A high-power constant-current driver based on a composite Darlington circuit topology

Abstract

The present invention discloses a high-power constant current driver based on a novel composite Darlington circuit topology structure, which includes a power amplifier module and a voltage control module. The power amplifier module includes an input stage, an output stage and a feedback module. The output stage includes a first resistor, a first transistor connected in series with the first resistor, and a plurality of array transistors connected in parallel to the emitter of the first transistor. The base of the array transistor is connected to the emitter of the first transistor, the emitter of the array transistor is connected to the feedback module, the collector of the first transistor and the common collector of the array transistor form the output end of the constant current driver connected to the load, and the collector of the first transistor is connected to the output end of the voltage control module. The present invention realizes a high-power constant current driving function with high stability and high precision by setting an improved composite Darlington circuit and based on a deep feedback module at the output end of the composite Darlington circuit.

Description

[Technical field]

[0001] The invention relates to the technical field of power amplification driving of electric power systems, and in particular to a high-power constant-current driver based on a novel composite Darlington circuit topology structure. [Background technology]

[0002] With the development of modern science and technology, electronic technology has become an indispensable part of almost all production and life fields. As an indispensable driving device in various electronic circuits, stable power supply is called the heart of electronic equipment, and its demand is increasing day by day. In scientific practices such as project research and product development, the research and design of stable power supply is often one of the key technologies that need to be overcome. If a power supply that does not meet the standards is used in the design, it is likely to affect the progress of the entire scientific research project. Constant current source and voltage regulator are two major branches of stable power supply. Among them, constant current source, as a stable power supply, has a very broad development space in the field of power supply research. For example, it plays a very important role in many fields such as electronic instruments, laser technology, modern communication technology, electric light source technology, sensor technology and measurement technology. Although with the high development of microelectronics technology, many miniaturized and integrated high-precision constant current sources have emerged, there are currently few cost-effective high-power constant current drivers. In actual applications, users often need to design and implement them according to their needs.

[0003] Among the various fields where high-power constant current sources are widely used, the constant current drivers required in power system equipment have the highest requirements for performance indicators. In recent years, the output characteristics of constant current drivers have been greatly improved, especially with the gradual improvement of the performance of continuous output power, which has gradually expanded the application scope of high-power constant current drivers, mainly used in many aspects such as industry and power fields. From the application perspective of high-power constant current drivers, their quality and reliability play a vital role in the application system, which puts higher requirements on the performance of constant current drivers. Since the power density of constant current drivers is very large and the quantum efficiency is very high, they are greatly affected by current shocks. Especially for high-power constant current drivers, the changes in their various performance parameters seriously endanger the safety of high-power constant current drivers. [Summary of the invention]

[0004] The main purpose of the present invention is to provide a high-power constant-current driver based on a novel composite Darlington circuit topology structure, which can achieve a constant-current output with high stability.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions: a high-power constant current driver based on a novel composite Darlington circuit topology structure, comprising a power supply system, a power amplifier module electrically connected to the power supply system, and a voltage control module, wherein the power amplifier module comprises an input stage composed of a differential amplifier, an output stage connected to the input stage and composed of a power transistor array, and a feedback module for collecting voltage and current information of the output stage and feeding it back to the input stage, wherein the output stage comprises a first resistor connected to the output end of the differential amplifier, a first transistor connected in series with the first resistor, and a plurality of array transistors arranged in parallel and connected to the emitter of the first transistor, wherein the base of the array transistor is connected to the emitter of the first transistor, the emitter of the array transistor is connected to the feedback module, the collector of the first transistor and the common collector of the array transistor form the output end of the constant current driver connected to the load, and the output end of the voltage control module is connected to the input stage.

[0006] Furthermore, the input stage is a differential amplifier circuit.

[0007] Furthermore, a voltage-dividing resistor is arranged on the base of each of the array transistors.

[0008] Furthermore, the emitter terminals of the array transistors are provided with voltage-dividing resistors in one-to-one correspondence, and the other ends of the voltage-dividing resistors are grounded.

[0009] Furthermore, the feedback module includes a sampling resistor array connected to the emitters of the array transistors in a one-to-one correspondence, an operational amplifier connected to the sampling resistor array, and an output end of the operational amplifier is connected to the positive input end of the differential amplifier in the input stage.

[0010] Furthermore, it also includes a human-computer interaction module electrically connected to the power supply system and the voltage control module.

[0011] Furthermore, the power supply system includes a first power supply and a second power supply, one end of which is connected to the mains and the other end of which is grounded.

[0012] Furthermore, the voltage control module includes a reference voltage source, a current limiting circuit and a regulating circuit.

[0013] Compared with the prior art, the beneficial effect of the high-power constant-current driver based on the novel composite Darlington circuit topology structure of the present invention is that a high-stability and high-precision high-power constant-current driving function is achieved by setting an improved composite Darlington circuit and a combined topology structure, and based on a deep feedback module at the output end of the composite Darlington circuit.

