Isolation circuit, power converter and isolation method

Abstract

The present invention discloses an isolation circuit, a power converter and an isolation method. The isolation circuit includes a switching circuit, a bipolar isolation circuit and a unipolar isolation circuit. The switching circuit has a signal input end, a controlled end, a first output end and a second output end. The signal input end of the switching circuit is used to connect the PWM signal input end, and the controlled end of the switching circuit is used to receive a polarity selection control signal. The input end of the bipolar isolation circuit is connected to the first output end of the switching circuit, and the output end of the bipolar isolation circuit is used to connect a drive switch. The input end of the unipolar isolation circuit is connected to the second output end of the switching circuit, and the output end of the unipolar isolation circuit is used to connect a drive switch. Under the control of the polarity selection control signal, the signal input end of the switching circuit is connected to the first output end or the second output end. The present invention reduces the jitter of the unipolar and bipolar PWM signals through the switching circuit, the first isolation circuit and the second isolation circuit, and the circuit structure is simple.

Description

Technical Field

[0001] The present invention relates to the field of motor drive and power supply, and in particular to an isolation circuit, a power converter and an isolation method. Background Art

[0002] Traditional PWM (Pulse width modulation) isolation drive circuit such as Figure 1 As shown, the PWM signal is sent by DSP / FPGA / MCU, and commercial chips such as optical isolation / magnetic isolation are used to achieve high and low voltage isolation, and the power device is driven by the gate drive circuit. The isolation circuit is implemented by a commercial isolation chip, and the PWM signal output by it has jitter. Even for the isolation chip with better jitter optimization, the jitter exists in the hundreds of ps or even ns level. In high-precision applications, such as in the fields of wafer inspection and photolithography, the output current of the power converter is required to have extremely low noise. The jitter of hundreds of ps will cause the output current to generate large noise and it is difficult to meet the requirements. On the other hand, in high-frequency (MHz switching frequency) power converters, the jitter of hundreds of ps or even ns level accounts for a large proportion of the switching cycle (a few percent of jitter), which will generate greater noise. In the prior art, the PWM isolation drive reduces the jitter of the PWM signal through a high-frequency transformer and a D trigger, and realizes the isolation of unipolar and bipolar PWM signals at the same time, but the circuit structure is relatively complex. Summary of the invention

[0003] The main purpose of the present invention is to provide an isolation circuit, a power converter and an isolation method, aiming at reducing PWM signal jitter.

[0004] To achieve the above object, the present invention provides an isolation circuit for a power converter, wherein the power converter has a PWM signal input terminal and a drive switch, wherein the PWM signal input terminal is used to access a unipolar PWM signal or a bipolar PWM signal, and the isolation circuit connects the PWM signal input terminal and the drive switch, and the isolation circuit comprises:

[0005] A switching circuit, wherein the switching circuit has a signal input terminal, a controlled terminal, a first output terminal and a second output terminal, wherein the signal input terminal of the switching circuit is used to connect to the PWM signal input terminal, and the controlled terminal of the switching circuit is used to receive a polarity selection control signal;

[0006] a bipolar isolation circuit, wherein an input end of the bipolar isolation circuit is connected to a first output end of the switching circuit, and an output end of the bipolar isolation circuit is used to connect to the driving switch;

[0007] a unipolar isolation circuit, wherein the input end of the unipolar isolation circuit is connected to the second output end of the switching circuit, and the output end of the unipolar isolation circuit is used to connect to the driving switch;

[0008] The switching circuit is used to connect the signal input end of the switching circuit to the first output end or the second output end under the control of the polarity selection control signal.

[0009] In one embodiment, the bipolar isolation circuit includes a first high-frequency transformer;

[0010] The primary side of the first high-frequency transformer is the output end of the bipolar isolation circuit, and the secondary side of the first high-frequency transformer is the output end of the bipolar isolation circuit;

[0011] The first high-frequency transformer is used for electrical isolation.

