Gallium nitride parallel current-sharing driving control circuit

Abstract

The invention belongs to the field of power electronic devices, and particularly relates to a gallium nitride parallel current-sharing driving control circuit which comprises parallel power devices, a temperature feedback circuit, a differential amplification circuit and a driving adjusting circuit. The output end of the parallel power device is connected with the driving adjusting circuit, and the parallel power device can generate set output power; the parallel power device adopts a GaN power device; the temperature feedback circuit is arranged on the parallel power device, collects temperature data on the parallel power device and sends the temperature data to the differential amplification circuit; the differential amplification circuit can judge the temperature difference in the parallel power devices and output the temperature difference to the driving regulation circuit; the drive adjusting circuit can process the collected temperature data. And the parameters of the driving circuit are adjusted by identifying different operation stages of the GaN power device in the period, so that the switching loss of the GaN power device in the switching-on and switching-off process is reduced, and the system efficiency is further improved.

Description

Technical Field

[0001] This application belongs to the field of power electronic devices, and specifically relates to a gallium nitride parallel current sharing drive control circuit. Background Technology

[0002] Thanks to the superior performance of enhancement-mode GaN devices, research on driving technologies for these devices has increased significantly in recent years. However, due to manufacturing process and cost limitations, the current-carrying capacity of a single GaN chip is only tens of amperes. In high-power applications such as power conversion and electric drives, it is often necessary to use modules with multiple chips connected in parallel. Parallel circuits inevitably encounter problems such as uneven distribution of parasitic parameters and inconsistent power transistor parameters. Achieving current sharing in parallel chips is a major challenge for GaN FET applications in high-power fields. Some researchers have proposed a GaN_FET parallel current sharing control circuit and method with multi-level drive signals. This mainly involves a current monitoring module that monitors the current flowing through each power module in real time. The control module adjusts the drive voltage signal of the corresponding power module based on the feedback current value, changing the turn-on time of the power module and thus affecting the current balance of the parallel power modules.

[0003] Furthermore, the high-frequency characteristics of GaN power devices present numerous challenges for driver design. For instance, the larger current change rate leads to greater voltage interference compared to Si devices, resulting in more severe current imbalance. Additionally, as the operating frequency increases, dead-time losses and turn-on / turn-off losses in GaN power devices contribute more to the overall losses.

[0004] Therefore, in the research of GaN parallel applications, improving the overall system efficiency while increasing the operating frequency is the key to the research of GaN power devices in parallel. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a gallium nitride parallel current sharing drive control circuit to resolve the problem that the high-frequency characteristics of GaN power devices in the prior art lead to increased overall losses.

[0006] The technical solution of this application is: a gallium nitride parallel current sharing drive control circuit, including parallel power devices, a temperature feedback circuit, a differential amplifier circuit and a drive adjustment circuit;

[0007] The output terminal of the parallel power device is connected to the drive adjustment circuit, and the parallel power device can generate a set output power; the parallel power device is a GaN power device.

[0008] The temperature feedback circuit is located on the parallel power device, collects the temperature data on the parallel power device, and sends it to the differential amplifier circuit;

[0009] The differential amplifier circuit can determine the temperature difference within the parallel power devices and output it to the drive adjustment circuit;

[0010] The drive regulation circuit can process the collected temperature data and control the switching on and off of parallel power devices.

[0011] Preferably, the parallel power device includes a first MOSFET and a second MOSFET, the sources of the first MOSFET and the drains of the second MOSFET are connected to each other, and the gates of the first MOSFET and the second MOSFET are connected to the drive adjustment circuit.

[0012] Preferably, the temperature feedback circuit includes a first thermistor and a second thermistor; the first thermistor and the second thermistor are respectively mounted on the heat dissipation pads of the first MOSFET and the second MOSFET, respectively, a first resistor is connected in series with the first thermistor, and a second resistor is connected in series with the second thermistor; the first resistor and the second resistor are connected to the power supply VCC.

[0013] Preferably, the differential amplifier circuit includes an operational amplifier, a capacitor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor;

[0014] The positive input terminal of the operational amplifier is connected to the third resistor, the negative input terminal is connected to the fourth resistor, and the output terminal is connected to the sixth resistor. The fifth resistor is connected between the fourth and sixth resistors. One end of the capacitor is connected to the sixth resistor, and the other end is grounded.

[0015] The third resistor is connected to the first thermistor, and the fourth resistor is connected to the second thermistor.

