CN203660891U - Isolation-type high-frequency switching constant current converter - Google Patents

Abstract

The utility model belongs to the technical field of power electronic conversion, in particular to an isolated high-frequency switch constant current converter. It includes a high-frequency switch constant-current conversion module, a constant-voltage power supply module, a drive module capable of outputting stable pulse waveforms, and a control module. The high-frequency switch constant-current conversion module includes a high-frequency constant-current conversion circuit and a rectification filter circuit. The control module It includes a start-up circuit and a protection circuit; the constant-voltage power supply module is connected to a drive module, a high-frequency constant-current conversion circuit and a start-up circuit, the drive module is connected to a high-frequency constant-current conversion circuit, the high-frequency constant-current conversion circuit is connected to a rectification and filtering circuit, and the rectification and filtering The circuit is connected with a protection circuit, and the starting circuit is connected with a high-frequency constant current conversion circuit. The utility model has the advantages of simple design and practical effect, simple constant current/constant current conversion process, no high-loss devices, high efficiency, and can achieve the purpose of outputting constant current, constant current conversion, branching and constant current circuit networking.

Description

Isolated High Frequency Switching Constant Current Converter

technical field

The utility model belongs to the technical field of power electronic conversion, in particular to an isolated high-frequency switch constant current converter.

Background technique

The DC converter in the prior art is a device that converts one voltage of direct current into another or several voltages of direct current. It is only suitable for the occasion of constant voltage power supply, and can only complete the conversion between constant voltages, but cannot complete constant voltage. The conversion between currents, that is, the constant current of one current cannot be converted into the constant current of another or several currents, and at the same time, it does not have the multi-channel branching capability of constant current, which cannot meet the networking needs of constant current circuits. . Therefore, in applications such as constant current power supply systems, such as remote power supply systems based on constant current power supply methods for submarine observation networks, traditional DC/DC converters do not have practical application value.

Utility model content

The purpose of this utility model is to solve the shortcomings of the above-mentioned background technology, and to provide an isolated high-frequency switch constant current that can convert one constant current into another or several constant currents, the conversion process is simple, and the reliability is high. stream converter.

The technical solution adopted by the utility model is: an isolated high-frequency switch constant current converter, including a high-frequency switch constant current conversion module, a constant voltage power supply module, a drive module and a control module capable of outputting stable pulse waveforms, the high The frequency switch constant current conversion module includes a high frequency constant current conversion circuit and a rectification filter circuit that can realize constant current/constant current conversion. The control module includes a start-up circuit and a protection circuit; A conversion circuit and a start-up circuit, the output end of the drive module is connected to the input end of the high-frequency constant-current conversion circuit, the output end of the high-frequency constant-current conversion circuit is connected to a rectification filter circuit, the output end of the rectification filter circuit is connected to a protection circuit, and the output end of the start-up circuit Connect the high frequency constant current conversion circuit.

Further, the constant voltage power supply module includes a pulse width modulation control chip U1 that can control the on-off of the switch tube by sampling the output voltage to maintain a stable output voltage, an NPN type MOS switch tube M3, a diode D7, a capacitor C5, a sampling resistor and an isolation In the module DC1, the gate of the switching tube M3 is connected to the control terminal of the pulse width modulation control chip U1, the source is connected to the high-frequency constant current conversion circuit and the starting circuit, the anode of the diode D7 is connected to the drain of the switching tube M3, and the cathode is connected to one end of the capacitor C5. The other end of the capacitor C5 is connected to the source of the switching tube M3, the capacitor C5 is connected in parallel with the sampling resistor, the sampling end of the pulse width modulation control chip U1 is connected to the sampling resistor, and the input end of the isolation module DC1 is connected to both ends of the sampling resistor and the output end Connect the driver module and start circuit.

Further, the sampling resistor includes a first sampling resistor R4 and a second sampling resistor R5 connected in series, the other end of the first sampling resistor R4 is connected to one end of the capacitor C5, and the other end of the second sampling resistor R5 is connected to the other end of the capacitor C5 The sampling terminal of the pulse width modulation control chip U1 is connected between the first sampling resistor R4 and the second sampling resistor R5.

