An isolated switch circuit and noise control circuit thereof

Abstract

A noise control circuit for an isolated switching circuit is disclosed. The noise control circuit generates a reverse noise signal by adjusting off-chip components or feedback signals from circuit noise points, and couples the reverse noise signal to a suitable end point of the circuit, thereby offsetting the noise at the circuit noise point, so as to prevent the noise from being transmitted to the power supply end of the isolated switching circuit and causing noise pollution. The noise control circuit of the present invention reduces the influence of the switching noise caused by the switching action of the isolated switching circuit on the power supply end, and improves the EMI (Electro-Magnetic Interference) characteristics of the circuit.

Description

Technical Field

[0001] The embodiments of the present invention relate to a switching power supply, and more specifically, to a noise control circuit of an isolated switching circuit. Background Art

[0002] The switching power supply converts input power into output power with a specific voltage and current and supplies it to the load. The switching power supply controls the power switch at a certain frequency or duty cycle to control its output power. Therefore, the switching power supply will inevitably generate switching noise during operation. This switching noise exists in the form of ripple voltage or ripple current at the switch end of the switching power supply, and is transmitted to the power supply end through some loops, causing noise interference to the power supply. In order for the switching power supply to meet the necessary international standards, it is necessary to eliminate these ripple voltages and ripple currents. Summary of the invention

[0003] To solve the above technical problems, the present invention provides a noise control circuit for an isolated switch circuit. The noise control circuit of the present invention cancels noise by creating reverse noise, or in other words, by creating a noise loop so that noise cannot be transmitted to the power supply end, thereby reducing the impact of noise on the power supply end.

[0004] According to an embodiment of the present invention, a noise control circuit of an isolated switch circuit is proposed, comprising: a reverse noise circuit having a first input terminal coupled to a signal jump terminal of a primary power switch of the isolated switch circuit to receive a noise signal, and a second input terminal to receive an adjustment signal, wherein the reverse noise circuit outputs a noise control signal at an output terminal based on the noise signal and the adjustment signal; wherein the noise control signal is coupled to one end of a secondary winding of the isolated switch circuit through a coupling circuit, and the signal jump terminal of the primary power switch is any end of the primary power switch except the end coupled to the primary ground.

[0005] According to an embodiment of the present invention, a noise control circuit of an isolated switching circuit is also proposed, including: a reverse noise circuit, having an input end coupled to a signal jump end of a secondary switch of the isolated switching circuit to receive a noise signal, and a control end to receive an adjustment signal. Based on the noise signal and the adjustment signal, the reverse noise circuit outputs a noise control signal at an output end, and couples the noise control signal to any end of the primary circuit of the isolated switching circuit.

[0006] According to an embodiment of the present invention, an isolated switching circuit is also proposed, including the aforementioned noise control circuit, and also including: a primary power switch, having a first end, a second end and a control end, the first end being coupled to an energy storage device of the isolated switching circuit, the second end being coupled to the primary ground, and the control end receiving a switch control signal, wherein the first end and the control end are signal jump ends of the primary power switch.

[0007] According to an embodiment of the present invention, the aforementioned isolated switch circuit further includes an energy storage device, wherein the energy storage device includes a transformer having a primary winding and a secondary winding, wherein the primary winding is coupled to the primary power switch.

[0008] According to an embodiment of the present invention, the aforementioned isolated switch circuit further comprises a secondary switch coupled to the secondary winding of the energy storage device, wherein the connection point between the secondary switch and the secondary winding of the energy storage device is the signal jump end of the secondary switch.

[0009] The noise control circuit provided in the embodiment of the present invention effectively and adjustably reduces the switching noise of the circuit through simple circuit components, thereby improving the EMI (Electro-Magnetic Interference) characteristics of the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to better understand the present invention, the present invention will be described in detail according to the following drawings:

[0011] Figure 1 A schematic diagram of the circuit structure of an existing isolated switch circuit 10 is shown;

[0012] Figure 2 A schematic diagram of the circuit structure of an isolated switch circuit 20 according to an embodiment of the present invention is shown;

[0013] Figure 3 A schematic diagram of the circuit structure of an isolated switch circuit 30 according to an embodiment of the present invention is shown;

[0014] Figure 4 A schematic diagram of the circuit structure of an isolated switch circuit 40 according to an embodiment of the present invention is shown;

[0015] Figure 5 A schematic diagram of the circuit structure of an isolated switch circuit 50 according to an embodiment of the present invention is shown;

[0016] Figure 6 A schematic diagram of the circuit structure of an isolated switch circuit 60 according to an embodiment of the present invention is shown;

[0017] Figure 7 A schematic diagram of the circuit structure of an isolated switch circuit 70 according to an embodiment of the present invention is shown;

[0018] Figure 8 A schematic diagram of the circuit structure of an isolated switch circuit 80 according to an embodiment of the present invention is shown; and

[0019] Fig. 9FIG. 4 is a schematic diagram showing a circuit structure of an isolated switch circuit 90 according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not have to be used to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, materials or methods are not specifically described.

[0021] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any appropriate combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The same reference numerals indicate the same elements. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Figure 1 FIG. 1 shows a schematic diagram of the circuit structure of an existing isolated switch circuit 10. Figure 1 As shown, the isolated switch circuit 10 includes: an energy storage device T1, that is, a transformer, including a primary winding Lp and a secondary winding Ls; a primary power switch P1 coupled to the primary winding Lp of the energy storage device T1; a secondary switch D1 coupled to the secondary winding Ls of the energy storage device T1; and an output capacitor COUT. The isolated switch circuit 10 is a typical flyback topology, in which the primary power switch P1 is turned on and off under the control of the switch control signal G1, transferring energy from the primary side to the secondary side, and outputting the output voltage VOUT and power required by the subsequent load.