[0016] Preferably, the drive adjustment circuit includes a drive power supply, a drive chip, a multi-channel input / output chip, a digital processing chip, and a drive resistor;

[0017] The output terminal of the driving power supply is connected to the driving chip. The input terminal of the driving chip receives control signals, and the output terminal is connected to the digital processing signal and the multi-channel input / output chip. The output terminal of the digital processing chip is connected to the multi-channel input / output chip. The multi-channel input / output chip has two OUT ports, which are respectively connected to the gates of the first MOSFET and the second MOSFET. There are a total of 8 sets of driving resistors connected in parallel on the multi-channel input / output chip.

[0018] The gallium nitride parallel current sharing drive control circuit of this application has the following advantages:

[0019] Using the operating temperature of GaN power devices as feedback, the driving circuit parameters are adjusted by the temperature difference of parallel GaN power devices to make the temperature of the parallel GaN power devices more uniform, thereby balancing the power dissipation of GaN power devices and achieving current sharing. At the same time, within a switching cycle, the driving circuit parameters are adjusted by identifying different stages of GaN power device operation within the cycle, so that the switching losses of GaN power devices during turn-on and turn-off are reduced, further improving system efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall circuit structure of this application.

[0021] 1. First MOSFET; 2. Second MOSFET; 3. First Thermistor; 4. Second Thermistor; 5. First Resistor; 6. Second Resistor; 7. Operational Amplifier; 8. Capacitor; 9. Third Resistor; 10. Fourth Resistor; 11. Fifth Resistor; 12. Sixth Resistor; 13. Driver Power Supply; 14. Driver Chip; 15. Multi-channel Input / Output Chip; 16. Digital Processing Chip; 17. Driver Resistor. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0023] The first aspect of this application provides a gallium nitride (GaN) parallel current sharing drive control circuit. Even devices of the same model and batch can have differences in parameters such as threshold voltage, transconductance, on-resistance, and inter-electrode capacitance. Due to these differences in devices, circuits, and drives, chips will inevitably experience varying degrees of current imbalance. This current imbalance leads to different losses and heat generation among the devices. The imbalance can cause asymmetrical switching speeds in parallel devices, making it easy for a faster-turning-on device to overload during turn-on, potentially damaging it and consequently the entire system. Therefore, improving the current sharing problem in GaN power devices in parallel is necessary.

[0024] like Figure 1As shown, it includes parallel power devices, a temperature feedback circuit, a differential amplifier circuit, and a drive regulation circuit.

[0025] The output terminal of the parallel power device is connected to the drive regulation circuit, and the parallel power device can generate the set output power. The parallel power device uses GaN power devices.

[0026] The temperature feedback circuit is located on the parallel power device, which collects the temperature data on the parallel power device and sends it to the differential amplifier circuit.

[0027] The differential amplifier circuit can determine the temperature difference within the parallel power devices and output it to the drive regulation circuit.

[0028] The drive regulation circuit can process the collected temperature data and control the switching on and off of parallel power devices.

[0029] Using the operating temperature of GaN power devices as feedback, the driving circuit parameters are adjusted by the temperature difference of parallel GaN power devices to make the temperature of the parallel GaN power devices more uniform, thereby balancing the power dissipation of GaN power devices and achieving current sharing. At the same time, within a switching cycle, the driving circuit parameters are adjusted by identifying different stages of GaN power device operation within the cycle, so that the switching losses of GaN power devices during turn-on and turn-off are reduced, further improving system efficiency.

[0030] Preferably, the parallel power device includes a first MOSFET 1 and a second MOSFET 2, the sources of the first MOSFET 1 and the drains of the second MOSFET 2 are connected to each other, and the gates of the first MOSFET 1 and the second MOSFET 2 are connected to the drive adjustment circuit.

[0031] Two parallel MOSFETs operate simultaneously, generating a temperature difference due to their different operating conditions. This temperature difference is then controlled by a drive regulation circuit to achieve power balance.

[0032] Preferably, the temperature feedback circuit includes a first thermistor 3 and a second thermistor 4, both of which are thermistors with a positive temperature coefficient. The first thermistor 3 and the second thermistor 4 are respectively mounted on the heat dissipation pads of the first MOSFET 1 and the second MOSFET 2 to monitor the temperature of the first MOSFET 1 and the second MOSFET 2 in real time. A first resistor 5 is connected in series with the first thermistor 3, and a second resistor 6 is connected in series with the second thermistor 4. The first resistor 5 and the second resistor 6 are connected to the power supply VCC.

