switching element (T2) can be controlled to open in the event of an interruption of the connection of the freewheel branch to ground. characterized by , - that the means (D2, C1, R1) for controlling a Zener diode (D2) includes, - that the Zener diode (D2) is arranged opposite to the forward direction between the first terminal (1) and the control terminal of the second controllable switching element (T2), and - that the breakdown voltage of the Zener diode (D2) ◯ is less than the voltage that results between the first terminal (1) and the second terminal (2) when or after the first controllable switching element (T1) is switched off and / or ◯ greater than the voltage that results from an interruption of the connection of the freewheel branch to ground (M) between the first terminal (1) and the second terminal (2). [2] Power supply arrangement according to claim 1, characterized by , that the control terminal of the second controllable switching element (T2) is connected via an ohmic resistor (R1) to a node between the freewheeling diode (D1) and the second controllable switching element (T2). [3] Power supply arrangement according to claim 1 or 2, characterized by , that the means (D2, C1, R1) for driving includes a capacitor (C1) which is arranged in parallel to the Zener diode (D2).

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