Voltage determination circuit

Abstract

The utility model discloses a voltage decision circuit, which comprises a voltage comparison unit and a voltage output unit, and the voltage comparison unit and the voltage output unit are connected in series and then connected in parallel between a transformer signal isolation conversion circuit and a quick discharge circuit. The voltage comparison unit is provided with a preset voltage threshold value, and when it is judged that the driving signal output voltage of the transformer signal isolation conversion circuit is larger than or equal to the preset voltage threshold value, the voltage comparison unit and the voltage output unit are both connected so that the driving signal can be output to the rapid discharging circuit to drive the power semiconductor device. And when it is judged that the driving signal output voltage of the transformer signal isolation conversion circuit is smaller than the preset voltage threshold value, the voltage comparison unit and the voltage output unit are not conducted, so that the driving signal cannot be output. Whether the driving signal is output or not can be controlled through the voltage judgment circuit, and the circuit is simple in structure, low in cost and easy to implement.

Description

Technical Field

[0001] The utility model relates to the technical field of voltage determination, in particular to a voltage determination circuit. Background Art

[0002] Transformer-isolated drive solutions for power semiconductor devices (such as SiC MOSFETs) are widely used in the photovoltaic energy storage field due to their simple structure, lack of secondary-side power supply requirements, and high insulation withstand voltage. Currently, three common architectures for transformer-isolated drive technology exist: CL, CLC, and forward topology. The CL architecture suffers from a strong correlation between output voltage and duty cycle, making it unable to meet the high-voltage drive requirements of SiC MOSFETs. The forward topology, on the other hand, suffers from issues such as the SiC MOSFET's GS voltage being affected by the DS voltage and delays at low duty cycles.

[0003] In contrast, the CLC architecture has the characteristics of fast response and basically stable output voltage, and is widely used in transformer isolation drive technology. Figure 1 As shown, the CLC architecture primarily includes a transformer signal isolation and conversion circuit, a rapid discharge circuit, and a silicon carbide MOS transistor (not shown) to be driven. This circuit structure causes output voltage oscillation at high duty cycles. This oscillating voltage is transmitted through the output terminal to the rapid discharge circuit, thereby affecting the operation of the silicon carbide MOS transistor. Therefore, a suitable circuit structure is required to eliminate the impact of this oscillating voltage on the GS drive voltage of the silicon carbide MOS transistor. Utility Model Content

[0004] The technical problem to be solved by the present invention is as follows: In response to the above-mentioned problems of the prior art, a voltage determination circuit with a simple structure and low cost is provided to determine whether to output to a fast discharge circuit based on the relationship between the output voltage amplitude of the transformer signal isolation conversion circuit and a preset voltage threshold, thereby avoiding the influence of the oscillating voltage on the operation of the silicon carbide MOS tube.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A voltage determination circuit, comprising a voltage comparison unit and a voltage output unit, which are connected in series between a transformer signal isolation conversion circuit and a fast discharge circuit; the voltage comparison unit is provided with a preset voltage threshold, when it is judged that the drive signal output voltage of the transformer signal isolation conversion circuit is greater than or equal to the preset voltage threshold, the voltage comparison unit and the voltage output unit are both turned on to make the drive signal output to the fast discharge circuit to drive the power semiconductor device; when it is judged that the drive signal output voltage of the transformer signal isolation conversion circuit is less than the preset voltage threshold, the voltage comparison unit and the voltage output unit are both not turned on, so that the drive signal cannot be output.

[0007] Further, the voltage comparison unit is a voltage stabilizing diode D7, the voltage output unit is a MOS tube Q2, the negative electrode of the voltage stabilizing diode D7 is connected with the gate of the MOS tube Q2, the source of the MOS tube Q2 and the positive electrode of the voltage stabilizing diode D7 are respectively connected to the first output end and the second output end of the transformer signal isolation conversion circuit, the drain of the MOS tube Q2 and the positive electrode of the voltage stabilizing diode D7 are respectively connected to the first input end and the second input end of the fast discharge circuit.

[0008] Further, the voltage determination circuit further comprises a voltage stabilizing diode D16, the positive electrode of the voltage stabilizing diode D16 is connected with the negative electrode of the voltage stabilizing diode D7, and the negative electrode of the voltage stabilizing diode D16 is connected to the first output end of the transformer signal isolation conversion circuit.

