Electrical switching device with charge pump

Abstract

The present invention provides an electrical switching device including a charge pump (NCP), the charge pump having at least two connection contacts (a1, a2), of which a first connection contact (a1) is connected to a first voltage potential (V1), a second connection contact (a2) is connected to a second voltage potential (V2) higher than the first voltage potential (V1) via a series circuit including at least one first capacitor (C1), a second capacitor (C2), and a first diode (D1) arranged between the two capacitors, and is also connected to the first capacitor (C1) via a switching element, and the charge pump (NCP) has a third connection contact (a3 ), the third connecting contact (a3) ​​is connected to the output (AK1) of a first comparator (K1) having first and second comparator inputs (K1-, K1+), the first comparator input (K1-) is connected to the anode potential (refP) of a second diode (D2) to which the second voltage potential (V2) is applied, the second diode (D2) is connected in series with the first diode (D1) and in parallel with the second capacitor (C1), and the second comparator input (K1+) is connected to the cathode potential (refN) of a third diode (D3) assigned to the anode to which the second voltage potential (V2) is applied.

Description

[Technical Field]

[0001] The present invention relates to an electrical switching device with a charge pump that is capable of generating a preferably DC voltage in the form of an operating voltage for controlling or operating various electrical components as required. [Background technology]

[0002] Electrical switching devices, also commonly known as voltage converters, can generate various high electrical output voltages using an electrical capacitor supplied with an input voltage and whose charge is regulated by periodically switching a switch. Depending on the type of circuit, they can generate either a higher output voltage with the same polarity as the input voltage or a negative output voltage. An oscillator is typically used to periodically switch the switch.

[0003] "On-chip High-Voltage Generator Design: Design Methodology for Charge Pumps", Tanzawa, Springer 2015, describes several known switching devices with charge pumps, including the so-called "Dixon charge pump", which is of particular interest below due to its ease of control for integrated circuits.

[0004] A particularly preferred application area requiring the use of charge pumps of the type in question relates to implantable electronic devices for the treatment of various types of neurological dysfunction through stimulation of nerves by electrical charge. The electrical switching devices that form the basis of these implants are multifunctional, highly integrated circuits designed for maximum operational safety, maximum energy efficiency, and the greatest possible miniaturization. Summary of the Invention

[0005] The present invention is based on the object of further developing an electrical switching device having a charge pump, so that at least one of the characteristics forming the basis of the above-mentioned conceptual objectives regarding operational safety, energy efficiency and compactness is significantly improved compared to previous switching devices of the type in question.

[0006] The solution to the problem forming the basis of the present invention is set out in claim 1. Features that further develop the inventive concept are the subject of the dependent claims and can be found in the detailed description, in particular with reference to the drawings.

[0007] The electrical switching device of the present invention includes a charge pump having at least two connection contacts, a first connection contact connected to a first potential and a second connection contact connected to a second potential higher than the first potential via a series circuit including at least one first capacitor, a second capacitor, and a first diode disposed between the first and second capacitors. The second potential is connected to the first capacitor via a switching unit. The charge pump further has a third connection contact connected to the output of a first comparator having two inputs, i.e., first and second comparator inputs. The first comparator input of the comparator is connected to the anode potential of a second diode to which the second potential is applied, and is also connected in series with the first diode and in parallel with the second capacitor. Meanwhile, the second comparator input of the comparator is connected to the cathode potential of a third diode, the anode of which is assigned to apply the second potential.

[0008] The switching solution according to the invention is based on an innovative construction concept, according to which the charge pump is arranged in the switching device in a low-voltage domain corresponding to a specified potential, i.e. the input voltage, whereas all electronic components involved in controlling the charge pump are arranged in a high-voltage domain within the switching device, i.e. the domain of the voltage resulting from the voltage transformation by the charge pump.

[0009] Although the terms low voltage region and high voltage region are used below, it is also possible with the switching device according to the invention to start from a specific negative voltage region and generate a numerically low voltage region by means of an inverted voltage transformation, which is also covered by the switching device according to the invention.

