System for controlling inductor freewheeling voltage - Patents.com
Patent Information
- Application Number
- JP2023578983
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2021-06-22
- Filing Date
- 2022-05-05
- Publication Date
- 2025-06-03
AI Technical Summary
Existing solutions for controlling inductor freewheeling voltage in synchronous motors/generators require multiple high-power components, leading to increased complexity and heat sink area, and lack efficient methods to manage current discharge without active loads or resistive elements.
A circuit comprising a first and second switch, a diode, and an inductor, controlled by a switch control circuit, reduces the number of high-power components by using a single power component with a gating circuit to manage freewheeling voltage, achieving a constant voltage drop across the second switch.
This approach minimizes the need for additional high-power components and reduces standby losses by using a single power component, while effectively controlling inductor freewheeling voltage.
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Abstract
Description
[Technical field]
[0001] The present invention relates to an electrical circuit for controlling an inductor freewheeling voltage. [Background technology]
[0002] In the excitation winding of a synchronous motor / generator, the DC current needs to be controlled. The current is increased by applying a positive voltage across it, which is controlled by a switch. To rapidly discharge the current in this inductance, a negative voltage needs to be applied across it. Feeding energy back to the DC bus is a common solution, but requires an active load consisting of a resistor and a switch to discharge the capacitor and prevent overvoltage. Other solutions include a resistor that provides a current-dependent ramp-down voltage, or a voltage clamp placed in parallel with the freewheeling switch.
[0003] Document US6288508B1 discloses a braking system for an electric motor operated vehicle, including a system for providing both regenerative braking and back-excitation braking and for transitioning between these braking modes in response to an operator's request. The solution provided in this document discloses slowing down the motor by using it as a generator and providing regenerative braking by either charging a battery or discharging the generated current through a resistive load.
[0004] The document EP 2 747 287 A1 discloses an arrangement with a freewheeling circuit comprising a freewheeling diode and a limiting element, e.g. a breakdown diode, connected in parallel with a switching element, e.g. a MOSFET. A further switching element is connected in series with the circuit. A control device has an evaluation and control unit for synchronously controlling the elements. The control unit is connected to galvanically separated control and control inputs, whereby controlling the elements is based on a determined control supply voltage.
[0005] The document EP 1 675 245 A2 discloses a circuit arrangement for the rapid reduction of induced currents, which can be used in particular with a voltage regulator for a generator in a vehicle electrical system, causing an increase in the freewheeling voltage, so that when consumers of the excitation winding are stopped, the induced overvoltages can be reduced quickly and the generator can therefore be de-energized quickly. Summary of the Invention
[0006] The object of the present invention is to provide a circuit for controlling the inductor freewheeling voltage which comprises fewer high-power components than the solutions known from the state of the art.
[0007] The present invention discloses a system for controlling an inductor freewheeling voltage, comprising a first switch, a second switch, a first diode, and an inductor. The first switch is connected such that in an open state it will connect a first terminal of the inductor to a power bus and the first switch is controlled by a first control signal. A first terminal of the first diode is connected to ground and a second terminal of the first diode is connected to the first terminal of the inductor. The first diode is connected such that it allows current to flow from ground to the first terminal of the inductor. The second switch is connected such that in an open state it will connect the second terminal of the inductor to ground. The system is characterized in that it comprises a switch control circuit, the switch control circuit being configured to be controlled by a second control signal delivered to an input terminal of the switch control circuit, whereby in a first state of the second control signal the switch control circuit keeps the second switch open and in a second state of the second control signal the switch control circuit keeps the second switch such that there is a voltage drop across the second switch.
[0008] In a preferred embodiment, the switch control circuit comprises a second diode configured to deliver a second control signal to the switch control circuit.
[0009] In yet another embodiment, at least one of the first switch and the second switch is a unipolar transistor or an IGBT transistor.
[0010] In another embodiment, the switch control circuit includes a first resistor and a Zener diode, the first terminal of the Zener diode being connected to the second terminal of the inductor and the second terminal of the Zener diode being connected to the first terminal of the first resistor, the gate terminal of the second switch, and the input terminal, the forward direction of the Zener diode is from the gate terminal of the second switch to the second terminal of the inductor, and the second terminal of the first resistor is connected to ground.
[0011] In a preferred embodiment, the switch control circuit comprises a second resistor, a third resistor, a fourth resistor, a third diode, a transistor, and at least one Zener diode. A first terminal of the first Zener diode is connected to a second terminal of the inductor, and a second terminal of the last Zener diode is connected to a first terminal of the third diode. All the Zener diodes are connected in series in the same direction, and the forward direction of the Zener diodes is from the first terminal of the third diode to the second terminal of the inductor. A second terminal of the third diode is connected to a first terminal of the second resistor and to a base terminal of the transistor. A forward direction of the third diode is from the second terminal of the last Zener diode to the first terminal of the second resistor. A second terminal of the second resistor is connected to ground. A collector terminal of the transistor is connected to an auxiliary power source configured to provide a stable DC voltage. An emitter terminal of the transistor is connected to the input terminal and to a first terminal of a third resistor. A second terminal of the third resistor is connected to a first terminal of a fourth resistor and to a gate terminal of the second switch. A second terminal of the fourth resistor is connected to ground.