Brief Description of the Drawings

[0014] Figure 1A schematic diagram of the structural principle of an embodiment of the present invention;

[0015] Figure 2 A schematic diagram of the structural principle of a power amplifier module in an embodiment of the present invention;

[0016] Figure 3 A schematic diagram of the location of a current-sharing resistor in a topological structure of a parallel power transistor array in an embodiment of the present invention;

[0017] Figure 4 A schematic diagram of another arrangement position of a current-sharing resistor in a topological structure of a parallel power transistor array in an embodiment of the present invention;

[0018] Figure 5 Schematic diagram of the structure principle of the voltage control module in an embodiment of the present invention. [Specific implementation method]

[0019] Example:

[0020] Please refer to Figure 1-Figure 5 This embodiment is a high-power constant current driver based on a novel composite Darlington circuit topology structure, which includes a power supply system, a power amplification module and a voltage control module electrically connected to the power supply system, and a human-computer interaction module electrically connected to the power supply system and the voltage control module.

[0021] The power supply system includes a first power source VCC1 and a second power source VCC2 connected to the mains at one end and grounded at the other end.

[0022] The power amplifier module includes an input stage composed of a differential amplifier, an output stage connected to the input stage and composed of a power transistor array, and a feedback module for collecting voltage and current information of the output stage and feeding it back to the input stage. The input stage is a differential amplifier circuit. The output stage includes a first resistor R8 connected to the output end of the differential amplifier circuit, a first transistor TE connected to the first resistor R8, and a plurality of array transistors T1, T2...Tn connected to the emitter of the first transistor TE in parallel. The base of the array transistor is connected to the emitter of the first transistor TE. In one embodiment, a voltage dividing resistor Rb1, Rb2...Rbn is arranged on the base of the array transistor; in another embodiment, the emitter end of the array transistor is provided with a voltage dividing resistor Re1, Re2...Ren. The emitter of the array transistor is connected to the feedback module, and the collector of the first transistor TE and the common collector of the array transistor form the output end of the constant current driver connected to the load. The output end of the voltage control module is connected to the input stage. The feedback module includes a sampling resistor array Ra1, Ra2...Ran connected to the emitters of the array transistors in a one-to-one correspondence, and an operational amplifier A5 connected to the sampling resistor array, the output end of the operational amplifier A5 is connected to the positive input end of the differential amplifier circuit in the input stage, and the feedback module also includes feedback resistors Rs1, Rs2...Rsn connected to the emitters of the array transistors in a one-to-one correspondence, and the other ends of the feedback resistors Rs1, Rs2...Rsn are grounded.

[0023] In this embodiment, the number of the array transistors is two, and the corresponding number of the voltage divider resistor and the sampling resistor in the sampling resistor array are both two. In other embodiments, the number can be flexibly set according to requirements.

[0024] The output stage described in this embodiment adopts a parallel transistor array to form a new type of composite Darlington structure, whose function is to realize large current conversion to meet the large current output of the current source circuit; because the output resistance of the differential amplifier is very large, it can meet the basic requirements of the voltage-controlled current source. The output stage should select a driving circuit with a high current gain to improve the performance of the current source.

[0025] In order to achieve high current output of high-power constant current driver, the output power of power amplifier module of voltage-controlled current source is high, which requires that the output of feedforward amplifier must have sufficient driving power, that is, to provide sufficient driving current and driving voltage for the output stage. To solve this problem, a novel composite Darlington structure is adopted in this design to achieve high current stable output, while increasing the open-loop gain of feedback system and improving system stability.

[0026] Power devices play a vital role in power amplifier modules and are the basis of power electronic circuits. This embodiment adopts a circuit topology structure in which multiple power devices (i.e., the voltage divider resistor and the parallel transistor array) are connected in parallel. The advantage is that the redundancy of the power module is increased and the reliability of the circuit is improved. However, actual components are not the same in parameters and characteristics, and each power device in parallel often carries different currents. When the operating current of one or more power devices exceeds its rated current, or the temperature rise caused by its power loss makes the heating and heat dissipation of the power device unbalanced, it is easy to damage the power device or cause the circuit to fail. This is the current concentration effect. Based on the above analysis, when constructing a parallel circuit of power transistors, in order to avoid the current concentration effect, in this embodiment, a resistor is connected in series at the base of each array transistor or in series at the emitter. In addition, devices (transistors and current-sharing resistors) with consistent performance parameters are selected, such as devices of the same model and the same batch; the topological structure of the parallel power transistors should be as symmetrical as possible, so that the leads can be as short as possible during wiring; materials with good conductive properties are selected to reduce the impact of unbalanced current distribution; a heat sink with good performance is selected to build a stable and reliable heat dissipation system to ensure that each power device works under the same heat dissipation conditions, so that the temperature difference between the devices is as small as possible to maintain thermal balance.

[0027] The power amplifier module in this embodiment improves the stability of the input and output ends of the amplifier circuit by setting a feedback module and combining an operational amplifier; the output stage of the feedforward amplifier adopts a power transistor array form to increase the current amplification gain multiple, thereby achieving a large current output and increasing the power; its core adopts a power amplifier circuit based on a feedforward amplifier circuit, a power transistor array form, a sampling resistor array and a feedback module to form a complete deep negative feedback voltage-controlled current source, thereby greatly improving the sensitivity of the output current control, thereby achieving a constant current output with high stability and high precision.