[0033] The first resistor 5 and the second resistor 6 provide power supply VCC to form a temperature feedback circuit, which converts the resistance change of the PTC resistor with temperature into voltage signals V_PTC1 and V_PTC2, which are output to the differential amplifier circuit respectively.

[0034] For a single GaN power device, both the turn-on and turn-off processes should be as fast as possible. However, during the switching process, EMI limitations on dv / dt and di / dt need to be considered. Therefore, the rate of change of voltage and current during the rise and fall phases needs to be controlled, while during the periods when voltage and current do not change, a large drive intensity is desired to accelerate the switching speed. Therefore, to improve system efficiency, this invention adjusts the drive current based on drive voltage feedback during the different turn-on and turn-off phases of the GaN power device. This shortens the switching cycle and reduces switching losses.

[0035] Since PTC resistors have a positive temperature coefficient (i.e., the higher the temperature, the greater the resistance), based on this linear relationship, to improve the uneven current problem that exists when GaN power devices are connected in parallel, PTC resistors are installed at the heat dissipation pads of the GaN power devices. As the temperature rise of the GaN power devices varies during operation, the corresponding PTC resistance changes. The PTC resistors are connected in series in the circuit, and the change in resistance is converted into a change in voltage signal, which is fed back to the digital processing unit. The processing unit adjusts the value of the drive resistor 17 to change the switching characteristics of the GaN power devices, so that the temperature rise of the parallel GaN power devices tends to be uniform. Combined with the control of the switching process of a single GaN power device by the processing unit, the effect of current sharing and power consumption reduction is finally achieved.

[0036] Preferably, the differential amplifier circuit includes an operational amplifier 7, a capacitor 8, a third resistor 9, a fourth resistor 10, a fifth resistor 11, and a sixth resistor 12.

[0037] The positive input terminal of operational amplifier 7 is connected to the third resistor 9, the negative input terminal is connected to the fourth resistor 10, and the output terminal is connected to the sixth resistor 12. The fifth resistor 11 is connected between the fourth resistor 10 and the sixth resistor 12. One end of capacitor 8 is connected to the sixth resistor 12, and the other end is grounded.

[0038] The third resistor 9 is connected to the first thermistor 3, and the fourth resistor 10 is connected to the second thermistor 4.

[0039] The voltage signals V_PTC1 and V_PTC2 output by the temperature feedback circuit enter the non-inverting and inverting terminals of the operational amplifier 7 through resistors 9 (third resistor) and 10 (fourth resistor) (resistors 9 and 10 have the same resistance value), respectively. Resistor 11 is connected in parallel to the inverting input and output terminals of the operational amplifier and is connected to resistor 12 (sixth resistor), mainly used to adjust the amplification factor. Resistor 12 (sixth resistor) and capacitor 8 form a low-pass filter circuit to filter out high-frequency interference noise.

[0040] The relationship between the output signal V_FB and the input of this circuit is: V_FB=(V_PTC1-V_PTC2)*R5 / R4. When the V_FB voltage is positive, it means that the temperature of the first MOSFET 1 is higher than that of the second MOSFET 2, and vice versa.

[0041] Preferably, the drive adjustment circuit includes a drive power supply 13, a drive chip 14, a multi-channel input / output chip 15, a digital processing chip 16, and a drive resistor 17; the drive resistor 17RG1~RG8, the resistance value can be determined by the actual selected GaN power device model, and the specific resistance value of the drive resistor 17 is determined according to the resistance value range.

[0042] The output terminal of the drive power supply 13 is connected to the drive chip 14. The input terminal of the drive chip 14 receives control signals, and its output terminal is connected to the digital processing signals and the multi-channel input / output chip 15. The output terminal of the digital processing chip 16 is connected to the multi-channel input / output chip 15. The multi-channel input / output chip 15 has two OUT ports, which are respectively connected to the gates of the first MOSFET 1 and the second MOSFET 2. There are eight sets of drive resistors 17 connected in parallel to the multi-channel input / output chip 15.

[0043] When driving the first MOSFET 1 and the second MOSFET 2, the control signal is converted into a GaN drive signal V_DRV through the driver chip 14U2 and the drive power supply 13U3. The V_DRV drive signal is input to the corresponding IN port of the multi-channel input / output chip 15 through the drive resistors 17RG1~RG8. According to the digital control ports X1~X3 and Y1~Y3 of the multi-channel input / output chip 15, the OUT port is connected to the corresponding IN port. The V_DRV drive signal is output from the corresponding OUT port and transmitted to the first MOSFET 1 and the second MOSFET 2 connected thereto, driving the first MOSFET 1 and the second MOSFET 2 to turn on and off. Different combinations of the output levels of the control ports X1~X3 and Y1~Y3 correspond to different OUT ports and IN ports connected, which means that the drive resistor 17 can be adjusted in real time according to different stages of the drive when the drive circuit is working, so as to meet the drive input requirements of the first MOSFET 1 and the second MOSFET 2 to turn on and off quickly at different stages.