[0012] In one embodiment, the bipolar isolation circuit further includes a first drive circuit;

[0013] The input end of the first driving circuit is connected to the output end of the bipolar isolation circuit, and the output end of the first driving circuit is used to be connected to a driving switch;

[0014] The first driving circuit is used to amplify the received PWM signal.

[0015] In one embodiment, the unipolar isolation circuit includes a first conversion circuit, a second high-frequency transformer, and a second conversion circuit;

[0016] The input end of the first conversion circuit is the input end of the unipolar isolation circuit, the output end of the first conversion circuit is connected to the primary side of the second high-frequency transformer, the secondary side of the second high-frequency transformer is connected to the input end of the second conversion circuit, and the output end of the second conversion circuit is the output end of the unipolar isolation circuit;

[0017] The first conversion circuit is used to convert the received unipolar PWM signal into a bipolar PWM signal, the second high-frequency transformer is used for electrical isolation, and the second conversion circuit is used to convert the bipolar PWM signal into a unipolar PWM signal.

[0018] In one embodiment, the unipolar isolation circuit further includes a second driving circuit;

[0019] The input end of the second driving circuit is connected to the output end of the unipolar isolation circuit, and the output end of the second driving circuit is used to be connected to the driving switch;

[0020] The second driving circuit is used to amplify the received PWM signal.

[0021] The present invention further provides a power converter, which includes a PWM signal input terminal, a drive switch and the isolation circuit as described above.

[0022] The present invention further provides an isolation method, which is applied to the power converter as described above, and the isolation method comprises:

[0023] When a bipolar PWM signal is received, the signal input end of the control switching circuit is connected to the first output end, so that the bipolar PWM signal is output after being isolated by the bipolar isolation circuit;

[0024] When a unipolar PWM signal is received, the signal input end of the control switching circuit is connected to the second output end, so that the unipolar PWM signal is output after being isolated by the unipolar isolation circuit.

[0025] In one embodiment, when a unipolar PWM signal is received, the signal input end of the control switching circuit is connected to the second output end, so that the bipolar PWM signal is output after being isolated by the unipolar isolation circuit. Specifically,

[0026] When a unipolar PWM signal is received, the signal input end of the control switching circuit is connected to the second output end, the first conversion circuit converts the unipolar PWM signal into a bipolar PWM signal, and after isolation by the second high-frequency transformer, the second conversion circuit converts the bipolar PWM signal into a unipolar PWM signal for output.

[0027] The present invention isolates a bipolar PWM signal through a first isolation circuit and then outputs it, converts, isolates and converts a unipolar PWM signal through a second isolation circuit and then outputs it, and switches when PWM signals of different polarities are connected through a switching circuit, thereby reducing jitter of unipolar and bipolar PWM signals and having a simple circuit structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0029] Figure 1 It is a structural schematic diagram of an embodiment of an isolation circuit in the prior art;

[0030] Figure 2 for Figure 1 PWM signal waveform of the isolation circuit;

[0031] Figure 3It is a structural schematic diagram of an embodiment of an isolation circuit in the prior art;

[0032] Figure 4 It is a structural schematic diagram of the isolation circuit of the present invention;

[0033] Figure 5 It is a structural schematic diagram of an embodiment of an isolation circuit of the present invention;

[0034] Figure 6 Schematic diagram of the isolation method of the present invention.

[0035] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0038] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0039] Reference Figures 1-2 , the traditional isolation circuit uses commercial chips such as optical isolation / magnetic isolation to achieve electrical isolation, and the PWM signal output by the isolation circuit has jitter of hundreds of ps or even ns. Figure 3 , while retaining the commercial isolation chip, a high-frequency transformer and a D flip-flop need to be added. The DSP outputs a synchronous clock, which is isolated by a high-frequency transformer to achieve a ps-level jitter clock and input to the clock end of the D flip-flop to synchronize the PWM signal, ultimately achieving an extremely low jitter of the PWM signal at the ps level. Figure 2 The isolation circuit can reduce the jitter of the PWM signal to the ps level, but the circuit structure is relatively complex.

