Current limiting circuit of switch circuit and switch circuit

Abstract

The present invention proposes a current limiting circuit of a switch circuit and a switch circuit, wherein the switch circuit adopts a gallium nitride power tube as a main power tube, the first end of the current limiting circuit is connected to the drain of the gallium nitride power tube, the second end of the current limiting circuit is connected to the controller of the switch circuit, and the current limiting circuit is used to limit the current from the power supply end of the controller. The present invention suppresses the negative current flowing through the controller.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and in particular to a current limiting circuit of a switch circuit and a switch circuit. Background Art

[0002] The PWM control chip of the switch circuit realizes high-voltage startup. Generally, there are two ways to obtain high-voltage power. One is to supply power to the high-voltage pin of the chip controller from the AC input through a full-wave rectifier circuit, and the other is to obtain power from the DC bus capacitor. If the control chip is an integrated MOSFET power tube, such as Figure 1 As shown, the chip itself has a Drain Pin. In order to save a high-voltage pin, the high-voltage startup power is usually taken from the Drain Pin.

[0003] Chips with integrated MOSFET power tubes can draw power from the Drain pin, but if chips with integrated GaN power tubes still draw power directly from the Drain pin, there will be the following problems: There is an important difference between the device characteristics of GaN power tubes and MOSFET power tubes: MOSFET power tubes have an integrated anti-parallel diode at both ends of the drain and source, while GaN power tubes do not have this diode. The voltage drop of GaN power tubes when conducting reverse current is much larger than that of MOSFET power tubes, so there will be a relatively large negative voltage at the drain end of the chip, affecting the normal operation of the chip or even damaging it. Summary of the invention

[0004] The purpose of the present invention is to provide a current limiting circuit and a switch circuit for limiting negative current flowing through a switch circuit controller, thereby solving the problem in the prior art that negative current flows through the switch circuit controller due to the use of gallium nitride power tubes, which easily causes damage to the controller.

[0005] Based on the above purpose, the present invention provides a current limiting circuit for a switching circuit, wherein the switching circuit includes a main power tube and a controller, the power supply end of the controller is connected to the drain of the main power tube, the first end of the current limiting circuit is connected to the drain of the main power tube, and the second end of the current limiting circuit is connected to the power supply end of the controller of the switching circuit.

[0006] Optionally, a gallium nitride power tube is used as the main power tube.

[0007] Optionally, the current limiting circuit includes a diode, the anode of the diode is connected to the drain of the power tube, and the cathode of the diode is connected to the power supply end of the controller.

[0008] Optionally, the current limiting circuit includes a voltage regulator tube, the positive electrode of the voltage regulator tube is connected to the drain of the main power tube, and the cathode of the diode is connected to the power supply end of the controller.

[0009] Optionally, the breakdown voltage of the voltage regulator tube is greater than the absolute value of the drain-source voltage difference of the main power tube when a negative current flows through the main power tube.

[0010] Optionally, the current limiting circuit includes a main diode and a plurality of auxiliary diodes, the anode of the main diode is connected to the drain of the power tube, and the cathode of the main diode is connected to the power supply end of the controller;

[0011] The plurality of auxiliary diodes are connected in series and then connected in reverse parallel to the main diode.

[0012] Optionally, the number of auxiliary diodes is selected according to the source-drain voltage of the main power tube.

[0013] Optionally, a total voltage drop of a plurality of auxiliary diodes connected in series is greater than an absolute value of a drain-source voltage difference of the main power tube when a negative current flows through the main power tube.

[0014] Optionally, the current limiting circuit includes a first resistor, a first end of the first resistor is connected to the drain of the main power tube, and a second end of the first resistor is connected to a power supply end of the controller.

[0015] The present invention also provides a switching circuit, comprising a main power tube and a controller, wherein a power supply end of the controller is connected to a drain of the main power tube, and comprises any one of the current limiting circuits described above.

[0016] Optionally, the main power tube is a gallium nitride main power tube.

[0017] Optionally, the main power tube is configured as an integrated power chip including the gallium nitride main power tube and the gallium nitride main power tube driver.

[0018] Optionally, a common connection point where the power supply end of the controller is connected to the drain of the main power tube is connected to a power loop node of the switching circuit.