[0012] In yet another embodiment, the system includes a capacitor connected such that a first terminal of the capacitor is connected to a gate terminal of the second switch and a second terminal of the capacitor is connected to ground.
[0013] The invention will now be described below with reference to the accompanying drawings. [Brief description of the drawings]
[0014] [Figure 1] FIG. 1 shows a general circuit topology according to the present invention. [Diagram 2] FIG. 2 presents the simplest implementation of the present invention. [Diagram 3] FIG. 3 presents a circuit with reduced standby losses. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] The general concept of the invention is illustrated in Figure 1. The novel implementation shown in its simplest form merges the functions of a power switch and preferably a constant voltage load in one component, namely switch M2. This reduces the number of power components and the required heat sink area since only one power component, namely switch M2, is needed to reduce the current.
[0016] During the current ramp-up phase, both switches M1 and M2 shown in FIG. 1 are turned on - the first control signal S1 and the second control signal S2 are in a first state. The power bus + is connected to the inductor L through the first switch M1, which is further connected to ground - by the second switch M2. Freewheeling is achieved by turning off the first switch M1 (by changing the state of the first control signal S1), forcing the current to flow through the freewheeling diode (first diode D1). When it is necessary to reduce the current in the inductor L, the gate voltage v G_M2 is set low by a change in the second control signal S2. This causes a reduction in the gate voltage of the second switch M2. The second switch M2 starts to close, which reduces its drain-source voltage v DS_M23. The switch control circuit SCC prevents the second switch M2 from closing completely. In a preferred embodiment, a constant voltage drop is achieved across the second switch M2, which makes it easier to regulate the current. Those skilled in the art will know that other transistor types can be used in the present application as the first switch M1 and / or the second switch M2, and the transistors shown in Figures 1-3 serve only as examples - bipolar transistors, unipolar transistors or IGBT transistors can be used in the present application. In a preferred embodiment, the capacitor C2 is connected such that a first terminal of the capacitor C2 is connected to the gate terminal of the second switch M2 and a second terminal of the capacitor C2 is connected to ground. This capacitor C2 provides a more gradual change in the voltage across the second switch S2.
[0017] Please note that in the figures and description, there is a power bus + that applies a positive voltage and a ground - that has a potential of 0V. Please note that in other cases, for example, where there is a ground - and a negative power bus, some components will be connected accordingly and the overall circuit connections may change. Those skilled in the art will know how to adjust the disclosed invention in such cases.
[0018] The switch control circuit SCC is a circuit that may be described as a signal converter that converts the second control signal S2 into a signal that controls the second switch M2 while preventing the second switch M2 from being fully closed. In the following, it is assumed that the second control signal S2 is a digital signal, but it should be noted that it may also be an analog signal.
[0019] In a preferred embodiment, the switch control circuit SCC comprises a second diode D2 configured to deliver a second control signal S2 to the switch control circuit SCC. The second diode D2 provides a safe input and prevents applying high voltages / currents to the source of the second control signal S2.
[0020] 2 shows the simplest implementation of the general concept of the present invention. In this circuit, the switch control circuit SCC comprises a first resistor R1 and a Zener diode DZ, the first terminal of which is connected to the second terminal of the inductor L and the second terminal of which is connected to the first terminal of the first resistor R1, the gate terminal of the second switch M2, and the input terminal. The forward direction of the Zener diode is from the gate terminal of the second switch M2 to the second terminal of the inductor L, and the second terminal of the first resistor R1 is connected to ground −. In this implementation, when it is necessary to reduce the current in the inductor L, the gate voltage v G_M2 is set low. This results in a reduction in the gate voltage of the second switch M2, caused by the pull-down resistor R1. The second switch M2 begins to close, which reduces its drain-source voltage v DS_M2 Eventually, the drain-source voltage reaches the breakdown voltage of the Zener diode DZ and the diode begins to conduct, preventing the second switch M2 from fully closing and causing a constant voltage drop across its drain-source junction.
[0021] The present invention, by means of suitable gate circuits, makes it possible to achieve the functions performed by the voltage clamp and second switch M2 known from the prior art by using a single power component, eliminating the need for additional high power components. Additionally, when used, the capacitance value as well as the voltage rating of the DC stabilization capacitor C1 is reduced.