[0040] Reference Figure 4 The present invention proposes an isolation circuit for a power converter, wherein the power converter has a PWM signal input terminal and a drive switch, wherein the PWM signal input terminal is used to receive a unipolar PWM signal or a bipolar PWM signal, wherein the isolation circuit connects the PWM signal input terminal and the drive switch, and wherein the isolation circuit includes a switching circuit 10, a bipolar isolation circuit 20, and a unipolar isolation circuit 30.

[0041] The switching circuit 10 has a signal input terminal, a controlled terminal, a first output terminal and a second output terminal. The signal input terminal of the switching circuit 10 is used to connect to the PWM signal input terminal, and the controlled terminal of the switching circuit 10 is used to receive a polarity selection control signal.

[0042] The input end of the bipolar isolation circuit 20 is connected to the first output end of the switching circuit 10 , and the output end of the bipolar isolation circuit 20 is used to connect to the driving switch.

[0043] The input end of the unipolar isolation circuit 30 is connected to the second output end of the switching circuit 10 , and the output end of the unipolar isolation circuit 30 is used to connect to the driving switch.

[0044] The switching circuit 10 is used to connect the signal input end of the switching circuit 10 to the first output end or the second output end under the control of the polarity selection control signal.

[0045] When the PWM signal input terminal is connected to a bipolar PWM signal, the switching circuit 10 connects the signal input terminal to the first output terminal under the control of the polarity selection control signal, and the bipolar PWM signal is electrically isolated by the first isolation circuit and then output to the drive switch. When the PWM signal input terminal is connected to a unipolar PWM signal, the switching circuit 10 connects the signal input terminal to the second output terminal under the control of the polarity selection control signal, and the unipolar PWM signal is converted into a bipolar PWM signal by the second isolation circuit and then isolated, and then the isolated bipolar PWM signal is converted into a unipolar PWM signal and then output to the drive switch.

[0046] The present invention isolates a bipolar PWM signal through a first isolation circuit and then outputs it, converts, isolates and converts a unipolar PWM signal through a second isolation circuit and then outputs it, and switches when PWM signals of different polarities are connected through a switching circuit, thereby reducing jitter of unipolar and bipolar PWM signals and having a simple circuit structure.

[0047] Reference Figure 5In one embodiment, the bipolar isolation circuit 20 includes a first high-frequency transformer 21 .

[0048] The primary side of the first high-frequency transformer 21 is the output end of the bipolar isolation circuit 20 , and the secondary side of the first high-frequency transformer 21 is the output end of the bipolar isolation circuit 20 .

[0049] The first high-frequency transformer 21 is used for electrical isolation.

[0050] This embodiment can reduce the jitter of bipolar PWM signals through a high-frequency transformer, and can achieve ps-level signal jitter in precision application fields or high-frequency fields such as wafer inspection and lithography, thereby reducing the noise of the output voltage and current of the isolation circuit.

[0051] In one embodiment, the bipolar isolation circuit 20 further includes a first driving circuit 22 .

[0052] The input end of the first driving circuit 22 is connected to the output end of the bipolar isolation circuit 20 , and the output end of the first driving circuit 22 is used to be connected to a driving switch.

[0053] The first driving circuit 22 is used to amplify the received PWM signal.

[0054] In this embodiment, the isolated PWM signal is amplified by the driving circuit to increase the driving force of the PWM signal, thereby preventing the driving switch from working unstably due to too low a voltage.

[0055] In one embodiment, the unipolar isolation circuit 30 includes a first conversion circuit 31 , a second high-frequency transformer 32 and a second conversion circuit 33 .

[0056] The input end of the first conversion circuit 31 is the input end of the unipolar isolation circuit 30, the output end of the first conversion circuit 31 is connected to the primary side of the second high-frequency transformer 32, the secondary side of the second high-frequency transformer 32 is connected to the input end of the second conversion circuit 33, and the output end of the second conversion circuit 33 is the output end of the unipolar isolation circuit 30.

[0057] The first conversion circuit 31 is used to convert the received unipolar PWM signal into a bipolar PWM signal, the second high-frequency transformer 32 is used for electrical isolation, and the second conversion circuit 33 is used to convert the bipolar PWM signal into a unipolar PWM signal.

