Voltage clamping device and method

Abstract

Method for protecting transistors in a DC / DC converter circuit (104), wherein the transistors in the DC / DC converter circuit (104) comprise a first transistor (270) and a second transistor (272), wherein converted energy is passed through an H-bridge circuit (204) and through a transformer (206), the method comprising: In the first operating state of the H-bridge circuit (204): Activating a third transistor (254) in a protection circuit (210) to discharge an inductor (256) in the DC / DC converter circuit (104) which was previously charged, wherein the inductor (256) is coupled to the third transistor (254), wherein the discharge of the inductor (256) amplifies an output current of the DC / DC converter circuit (104); Charging a capacitor (249) by means of a diode (240), wherein the capacitor (249) and the diode (240) are arranged in the protection circuit (210), wherein the diode (240) is coupled to the first transistor (270), wherein the charging of the capacitor (249) causes the voltage across the first transistor (270) to be limited, the procedure further includes: In a second operating state of the H-bridge circuit (204): Activating the first transistor (270); Continue to fully discharge the coil (256), thereby increasing the output current of the DC / DC converter circuit (104); Discharging the capacitor (249) by activating a fourth transistor (242) in the protection circuit (210), wherein the fourth transistor (242) is coupled to the diode (240), wherein the activation of the fourth transistor (242) charges a second coil (246) coupled to the fourth transistor (242).

Description

Technical field

[0001] This application concerns energy conversion circuits, and in particular protective devices in these circuits. Background of the invention

[0002] Batteries (and sometimes multiple batteries) are used to supply energy to various types of systems. For example, batteries are used to power electric vehicles or hybrid electric vehicles. The batteries in these systems can be arranged as battery packs, providing voltages in the range of 150–600 volts.

[0003] However, equipment used in the same vehicle typically requires voltages much lower than 150-600 volts. Therefore, the vehicle must have a conversion device or circuit that reduces the battery voltage to a usable level. One such usable conversion system is a DC / DC converter. In some cases, the DC / DC converter reduces the voltage from the 150-600 volt range to 12 volts (or less).

[0004] Despite using DC / DC converters, these typically have operational problems and limitations. For example, the conversion circuitry in a DC / DC converter typically uses transistors. If the applied voltage is too high, transistors can be damaged or destroyed. Some earlier solutions relied solely on resistors, capacitors, and diodes to limit the voltages that could be applied to the transistors. However, this approach wastes energy that could be used as excess power in the system, as the voltage is simply consumed by the resistor. Electric or hybrid vehicles must use energy as efficiently as possible, and wasting energy hinders this goal.

[0005] DE 10 2012 202 869 A1 discloses a DC-DC converter with a transformer having a primary winding and a secondary winding with a center tap, a storage choke coupled between the center tap and a first output of the DC-DC converter, a rectifier circuit connected to the end taps of the secondary winding and designed to generate a rectified output voltage at a second output of the DC-DC converter, a snubber circuit connected via the rectifier circuit designed to store resonant vibration energy occurring in the rectifier circuit, and a control device.

[0006] Overall, previous attempts to overcome these problems were generally unsuccessful. These earlier systems and solutions resulted in poor energy conversion performance, ultimately leading to customer dissatisfaction or a lack of customer interest. Brief description of the drawings

[0007] For a more complete understanding of the revelation, the following detailed description and accompanying drawings should be consulted, whereby: Fig. 1 comprising a block diagram of a system which uses a DC / DC conversion circuit with overvoltage protection, in accordance with various embodiments of the present invention; Fig. 2. A circuit diagram of a voltage conversion circuit comprising a protection circuit which limits voltages across the transistors of the DC / DC conversion circuits, in accordance with various embodiments of the present invention; and Fig. 3 comprises three curves which show the operation of the voltage limiting methods for transistors in DC / DC conversion circuits, in accordance with different embodiments of the present invention.

[0008] The person skilled in the art will recognize that elements in the figures are depicted accordingly for the sake of simplicity and clarity. It is also assumed that the terms used herein retain their original meanings in relation to their respective fields of application, unless specific meanings are expressly stated herein. Detailed description

[0009] This document describes methods for clamping or limiting voltages applied to transistors in a DC / DC conversion circuit. Specifically, a battery circuit (for example, a battery pack) supplies a DC / DC conversion circuit with voltage, current, and energy. The DC / DC conversion circuit converts the high DC voltage of the battery into a reduced voltage. This function is partially achieved through the use of transistors. A voltage protection circuit limits the voltage applied to the transistors. The method uses combinations of transistors, capacitors, inductors, and diodes to actively limit the voltage across the driver transistors of the DC / DC conversion circuit. The methods described herein also perform energy recovery. In other words, the energy that is not supplied to the transistors is recovered.Where an energy supply has been prevented, it is stored and then consumed by loads (for example, vehicle equipment) which are coupled to the DC / DC conversion circuit so that it is not lost (for example, consumed by resistors).