[0019] Compared with the prior art, the present invention has the following advantages: by connecting a current limiting circuit between the Drain pin and the high-voltage controller, the negative voltage or negative current flowing to the controller is limited, so that the controller is protected from large negative voltage or negative current, thereby avoiding the problem of abnormal operation of the controller caused by this. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a switch circuit based on a MOS tube in the prior art;

[0021] Figure 2 This is a schematic diagram of a switch circuit according to Embodiment 1 of the present invention using a current limiting circuit;

[0022] Figure 3This is a schematic diagram of a switch circuit according to a second embodiment of the current limiting circuit of the present invention;

[0023] Figure 4 The schematic diagram of the switch circuit of the third embodiment of the current limiting circuit of the present invention;

[0024] Figure 5 This is a schematic diagram of a switch circuit according to a fourth embodiment of the current limiting circuit of the present invention. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitution, modification, equivalent method and scheme made on the spirit and range of the present invention.

[0026] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without these detailed descriptions.

[0027] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all simplified and not in exact proportions, in order to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0028] In an embodiment of the present invention, the switching circuit is based on a gallium nitride power tube as the main power tube, the controller is used to control the switching state of the main power tube, the power supply end of the controller is connected to the drain of the main power tube, the gallium nitride power tube and the controller are integrated in a chip, and the common connection end of the controller and the gallium nitride power tube serves as the drain of the chip, that is, the Drain end of the chip. The current flowing from the power supply end of the controller to the drain of the main power tube and the current flowing from the source of the main power tube to its drain are defined as negative currents, and the power supply end of the controller is the high-voltage power input end of the controller. The current limiting circuit of the present invention limits the current flowing out of the power supply end of the controller, that is, limits the current flowing to the drain of the main power tube.

[0029] like Figure 2 As shown, the schematic diagram of the switch circuit of the first embodiment of the current limiting circuit of the present invention is illustrated. The current limiting circuit includes a diode D1. In order to ensure the safe operation of the circuit, the diode D1 is usually set as a high-voltage diode. The positive electrode of the high-voltage diode D1 is connected to the drain of the gallium nitride power tube, and the negative electrode of the high-voltage diode is connected to the power supply end of the controller of the switch circuit. When the drain end of the gallium nitride power tube is negative, the diode D1 is cut off, and the current is blocked from flowing out of the power supply end of the controller through the diode D1, ensuring the normal and safe operation of the controller.

[0030] like Figure 3As shown, the schematic diagram of the switch circuit of the second embodiment of the current limiting circuit of the present invention is illustrated, and the current limiting circuit includes a voltage regulator tube Dz, the positive electrode of the voltage regulator tube Dz is connected to the drain of the gallium nitride power tube, and the negative electrode of the high-voltage diode is connected to the power supply end of the controller of the switch circuit. The breakdown voltage of the voltage regulator tube is greater than the absolute value of the drain-source voltage difference of the main power tube when a negative current flows through the main power tube. When there is a negative current in the system, the breakdown voltage of the voltage regulator tube Dz is greater than the source-drain voltage of the gallium nitride power tube, and the voltage regulator tube will not be broken down, so the voltage regulator tube blocks the current from flowing out of the power supply end of the controller, ensuring the normal and safe operation of the controller.

[0031] like Figure 4 As shown, the schematic diagram of the switch circuit of the third embodiment of the current limiting circuit of the present invention is illustrated. The connection relationship of the switch circuit is the same as that of the first embodiment. The current limiting circuit includes a main diode D1 and multiple auxiliary diodes. The positive electrode of the main diode is connected to the drain of the gallium nitride power tube, and the negative electrode of the main diode is connected to the power supply end of the controller; the multiple auxiliary diodes are connected in series and reversely connected in parallel with the main diode. The function of the auxiliary diode string is that when the drain voltage of the gallium nitride power tube changes from high to low, the withstand voltage of the main diode D1 is only the sum of the voltage drops Vf of the auxiliary diode string, so that the main diode D1 can choose a low-voltage diode.