[0009] Further, the voltage determination circuit further comprises a diode D11, the positive electrode and the negative electrode of the diode D11 are connected between the drain and the source of the MOS tube Q2.

[0010] Further, the voltage determination circuit further comprises a resistor R1, the resistor R1 is connected between the gate and the source of the MOS tube Q2.

[0011] Further, the voltage determination circuit further comprises a capacitor C1, one end of the capacitor C1 is connected to the gate of the MOS tube Q2, and the other end is connected to the second input end of the fast discharge circuit.

[0012] Further, the voltage determination circuit further comprises a diode D4, the positive electrode of the diode D4 is connected with the negative electrode of the voltage stabilizing diode D7, and the negative electrode of the diode D4 is connected to the first output end of the transformer signal isolation conversion circuit.

[0013] Further, the stable voltage of the voltage stabilizing diode D7 is 6V-15V.

[0014] Furthermore, the voltage comparison unit is a TL431 device, the voltage output unit is a MOS transistor Q2, the cathode of the TL431 device is connected to the gate of the MOS transistor Q2, the anode of the TL431 device and the source of the MOS transistor Q2 are respectively connected to the output end of the transformer signal isolation conversion circuit, the anode of the TL431 device and the drain of the MOS transistor Q2 are respectively connected to the input end of the fast discharge circuit, and the reference end REF of the TL431 device is connected to the gate of the MOS transistor Q2.

[0015] Furthermore, the number of the voltage determination circuit, the secondary winding of the transformer signal isolation conversion circuit, and the rapid discharge circuit is consistent, and there are one or more of them. Each of the voltage determination circuits is respectively connected between the secondary winding of the corresponding transformer signal isolation conversion circuit and the corresponding rapid discharge circuit.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] The utility model adds a voltage determination circuit between the transformer signal isolation conversion circuit and the rapid discharge circuit, and can determine whether to output the drive signal to the subsequent rapid discharge circuit to drive the silicon carbide MOS tube to operate according to the magnitude of the drive signal voltage of the transformer signal isolation conversion circuit and a preset voltage threshold. When the drive signal voltage is less than the preset voltage threshold, the drive signal is actually an oscillating voltage signal generated by the LC oscillation of the circuit. The voltage determination circuit can prevent the output of the oscillating signal, thereby preventing it from affecting the GS drive voltage of the silicon carbide MOS tube. The circuit structure is simple, the cost is low, and it is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure is a schematic diagram of the specific structure of the existing CLC architecture transformer isolation drive circuit.

[0019] Figure 2 The utility model is a schematic block diagram of a transformer isolation drive circuit using the voltage determination circuit of the utility model.

[0020] Figure 3 This is a schematic structural diagram of a voltage determination circuit according to Example 1 of the present utility model.

[0021] Figure 4 The figure is a schematic diagram of the specific structure of the transformer isolation drive circuit using the voltage determination circuit of Example 1 of the present utility model.

[0022] Figure 5 This is a schematic diagram of the structure of the voltage determination circuit of Example 2 of the present utility model. DETAILED DESCRIPTION

[0023] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0024] like Figure 1 The circuit diagram of a CLC architecture for a conventional SiC MOS transistor transformer isolation drive circuit used in high-voltage power supplies is shown. The circuit primarily includes a transformer signal isolation and conversion circuit, a rapid discharge circuit, and the SiC MOS transistor to be driven (not shown). The PWM signal is processed by a driver chip (such as the ADP3654) before entering the transformer signal isolation and conversion circuit. The drive signal is then transmitted from the input end to the output end (the secondary winding) via electromagnetic induction through the transformer, achieving electrical isolation of the drive signal. The drive signal is then filtered at the output end before being transmitted to the SiC MOS transistor via the rapid discharge circuit to turn it on. The rapid discharge circuit accelerates the SiC MOS transistor's shutdown process. When the drive signal is low, it quickly pulls down the SiC MOS transistor's voltage, achieving rapid shutdown. The inherent characteristics of this CLC architecture circuit can cause LC oscillations in the circuit, causing the output voltage to oscillate at high duty cycles. This oscillating voltage is then transmitted through the output end to the rapid discharge circuit, affecting the operation of the SiC MOS transistor. Although the oscillation voltage cannot be eliminated, its oscillation amplitude can be clearly calculated and is lower than the normal driving voltage. Therefore, the impact of the oscillation on the GS voltage of the silicon carbide MOS tube can be eliminated by adding a new circuit structure: a voltage determination circuit is added to the output end of the transformer signal isolation conversion circuit. When the output voltage is higher than the preset voltage threshold, the normal driving voltage is allowed to be output, otherwise it is not output.