[0010] To achieve the essential functional goal of the switching device, a voltage difference of, for example, 1.8 V must be transferred from the low-voltage domain to the high-voltage domain, thereby ensuring that the converted or transformed 1.8 V voltage difference is maintained in the high-voltage domain. That is, the voltage conversion by the charge pump must be controlled so that the charge pump is activated until the 1.8 V voltage difference is completely converted to the high-voltage domain. Thus, the voltage difference in the low-voltage domain corresponds to a potential value of, for example, 0 V to 1.8 V, and the voltage difference in the high-voltage domain corresponds to a potential value of, for example, 11 V to 12.8 V. The reference points of the low-voltage domain and the high-voltage domain can differ from each other by preferably 18 V or more, i.e., up to 60 V, but can also overlap. In this example, the reference points are 0 V and 11 V.

[0011] The regulation or activation or deactivation of the charge pump is performed in a controlled manner as part of a first control circuit essentially consisting of a comparator acting primarily as a reference point generator and second and third diodes, all of which are located in the high voltage region of the switching device formed by the continuous charge accumulation in the second capacitor, while the charge pump itself is located in the low voltage region.

[0012] As a result, the current flow required for regulation is minimal between the low and high voltage domains, and only a small current bias is required for regulation, allowing the individual switching domains ("on", i.e., charge pump activated, "off", i.e., charge pump deactivated) to operate at the lowest supply voltage and therefore be very efficient at delivering power.

[0013] Preferably, the so-called first comparator defining the first control circuit has two operating voltage contacts, one of which is connected to the cathode assigned to the second diode and the other of which is connected to the second potential.

[0014] If a power surge is detected by the first comparator, it generates a corresponding compactor signal, which is converted from a high voltage domain to a low voltage domain and applied to the connection contacts of the charge pump, deactivating or turning off the charge pump, so that the power surge is reduced by its own consumption in the dissipation elements connected to this voltage domain. Suitable for the purpose of converting the comparator signal from a high voltage domain to a low voltage domain are known level shifters or level converters connected between the first comparator and the charge pump or which are part of the comparator and / or the charge pump.

[0015] If the charge pump continues to pump, either accidentally or intentionally, or if another event unintentionally increases the power surge, the voltage must be limited.

[0016] Optionally, to further improve the operational safety of the switching device, in addition to the first on-off control loop, a second control loop is provided in the high-voltage area of ​​the switching device. If a power surge exceeds the maximum value, a switch is activated, which instantly reduces the voltage difference.

[0017] To this end, the operating voltage terminal of a second comparator having first and second comparator inputs is connected in parallel to the operating voltage terminal of the first comparator. The first comparator input of the second comparator, like the first comparator input of the first comparator, is connected to the anode potential of a second diode. The second comparator input of the second comparator is connected to a reference potential formed between the load and the first supply potential, and the load is a constant load connected between a third diode and the first potential.

[0018] The output of the second comparator controls a switch in the form of a transistor, the source-drain section of which is connected in parallel to the operating voltage contacts of the first and second comparators. The second comparator and the transistor it controls form an active diode, which acts autonomously as a safety element outside the first control circuit. The active diode is operated by or with two bipolar reference voltages, each of which is supplied with a constant current. This makes the safety provided by the active diode highly reliable. Essentially, passive protection elements are an alternative protection option to the proposed active diodes, but they are highly current-dependent and therefore may exceed the set voltage limit.

[0019] If the specified voltage difference, for example 1.8V, is exceeded and the first control circuit is not activated, or if it is activated but is unable to effectively reduce the power surge, an active diode switch, i.e., a transistor short circuit, occurs, allowing the accumulated charge in the second capacitor to drain through the transistor, through which the power surge can be dissipated.

[0020] All components and features which advantageously further develop the electrical switching device according to the invention, as well as their function, are explained below with reference to specific switching topologies. [Brief explanation of the drawings]

[0021] The invention will now be described by way of example below with reference to the drawings, by way of example of an embodiment, without limiting the general inventive concept. [Figure 1] The switching topology and potentials are shown. DETAILED DESCRIPTION OF THE INVENTION

[0022] Figure 1 shows the switching topology of an electrical switching device with a charge pump NCP, whose operation, i.e., its activation and deactivation, is controlled by two redundantly coordinated control circuits. Directly adjacent to the switching topology, voltage or potential values ​​are indicated along the voltage axis. Thus, the first potential V1 is 0 V, which also corresponds to ground potential GND. Positive potential values ​​marked upward along the voltage axis lead to the designated second potential V2 of 18 V.