[0010] In many of these embodiments, a protection circuit safeguards transistors in a DC / DC conversion circuit from overvoltages. The transistors in the conversion circuit comprise a first transistor and a second transistor. Converted energy is passed through a transformer and an H-bridge circuit. In a first operating state of the H-bridge circuit, a third transistor in the protection circuit is activated to discharge a previously charged inductor in the DC / DC conversion circuit. The inductor is coupled to the third transistor. Discharging the inductor amplifies an output current of the conversion circuit. A capacitor is charged via a diode. The capacitor and diode are located in the protection circuit. The diode is coupled to the first transistor, and charging the capacitor limits the voltage across the first transistor.

[0011] Under further conditions and in a second operating state of the H-bridge circuit, the first transistor is activated. The inductor continues to discharge until completely discharged, thereby increasing the output current of the conversion circuit. The capacitor is discharged by activating a fourth transistor in the protection circuit, which is coupled to the diode. Activating the fourth transistor charges a second inductor, which is coupled to the fourth transistor.

[0012] In other aspects, the H-bridge uses four transistors, which can be selectively activated. In further examples, the output current is used by or consumed from a load. In still other examples, the load comprises an auxiliary vehicle device.

[0013] In other respects, a battery supplies the H-bridge circuit with voltage. In yet other respects, the battery is a battery pack in a hybrid vehicle or an electric vehicle.

[0014] Now with reference to Fig. In Figure 1, a system is described which provides overvoltage protection for transistors. The system 100 comprises a battery 102, a transformation circuit 104, and auxiliary equipment 106. This exemplary system is designed and arranged for use in a vehicle; however, it is preferred that it can also be used in other applications or in other environments not limited to vehicles.

[0015] The 102 battery can consist of one or more batteries. When using one or more batteries, the individual batteries are connected together in a battery pack to generate a direct current (DC) voltage and current. For example, the voltage can range from 150 to 600 volts DC when the battery pack is used in an electric or hybrid vehicle.

[0016] The transformation circuit 104 transforms the voltage from the battery 102 into a lower (or higher) voltage. In one example, the transformation circuit 104 is a DC / DC converter that uses an H-bridge to pass energy through a transformer. A rectifier circuit within the DC / DC converter rectifies the voltage, the rectifier circuit comprising one or more transistors that transfer or conduct the rectified voltage (and current) to the auxiliary equipment 106. For example, 200 volts DC are converted into 12 volts DC. Other examples are possible.

[0017] The rectifier circuit is coupled to a voltage limiting or protection circuit, which clamps or otherwise limits the voltage that can be applied to these transistors and also controls the activated transistors. The protection circuit not only limits the voltage applied to the transistors but also performs energy recovery. In other words, the energy not applied to the transistors is stored and then consumed by loads (for example, vehicle accessory 106) that are coupled to the DC / DC conversion circuit. The structure and use of this protection circuit are described in detail elsewhere.

[0018] Now with reference to Fig. Figure 2 describes a circuit diagram with a protection circuit arranged in a DC / DC conversion circuit. The circuit comprises a battery pack 202, a bridge circuit 204 (H-bridge circuit), a transformer 206, a synchronous current doubling rectifier 208, and an overvoltage protection element or protection circuit 210. Transistor operation is controlled by a controller 212.

[0019] The bridge circuit 204 includes a first transistor 220 (M a ), a second transistor 222 (M b ), a third transistor 224 (M c ), a fourth transistor 226 (M d), a first diode 228 and a second diode 330. Transistors 220, 222, 224, and 226 operate in a first pair (transistors 220 and 226), a second pair (transistors 220 and 224), a third pair (224 and 222), and a fourth pair (222 and 226). That is, full-bridge transistors are switched on and off in pairs to alternately charge and discharge the transformer's primary winding, generating a waveform 232. The waveform 232 is the alternating voltage transformed by transformer 206, which is then rectified and supplied to the load 248. As mentioned earlier, the load 248 can be an auxiliary vehicle component (for example, windshield wipers, radio, speakers, lights, headlights, pumps, other batteries, or any combination of these elements, to name just a few).

