An AC-DC converter

Abstract

The present invention provides an AC-DC converter, comprising a front-stage rectifier circuit, a first resistor, a thyristor, a first capacitor and a rear-stage DC conversion circuit, wherein the first capacitor is connected in series with the first resistor and then connected in parallel with the output end of the front-stage rectifier circuit, the input end of the rear-stage DC conversion circuit is connected in parallel with the first capacitor, the thyristor is connected in parallel with the first resistor, the rear-stage DC conversion circuit comprises a transformer, the primary winding of the transformer is connected in parallel with the series branch of the second resistor and the first diode, the second resistor is connected in parallel with the second capacitor, and the gate of the thyristor is connected to the series midpoint of the second resistor and the first diode. The present invention is a new thyristor drive circuit power supply method, which simplifies the circuit and reduces the drive loss.

Description

Technical Field

[0001] The present invention relates to the technical field of AC / DC converters, and in particular to the technology of suppressing surge current of AC / DC converters. Background Art

[0002] In the AC-DC converter, a capacitor is arranged after the front-stage rectifier bridge circuit. Before the AC-DC converter is powered on, there is no voltage on the capacitor, which can be approximated as a short circuit. When the AC-DC converter is powered on, the input end of the AC-DC converter is connected to the power grid, and its voltage is very high, resulting in a high surge current at the moment of power on.

[0003] In order to suppress the startup surge current, a common practice is to connect a resistor in series between the input end of the AC-DC converter and the capacitor, which can suppress the surge current. However, when the resistor is connected in series to the power circuit, a certain amount of power loss will occur. On the one hand, this loss will reduce the conversion efficiency of the product and cause energy waste; on the other hand, it will increase the product temperature and reduce reliability. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art, use a thyristor in parallel with a resistor for suppressing surge current, and provide a new thyristor gate drive circuit, which can simplify the circuit and reduce the thyristor drive loss.

[0005] In order to achieve the above purpose and other purposes, the present invention is implemented through the following technical solutions: an AC-DC converter, including a front-stage rectifier circuit, a first resistor, a thyristor, a first capacitor and a rear-stage DC conversion circuit, the first capacitor is connected in series with the first resistor and then connected in parallel with the output end of the front-stage rectifier circuit, the input end of the rear-stage DC conversion circuit is connected in parallel with the first capacitor, and the thyristor is connected in parallel with the first resistor, characterized in that the rear-stage DC conversion circuit includes a transformer, the primary winding of the transformer is connected in parallel with the series branch of a second resistor and a first diode, the second resistor is connected in parallel with a second capacitor, and the gate of the thyristor is connected to the series midpoint of the second resistor and the first diode.

[0006] In a specific embodiment of the present invention, the thyristor includes a first thyristor and a second thyristor, the front-stage rectifier circuit includes a second diode, a third diode, a fourth diode, and a fifth diode, the second diode, the third diode, the fourth diode and the fifth diode form a full-bridge rectifier circuit, the second diode and the third diode are connected in series, the fourth diode and the fifth diode are connected in series, the first thyristor is connected in parallel with the first resistor through the second diode, the anode of the first thyristor is connected in parallel with the anode of the second diode, the second thyristor is connected in parallel with the first resistor through the third diode, the anode of the second thyristor is connected in parallel with the anode of the third diode, the gate of the first thyristor is connected to the midpoint of the series connection of the second resistor and the first diode through the third resistor, and the gate of the second thyristor is connected to the midpoint of the series connection of the second resistor and the first diode through the fourth resistor.

[0007] In a specific embodiment of the present invention, the AC-DC converter further includes a first switch, and the primary winding of the transformer is connected in series with the first switch.

[0008] In a specific embodiment of the present invention, the like-named ends of the secondary winding of the transformer are opposite to the like-named ends of the primary winding.

[0009] In a specific embodiment of the present invention, the secondary winding of the transformer is connected in series with a sixth diode.

[0010] In a specific embodiment of the present invention, the secondary winding of the transformer is connected in series with a sixth diode and then connected in parallel with a third capacitor.

[0011] In a specific embodiment of the present invention, the first capacitor is an electrolytic capacitor.

[0012] In a specific embodiment of the present invention, the first end of the first resistor is connected to the output end of the front-stage rectifier circuit, the second end of the first resistor is connected to the first capacitor, the anode of the thyristor is connected to the first end of the first resistor, and the cathode of the thyristor is connected to the second end of the first resistor.

[0013] The present invention uses the electric energy of the RCD absorption circuit to drive the thyristor to achieve short-circuit surge current suppression resistance and reduce circuit loss. The present invention has a simple structure and is easy to use, and has the value of promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is shown as a first embodiment of the present invention.

[0015] Figure 2 This is shown as a second embodiment of the present invention. DETAILED DESCRIPTION

[0016] See also Figure 1 to Figure 2 The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0017] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for the understanding and reading of those skilled in the art, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship, or adjustment of the size should still fall within the scope of the technical contents disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "front", "back", "upper", "lower", "left", "right", "middle", and "one" cited in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical contents.