Further, the high-frequency constant current conversion circuit includes a switch tube M1, a switch tube M2, a capacitor C1, and a high-frequency transformer TX, and the switch tube M1 and the switch tube M2 are both NPN type MOS tubes, and the high-frequency transformer TX includes a primary winding and a secondary winding, the primary winding is composed of two coils in series, the gates of the switching tube M1 and the switching tube M2 are respectively connected to the two output terminals of the drive module, and the drains are respectively connected to both ends of the primary winding and the source Both are connected to one end of the capacitor C1 and the output end of the start-up circuit, and the other end of the capacitor C1 is connected between the source of the switch tube M3 and the two coils.

Further, the starting circuit includes a relay J1, a regulator tube D8, an NPN type MOS switch tube M4, a resistor R9, a resistor R10, and a resistor R11, the input end of the relay J1 is connected to the output end of the isolation module DC1, and the relay J1 One pin of the output end is connected to the gate of the switching tube M4, the other pin of the output end of the relay J1 is connected to the source of the switching tube M4, the source of the switching tube M1 and the source of the switching tube M2, and the drain of the switching tube M4 is connected to a resistor R11, the other end of the resistor R11 is connected to the source of the switch tube M3, the anode of the regulator tube D8 is connected to the source of the switch tube M4, and the cathode is connected to the gate of the switch tube M4, the resistor R10 is connected in parallel with the regulator tube D8, the One end of the resistor R9 is connected to the gate of the switching tube M4, and the other end is connected to the source of the switching tube M3.

Furthermore, the protection circuit includes a voltage regulator D6, a resistor R1, and a thyristor S1. The anode of the voltage regulator D6 is connected in series with a resistor R1. The anode of the thyristor S1 is connected to the cathode of the voltage regulator D6, and the cathode is connected to the other end of the resistor R1. The gate level is connected between the regulator tube D6 and the resistor R1.

The starting circuit of the constant current converter of the utility model provides an internal path for the converter in the initial starting state; the constant voltage power supply module uses a pulse modulation chip to control the current flow path, converts the constant current into a constant voltage, supplies power for the internal power module, and outputs The voltage is stable, the conversion process is simple, and the efficiency is high; the constant current conversion is realized by the constant current conversion module, and the size and number of the output constant current can be changed according to the turns ratio and winding of the high-frequency transformer; the protection circuit limits the output voltage to the rated value Within the range, it can ensure the safety of the circuit and load equipment when the circuit is abnormal, and the reliability is high.

The utility model has a simple and effective design, does not need a complicated conversion process, and can achieve the purpose of outputting constant current, constant current conversion, branching and constant current circuit networking; within the rated range, when the load changes, the output current is stable; due to the The converter does not have components that consume large amounts of energy, and the conversion efficiency is relatively high. At the same time, the converter can be combined in series to increase the output power, or the output current can be kept constant through series combination to meet the networking requirements of the constant current circuit.

Description of drawings

Fig. 1 is a functional block diagram of the utility model.

Fig. 2 is a circuit topology example diagram of the utility model.

Fig. 3 is a schematic diagram of the networking application of the present invention.

Fig. 4 is a simulation diagram (1) of a part of the device of the present invention.

Fig. 5 is a simulation diagram (2) of another part of the device of the present invention.

Fig. 6 is a measured waveform diagram of some devices of the present invention.

Fig. 7 is the output volt-ampere characteristic curve of the utility model.

Fig. 8 is a schematic diagram of circuit board series voltage division of the present invention.

Fig. 9 is an efficiency diagram of the utility model.

Detailed ways

The utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments to facilitate a clear understanding of the utility model, but they do not limit the utility model.

As shown in FIG. 1 , the utility model includes a high frequency switch constant current conversion module 1 , a constant voltage power supply module 2 , a drive module 3 and a control module 4 . The high frequency switch constant current conversion module 1 includes a high frequency constant current conversion circuit 5 and a rectification filter circuit 6, the high frequency constant current conversion circuit 5 completes the constant current/constant current conversion, and the rectification filter circuit 6 completes the rectification and filtering of the output current. The control module 4 includes a start-up circuit 7 and a protection circuit 8. The start-up circuit 7 controls the start-up of the high-frequency switch constant current conversion module 1 in an initial state, and the protection circuit 8 provides overvoltage protection for the converter output. The drive module 3 uses a hardware circuit or a single-chip microcomputer to generate pulse waveforms, and the output is controlled by the drive chip to provide drive waveforms for the high-frequency switch constant current conversion module. The output end of the constant voltage power supply module 2 is connected to the drive module 3, the high-frequency constant current conversion circuit 5 and the start-up circuit 7, the output end of the drive module 3 is connected to the input end of the high-frequency constant current conversion circuit 5, and the output end of the high-frequency constant current conversion circuit 5 is connected to A rectification and filtering circuit 6 , the output end of the rectification and filtering circuit 6 is connected to the protection circuit 8 , and the output end of the starting circuit 7 is connected to the high frequency constant current conversion circuit 5 .