[0020] The active protection circuit 210 will now be described. It includes a diode 240 (D s1), a transistor 242 (M s1a ), a transistor 244 (M s1b ), and a coil 246 (L s1 ). The coil 246 (L s1 ) is coupled to a load 248. A capacitor 249 (C s1 ) is connected to transistor 242 (M s1a ) and diode 240 (D s1 ) connected. The overvoltage protection element or protection circuit 210 includes a second diode 250 (D s2 ), a transistor 252 (M s2a ), a transistor 254 (M s2b ) and a coil 256 (L s2 ). The coil 256 (L s2 ) is coupled to the load 248. A capacitor 251 (C s2 ) is connected to transistor 252 (M s2a ) and the diode 250 (D s2 ) tied together.

[0021] The controller 212 is coupled to the various transistors and controls their operation. The controller 212 is programmed to selectively activate or deactivate the different transistors in the circuit.

[0022] The synchronous Doppler rectifier circuit 208 comprises a transistor 270 (M1), a transistor 272 (M2), an inductor 274 (L 01 ), another coil 276 (L 02 ) and a capacitor 278 (C0).

[0023] Now with reference to Fig. Section 3 describes several curves that show how the transistors are activated and deactivated. Fig. 3 assumes that the circuit consists of Fig. 2 is used, whereby the components which relate to Fig. 3 refer to, with reference to Fig. The two components described refer to the following. Three curves are shown: an upper curve, which shows the charging and discharging of coils, a middle curve, which shows the absolute value of the voltage (V). T ) at transistors 270 and 272 (M1 and M2), and a lower curve which shows the state of the different transistors in the system.

[0024] In a company example from Fig. 2 and also with reference to Fig. 3. Transistors 226 and 272 are activated from a previous operating state, transistors 220 and 254 are activated, and transistor 270 is deactivated by the controller 212. Transistor 254 allows a lossless discharge of the coil 256, which was charged in a previous state. Under the H-bridge configuration, the voltage between the drain and source of transistor 270 becomes positive, and thus diode 240 begins to charge capacitor 249, clamping the voltage "seen" by transistor 270 to a safe level. During this step, coil 274 is charged. These operating states occur between times t0 and t1 in Fig. 3 up.

[0025] In a subsequent operating step, the controller 226 deactivates transistor 226 and activates transistors 224, 270, and 242. Transistors 220, 272, and 254 remain in their original state (i.e., activated). With transistors 220 and 224 activated, the voltage across the secondary coil is zero, causing the current-doubling rectifier coils 274 and 276 to discharge. During this 0-volt state at the secondary coil, neither diode 240 nor diode 250 conducts. Transistor 242 is activated to discharge capacitor 249 without loss via coil 246, thus charging coil 246. These operating steps occur between times t1 and t2. Fig. 3 up.

[0026] Then, in a subsequent operating step, the controller 212 activates transistors 222 and 244 and deactivates transistors 272, 254, and 242. Transistors 224 and 270 remain in their original state (i.e., activated). Transistor 244 allows for a lossless discharge of coil 246, which was charged in a previous state.

[0027] When the H-bridge circuit is configured, the voltage between the drain and source of transistor 272 becomes positive, and therefore diode 250 begins to conduct to charge capacitor 251, effectively clamping the voltage "seen" by transistor 272 to a safe level. During this state, inductor 276 is charged. These operating steps occur between times t2 and t3. Fig. 3 up.

[0028] Then, in the last of four time-repeating steps, the controller 212 deactivates transistor 224 and activates transistors 226, 272, and 252. Transistors 222, 270, and 244 remain in an unchanged state (i.e., activated). With transistors 222 and 226 activated, the voltage across the secondary coil is zero, causing the current-doubling rectifier coils 274 and 276 to discharge. During this 0-volt operating state at the secondary coil, neither diode 240 nor diode 250 conducts. Transistor 252 is activated to discharge capacitor 251 through coil 256 without loss, thus charging coil 256. These operating steps occur between times t3 and t4. Fig. 3 up.

[0029] It is assumed that the control system or the external facilities comprising the load can use a computer system to implement various functionalities and operations of these facilities. With regard to hardware architecture, such a computer system can, but is not limited to, include a processor, memory, and one or more input and / or output (I / O) interfaces, which are communicatively coupled via a local interface. The local interface can, for example, but is not limited to, include one or more buses and / or other wired or wireless connections. The processor can be a hardware device for executing software, in particular software stored in memory.The processor can be a specifically manufactured or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors assigned to the computer system, a semiconductor-based microprocessor (in the form of a microchip or chipset), or generally any device for executing software instructions.

[0030] The memory devices described and used herein may include any of the following elements or a combination thereof: volatile memory elements (for example, random access memory (RAM), such as dynamic RAM (DRAM), static RAM (SRAM), synchronous dynamic RAM (SDRAM), video RAM (VRAM), etc.) and / or non-volatile memory elements (for example, read-only memory (ROM), a hard disk, a tape, a CD-ROM, etc.). Furthermore, the memory may include electronic, magnetic, optical, and / or other types of storage media. The memory may also have a distributed architecture, where different components are located remotely but are accessible to the processor.

