Level-increasing switching arrangement with a charge pump
Patent Information
- Application Number
- EP2024706953
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-20
- Filing Date
- 2024-02-16
- Publication Date
- 2025-12-31
AI Technical Summary
Existing electrical circuit arrangements with charge pumps face challenges in achieving high operational safety, energy efficiency, and miniaturization, particularly in applications like implantable electronic devices that require reliable voltage conversion and efficient energy use.
The proposed electrical circuit arrangement features a charge pump with a novel configuration where components for voltage regulation are in a higher voltage domain, and the charge pump itself operates in a lower voltage domain, utilizing a first comparator and diodes for controlled activation and deactivation, and an optional second control loop with an active diode for overvoltage protection, ensuring minimal current flow and enhanced reliability.
This configuration enables efficient voltage conversion with minimal current bias, maintaining power efficiency and operational reliability by controlling the charge pump's activation and deactivating, and providing robust overvoltage protection, thus improving the circuit's performance in generating high output voltages.
Smart Images
Figure EP2024053979_29082024_PF_FP_ABST
Abstract
Description
[0001] Electrical circuit arrangement with a charge pump
[0002] Technical area
[0003] The invention relates to an electrical circuit arrangement with a charge pump, with which it is possible to generate preferably electrical direct voltages in the form of operating voltages for the control or operation of different electrical components as required.
[0004] State of the art
[0005] Electrical circuits, also commonly referred to as voltage converters, are powered by an input voltage. Different output voltages can be generated using capacitors whose charging is coordinated by periodically switching switches. Depending on the circuit type, either higher output voltages with the same polarity or a negative output voltage compared to the input voltage can be generated. An oscillator is typically used to periodically switch the switches.
[0006] The book "On-chip High-Voltage Generator Design: Design Methodology for Charge Pumps," published by Tanzawa and Springer in 2015, explains a variety of well-known circuit arrangements using charge pumps. Among these, the so-called "Dickson charge pump" is of particular interest due to its simple control for integrated circuits. A particularly preferred application requiring the use of charge pumps of this type concerns implantable electronic devices used to treat various types of neurological disorders by stimulating nerves with electrical charge. The electrical circuit arrangements underlying these implants represent multifunctional, highly integrated circuits designed for maximum operational reliability, maximum energy efficiency, and the greatest possible miniaturization.
[0007] Description of the invention
[0008] The invention is based on the object of developing an electrical circuit arrangement with a charge pump in such a way that at least one property underlying the above-mentioned design objectives, relating to operational reliability, energy efficiency and miniaturizability, is to be significantly improved compared to previously realized, generic circuit arrangements.
[0009] The solution to the problem underlying the invention is defined in claim 1. Features that advantageously further develop the inventive concept are the subject of the dependent claims and the further description, in particular with reference to the figures.
[0010] The electrical circuit arrangement according to the solution provides a charge pump with at least two connection contacts, of which a first connection contact is connected to a first voltage potential and a second connection contact is connected to a second voltage potential higher than the first voltage potential via a series circuit having at least a first capacitor, a second capacitor, and a first diode arranged between the two capacitors. The second voltage potential is connected to the first capacitor via a switching unit. Furthermore, the charge pump has a third connection contact, which is connected to an output of a first comparator having two comparator inputs, i.e., a first and a second comparator input.The first comparator input of the comparator is connected to an anode potential of a second diode, to which the second voltage potential is applied and which is further connected in series with the first diode and in parallel with the second capacitor. The second comparator input of the comparator, on the other hand, is connected to a cathode potential of a third diode, to whose associated anode the second voltage potential is applied.
[0011] The circuit arrangement according to the invention is based on a novel arrangement concept, according to which the charge pump is arranged in a low voltage domain within the circuit arrangement, which corresponds to a predetermined voltage potential, i.e., the input voltage. In contrast, all electrical components responsible for regulating the charge pump are arranged in a higher voltage domain within the circuit arrangement, i.e., the voltage domain that is established by means of voltage conversion by the charge pump.
[0012] Although we will refer to a lower and a higher voltage domain in the following, the circuit arrangement according to the solution also makes it possible to create a numerically lower voltage domain starting from a given negative voltage domain through inverted voltage conversion. This case is also covered by the circuit arrangement according to the solution.