The constant voltage power supply module 2 converts the constant current provided by the external constant current source into a stable voltage to provide power for the drive module 3 and the start-up circuit 7, and at the same time introduces the constant current to the high-frequency constant current conversion circuit, which is sampled by the control chip. The output voltage is passed The PWM signal controls the on and off of the switching tube, changes the flow path of the constant current, controls the charging and discharging of the capacitor, and outputs a stable voltage.

As shown in Figure 2, it includes a pulse width modulation control chip U1, an NPN type MOS switch tube M3, a diode D7, a capacitor C5, a sampling resistor and an isolation module DC1, and the pulse width modulation control chip U1 controls the switching of the switch tube by sampling the output voltage , to change the constant current flow path to maintain the output voltage stability. The connection relationship among them is as follows: the gate of the switching tube M3 is connected to the control terminal of the pulse width modulation control chip U1, the source is connected to the high-frequency constant current conversion circuit and the starting circuit, and the anode of the diode D7 is connected to the drain and cathode of the switching tube M3 Connect one end of the capacitor C5, the other end of the capacitor C5 is connected to the source of the switch tube M3, the capacitor C5 is connected in parallel with the sampling resistor, the sampling end of the pulse width modulation control chip U1 is connected to the sampling resistor, and the input end of the isolation module DC1 is connected to the sampling resistor The two ends of the resistor and the output end are connected to the driving module and the starting circuit. The sampling resistor includes a first sampling resistor R4 and a second sampling resistor R5 connected in series, the other end of the first sampling resistor R4 is connected to one end of the capacitor C5, the other end of the second sampling resistor R5 is connected to the other end of the capacitor C5, and the pulse width The sampling end of the modulation control chip U1 is connected between the first sampling resistor R4 and the second sampling resistor R5.

The high-frequency switch constant current conversion module uses high-frequency drive to control the on and off of the power switch tube, changes the flow path of the constant current, and converts the constant current into AC at the input end. Since high-frequency transformers are inductive, the current flowing into the transformer changes gradually. Correspondingly, the input current charges and discharges the capacitance at the input terminal within a small range to maintain a constant output current at the input terminal. The input capacitor plays the role of controlling the voltage, storing energy and maintaining the stability of the input current, and its voltage is determined by the load. After high-frequency transformer transformation and output circuit rectification and filtering, the output terminal outputs a stable current, and the current size is determined by the high-frequency transformer turns ratio. Within the rated range, the output terminal of the conversion module is equivalent to a constant current source with relatively high internal resistance.

The high-frequency constant current conversion circuit includes a switch tube M1, a switch tube M2, a capacitor C1, and a high-frequency transformer TX. The switch tube M1 and the switch tube M2 are both NPN type MOS tubes. The high-frequency transformer TX includes a primary winding and a secondary winding , the primary winding is formed by two coils connected in series, the gates of the switching tube M1 and the switching tube M2 are respectively connected to the two output terminals of the drive module through the resistor Ro1 and the resistor Ro2, and the drain is respectively connected to both ends of the primary winding, the source One end of the capacitor C1 is evenly connected to the output end of the start-up circuit, the other end of the capacitor C1 is connected between the source of the switch tube M3 and the two coils, and a protection resistor Rm1 and a capacitor Cm1 are also provided between the source and drain of the switch tube M1 , A protective resistor Rm2 and a capacitor Cm2 are also provided between the source and drain of the switch tube M2.

The rectification and filtering circuit includes a rectification diode D1, a rectification diode D2, a rectification diode D3, a rectification diode D4, a freewheeling diode D5, an inductor L1, a capacitor C2 and a capacitor C3.