[0023] Using the charge pump NCP, the goal is to convert or transform a voltage difference of 1.8 V from a low voltage range VD_base, for example, 0 V to 1.8 V, to a high voltage range VD_hv, for example, 16.2 to 18 V. For completeness, negative potential values, 0 V to -18 V, are also shown to make it clear that with properly designed switching devices, it is also possible to perform voltage conversion in the negative voltage range. The following description is limited to voltage conversion in the positive potential range.

[0024] The charge pump NCP has two connection contacts a1, a2, the first connection contact a1 being connected to a first potential V1=0 V and the second connection contact a2 being connected to a second potential V2=18 V, higher than the first potential V1, via a series circuit comprising a first capacitor C1, a second capacitor C2 and a first diode D1 arranged between the two capacitors C1, C2. Furthermore, for controlled charge dissipation from the first capacitor C1, a current path having a switch in the form of a diode D4 is provided in parallel with the second capacitor C2 and the first diode D2 between the first capacitor C1 and the high potential, in a manner similar to that of a conventional Dickson charge pump.

[0025] The charge pump NCP has an oscillator O1 having an input and an output, and an electronic driver T1, the input of the oscillator O1 being connected to a third connection contact a3 of the charge pump NCP, and its output being connected to the driver T1, the output assigned to the driver T1 forming a second connection contact a2 directly connected to the first capacitor C1.

[0026] The third connection contact a3 of the charge pump NCP is connected to the output AK1 of the first comparator K1. If the first comparator K1 is arranged in the high-voltage domain and the charge pump NCP is arranged in the low-voltage domain, a level converter, i.e., a level shifter, is arranged between the connection contact a3 of the charge pump NCP and the output AK1 of the first comparator K1, and may optionally be part of the comparator K1 and / or the charge pump NCP.

[0027] The first comparator K1 has two comparator inputs K1- and K1+, the first of which is connected to the anode potential refP of a second diode D2, to which a second potential V2 is applied, and which is connected in series with the first diode D2 and in parallel with a second capacitor C2. The second comparator input K1+ of the first comparator K1 is connected to the cathode potential refN of a third diode D3, the anode of which is connected to the second potential V2, the cathode of which is connected to the first potential V1 via a constant load R. A constant current source KS1 is arranged between the constant load R and the first potential V1. A further constant current source KS1', mirrored with respect to the first constant current source KS1, is connected to the anode of the second diode D2, the cathode of which is connected to the anode of the first diode D1. Furthermore, the first comparator K1 has two operating voltage contacts B1, B2, the first operating voltage contact B1 being connected to the cathode of the second diode D2, and the second operating voltage contact B2 being connected to the second potential V2.

[0028] Finally, the first comparator K1 is connected via a further control input to an output APOR or reset switch (POR = power on reset), which has two operating voltage contacts B5, B6 connected in parallel to the operating voltage contacts B1, B2 of the first comparator K1.

[0029] Therefore, the first control circuit R1 for controlling the charge pump NCP is composed of a first comparator K1, a charge pump NCO, and first and second capacitors C1, C2 connected thereto, and the cathode potential refN of the third diode D3 and the anode potential refP of the second diode D3 form the basis of control as control variables.

[0030] To realize a second control circuit R2 that further controls the operation of the charge pump NPC and becomes active when the first control circuit R1 is not operating sufficiently, a second comparator K2 is provided, whose operating voltage contacts B3, B4 are connected in parallel to the operating voltage contacts B1, B2 of the first comparator K1. The second comparator K2 has two comparator inputs K2-, K2+, of which the first comparator input K2- is connected to the anode potential refP of the second diode D2 and the second comparator input K2+ is connected to a reference potential refL generated between the load R and the first constant current source KS1.

[0031] The second comparator K2 controls, via its output AK2, a transistor T, the source-drain of which is connected in parallel to the operating voltage nodes B1, B2, B3, B4 of the first and second comparators K1, K2. The load RL connected in parallel to the second capacitor C2 and all operating voltage contacts B1, B2, B3, B4 of the first and second comparators K1, K2 represents a switching device and constitutes a local dissipation element that ensures instantaneous charge equalization and an associated voltage drop on the second capacitor as VD_hv decreases. The first comparator detects this voltage drop and subsequently switches on the oscillator O1 to replenish the charge.

[0032] Switching device operation When the charge pump NCP is switched on, it is assumed that the high voltage region is not yet established, i.e. VD_hv ~ 0V.