[0013] In order to achieve an essential functional objective of the circuit arrangement, a voltage difference of, for example, 1.8 V must be transferred from a low voltage domain to a higher voltage domain, whereby it must be ensured that the voltage difference of 1.8 V converted or transformed into the higher voltage domain is maintained, i.e. the voltage conversion by means of the charge pump must be controlled such that the charge pump remains activated until the voltage difference of, for example, 1.8 V has been completely mapped or converted into a higher voltage domain. For example, the voltage difference in the lower voltage domain relates to potential values from 0V to 1.8 V and in the upper voltage domain, for example, 11 V to 12.8 V. The reference points of the respective lower and higher voltage domains can preferably differ from one another by up to 18 V and more, i.e. up to 60 V, but they can also overlap.In the example above, the reference points are 0 V and 11 V.
[0014] The control or activation and deactivation of the charge pump is carried out in a controlled manner within the framework of a first control circuit, which essentially consists of the first comparator and the second and third diodes, which primarily serve as reference potential generators and are all arranged in the region of the higher voltage domain of the circuit arrangement, which is formed by the successive charge accumulation in the second capacitor.
[0015] In contrast, the charge pump itself is located in the lower voltage domain.
[0016] This means that the current flow required for regulation between the lower and higher voltage domains is minimal; only a small current bias is required for regulation. This allows the individual circuit sections—"ON," meaning the charge pump is activated, and "OFF," meaning the charge pump is deactivated—to operate with minimal supply voltage, making them highly power-efficient.
[0017] Preferably, the so-called first comparator determining the first control circuit has two operating voltage contacts, of which one operating voltage contact is connected to the cathode associated with the second diode and the other operating voltage contact is connected to the second voltage potential.
[0018] If an overvoltage is detected by the first comparator, it generates a corresponding comparator signal, which is transformed from the upper to the lower voltage domain and applied to a terminal of the charge pump, deactivating or turning it off. This reduces the overvoltage through the internal consumption of the loads connected to this voltage domain. A conventional level shifter, connected between the first comparator and the charge pump or as part of the comparator and / or the charge pump, is suitable for converting the comparator signal from the upper to the lower voltage domain.
[0019] If the charge pump continues to pump, either intentionally or incorrectly, or if another event increases the overvoltage unintentionally, the voltage must be limited.
[0020] To further improve the operational reliability of the circuit arrangement, a second control loop is optionally provided in the upper voltage domain of the circuit arrangement in addition to the first ON-OFF control loop. If the overvoltage exceeds a maximum value, a switch is activated, instantly reducing the voltage difference.
[0021] For this purpose, the operating voltage contacts of a second comparator, which has a first and a second comparator input, are connected in parallel to the operating voltage contacts of the first comparator. The first
[0022] The comparator input of the second comparator is connected to the anode potential of the second diode, similar to the first comparator input of the first comparator. The second comparator input of the second comparator is connected to a reference potential formed between a load and the first supply potential, the load being a constant load connected between the third diode and the first voltage potential.
[0023] The output of the second comparator controls a switch in the form of a transistor, whose associated source-drain path is connected in parallel to the operating voltage contacts of the first and second comparators. The second comparator and the transistor controlled by it form an active diode, which serves autonomously outside the first control loop as a safety element. The active diode is supplied with, or driven by, bipolar reference voltages from two diodes, each supplied with a constant current, thus ensuring a very high level of reliability of the safety feature implemented by the active diode. While the provision of passive protection elements fundamentally represents an alternative protection option to the proposed active diode, they are highly current-dependent, meaning that a set voltage limit could still be exceeded.
[0024] If the case occurs that the specified voltage difference of, for example, 1.8 V is exceeded and the first control circuit is not activated or is not able to effectively reduce the developing overvoltage despite activation, the active diode switches, ie the transistor short-circuits, whereby the electrical charge accumulated in the second capacitor can flow through the transistor and thus the overvoltage can be reduced.
[0025] All other components and features that advantageously further develop the electrical circuit arrangement according to the solution, as well as their mode of operation, are explained below with reference to a concrete circuit topology.
[0026] Brief description of the invention
[0027] The invention is described below, without limiting the general inventive concept, using an exemplary embodiment with reference to the drawing. It shows:
[0028] Fig. 1 Circuit topology with electrical potential information.