[0025] Example 1

[0026] like Figure 2 As shown, this embodiment provides a voltage determination circuit, which includes a voltage comparison unit and a voltage output unit. The voltage comparison unit and the voltage output unit are connected in series and connected between the transformer signal isolation conversion circuit and the fast discharge circuit; the voltage comparison unit is provided with a preset voltage threshold. When it is determined that the output voltage of the drive signal of the transformer signal isolation conversion circuit is greater than or equal to the preset voltage threshold, the voltage comparison unit and the voltage output unit are both turned on so that the drive signal is output to the fast discharge circuit to drive the power semiconductor device; when it is determined that the output voltage of the drive signal of the transformer signal isolation conversion circuit is less than the preset voltage threshold, the voltage comparison unit and the voltage output unit are both turned off, so that the drive signal cannot be output.

[0027] It can be understood that this embodiment, by adding a voltage determination circuit between the transformer signal isolation conversion circuit and the rapid discharge circuit, can determine whether to output the drive signal to the subsequent rapid discharge circuit to drive the silicon carbide MOS tube to operate based on the difference between the drive signal voltage of the transformer signal isolation conversion circuit and the preset voltage threshold. When the drive signal voltage is less than the preset voltage threshold, the drive signal is actually an oscillating voltage signal generated by the LC oscillation of the circuit. The voltage determination circuit can prevent the output of the oscillating signal to prevent it from affecting the GS drive voltage of the silicon carbide MOS tube. The circuit structure is simple, the cost is low, and it is easy to implement.

[0028] In this embodiment, Figure 3 As shown, the voltage comparison unit is a Zener diode D7, and the voltage output unit is a MOS transistor Q2. The cathode of the Zener diode D7 is connected to the gate of the MOS transistor Q2. The source of the MOS transistor Q2 and the anode of the Zener diode D7 are respectively connected to the first output terminal and the second output terminal of the transformer signal isolation conversion circuit. The drain of the MOS transistor Q2 and the anode of the Zener diode D7 are respectively connected to the first input terminal and the second input terminal of the fast discharge circuit. Specifically, since the voltage amplitude of the normal drive signal is 15V, the oscillation voltage amplitude of the oscillation signal during high duty cycle shutdown is approximately 5V. Therefore, the stable voltage parameter of the Zener diode D7 can be set between 6V and 15V, preferably 6.8V, and a BZX85-6V8 Zener diode is used. MOS transistor Q2 is preferably a BSP230 / PS insulated gate enhancement mode PMOS transistor. This ensures that when Zener diode D7 is turned on, MOS transistor Q2 is also turned on, thereby outputting a drive signal to the fast discharge circuit to drive the silicon carbide MOS transistor. During high duty cycle shutdown, since the oscillation voltage is approximately 5V, Zener diode D7 is not turned on, and MOS transistor Q2 is in the off state, thus preventing the output of the oscillation signal. Of course, the models of Zener diode D7 and MOS transistor Q2 can be adjusted accordingly based on the specific circuit structure and requirements, as long as the above-mentioned effects are achieved.

[0029] In this embodiment, Figure 3 As shown, the voltage determination circuit further includes a Zener diode D16. The anode of Zener diode D16 is connected to the cathode of Zener diode D7, and the cathode of Zener diode D16 is connected to the first output terminal of the transformer signal isolation and conversion circuit. Specifically, Zener diode D16 is BZX8518V / PS, and its regulated voltage is preferably 18V. Zener diode D16 limits the voltage across the GS terminal of MOS transistor Q2 to prevent damage to MOS transistor Q2 due to excessive driving voltage.