[0028] The voltage control module includes a reference voltage source, a current limiting circuit and a regulating circuit. The function of the reference voltage source is to obtain a stable DC voltage from a slightly less stable power supply. The reference voltage source is a reference for the stable operation of the entire system, and the performance of the reference voltage circuit determines the current stability performance of the constant current driver. The reference source chip can be divided into a temperature compensated Zener reference source, a buried Zener source and a bandgap reference source according to the structure. Since the performance of electronic components is greatly affected by temperature, temperature stability is the most stringent requirement for voltage reference performance. The parameter for measuring temperature stability is the temperature coefficient, which is used to measure the ability of the circuit to maintain a predetermined output voltage under changing temperature conditions. This design uses a high-performance bandgap reference source and combines it with a current limiting and conditioning circuit to achieve a stable DC voltage control module.

[0029] The working principle of the high-power constant current driver based on the novel composite Darlington circuit topology structure in this embodiment is as follows: first, the output power is set in the interface of the human-computer interaction module. Figure 5 The voltage control module generates a reference voltage according to the set value. The reference voltage output by the voltage control module is input to the input terminal (Vi) of the power amplifier module. The reference voltage is compared with the feedback voltage (Vf) and output. The signal enters the collector of the first transistor TE of the output stage to complete the first amplification, and then is amplified again through the array transistors T1 and T2 to achieve power amplification output. The output current enters the feedback module through the sampling resistor array Ra1 and Ra2, and the feedback resistors Rs1 and Rs2 to output Vf to the input stage, thereby achieving stable high-power constant current output.

[0030] This embodiment is based on a high-power constant current driver with a novel composite Darlington circuit topology structure. The high-power constant current driver is studied, and the actual needs are determined, and then a system design scheme is proposed. The core circuit of the designed constant current driver is a voltage-controlled current source based on a negative feedback system to achieve a highly stable output current; in order to enhance the high-current output capability of the power amplifier module, a composite Darlington circuit topology structure is designed; the present invention mainly designs a system of high-power constant current drivers based on a deep negative feedback structure, and realizes a high-stability high-power constant current power supply driving function. Specifically,

[0031] 1) A feedforward amplifier circuit (input stage module), a power amplifier circuit (output stage module), a sampling resistor array and a feedback module are arranged in the power amplifier module to form a complete deep negative feedback voltage-controlled current source, thereby obtaining an output current control sensitivity that meets the design requirements, thereby achieving a highly stable constant current output;

[0032] 2) The reference voltage, current limiting circuit and regulating circuit module are combined to form a voltage control module, in which a high-precision reference power supply is used to ensure that the constant current driver can output a highly stable output current when actually working;

[0033] 3) By analyzing the causes of unbalanced current shunting in parallel of power devices, a specific and feasible method for selecting the optimal value of the current-sharing resistor is proposed, which solves the problem of unbalanced current shunting in the transistor array in parallel of the power amplifier module, thereby further providing a guarantee for the driving function of a high-stability high-power constant current driver.

[0034] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A high-power constant-current driver based on a composite Darlington circuit topology, characterized in that: It includes a power supply system, a power amplifier module and a voltage control module electrically connected to the power supply system, the power amplifier module includes an input stage composed of a differential amplifier, an output stage connected to the input stage and composed of a power transistor array, and a feedback module for collecting voltage and current information of the output stage and feeding it back to the input stage, the output stage includes a first resistor connected to the output end of the differential amplifier, a first transistor connected in series with the first resistor, and a plurality of array transistors connected in parallel to the emitter of the first transistor, the base of the array transistor is connected to the emitter of the first transistor, and the emitter of the array transistor is connected to the feedback module. The collector of the first transistor and the common collector of the array transistor form an output end of the constant current driver connected to a load, and the output end of the voltage control module is connected to the input stage; a voltage divider resistor is arranged at the base end or the emitter end of the array transistor; the feedback module includes a sampling resistor array connected to the emitters of the array transistors in a one-to-one correspondence, an operational amplifier connected to the sampling resistor array, and the output end of the operational amplifier is connected to the positive input end of the differential amplifier in the input stage; the feedback module also includes a feedback resistor connected to the emitters of the array transistors in a one-to-one correspondence, and the other end of the feedback resistor is grounded.

2. The high-power constant-current driver based on the composite Darlington circuit topology structure as claimed in claim 1, characterized in that: The input stage is a differential amplifier circuit.

3. The high-power constant-current driver based on the composite Darlington circuit topology structure as claimed in claim 1, characterized in that: It also includes a human-machine interaction module electrically connected to the power supply system and the voltage control module.

4. The high-power constant current driver based on the composite Darlington circuit topology structure as claimed in claim 1, characterized in that: The power supply system comprises a first power supply and a second power supply with one end connected to the mains and the other end grounded.

5. The high-power constant current driver based on the composite Darlington circuit topology structure as claimed in claim 1, characterized in that: The voltage control module includes a reference voltage source, a current limiting circuit and a regulating circuit.

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