[0029] Ways of implementing the invention, industrial applicability
[0030] Figure 1 shows a circuit topology of an electrical circuit arrangement with a charge pump (NCP), whose operation—i.e., its activation and deactivation—is controlled by two redundant, coordinated control circuits. Directly adjacent to the circuit topology shown, electrical voltage or potential values are shown along a voltage axis. A first voltage potential V1 is located at 0V, which also corresponds to the ground potential GND. The positive potential values plotted upwards along the voltage axis extend up to a predetermined second voltage potential V2 of 18 V.
[0031] The goal is to use the NCP charge pump to convert or transform a voltage difference of 1.8 V from a lower voltage domain (VD_base, for example, from 0 V to 1.8 V) into a higher voltage domain (VD_hv, for example, from 16.2 V to 18 V). For the sake of completeness, negative potential values (0 V to -18 V) are also shown to illustrate that, with an appropriately designed circuit, voltage transformations in a negative voltage domain are also possible. The following description is limited to voltage transformations in the positive potential range.
[0032] The charge pump NCP has two connection contacts a1, a2, of which a first connection contact a1 is connected to the first voltage potential V1 = 0V and the second connection contact a2 is connected 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 to a second voltage potential V2 = 18 V which is higher than the first voltage potential V1. Furthermore, for the purpose of controlled charge discharge from the first capacitor C1, a current path with a switch in the form of a diode D4 is provided in parallel to the second capacitor C2 and the first diode D1, between the first capacitor C1 and the higher voltage potential, comparable to a conventional Dickson charge pump.
[0033] The charge pump NCP comprises an oscillator O1 with an input and output, as well as an electronic driver T1. The input of the oscillator O1 is connected to a third connection contact a3 of the charge pump NCP, and its output is connected to the driver T1. An output associated with the driver T1 forms the second connection contact a2, which is directly connected to the first capacitor C1.
[0034] The third connection contact a3 of the charge pump NCP is connected to an output AK1 of a first comparator K1. Since the first comparator K1 is located in the higher voltage domain and the charge pump NCP is located in the lower 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. This level shifter can optionally also be part of the comparator K1 and / or the charge pump NCP.
[0035] The first comparator K1 has two comparator inputs K1-, K1+, of which 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 and which is connected in series with the first diode D1 and parallel with the 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, to whose associated anode the second voltage potential V2 is applied and whose cathode is connected to the first voltage potential V1 via a constant load R. A first constant current source KS1 is arranged between the constant load R and the first voltage potential V1. A further constant current source KST, mirrored 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 associated with the first diode D1.In addition, the first comparator K1 has two operating voltage contacts B1, B2, of which a first operating voltage contact B1 is connected to the cathode of the second diode D2 and the second operating voltage contact B2 is connected to the second voltage potential V2.
[0036] Finally, the first comparator K1 is connected via a further control input to the output APOR of a reset circuit (POR = power on reset), which in turn has two operating voltage contacts B5, B6 connected in parallel to the operating voltage contacts B1, B2 of the first comparator K1. The first control circuit R1 controlling the charge pump NCP is thus composed of the first comparator K1, the charge pump NCO, and the first and second capacitors C1, C2 connected to it. The cathode potential refN of the third diode D3 and the anode potential refP of the second diode D2 form the basis of the control.
[0037] To implement a second control circuit R2 that additionally controls the activity of the charge pump NCP and becomes active when the first control circuit R1 is not operating satisfactorily, 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 that is established between the load R and the first constant current source KS1.
[0038] The second comparator K2 controls a transistor T via its output AK2, the associated source-drain path of which is connected in parallel to the operating voltage contacts B1, B2, B3, B4 of the first and second comparator K1, K2.
[0039] A 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 circuit arrangement and a local consumer that ensures instantaneous charge equalization and a corresponding voltage drop across the second capacitor, causing VD_hv to drop. The first comparator K1 detects this voltage drop and subsequently switches on the oscillator O1 to supply additional electrical charge.
[0040] How the circuit works:
[0041] When the charge pump NCP is switched on, it is assumed that an upper voltage domain has not yet developed, i.e., VD_hv ~ OV. The switching-on process itself involves only the activation of 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, especially since the voltage difference VD is still smaller than a diode voltage of approximately 0.8 V.