[0030] In this embodiment, Figure 3As shown, the voltage determination circuit further comprises a diode D11, the anode and cathode of which are connected between the drain and source of the MOS tube Q2. Specifically, the diode D11 is a Schottky diode of BAS40 / SIE type, which is used to protect the MOS tube Q2 circuit and provide a reverse path and freewheeling path for the MOS tube Q2.

[0031] In the embodiment, as shown in Figure 3 As shown, the voltage determination circuit further comprises a resistor R1, which is connected between the gate and source of the MOS tube Q2. Specifically, the resistor R1 has a resistance of 4.7 kΩ, which functions as a bleeder resistor and fixed bias to provide a power consumption path for the MOS tube Q2 and ensure the safety of the circuit.

[0032] In the embodiment, as shown in Figure 3 As shown, the voltage determination circuit further comprises a capacitor C1, one end of which is connected to the gate of the MOS tube Q2 and the other end of which is connected to the second input end of the fast discharge circuit. Specifically, the capacitor C1 has a capacitance of 100 pF, which is used to form an RC charging and discharging circuit with the resistor R1 to reduce voltage fluctuations and facilitate voltage determination by the voltage stabilization diode D7 and improve the accuracy of voltage determination.

[0033] In the embodiment, as shown in Figure 3 As shown, the voltage determination circuit further comprises a diode D4, the anode of which is connected to the cathode of the voltage stabilization diode D7 and the cathode of which is connected to the first output end of the transformer signal isolation and conversion circuit. Specifically, the diode D4 is a Schottky diode of BAS40 / SIE type, which is used to protect the MOS tube Q2 circuit and prevent reverse breakdown of the MOS tube Q2.

[0034] In the embodiment, the number of voltage determination circuits, secondary winding of the transformer signal isolation and conversion circuit, and fast discharge circuits are consistent, each being one or more, and each voltage determination circuit is connected between the corresponding secondary winding of the transformer signal isolation and conversion circuit and the corresponding fast discharge circuit.

[0035] In a specific application embodiment, as shown in Figure 4 To reduce costs, the circuit can adopt a one-to-two architecture, i.e., the primary winding load of the transformer signal isolation and conversion circuit is doubled, and the secondary winding adopts a form of two groups of the same structure circuit to realize two-way output. At this time, the structures of the voltage determination circuit and the fast discharge circuit are also two groups, and the connection relationship between each group is consistent with that when there is only one group as described above, which will not be repeated here.

[0036] Compared with the prior art, the silicon carbide MOS tube transformer isolation drive circuit with the voltage determination circuit of this embodiment is added. Through theoretical analysis and simulation verification, the circuit meets the application requirements and has the following beneficial effects:

[0037] The power on / off delay can be controlled within 100ns;

[0038] The high level amplitude of the driving voltage can meet the application requirements;

[0039] The low-level amplitude of the driving voltage is controlled within 0.7V (a fast recovery diode voltage drop) at a very small duty cycle. At a large duty cycle, the low-level amplitude is about -0.3V (a Schottky diode voltage drop).

[0040] There is slight oscillation when starting up with a large duty cycle, which has little effect on the drive and can be completely eliminated by soft starting (slowly opening the duty cycle);

[0041] When the power is turned off with a large duty cycle, the oscillation can be completely eliminated by means of electronic switching, without affecting the drive.

[0042] Example 2

[0043] like Figure 5 As shown, this embodiment provides a voltage determination circuit, which differs from Embodiment 1 in the voltage comparison unit. The voltage comparison unit is a TL431 device, and the voltage output unit is a MOS transistor Q2. The cathode of the TL431 device is connected to the source of the MOS transistor Q2 via a diode D4. The anode of the TL431 device and the source of the MOS transistor Q2 are respectively connected to the output of the transformer signal isolation and conversion circuit. The anode of the TL431 device and the drain of the MOS transistor Q2 are respectively connected to the input of the rapid discharge circuit. The reference terminal REF of the TL431 device is connected to the gate of the MOS transistor Q2. In addition, a resistor R103 is connected in parallel across capacitor C7 to act as a voltage divider with resistor R1 to provide a determination voltage for the TL431 device. The TL431 device also has a preset voltage threshold (e.g., 6.8V). By determining whether the output voltage reaches the preset voltage threshold, the TL431 device is turned on and off, thereby controlling the conduction of the MOS transistor Q2, thereby achieving voltage determination. The other structures of the voltage determination circuit can be consistent with those in Example 1, or a one-drive-two architecture can be adopted. The specific structure of each part is consistent with that in Example 1, except that the voltage comparison unit is different. It also has the advantages described in Example 1 and will not be repeated here.