[0033] The ON step simply involves activating a bias current through the current source KS1. This current generates the reference voltages refN and refL. The additional reference voltage refP is not yet formed, given that the voltage difference VD is still smaller than the diode voltage of approximately 0.8 V.

[0034] The first comparator K1 connected to the charge pump NCP is the only signal connection between the low-voltage and high-voltage domains. To ensure a successful switch-on procedure (start-up or ramp-up), the first comparator K1 is pre-configured by a global reset signal received by the first comparator K1 from a reset switch (POR = power-on reset). The first comparator K1 enables the oscillator O1 in the charge pump NCP to start and is turned on, i.e., charge is drawn from the second capacitor C2 and pumped via the driver T1 and the first capacitor C1.

[0035] The charge pump NCP operates as a negative charge pump and is supplied from two different voltage domains: on the one hand, the base domain (VDD - VSS = 1.8 V) corresponding to the low-voltage domain VD_base, and on the other hand, the battery voltage domain VBAT - VSSBAT = 3 to 4.2 V. VSSBAT is always VSS, corresponding to the ground potential GND. The driver T1, which charges the first capacitor C1, is connected to the battery voltage domain VBAT / VSSBAT, i.e., a square-wave signal between VSSBAT and VBAT is applied to the second connection contact a2 of the charge pump NCP. Since the connection point of the fourth diode D4 to the first capacitor C1 and the equalizing diode D1 is a high-resistance node, the potential V4 changes there in a short time with transitions having approximately the same amplitude as the potential on the connection contact a2 of the charge pump NCP. Only when the potential V4 reaches or exceeds the sum of the second potential V2 and the threshold voltage assigned to the fourth diode D4 does the fourth diode D4 open, through which excess charge flows from the first capacitor C1 to V2, thereby allowing a charge flow to occur in the next phase that pumps charge from the second capacitor C2.

[0036] As a result of this charge dissipation, for the most recent potential shift on capacitor C1, a charge imbalance occurs between the first capacitor C1 and the second capacitor C2, which acts as a charge equalization driver, causing charge from the second capacitor C2 to reach the first capacitor C1. Furthermore, the voltage difference between V2 and C3 increases.

[0037] Through pumping charge from the second capacitor C2, the voltage difference CD increases across the second capacitor C2. During this "ramp-up" phase, the reset switch POR monitors the conditions at the first and second comparators. Only upon achieving a certain "ramp-up" rate (transient in V / s) and a voltage difference VD of approximately 1 V does the reset switch POR transfer periodic operation to the first and second comparators K1, K2 for further control of the charge pump.

[0038] The voltage difference VD is already high enough that the reference voltage refP also provides a measurable voltage, which increases linearly with VD. When the reference voltage refP overlaps the reference voltage refN, the first comparator K1 becomes active and switches the charge pump NCP to the OFF state. Generally, only small bias currents for the reference, sensor, and comparators K1 and K2 flow into the high-voltage region VD_hv. Here, refN and refL are the references, and refP is the sensor. In this way, if the dissipation element RL is not active (e.g., RL is very resistant), the change to ON operation (due to inherent use) can be delayed as long as possible.

[0039] The dissipation element RL, connected in parallel to the second capacitor C2, is equivalent to a switching device located between V2 and V3 and drawing current from the second capacitor C2 as the voltage difference VD decreases. As the reference voltage refP linearly follows the voltage difference VD, it reaches the intersection of potentials refN and refP, at which point refP becomes less than the reference value refN, and the first comparator K1 switches the charge pump NCP back on.

[0040] The dynamics of the so-called "ramp up" and "ramp down" phases depend on various factors, for example, the capacitances of capacitors C1 and C2 and the frequency of oscillator O1, according to which transients occur on the second capacitor C2, resulting in temporary voltage changes.