[0031] The software described herein, contained in each of the storage devices, may comprise one or more separate programs, all of which contain an ordered list of executable instructions for implementing the functions described herein. When structured as a single source program, the program is translated by a compiler, assembler, interpreter, or the like, which may optionally be included in the memory.

[0032] It is preferred that each of the methods described herein be at least partially implementable as computer instructions stored on a computer medium (for example, a computer memory as described above), wherein these instructions are executable on a processing device, such as a microprocessor. These methods can be implemented as any combination of electronic hardware and / or software.

[0033] This document describes preferred embodiments of this invention, including the best embodiment known to the inventors for implementing the invention. It is understood that the embodiments described are merely exemplary and are not intended to limit the scope of the invention.

Claims

[1] Method for protecting transistors in a DC / DC converter circuit (104), wherein the transistors in the DC / DC converter circuit (104) comprise a first transistor (270) and a second transistor (272), wherein converted energy is passed through an H-bridge circuit (204) through a transformer (206), the method comprising: In the first operating state of the H-bridge circuit (204): Activating a third transistor (254) in a protection circuit (210) to discharge an inductor (256) in the DC / DC converter circuit (104) which was previously charged, wherein the inductor (256) is coupled to the third transistor (254), wherein the discharge of the inductor (256) amplifies an output current of the DC / DC converter circuit (104); Charging a capacitor (249) by means of a diode (240), wherein the capacitor (249) and the diode (240) are arranged in the protection circuit (210), wherein the diode (240) is coupled to the first transistor (270), wherein the charging of the capacitor (249) causes the voltage across the first transistor (270) to be limited, the procedure further includes: In a second operating state of the H-bridge circuit (204): Activating the first transistor (270); Continue to fully discharge the coil (256), thereby increasing the output current of the DC / DC converter circuit (104); Discharging the capacitor (249) by activating a fourth transistor (242) in the protection circuit (210), wherein the fourth transistor (242) is coupled to the diode (240), wherein the activation of the fourth transistor (242) charges a second coil (246) coupled to the fourth transistor (242). [2] Method according to claim 1, wherein the H-bridge circuit (204) uses four transistors (220, 222, 224, 226) which are selectively activated. [3] Method according to claim 1, wherein the output current is consumed by a load (248). [4] Method according to claim 3, wherein the load (248) comprises a vehicle accessory device. [5] Method according to claim 1, wherein a battery (202) supplies voltages to the H-bridge circuit (204). [6] Method according to claim 1, wherein the battery (202) is a battery pack in a hybrid vehicle or in an electric vehicle. [7] DC / DC converter circuit comprising: A first transistor (270) and a second transistor (272) for receiving converted energy applied to a transformer (206) by an H-bridge circuit (204), wherein the first transistor (270) and the second transistor (272) are coupled to a load (248); a coil (256); a protection circuit (210) which is coupled to the first transistor (270) and the second transistor (272), wherein the protection circuit (210) comprises a third transistor (254), a capacitor (249) and a diode (240), wherein the diode (240) is coupled to the first transistor (270); wherein in a first operating state of the H-bridge circuit (204) the third transistor (254) in the protection circuit (210) is activated to discharge the coil (256) which was previously charged, wherein the coil (256) is coupled to the third transistor (254), wherein the discharge of the coil (256) amplifies an output current of the DC / DC converter circuit (104), wherein the capacitor (249) is charged by the diode (240), wherein the capacitor (249) and the diode (240) are arranged in the protection circuit (210), and wherein the charging of the capacitor (249) causes the voltage across the first transistor (270) to limit, wherein in a second operating state of the H-bridge circuit (204) the first transistor (270) is activated, wherein the coil (256) continues to discharge completely, thereby increasing the output current of the DC / DC converter circuit, and wherein the capacitor (249) is discharged by activating a fourth transistor (242) in the protection circuit (210), wherein the fourth transistor (242) is coupled to the diode (240), wherein the activation of the fourth transistor (242) charges a second coil (246) coupled to the fourth transistor (242). [8] Circuit according to claim 7, wherein the H-bridge circuit (204) comprises four transistors (220, 222, 224, 226) which are selectively activated. [9] Circuit according to claim 7, wherein the output current is consumed by the load (248). [10] Circuit according to claim 9, wherein the load (248) comprises a vehicle accessory device. [11] Circuit according to claim 7, wherein a battery (202) supplies voltages to the H-bridge circuit (204). [12] Circuit according to claim 11, wherein the battery (202) is a battery pack in a hybrid vehicle or in an electric vehicle.

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