[0032] In one embodiment, the number of auxiliary diode strings is also determined by the source-drain voltage Vsd of the GaN power tube. When there is a negative current in the system, the total voltage drop Vf of the auxiliary diode string must be greater than the source-drain voltage Vsd of the GaN power tube. In this way, when there is a negative current in the system, it will flow through the GaN power tube, and no current will flow out from the power supply end of the controller, ensuring that the controller works normally. Through this method, the diodes can all be selected as low-voltage diodes, which is convenient for design.

[0033] like Figure 5 As shown, the schematic diagram of the switch circuit of the fourth embodiment of the current limiting circuit of the present invention is illustrated. The current limiting circuit includes a resistor, and a resistor is connected in series between the drain pin DRAIN pin of the chip and the high-voltage HV input terminal of the controller, that is, the power supply terminal. When there is a reverse current in the system, for example, the DRAIN pin voltage is about -2V, the ESD diode of the controller HV input terminal to the ground is turned on, and the voltage of the HV input terminal is the ESD diode voltage drop, which is about 0.7V. Although the HV input terminal is a negative voltage at this time, the current limiting of the series resistor R makes most of the reverse current of the system flow through the path where the gallium nitride power tube is located, and the reverse current flowing through the controller is only (2V-0.7V) / R. Usually, the resistor R takes a few k ohms, which does not affect the normal high-voltage startup charging, and effectively suppresses the negative current of the controller, and also limits the negative voltage of the HV input terminal to only about -0.7 volts.

[0034] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0035] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A current limiting circuit for a switch circuit, the switch circuit comprising a main power tube and a controller, the power supply end of the controller is connected to the drain of the main power tube, characterized in that: The first end of the current limiting circuit is connected to the drain of the main power tube, and the second end of the current limiting circuit is connected to the power supply end of the controller of the switch circuit; The current limiting circuit is used to limit the current flowing from the power supply end to the drain of the power tube; Use gallium nitride power tube as the main power tube; The controller and the main power tube are integrated in a chip, and the drain of the main power tube is connected to the chip pin.

2. The current limiting circuit of the switch circuit according to claim 1, characterized in that: The current limiting circuit includes a diode, the anode of the diode is connected to the drain of the power tube, and the cathode of the diode is connected to the power supply end of the controller.

3. The current limiting circuit of the switch circuit according to claim 1, characterized in that: The current limiting circuit includes a voltage regulator tube, the positive electrode of the voltage regulator tube is connected to the drain of the main power tube, and the negative electrode of the voltage regulator tube is connected to the power supply end of the controller.

4. The current limiting circuit of the switch circuit according to claim 3, characterized in that: The breakdown voltage of the voltage regulator tube is greater than the absolute value of the drain-source voltage difference of the main power tube when a negative current flows through the main power tube.

5. The current limiting circuit of the switch circuit according to claim 1, characterized in that: The current limiting circuit includes a main diode and a plurality of auxiliary diodes, the anode of the main diode is connected to the drain of the power tube, and the cathode of the main diode is connected to the power supply end of the controller; The plurality of auxiliary diodes are connected in series and then connected in reverse parallel to the main diode.

6. The current limiting circuit of the switch circuit according to claim 5, characterized in that: The number of auxiliary diodes is selected according to the source-drain voltage of the main power tube.

7. The current limiting circuit of the switch circuit according to claim 5, characterized in that: The total voltage drop of the plurality of auxiliary diodes connected in series is greater than the absolute value of the drain-source voltage difference of the main power tube when a negative current flows through the main power tube.

8. The current limiting circuit of the switch circuit according to claim 1, characterized in that: The current limiting circuit includes a first resistor, a first end of the first resistor is connected to the drain of the main power tube, and a second end of the first resistor is connected to the power supply end of the controller.

9. A switch circuit, comprising a main power tube and a controller, wherein a power supply terminal of the controller is connected to a drain of the main power tube, characterized in that: The invention comprises the current limiting circuit described in any one of claims 1 to 8.

10. The switch circuit according to claim 9, characterized in that: The main power tube is a gallium nitride main power tube.

11. The switch circuit according to claim 9, characterized in that: The main power tube is configured as an integrated power chip including a gallium nitride main power tube and the gallium nitride main power tube driver.

12. The switch circuit according to claim 11, characterized in that: A common connection point where the power supply end of the controller is connected to the drain of the main power tube is connected to a power loop node of the switch circuit.

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