[0041] If excessively rapid transients and / or constant on-states cause the voltage difference VD to leave its normal operating range and the first comparator K1 is unable to prevent this, individual components may be destroyed. In this case, the active diode AD, i.e., the second comparator K2, in combination with the transistor T, acts as a protection mechanism, blocking the current VD by switching the transistor T through the second capacitor C2. In this case, the transistor T opens, causing a short circuit, through which charge flows out of the transistor. The transistor continues to switch until the hysteresis of the second comparator K2 drops again. [Explanation of symbols]

[0042] R1 First control circuit R2 Second control circuit NCP Charge Pump C1 First capacitor C2 Second capacitor D1, D2, D3, D4 1st, 2nd, 3rd, 4th diodes refN, refPrefL reference voltage B1, B2, B3, B4, B5, B6 Operating voltage contacts K1, K2 1st and 2nd comparator a1, a2, a3 connection contacts K1-, K1+; K2-, K2+ comparator inputs AK1, AK2 comparator outputs KS1, KS1' constant current source POR Reset Switch APOR Output Reset Switch AD Active Diode R, RL load V1, V2, V3, V4 1st, 2nd, 3rd, 4th voltage O1 Oscillator T1 Driver T transistor

Claims

1. 1. An electrical switching device comprising a charge pump (NCP), The charge pump has at least two connection contacts (a1, a2), Of the at least two connection contacts, a first connection contact (a1) is connected to a first voltage potential (V1), and a second connection contact (a2) is connected to a second voltage potential (V2) higher than the first voltage potential (V1) via a series circuit including at least one first capacitor (C1), a second capacitor (C2), and a first diode (D1) arranged between the two capacitors, and is also connected to the first capacitor (C1) via a switching element; the charge pump (NCP) has a third connection contact (a3); the third connecting contact (a3) ​​is connected to the output (AK1) of a first comparator (K1) having first and second comparator inputs (K1-, K1+); the first comparator input (K1-) is connected to an anode potential (refP) of a second diode (D2) to which the second voltage potential (V2) is applied, the second diode (D2) is connected in series with the first diode (D1) and in parallel with the second capacitor (C1); the second comparator input (K1+) is connected to the cathode potential (refN) of a third diode (D3) to which the second voltage potential (V2) is applied, the anode of which is assigned to the third diode (D3); Electrical switching devices.

2. 2. The electrical switching device of claim 1, wherein the cathode of the third diode (D1) is connected to the first potential (V1) via a constant load (R).

3. 3. An electrical switching device according to claim 2, wherein a first constant current source (KS1) is arranged between said constant load (R) and said first potential (V1).

4. the anode assigned to the second diode (D2) is connected to the second potential (V2) via a constant current source (KS1'), the anode of which is connected to the anode assigned to the first diode (D1); 4. An electrical switching device according to any one of claims 1 to 3.

5. The charge pump (NCP) comprises an oscillator (O1) having an input and an output, and an electronic driver (T1); The input of the oscillator (O1) is connected to the third connection contact (a3), and the output of the oscillator (O1) is connected to the driver (T1); the output assigned to the driver (T1) corresponds to the second connection contact (a2) of the charge pump (NCP); 5. An electrical switching device according to any one of claims 1 to 4.

6. the first comparator (K1) has two operating voltage contacts (B1, B2), one of which (B1) is connected to the cathode assigned to the second diode (D2) and the other of which (B2) is connected to the second potential (V2); 6. An electrical switching device according to any one of claims 1 to 5.

7. the operating voltage contacts (B1, B2) of the first comparator (K1) are connected in parallel to the operating voltage contacts (B3, B4) of a second comparator (K2) having first and second comparator inputs (K2-, K2+); The first comparator input (K2-) is connected to the anode potential (refP) of the second diode (D2) to which the second potential (V2) is applied, the second comparator input (K2+) is connected to a reference potential (refL) generated between the load (R) and the first supply potential (V1); an output (AK2) assigned to the second comparator (K2) controls a transistor (T) whose source-drain section is connected in parallel to the operating voltage contacts (B1, B2, B3, B4) of the first and second comparators (K1, K2); 7. The electrical switching device of claim 6.

8. the first comparator (K1) is connected to the output (APOR) of a reset switch (POR = power on reset) having two operating voltage contacts (B5, B6) connected in parallel to the operating voltage contacts (B1, B2) of the first comparator (K1); 8. An electrical switching device according to claim 6 or 7.

9. a second constant current path (KS1′) is disposed between the second potential (V2) and the second diode (D2); 9. An electrical switching device according to any one of claims 1 to 8.

10. the switching element is connected in parallel to the first diode (D1) and the second capacitor (C2) between the second potential (V2) and the first capacitor (C1); 10. An electrical switching device according to any one of claims 1 to 9.

11. the switching element is designed as a fourth diode (D4) connected flow-wise to the second potential (V2) in order to discharge the first capacitor (C1); 11. An electrical switching device according to any one of claims 1 to 10.

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