The starting circuit is controlled by a relay. In the initial state, the switch at the output end of the relay is normally open to control the conduction of the power switch tube, and the starting circuit is in the on state. After the constant voltage power supply module is activated, the control drive module starts to work, and the corresponding power switch tube is turned on and off to make the input terminal of the high frequency switch constant current conversion module form a path. At the same time, the output terminal of the control relay is closed, so that the original path is transformed into an open circuit, and the high-frequency switch constant current conversion module starts to work normally.

As shown in FIG. 2, the start-up circuit includes a relay J1, a regulator tube D8, an NPN type MOS switch tube M4, a resistor R9, a resistor R10, and a resistor R11. The connection relationship between them is as follows: the input end of the relay J1 is connected to the output end of the isolation module DC1, one pin of the output end of the relay J1 is connected to the gate of the switching tube M4, and the other pin of the output end of the relay J1 is connected to The source of the switching tube M4, the source of the switching tube M1 and the source of the switching tube M2, the drain of the switching tube M4 is connected to the resistor R11, the other end of the resistor R11 is connected to the source of the switching tube M3, and the anode of the voltage regulator tube D8 is connected to The source and cathode of the switch tube M4 are connected to the gate of the switch tube M4, the resistor R10 is connected in parallel with the regulator tube D8, one end of the resistor R9 is connected to the gate of the switch tube M4, and the other end is connected to the source of the switch tube M3.

The protection circuit limits the output voltage within the rated range. When the circuit is abnormal, the output voltage rises to the limit value, the protection circuit is activated, the thyristor is controlled to be stimulated to conduct, and the output end is equivalent to a short circuit, which protects the output end load equipment. It includes a voltage regulator D6, a resistor R1, and a thyristor S1. The anode of the voltage regulator D6 is connected in series with a resistor R1. The anode of the thyristor S1 is connected to the cathode of the voltage regulator D6, the cathode is connected to the other end of the resistor R1, and the gate is connected to the voltage regulator. Between D6 and resistor R1.

The concrete control process of the utility model converter is:

As shown in Figure 2, the constant current source Ii inputs a constant current, and the filter inductor L2 is connected between the constant current source and the constant voltage power supply module to make the constant current input more stable. The output port of the relay J1 of the starting circuit is open, and the regulator tube D8 The power switch tube M4 is controlled to be turned on, and the circuit formed by the switch tube M3 and the switch tube M4 is in an on state. The current Ii passes through the constant voltage power supply module, and is controlled by the pulse width modulation control chip U1 in a closed loop to control the on and off of the switch tube M3, change the current flow path, charge and discharge the capacitor C5, and then complete the constant current/constant voltage Converted, isolated and output by the isolation module DC1, to provide stable voltage for the drive module and control module. The driving module is controlled by the chip U2, outputs two driving waveforms, and controls the switching on and off of the switching tube M1 and the switching tube M2. After the drive module works, the constant voltage power supply module controls the output port of the relay J1 to close, the switch tube M4 is turned off, the original circuit is in an open state, the high frequency switch constant current conversion module starts to work normally, and the capacitor C1 is rapidly charged according to the input current and load size , as the switching tube M1 and the switching tube M2 are turned on and off to charge and discharge in a small range, the current flowing into the high frequency transformer also changes accordingly. The input end of the high-frequency switch constant current conversion module adopts a push-pull circuit, the constant current flows into the input end of the conversion module through the constant voltage power supply module, and the current I ₁ flows out from the input end, where I _i =I ₁ . The output end adopts full-wave rectification and π-type filter circuit, which is converted by power tube switch and high-frequency transformer TX. After rectification and filtering, the output current _Io is obtained. If the output voltage is abnormal and higher than the limit value, the branch circuit composed of the voltage regulator tube D6 and the resistor R1 at the output end is turned on, and the thyristor S1 is controlled to turn on, and the output end is short-circuited to ensure the safety of the circuit and load equipment. When the turns ratio of the high-frequency transformer is n=1, I _i =I _o .