[0044] The high and low levels of control ports X1~X3 and Y1~Y3 are determined by the feedback input drive signal V_DRV and the temperature feedback signal V_FB. The digital processing chip 16 adjusts the connected drive resistor 17RG* by identifying the different voltage values ​​corresponding to the different stages of driving the first MOSFET 1 and the second MOSFET 2 to turn on or off, thereby shortening the turn-on and turn-off time and reducing losses. By identifying the amplitude and sign of the V_FB voltage, the temperature difference between the parallel first MOSFET 1 and the second MOSFET 2 is determined, thus identifying the current imbalance between them. Based on the adjustment via V_DRV, the drive resistor values ​​17RG* for the first MOSFET 1 and the second MOSFET 2 are further adjusted to achieve current sharing and reduce switching losses during operation.

[0045] In summary, this application addresses the varying drive current requirements of GaN power devices during different turn-on and turn-off stages. It also utilizes a PTC thermistor to feedback current imbalances in parallel GaN power devices and designs a variable drive resistor 17 to adjust the drive current, enabling rapid turn-on or turn-off of the parallel GaN power devices and reducing switching losses during turn-on and turn-off. Furthermore, by adjusting the resistance value of the corresponding drive resistor 17, the temperature of the parallel GaN power devices is balanced. This further reduces switching losses while maintaining the parallel GaN power devices within a relatively balanced current and temperature range, achieving the effect of GaN current sharing and power reduction.

[0046] This application eliminates the need for sensor sampling, reducing operating costs; it also eliminates the need for coupling inductors, reducing size and system complexity; and it is easily expandable for multi-channel parallel connection. It has significant application potential.

[0047] In actual GaN parallel operation, the control signal is converted into a driving signal V_DRV that can drive GaN via the driver chip 14 and the driving power supply 13. V_DRV is driven by driving resistors 17RG1~RG8 with different resistance values, where the resistance values ​​decrease sequentially from RG1 to RG8. The signal is output to the parallel GaN power devices, the first MOSFET 1 and the second MOSFET 2, through the output ports OUTX and OUTY of the multi-channel input / output chip 15. The PTC thermistors at the heat sinks of the first MOSFET 1 and the second MOSFET 2 provide feedback on their temperature rise. When the temperatures of the first MOSFET 1 and the second MOSFET 2 are inconsistent, the temperature difference is output as a voltage signal from the differential amplifier circuit. This signal is processed by the digital processing chip 16, which outputs a logic control signal to select the driving resistor 17 to the multi-channel input / output chip 15. In actual operation, the control signal is converted into a driving signal V_DRV that can drive GaN by the driver chip 14 and the driving power supply 13. The digital processing chip 16U4 defaults to logic outputs DO1~DO6 ​​being 0, and OUTX and OUTY are both connected to IN1, that is, connected to the driving resistor 17RG1. The driving resistors 17 for the first MOSFET 1 and the second MOSFET 2 are both RG1. When the temperature of the first MOSFET 1 is higher than that of the second MOSFET 2, the resistance of PTC1 is higher than that of PTC2, and the voltage of V_PTC1 is higher than that of V_PTC2. V_PTC1 and V_PTC2 are amplified by an operational amplifier to obtain a temperature feedback signal V_FB. At this time, V_FB is a positive voltage (V_FB>0V). V_FB is fed back to U4. U4 determines that the junction temperature of the first MOSFET 1 is higher than that of the second MOSFET 2 based on the magnitude of the V_FB voltage. According to the characteristic that the larger the driving resistor 17 of the GaN power device, the smaller the driving current, the greater the power consumption and the higher the temperature rise, the driving resistor 17 of the first MOSFET 1 is reduced to lower the junction temperature of the first MOSFET 1.