[0022] A more complex circuit is presented in FIG. 3 (only the switch control circuit SSC and the second switch M2 are presented). In this embodiment, a first terminal of the first Zener diode DZ1 is connected to the second terminal of the inductor L, and a second terminal of the last Zener diode DZ1 is connected to the first terminal of the third diode D3. All Zener diodes DZ1 are connected in series in the same direction, and the forward direction of the Zener diode DZ1 is from the first terminal of the third diode D3 to the second terminal of the inductor L. The second terminal of the third diode D3 is connected to the first terminal of the second resistor R2 and to the base terminal of the transistor Q1. The forward direction of the third diode D3 is from the second terminal of the last Zener diode DZ1 to the first terminal of the second resistor R2. The second terminal of the second resistor R2 is connected to ground −. The collector terminal of the transistor Q1 is connected to an auxiliary power supply PS configured to provide a stable DC voltage. An emitter terminal of the transistor Q1 is connected to the input terminal and a first terminal of a third resistor R3, a second terminal of the third resistor R3 is connected to a first terminal of a fourth resistor R4 and to a gate terminal of the second switch M2, and a second terminal of the fourth resistor R4 is connected to ground.
[0023] This adds an additional low-voltage, low-power transistor Q1. Its purpose is to reduce the current flow in the Zener diode and thus minimize the overall standby losses of the circuit. The drawback is that a stable auxiliary power supply for the gate circuit is required.
[0024] It should be noted that in this embodiment, transistor Q1 is shown and described as a bipolar transistor, although a unipolar transistor may also be used.
[0025] [List of reference numbers in the drawings] M1 - First switch M2 - Second switch D1 - First diode D2 - Second diode D3 - Third diode DZ, DZ1 - Zener diode L-inductor +-Power bus --ground S1 - First control signal S2 - Second control signal R1 - First resistor R2 - Second resistor R3 - Third resistor R4 - Fourth resistor Q1 - Transistor C1 - Stabilizing capacitor C2 - Capacitor SCC - Switch Control Circuit PS-auxiliary power supply
Claims
1. A system for controlling an inductor-free wheeling voltage, comprising a first switch (M1), a second switch (M2), a first diode (D1), and an inductor (L), wherein in an open state, the first switch (M1) is connected such that it connects the first terminal of the inductor (L) to a power bus (+), and the first switch (M1) is controlled by a first control signal (S1); a first terminal of the first diode (D1) is connected to ground (-), and a second terminal of the first diode (D1) is connected to the first terminal of the inductor (L), wherein the first diode (D1) is connected such that it allows current to flow from the ground (-) to the first terminal of the inductor (L); in an open state, the second switch (M2) is connected such that it connects the second terminal of the inductor (L) to the ground (-); the system further comprises a switch control circuit (SCC), which is configured to be controlled by a second control signal (S2) delivered to an input terminal of the switch control circuit (SCC). Thus, in a first state of the second control signal (S2), the switch control circuit (SCC) keeps the second switch (M2) open, and in a second state of the second control signal (S2), the switch control circuit (SCC) keeps the second switch (M2) such that there is a voltage drop across both ends of the second switch (M2).
2. The system according to claim 1, wherein the switch control circuit (SCC) comprises a second diode (D2) configured to deliver the second control signal (S2) to the switch control circuit (SCC).
3. The system according to claim 1 or 2, wherein at least one of the first switch (M1) and the second switch (M2) is a unipolar transistor or an IGBT transistor.
4. The switch control circuit (SCC) is such that a first terminal of a Zener diode (DZ) is connected to the second terminal of the inductor (L), The second terminal of the Zener diode (DZ) is connected to the first terminal of the first resistor (R1), the gate terminal of the second switch (M2), and the input terminal, where the forward direction of the Zener diode (DZ) is from the gate terminal of the second switch (M2) to the second terminal of the inductor (L). The second terminal of the first resistor (R1) is connected to the ground (-). The system according to claim 3, characterized in that it comprises the first resistor (R1) and the Zener diode (DZ) connected as described above.
5. The switch control circuit (SCC) is such that The first terminal of the first Zener diode (DZ1) is connected to the second terminal of the inductor (L). The second terminal of the last Zener diode (DZ1) is connected to the first terminal of the third diode (D3), where all the Zener diodes (DZ1) are connected in series in the same direction, and the forward direction of the Zener diode (DZ1) is from the first terminal of the third diode (D3) to the second terminal of the inductor (L). The second terminal of the third diode (D3) is connected to the first terminal of the second resistor (R2) and the base terminal of the transistor (Q1), where the forward direction of the third diode (D3) is from the second terminal of the last Zener diode (DZ1) to the first terminal of the second resistor (R2). The second terminal of the second resistor (R2) is connected to the ground (-). The collector terminal of the transistor (Q1) is connected to an auxiliary power supply (PS) configured to supply a stable DC voltage. The emitter terminal of the transistor (Q1) is connected to the input terminal and the first terminal of the third resistor (R3). The second terminal of the third resistor (R3) is connected to the first terminal of the fourth resistor (R4) and the gate terminal of the second switch (M2). The second terminal of the fourth resistor (R4) is connected to the ground (-). The system according to claim 3, further comprising a second resistor (R2), a third resistor (R3), a fourth resistor (R4), a third diode (D3), a transistor (Q1), and at least one Zener diode (DZ1), which are connected as described above.
6. The system according to claim 3, further comprising a capacitor (C2) connected such that a first terminal of the capacitor (C2) is connected to the gate terminal of the second switch (M2) and a second terminal of the capacitor (C2) is connected to the ground (-).