[0044] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, certain improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A voltage determination circuit, characterized in that: The voltage determination circuit includes a voltage comparison unit and a voltage output unit, which are connected in series and connected between the transformer signal isolation conversion circuit and the rapid discharge circuit. The voltage comparison unit is provided with a preset voltage threshold. When it is determined that the output voltage of the drive signal of the transformer signal isolation conversion circuit is greater than or equal to the preset voltage threshold, the voltage comparison unit and the voltage output unit are both turned on to output the drive signal to the rapid discharge circuit to drive the power semiconductor device. When it is determined that the output voltage of the driving signal of the transformer signal isolation conversion circuit is less than the preset voltage threshold, both the voltage comparison unit and the voltage output unit are turned off, so that the driving signal cannot be output.

2. The voltage determination circuit according to claim 1, wherein: The voltage comparison unit is a Zener diode D7, and the voltage output unit is a MOS transistor Q2. The cathode of the Zener diode D7 is connected to the gate of the MOS transistor Q2, the source of the MOS transistor Q2 and the anode of the Zener diode D7 are respectively connected to the first output terminal and the second output terminal of the transformer signal isolation conversion circuit, and the drain of the MOS transistor Q2 and the anode of the Zener diode D7 are respectively connected to the first input terminal and the second input terminal of the fast discharge circuit.

3. The voltage determination circuit according to claim 2, wherein: The voltage determination circuit further includes a voltage stabilizing diode D16 , the anode of the voltage stabilizing diode D16 is connected to the cathode of the voltage stabilizing diode D7 , and the cathode of the voltage stabilizing diode D16 is connected to the first output end of the transformer signal isolation conversion circuit.

4. The voltage determination circuit according to claim 2, wherein: The voltage determination circuit further includes a diode D11 , wherein the anode and cathode of the diode D11 are connected in parallel between the drain and source of the MOS transistor Q2 .

5. The voltage determination circuit according to claim 2, wherein: The voltage determination circuit further includes a resistor R1 , which is connected in parallel between the gate and source of the MOS transistor Q2 .

6. The voltage determination circuit according to claim 2, wherein: The voltage determination circuit further includes a capacitor C1 , one end of the capacitor C1 is connected to the gate of the MOS transistor Q2 , and the other end is connected to the second input end of the fast discharge circuit.

7. The voltage determination circuit according to claim 2, wherein: The voltage determination circuit further includes a diode D4 , the anode of the diode D4 is connected to the cathode of the voltage stabilizing diode D7 , and the cathode of the diode D4 is connected to the first output end of the transformer signal isolation conversion circuit.

8. The voltage determination circuit according to any one of claims 2 to 7, wherein: The stable voltage of the voltage stabilizing diode D7 is 6V-15V.

9. The voltage determination circuit according to claim 1, wherein: The voltage comparison unit is a TL431 device, and the voltage output unit is a MOS transistor Q2. The cathode of the TL431 device is connected to the gate of the MOS transistor Q2, the anode of the TL431 device and the source of the MOS transistor Q2 are respectively connected to the output end of the transformer signal isolation conversion circuit, the anode of the TL431 device and the drain of the MOS transistor Q2 are respectively connected to the input end of the fast discharge circuit, and the reference end REF of the TL431 device is connected to the gate of the MOS transistor Q2.

10. The voltage determination circuit according to claim 1, 2 or 9, wherein: The number of the voltage determination circuit, the secondary winding of the transformer signal isolation conversion circuit, and the rapid discharge circuit is consistent, and they are all one or more. Each of the voltage determination circuits is respectively connected between the secondary winding of the corresponding transformer signal isolation conversion circuit and the corresponding rapid discharge circuit.

Images