The converters of the utility model can be combined in series to increase the output power; or the networking requirements of the constant current circuit can be completed through combination. As shown in Figure 3, the converters are used in combination in the constant current system. Taking the part 1 as an example, both the sub-converter I and the sub-converter II are constant current converters of the present utility model, and the sub-converter I and the sub-converter II are The input and output terminals are connected in series to form a converter A to increase the output power. The input and output currents of the converter A are I _i =I ₂ =I ₃ to complete the conversion and branching of the constant current. Converters A and B, and converters C and D are equivalent to a long-distance series combination. Through the combined connection of the corresponding interfaces of the four converters, the current of the system remains unchanged to meet the networking requirements of the constant current circuit.

In order to deepen the understanding of the circuit principle and working process of the converter, verify the function and function of the converter, and test the component parameters, the circuit is built and simulated by the professional circuit simulation software PSPICE. The simulation assumes that the input current I _i =1A, Take the load R _o =100Ω. Figure 4 is a part of the device simulation diagram of the converter (1). Figure 5 is another part of the device simulation diagram of the converter (2). The voltage of the capacitor C1 is related to the output voltage, that is, the voltage of the load R _o , and it charges and discharges in a small range during the switching period. The output pulse of the drive module is the gate-source voltage of the switch tube, and the drain-source voltage of the switch tube changes accordingly with the driving waveform based on the capacitor voltage, and the output current is about 1A.

According to the simulation results, the hardware circuit is built and related experiments are carried out. The test takes I _i =1A, R _o =120Ω. Figure 6 is a waveform diagram of some components of the converter. The voltage of the capacitor C1 is stable at about 120V. The drive circuit provides a pulse signal of 12V, the drive pulse has a "dead zone", and the switch tube is turned on and off alternately under the control of the drive pulse. Taking the power switch M2 as an example, when the switch M2 is turned off, the drain-source voltage is about 240V, which is twice the load voltage; when the switch M2 is turned on, the drain-source voltage is 0.

Figure 7 is the output volt-ampere characteristic curve of the converter, including the simulated curve and the measured curves of two hardware circuit boards A and B. A and B boards are made with the same devices and parameters. Simulation and measured simulation curves show that the change of load voltage has little influence on the current, and within the rated range, the output terminal of the converter can be regarded as a constant current source. Definition R _X1 and R _X2 are used to describe the core loss of the high-frequency transformer and the switching loss of the switch tube. The slope of the measured curve is about 4.6KΩ, and the coupling coefficient of the high frequency transformer is about 0.999. The parameters of the simulation curve are R _X1 =R _X2 =10K, K=0.999. The simulation curve under this parameter is in good agreement with the actual measurement. The output slope of the converter is related to the core loss of the high-frequency transformer and the switching loss of the switch tube. In Fig. 7, (R _X1 +R _X2 )2=5K, which is approximate to the output slope of the measured curve. In practical applications, if the load of the converter changes suddenly, the current of the system can remain constant due to the characteristics of the output terminal of the converter similar to a constant current source, ensuring stable operation of the system.

In practical applications, the output power of a single converter may not meet the actual power demand, and the constant current circuit has the possibility of networking applications. On the one hand, in order to verify whether the output power can be increased by connecting multiple converters in series, and on the other hand, to verify whether the combination can be used to meet the networking requirements of the constant current circuit, a series connection test is carried out on the A and B boards. In Figure 7, the output volt-ampere characteristic curves of boards A and B are basically consistent. Theoretically, if the output characteristics match, the two boards will divide the voltage evenly when they are connected in series, and there will be no circuit damage due to the overload of a certain converter. Figure 8 is a schematic diagram of the series voltage division of boards A and B. This figure shows that in the actual working environment, within the range of the output rated power of the converter, the two can basically bear the load power on average. Therefore, this type of converter can be used in the actual system. Used in series to meet the requirements of networking and increasing output power proposed in Figure 3.

Figure 9 is an efficiency diagram of the converter. Since the power consumed by the drive module and the control module is ignored in the simulation, and the components are all in an ideal state, the efficiency is slightly higher than the actual measurement. Overall, the conversion efficiency of this type of equipment is high, up to 93%. Therefore, in terms of efficiency, the converter has a high conversion efficiency. In the actual application process, the output power redundancy of the converter should be fully considered.

The content not described in detail in this specification belongs to the prior art known to those skilled in the art.