[0042] The first comparator K1, connected to the charge pump NCP, represents the only signal connection between the lower and upper voltage domains. To ensure a successful start-up or ramp-up, the first comparator K1 is preconfigured by a global reset signal that the first comparator K1 receives from the reset circuit (POR = power on reset). The first comparator K1 allows the oscillator O1 in the charge pump NCP to start and is placed in the ON state, meaning that electrical charge is drawn from the second capacitance C2 via the driver T1 and the first capacitance C1—it is "pumped."
[0043] The charge pump NCP operates as a negative charge pump and is supplied by two different voltage domains. Firstly, the base domain (VDD- VSS=1.8V), which corresponds to the lower voltage domain VD_base, and secondly, the battery voltage domain VBAT-VSSBAT=3 to 4.2V. VSSBAT is always VSS and corresponds 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 present at the second connection contact a2 of the charge pump NCP. Since the connection point of the fourth diode D4 with the first capacitor C1 and the diode D1 represents a high-impedance node in the balanced state, the potential V4 there changes briefly during the transitions with approximately the same amplitude as the potential at connection contact a2 of the charge pump NCP.Only when the potential V4 reaches or exceeds the second voltage potential V2 plus a threshold voltage assigned to the fourth diode D4 does the fourth diode D4 open, allowing excess charge to flow from the first capacitance C1 to V2. This can result in a charge flow in the subsequent phase, which pumps charge away from the second capacitance C2. As the charges flow away, the renewed potential shift in the capacitance C1 creates a charge imbalance between the first capacitance C1 and the second capacitance C2. This is the driving force for charge equalization, causing charges to flow from the second capacitance C2 to the first capacitance C1 and also increasing the voltage difference between V2 and V3.
[0044] By pumping charge from the second capacitor C2, the voltage difference VD across the second capacitor C2 increases. During this "ramp-up" phase, the reset circuit POR monitors the states in the first and second comparators K1, K2. Only when a certain "ramp-up" speed (transients in V / s) is reached and a voltage difference VD of approximately 1 V or higher does the reset circuit POR transfer regular operation to the first and second comparators K1, K2 for further control of the charge pump.
[0045] The voltage difference VD is already so high that the reference voltage refP also supplies a measurably correct voltage, which now increases linearly with VD. If the reference voltage refP overlaps the reference voltage refN, the first comparator K1 becomes active and transfers the charge pump NCP to the OFF state. Generally speaking, in the upper voltage range VD_hv, only a small bias current flows for the reference, sensor and the comparators K1, K2. Here, refN and refL represent the references and refP the sensor. In this way, it can be achieved that, if no consumer RL is active (i.e. RL is high-impedance), a change to ON operation (due to internal consumption) is delayed as long as possible.
[0046] The load RL, connected in parallel with the second capacitor C2, is synonymous with a circuit arrangement arranged between V2 and V3, which draws current from the second capacitor C2, thereby reducing the voltage difference VD. Since the reference voltage refP follows the voltage difference VD linearly, the intersection point between the potentials refN and refP is also reached, and refP falls below the reference voltage refN, so that the first comparator K1 returns the charge pump NCP to the ON state.
[0047] The dynamics of the so-called “ramp-up” and “ramp-down” phases depend on various factors, such as the capacitances C1 and C2 as well as the frequency of the oscillator O1. Depending on this, the transient is formed at the second capacitance C2, with which voltage changes take place over time.
[0048] If the voltage difference VD leaves the normal operating range due to an excessively fast transient and / or continuous ON operation, and the first comparator K1 is still unable to prevent this, individual components could be destroyed. In this case, the active diode AD, i.e. the second comparator K2 in conjunction with the transistor T, serves as a protective mechanism that collapses the voltage VD by switching the transistor T across the second capacitor C2. In this case, the transistor T opens and forces a short circuit, causing the charge to flow through the transistor T. The transistor T continues to switch until the hysteresis of the second comparator K2 is again undershot.