[0048] Meanwhile, when GaN is turned on, according to the threshold voltage Vth and the Miller plateau voltage Vmiller, the turn-on of GaN is divided into three stages: Vgs ≤ Vth; Vth < Vgs ≤ Vmiller; Vgs > Vmiller. The digital processing chip divides the turn-on stage by obtaining whether V_DRV reaches Vth or Vmiller. In the stages of Vgs ≤ Vth and Vgs > Vmiller, the changes in Vds and Ids are small, and a large driving current is required to shorten the time of these two stages and reduce losses. Therefore, the digital processing chip selects to connect the driving signal V_DRV with a smaller driving resistance and outputs it to the first MOS transistor and the second MOS transistor; in the stage of Vth < Vgs ≤ Vmiller, due to the existence of large dv / dt and di / dt, considering the balance between the driving speed and the anti-interference ability for EMI electromagnetic interference, the driving resistance is selected as a compromise, such as RG4, to drive and control the first MOS transistor and the second MOS transistor. The relationship between the selection of the driving resistance and the output logic of the digital processing chip is shown in Table 1. By selecting appropriate driving resistances according to the different driving requirements in different stages of the turn-on process of the first MOS transistor and the second MOS transistor, the turn-on losses in different stages are reduced and the device junction temperature is lowered. The control method during turn-off is the same and will not be elaborated here.

[0049] Table 1

[0050] X1-X2-X3 (DO1-DO2-DO3) 0-0-0 0-0-1 0-1-0 1-0-0 0-1-1 1-1-0 1-0-1 1-1-1 OUTX RG1 RG2 RG3 RG4 RG5 RG6 RG7 RG8 Y1-Y2-Y3 (DO4-DO5-DO6) 0-0-0 0-0-1 0-1-0 1-0-0 0-1-1 1-1-0 1-0-1 1-1-1 OUTY RG1 RG2 RG3 RG4 RG5 RG6 RG7 RG8

[0051] As described above, this is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A gallium nitride parallel current sharing drive control circuit, characterized in that, This includes parallel power devices, temperature feedback circuits, differential amplifier circuits, and drive regulation circuits; The output terminal of the parallel power device is connected to the drive adjustment circuit, and the parallel power device can generate a set output power; the parallel power device is a GaN power device. The temperature feedback circuit is located on the parallel power device, collects the temperature data on the parallel power device, and sends it to the differential amplifier circuit; The differential amplifier circuit can determine the temperature difference within the parallel power devices and output it to the drive adjustment circuit; The drive regulation circuit can process the collected temperature data and control the switching on and off of parallel power devices.

2. The gallium nitride parallel current sharing drive control circuit as described in claim 1, characterized in that, The parallel power device includes a first MOSFET (1) and a second MOSFET (2). The sources of the first MOSFET (1) and the drains of the second MOSFET (2) are connected to each other, and the gates of the first MOSFET (1) and the second MOSFET (2) are connected to the drive adjustment circuit.

3. The gallium nitride parallel current sharing drive control circuit as described in claim 2, characterized in that, The temperature feedback circuit includes a first thermistor (3) and a second thermistor (4); the first thermistor (3) and the second thermistor (4) are respectively mounted on the heat dissipation pads of the first MOSFET (1) and the second MOSFET (2); a first resistor (5) is connected in series with the first thermistor (3), and a second resistor (6) is connected in series with the second thermistor (4); the first resistor (5) and the second resistor (6) are connected to the power supply VCC.

4. The gallium nitride parallel current sharing drive control circuit as described in claim 3, characterized in that, The differential amplifier circuit includes an operational amplifier (7), a capacitor (8), a third resistor (9), a fourth resistor (10), a fifth resistor (11), and a sixth resistor (12); The positive input terminal of the operational amplifier (7) is connected to the third resistor (9), the negative input terminal is connected to the fourth resistor (10), and the output terminal is connected to the sixth resistor (12). The fifth resistor (11) is connected between the fourth resistor (10) and the sixth resistor (12). One end of the capacitor (8) is connected to the sixth resistor (12), and the other end is grounded. The third resistor (9) is connected to the first thermistor (3), and the fourth resistor (10) is connected to the second thermistor (4).

5. The gallium nitride parallel current sharing drive control circuit as described in claim 4, characterized in that, The drive adjustment circuit includes a drive power supply (13), a drive chip (14), a multi-channel input / output chip (15), a digital processing chip (16), and a drive resistor (17). The output terminal of the driving power supply (13) is connected to the driving chip (14). The input terminal of the driving chip (14) receives control signals, and the output terminal is connected to the digital processing signal and the multi-channel input / output chip (15). The output terminal of the digital processing chip (16) is connected to the multi-channel input / output chip (15). The multi-channel input / output chip (15) is provided with two OUT ports, which are respectively connected to the gates of the first MOSFET (1) and the second MOSFET (2). There are a total of 8 driving resistors (17) connected in parallel on the multi-channel input / output chip (15).

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