[0058] A high-frequency transformer can reduce the jitter of a bipolar PWM signal, but the isolation signal of a high-frequency transformer requires positive and negative alternation, and cannot transmit a unipolar PWM signal. In this embodiment, after the unipolar PWM signal is converted into a bipolar PWM signal by the first conversion circuit 31, isolation transmission is achieved through a high-frequency transformer to reduce signal jitter, and then the bipolar PWM signal is converted into a unipolar PWM signal through the second conversion circuit 33 and output to the drive switch.

[0059] In one embodiment, the unipolar isolation circuit 30 further includes a second driving circuit 34 .

[0060] The input end of the second driving circuit 34 is connected to the output end of the unipolar isolation circuit 30 , and the output end of the second driving circuit 34 is used to be connected to a driving switch.

[0061] The second driving circuit 34 is used to amplify the received PWM signal.

[0062] In this embodiment, the isolated PWM signal is amplified by the driving circuit to increase the driving force of the PWM signal, thereby preventing the driving switch from working unstably due to too low a voltage.

[0063] The present invention further provides a power converter, which includes a PWM signal input terminal, a drive switch and the isolation circuit as described above.

[0064] It can be understood that, since the above-mentioned isolation circuit is used in the above-mentioned power converter, the embodiment of the power converter includes all technical solutions of all embodiments of the above-mentioned isolation circuit, and the technical effects achieved are also exactly the same, which will not be repeated here.

[0065] Reference Figure 6 The present invention further proposes an isolation method, which is applied to the power converter as described above, and the isolation method comprises:

[0066] S100: When a bipolar PWM signal is received, the signal input terminal of the control switching circuit is connected to the first output terminal, so that the bipolar PWM signal is output after being isolated by the bipolar isolation circuit;

[0067] S200: When a unipolar PWM signal is received, the signal input terminal of the control switching circuit is connected to the second output terminal, so that the unipolar PWM signal is output after being isolated by the unipolar isolation circuit.

[0068] When the PWM signal input terminal is connected to a bipolar PWM signal, the switching circuit connects the signal input terminal to the first output terminal under the control of the polarity selection control signal, and the bipolar PWM signal is output to the drive switch after being electrically isolated by the first isolation circuit. When the PWM signal input terminal is connected to a unipolar PWM signal, the switching circuit connects the signal input terminal to the second output terminal under the control of the polarity selection control signal, and the unipolar PWM signal is converted into a bipolar PWM signal by the second isolation circuit and then isolated, and then the isolated bipolar PWM signal is converted into a unipolar PWM signal and then output to the drive switch.

[0069] The present invention switches when accessing PWM signals of different polarities through a switching circuit, isolates the bipolar PWM signal through a first isolation circuit and then outputs it, and converts, isolates and converts the unipolar PWM signal through a second isolation circuit and then outputs it, thereby reducing jitter of the unipolar and bipolar PWM signals.

[0070] In one embodiment, when a unipolar PWM signal is received, the signal input end of the control switching circuit is connected to the second output end, so that the bipolar PWM signal is output after being isolated by the unipolar isolation circuit. Specifically,

[0071] When a unipolar PWM signal is received, the signal input end of the control switching circuit is connected to the second output end, the first conversion circuit converts the unipolar PWM signal into a bipolar PWM signal, and after isolation by the second high-frequency transformer, the second conversion circuit converts the bipolar PWM signal into a unipolar PWM signal for output.

[0072] A high-frequency transformer can reduce the jitter of a bipolar PWM signal, but the isolation signal of a high-frequency transformer requires positive and negative alternation, and cannot transmit a unipolar PWM signal. In this embodiment, after the unipolar PWM signal is converted into a bipolar PWM signal by a first conversion circuit, isolation transmission is achieved through a high-frequency transformer to reduce signal jitter, and then the bipolar PWM signal is converted into a unipolar PWM signal by a second conversion circuit and output to the drive switch.