[0018] like Figure 1 As shown, in this embodiment, the front-stage rectifier circuit 11 includes diodes D1-D4, and the diodes D1-D4 constitute a full-bridge rectifier circuit. The input end IN of the front-stage rectifier circuit 11 inputs the alternating current vin, and the output end P1-P0 of the front-stage rectifier circuit 11 is connected in parallel with the series branch of the resistor R1 and the capacitor C1, and the two ends P2-P0 of the capacitor C1 are connected in parallel with the post-stage DC conversion circuit 12. In this embodiment, the rear-stage DC conversion circuit 12 is a flyback conversion circuit, which includes a transformer T1, a series branch of a resistor R2 and a diode D5 connected in parallel on the primary side of the transformer T1, a capacitor C2 connected in parallel at both ends of the resistor R2, when the switch S1 is turned on, the AC power vin inputs the electric energy into the primary inductance Lp and the leakage inductance Lk of the transformer T1, when the switch S1 is turned off, the electric energy of the primary inductance Lp is transmitted to the secondary side, the electric energy in the leakage inductance Lk is transferred to the capacitor C2 through the diode D5, the two ends of the capacitor C2 are connected P3 and P2, wherein the voltage of P3 is higher than the voltage of P2, and the electric energy in the capacitor C2 is consumed on the resistor R2. The secondary side of the transformer T1 is connected in series with a diode D6 and a capacitor C3, the two ends of the capacitor C3 are connected in parallel with a load, and a DC power Vo is provided to the load. The thyristor SCR1 is connected in parallel with the resistor R1, wherein the anode is connected to the terminal P1, the cathode is connected to the terminal P2, and the gate is connected to the terminal P3 through the resistor R3. When the AC-DC converter is turned on, the thyristor SCR1 is disconnected, and the resistor R1 is connected in series between the terminals P1 and P2 to suppress the startup surge current. After the startup is completed, the voltage of the terminal P3 is higher than the voltage of the terminal P2, the thyristor SCR1 is turned on, and the resistor R1 is short-circuited. The driving method of the thyristor SCR1 in this embodiment does not require an additional transformer auxiliary winding, which simplifies the driving circuit and the winding structure of the transformer.

[0019] The RCD absorption module of the flyback conversion circuit is used to absorb the energy of the transformer leakage inductance, which is stored in the capacitor C2 and generates loss on the resistor R2. In this embodiment, part of the energy stored in the capacitor C2 is used to drive the thyristor SCR1, which reduces the loss on the resistor R2 and effectively utilizes the energy on the capacitor C2.

[0020] Figure 2 Another embodiment of the present invention is shown. Figure 1 The difference between the embodiment shown is that, in this embodiment, the cathode of thyristor SCR1 and the cathode of thyristor SCR2 are connected in parallel and then connected to terminal P4, the cathode of thyristor SCR1 and the gate of thyristor SCR2 are connected in parallel and then connected to terminal P3, the cathode of thyristor SCR1 and the anode of thyristor SCR2 are respectively connected to the two terminals of input terminal IN, when the AC-DC converter is turned on, the AC power vin provides power to the load through the rectifier bridge composed of diodes D1-D4, and the resistor R1 realizes surge current suppression. After turning on, thyristor SCR1 and thyristor SCR2 are turned on, diode D1, diode D3 and resistor R1 are short-circuited, and the AC power vin provides power to the subsequent DC conversion circuit 22 through the rectifier bridge composed of diode D2, diode D4, thyristor SCR1 and thyristor SCR2.

[0021] The circuit structure of the surge current suppression in the AC-DC conversion circuit of the present invention is simple, and the driving loss of the thyristor is saved, thereby reducing the energy loss.

[0022] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value. The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology can modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An AC-DC converter, comprising a front-stage rectifying circuit, a first resistor, a thyristor, a first capacitor and a rear-stage DC conversion circuit, wherein the first capacitor is connected in series with the first resistor and then connected in parallel with the output end of the front-stage rectifying circuit, the input end of the rear-stage DC conversion circuit is connected in parallel with the first capacitor, and the thyristor is connected in parallel with the first resistor, characterized in that: The post-stage DC conversion circuit includes a transformer, the primary winding of the transformer is connected in parallel with the series branch of a second resistor and a first diode, the second resistor is connected in parallel with a second capacitor, and the gate of the thyristor is connected to the series midpoint of the second resistor and the first diode; the pre-stage rectifier circuit includes a second diode, a third diode, a fourth diode, and a fifth diode, the second diode, the third diode, the fourth diode and the fifth diode form a full-bridge rectifier circuit, the second diode and the third diode are connected in series, and the fourth diode and the fifth diode are connected in series; the anode of the thyristor is connected to the pre-stage rectifier circuit.

2. An AC-DC converter as claimed in claim 1, characterized in that: The thyristor includes a first thyristor and a second thyristor, the first thyristor is connected in parallel with the first resistor via a second diode, the anode of the first thyristor is connected in parallel with the anode of the second diode, the second thyristor is connected in parallel with the first resistor via a third diode, the anode of the second thyristor is connected in parallel with the anode of the third diode, the gate of the first thyristor is connected to the midpoint of the series connection of the second resistor and the first diode via a third resistor, and the gate of the second thyristor is connected to the midpoint of the series connection of the second resistor and the first diode via a fourth resistor.

3. An AC-DC converter as claimed in claim 1, characterized in that: It also includes a first switch, and the primary winding of the transformer is connected in series with the first switch.

4. An AC-DC converter as claimed in claim 3, characterized in that: The same-named ends of the secondary winding of the transformer are opposite to the same-named ends of the primary winding.

5. An AC-DC converter as claimed in claim 4, characterized in that: The secondary winding of the transformer is connected in series with the sixth diode.

6. An AC-DC converter as claimed in claim 5, characterized in that: The secondary winding of the transformer is connected in series with the sixth diode and then connected in parallel with the third capacitor.

7. The AC-DC converter according to claim 1, characterized in that: The first capacitor is an electrolytic capacitor.

8. An AC-DC converter as claimed in claim 1, characterized in that: The first end of the first resistor is connected to the output end of the front-stage rectifier circuit, the second end of the first resistor is connected to the first capacitor, the anode of the thyristor is connected to the first end of the first resistor, and the cathode of the thyristor is connected to the second end of the first resistor.

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