[0049] List of reference symbols
[0050] R1 First control loop
[0051] R2 Second control loop
[0052] NCP charge pump
[0053] C1 First Capacity
[0054] C2 Second capacity
[0055] D1 , D2, D3, D4 First, second third, fourth diode refN, refP, refL Reference voltage
[0056] B1, B2, B3, B4, B5, B6 operating voltage contacts
[0057] K1 , K2 First, Second Comparator a1 , a2, a3 Connection contacts
[0058] K1 -, K1 +; K2-, K2+ comparator inputs
[0059] AK1 , AK2 comparator outputs
[0060] KS1, KST constant current sources
[0061] POR reset circuit
[0062] APOR output reset circuit
[0063] AD Active Diode
[0064] R, RL loads
[0065] V1, V2, V3, V4 First, second, third, fourth voltage potential
[0066] 01 Oscillator
[0067] T1 driver
[0068] T Transistor
Claims
Patent claims 1. An electrical circuit arrangement comprising a charge pump (NCP) having at least two terminal contacts (a1, a2), of which a first terminal contact (a1) is connected to a first voltage potential (V1) and a second terminal contact (a2) is connected via a series circuit having at least a first capacitor (C1), a second capacitor (C2) and a first diode (D1) arranged between the two capacitors to a second voltage potential (V2) which is higher than the first voltage potential (V1), and which is also connected to the first capacitor (C1) via a switching element, wherein the charge pump (NCP) has a third terminal contact (a3) which is connected to an output (AK1) of a first comparator (K1) having first and second comparator inputs (K1-, K1+), of which 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 and which is connected in series with the first diode (D1 ) and in parallel with the second capacitor (C2), and of which the second comparator input (K1 +) is connected to a cathode potential (refN) of a third diode (D3), to whose associated anode the second voltage potential (V2) is applied.
2. Electrical circuit arrangement according to claim 1, characterized in that the cathode of the third diode (D1) is connected to the first voltage potential (V1) via a constant load (R).
3. Electrical circuit arrangement according to claim 2, characterized in that a first constant current source (KS1) is arranged between the constant load (R) and the first voltage potential (V1).
4. Electrical circuit arrangement according to one of claims 1 to 3, characterized in that the anode assigned to the second diode (D2) is connected via a constant current source (KS1 ') to the second voltage potential (V2) and its cathode is connected to the anode assigned to the first diode (D1).
5. Electrical circuit arrangement according to one of claims 1 to 4, characterized in that the charge pump (NCP) comprises an oscillator (01) with an input and output and an electronic driver (T1), that the input of the oscillator (01) is connected to the third connection contact (a3) and its output is connected to the driver (T1), and that an output assigned to the driver (T1) corresponds to the second connection contact (a2) of the charge pump (NCP).
6. Electrical circuit arrangement according to one of claims 1 to 5, characterized in that the first comparator (K1) has two operating voltage contacts (B1, B2), of which one operating voltage contact (B1) is connected to the cathode associated with the second diode (D2) and the other operating voltage contact (B2) is connected to the second voltage potential (V2).
7. Electrical circuit arrangement according to claim 6, characterized in that the operating voltage contacts (B1, B2) of the first comparator (K1) are connected in parallel to operating voltage contacts (B3, B4) of a second comparator (K2) which has a first and a second comparator input (K2-, K2+), of which the first comparator input (K2-) is connected to the anode potential (refP) of the second diode (D2), to which the second voltage potential (V2) is applied, and of which the second comparator input (K2+) is connected to a reference potential (refL) which is built up between the load (R) and the first supply potential (V1), and in that an output (AK2) assigned to the second comparator (K2) has a Transistor (T) controls the associated source-drain path of which is connected in parallel to the operating voltage contacts (B1, B2, B3, B4) of the first and second comparator (K1, K2).
8. Electrical circuit arrangement according to claim 6 or 7, characterized in that the first comparator (K1) is connected to an output (APOR) of a reset circuit (POR = power on reset) which has two operating voltage contacts (B5, B6) which are connected in parallel to the operating voltage contacts (B1, B2) of the first comparator (K1).
9. Electrical circuit arrangement according to one of claims 1 to 8, characterized in that a second constant current source (KST) is arranged between the second voltage potential (V2) and the second diode (D2).
10. Electrical circuit arrangement according to one of claims 1 to 9, characterized in that the switching element is connected in parallel to the first diode (D1) and the second capacitor (C2) between the second voltage potential (V2) and the first capacitor (C1).
11. Electrical circuit arrangement according to one of claims 1 to 10, characterized in that the switching element is designed as a fourth diode (D4) which is connected to the second voltage potential (V2) for discharging the first capacitor (C1) in the forward direction.