[0073] The above are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. An isolation circuit for a power converter, wherein the power converter has a PWM signal input terminal and a drive switch, wherein the PWM signal input terminal is used to receive a unipolar PWM signal or a bipolar PWM signal, and the isolation circuit connects the PWM signal input terminal and the drive switch, wherein: The isolation circuit comprises: A switching circuit, wherein the switching circuit has a signal input terminal, a controlled terminal, a first output terminal and a second output terminal, wherein the signal input terminal of the switching circuit is used to connect to the PWM signal input terminal, and the controlled terminal of the switching circuit is used to receive a polarity selection control signal; a bipolar isolation circuit, wherein an input end of the bipolar isolation circuit is connected to a first output end of the switching circuit, and an output end of the bipolar isolation circuit is used to connect to the driving switch; a unipolar isolation circuit, wherein the input end of the unipolar isolation circuit is connected to the second output end of the switching circuit, and the output end of the unipolar isolation circuit is used to connect to the driving switch; The switching circuit is used to connect the signal input end of the switching circuit to the first output end or the second output end under the control of the polarity selection control signal.

2. The isolation circuit according to claim 1, characterized in that: The bipolar isolation circuit includes a first high-frequency transformer; The primary side of the first high-frequency transformer is the output end of the bipolar isolation circuit, and the secondary side of the first high-frequency transformer is the input end of the bipolar isolation circuit; The first high-frequency transformer is used for electrical isolation.

3. The isolation circuit according to claim 2, characterized in that: The bipolar isolation circuit also includes a first drive circuit; The input end of the first driving circuit is connected to the output end of the bipolar isolation circuit, and the output end of the first driving circuit is used to be connected to a driving switch; The first driving circuit is used to amplify the received bipolar PWM signal.

4. The isolation circuit according to claim 1, characterized in that: The unipolar isolation circuit includes a first conversion circuit, a second high-frequency transformer and a second conversion circuit; The input end of the first conversion circuit is the input end of the unipolar isolation circuit, the output end of the first conversion circuit is connected to the primary side of the second high-frequency transformer, the secondary side of the second high-frequency transformer is connected to the input end of the second conversion circuit, and the output end of the second conversion circuit is the output end of the unipolar isolation circuit; The first conversion circuit is used to convert the received unipolar PWM signal into a bipolar PWM signal, the second high-frequency transformer is used for electrical isolation, and the second conversion circuit is used to convert the bipolar PWM signal into a unipolar PWM signal.

5. The isolation circuit according to claim 4, characterized in that: The unipolar isolation circuit also includes a second driving circuit; The input end of the second driving circuit is connected to the output end of the unipolar isolation circuit, and the output end of the second driving circuit is used to be connected to the driving switch; The second driving circuit is used for amplifying the received unipolar PWM signal.

6. A power converter, characterized in that: The power converter comprises a PWM signal input terminal, a drive switch and an isolation circuit as claimed in any one of claims 1 to 5.

7. An isolation method, applied to the power converter as claimed in claim 6, characterized in that: The isolation method comprises: When a bipolar PWM signal is received, the signal input end of the control switching circuit is connected to the first output end, so that the bipolar PWM signal is output after being isolated by the bipolar isolation circuit; When a unipolar PWM signal is received, the signal input end of the control switching circuit is connected to the second output end, so that the unipolar PWM signal is output after being isolated by the unipolar isolation circuit.

8. The isolation method according to claim 7, characterized in that: The unipolar isolation circuit in the power converter includes a first conversion circuit, a second high-frequency transformer and a second conversion circuit; when a unipolar PWM signal is received, the signal input end of the control switching circuit is connected to the second output end, so that the unipolar PWM signal is output after being isolated by the unipolar isolation circuit. Specifically: When a unipolar PWM signal is received, the signal input end of the control switching circuit is connected to the second output end, the first conversion circuit converts the unipolar PWM signal into a bipolar PWM signal, and after isolation by the second high-frequency transformer, the second conversion circuit converts the bipolar PWM signal into a unipolar PWM signal for output.

Images