Claims (6)

1. an isolated form HF switch constant-current converter, it is characterized in that: the driver module (3) and the control module (4) that comprise HF switch constant current conversion module (1), constant voltage supply module (2), exportable stable pulse waveform, described HF switch constant current conversion module (1) comprises high-frequency constant stream translation circuit (5) and the current rectifying and wave filtering circuit (6) that can realize constant current/constant current conversion, and described control module (4) comprises start-up circuit (7) and protective circuit (8); Described constant voltage supply module (2) output connects driver module (3), high-frequency constant stream translation circuit (5) and start-up circuit (7); described driver module (3) output connects high-frequency constant stream translation circuit (5) input; described high-frequency constant stream translation circuit (5) output connects current rectifying and wave filtering circuit (6); described current rectifying and wave filtering circuit (6) output connects protective circuit (8), and described start-up circuit (7) output connects high-frequency constant stream translation circuit (5).

2. isolated form HF switch constant-current converter according to claim 1, it is characterized in that: described constant voltage supply module (2) comprises can be by sampling and outputting voltage control switch pipe break-make to maintain the pulse width modulation controlled chip U1 of output voltage stabilization, NPN type MOS switching tube M3, diode D7, capacitor C 5, sampling resistor and isolation module DC1, described switching tube M3 grid connects pulse width modulation controlled chip U1 control end, source electrode connects high-frequency constant stream translation circuit and start-up circuit, described diode D7 anodic bonding switching tube M3 drain electrode, negative electrode connects capacitor C 5 one end, described capacitor C 5 other end connecting valve pipe M3 source electrodes, described capacitor C 5 is in parallel with sampling resistor, described pulse width modulation controlled chip U1 sampling end connects sampling resistor, described isolation module DC1 input connects sampling resistor two ends, output connects driver module and start-up circuit.

3. isolated form HF switch constant-current converter according to claim 2, it is characterized in that: described sampling resistor comprises the first sampling resistor R4 and the second sampling resistor R5 of series connection, the described first sampling resistor R4 other end connects capacitor C 5 one end, the described second sampling resistor R5 other end connects capacitor C 5 other ends, and described pulse width modulation controlled chip U1 sampling end is connected between the first sampling resistor R4 and the second sampling resistor R5.

4. isolated form HF switch constant-current converter according to claim 2, it is characterized in that: described high-frequency constant stream translation circuit (5) comprises switching tube M1, switching tube M2, capacitor C 1, high frequency transformer TX, described switching tube M1, switching tube M2 is NPN type metal-oxide-semiconductor, described high frequency transformer TX comprises armature winding and secondary winding, described armature winding is in series by two coils, the grid of described switching tube M1 and switching tube M2 is connected respectively two outputs of driver module, drain electrode connects respectively armature winding two ends, source electrode all connects capacitor C 1 one end and start-up circuit output, described capacitor C 1 other end is connected between switching tube M3 source electrode and two coils.

5. isolated form HF switch constant-current converter according to claim 4, it is characterized in that: described start-up circuit (7) comprises relay J 1, voltage-stabiliser tube D8, NPN type MOS switching tube M4, resistance R 9, resistance R 10, resistance R 11, the input of described relay J 1 connects isolation module DC1 output, one pin connecting valve pipe M4 grid of described relay J 1 output, another pin connecting valve pipe M4 source electrode of described relay J 1 output, switching tube M1 source electrode and switching tube M2 source electrode, described switching tube M4 drain electrode contact resistance R11, described resistance R 11 other end connecting valve pipe M3 source electrodes, described voltage-stabiliser tube D8 anodic bonding switching tube M4 source electrode, negative electrode connecting valve pipe M4 grid, described resistance R 10 is in parallel with voltage-stabiliser tube D8, described resistance R 9 one end connecting valve pipe M4 grids, other end connecting valve pipe M3 source electrode.

6. isolated form HF switch constant-current converter according to claim 1; it is characterized in that: described protective circuit (8) comprises voltage-stabiliser tube D6, resistance R 1, thyristor S1; described voltage-stabiliser tube D6 anode series connection resistance R 1, described thyristor S1 anodic bonding voltage-stabiliser tube D6 negative electrode, the negative electrode contact resistance R1 other end, gate leve are connected between voltage-stabiliser tube D6 and resistance R 1.

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