[0023] In the isolated switch circuit 10, the primary winding Lp is connected or disconnected with the primary ground PGND through the primary power switch P1, thereby generating a switching signal at the connection point C between the primary winding Lp and the primary power switch P1. Similarly, the secondary winding Ls is connected or disconnected with the secondary switch D1, and a switching signal is generated at the connection point B between the secondary winding Ls and the secondary switch D1. The switching signal at the connection point C is coupled to the secondary winding Ls through the parasitic capacitance Cp1 between the primary and secondary sides of the transformer T1, and the noise flows back to the power supply terminal A with the help of the parasitic capacitance of the secondary side to the ground, thereby forming noise pollution. The switching noise at the connection point B is coupled to the power supply terminal A of the primary winding Lp through the parasitic capacitance Cp2 of the secondary winding Ls of the transformer T1 to the primary side, thereby causing noise pollution to the power supply.

[0024] Figure 2 The circuit structure diagram of the isolated switch circuit 20 according to an embodiment of the present invention is shown. The isolated switch circuit 20 has a Flyback topology structure, including a transformer T1, a primary power switch P1, a secondary switch D1 and a noise control circuit 200 of the illustrated connection structure. The noise control circuit 200 includes: a reverse noise circuit 201, having a first input terminal receiving a noise signal Vn, a second input terminal receiving an adjustment signal Vadj, and based on the noise signal Vn and the adjustment signal Vadj, the reverse noise circuit 201 outputs a noise control signal Vp1 at an output terminal; a coupling circuit 202, having a first terminal coupled to the output terminal of the reverse noise circuit 201 to receive the noise control signal Vp1, and a second terminal coupled to the ground terminal SGND of the isolated switch circuit 20; and an adjustment circuit 203, having a first terminal coupled to the second input terminal of the reverse noise circuit 201, and a second terminal coupled to the primary ground PGND of the isolated switch circuit 20.

[0025] The reverse noise circuit 201 receives the noise signal Vn and outputs a noise control signal Vp1 based on the noise signal Vn. Figure 2 In the embodiment, the noise signal Vn is a signal of the gate of the primary power switch P1. In some embodiments, the reverse noise circuit 201 detects a signal at the coupling point between the primary power switch P1 and the primary winding Lp, and outputs a noise control signal Vp1 based on the signal. It should be understood that Figure 2The primary power switch P1 is an N-type transistor, and the phases of the signals at its gate and drain are opposite. When the gate signal of the primary power switch P1 is high, the primary power switch P1 is turned on, and its drain signal is low. When the gate signal of the primary power switch P1 is low, the primary power switch P1 is turned off, and its drain signal is high. In some embodiments, when the primary power switch P1 is a P-type transistor, the source of the P-type transistor is coupled to the primary winding Lp. When the gate signal of the P-type transistor is high, the P-type transistor is turned off, and its source signal is high. When the gate signal of the P-type transistor is low, the P-type transistor is turned on, and its source signal is low. In other words, the signal at the control end (gate) of the primary power switch P1 corresponds to the signal at one end (drain or source) connected to the primary winding Lp, and the phases are the same or opposite. Therefore, the noise signal Vn can be a signal at the signal transition end of the primary power switch P1, that is, a signal at the control end of the primary power switch P1 or a signal at the coupling point between the primary power switch P1 and the primary winding Lp. Further, a signal at other ends of the isolated switch circuit 20 that is the same or opposite in phase to the switch control signal G1 of the gate of the primary power switch P1 can also be used as the noise signal Vn.

[0026] In one embodiment, the regulating circuit 203 includes resistors, and the amplitude of the noise control signal Vp1 can be adjusted by coupling resistors with different resistance values. In other embodiments, the regulating circuit 203 may also include capacitors, that is, the amplitude of the noise control signal Vp1 can be adjusted by coupling capacitors with different capacitance values.

[0027] In one embodiment, the coupling circuit 202 includes a capacitor, and the capacitor couples the noise control signal Vp1 to the secondary ground SGND to cancel the noise signal at the secondary ground SGND.

[0028] As mentioned above, the noise at the secondary ground SGND can be coupled to the non-grounded terminal B of the secondary winding Ls through other circuit structures connected to the secondary winding Ls. The on-off of the secondary switch D1 will also generate switching noise at the non-grounded terminal B of the secondary winding Ls, and may be coupled to the secondary ground SGND. Therefore, in some embodiments, one end of the coupling circuit 202 is coupled to the output end of the reverse noise circuit 201 to receive the noise control signal Vp1, and the other end is coupled to the non-grounded terminal B of the secondary winding Ls. In other words, the coupling circuit 202 can be coupled to any end of the secondary winding Ls.

[0029] In one embodiment, the reverse noise circuit 201 and the control circuit generating the switch control signal G1 are integrated into the same chip, while the coupling circuit 202 and the regulating circuit 203 are discrete devices independent of the reverse noise circuit 201. In other embodiments, the coupling circuit 202 or the regulating circuit 203 may also be integrated into the same chip as the reverse noise circuit 201, or all three may be integrated into the same chip.

[0030] Figure 3 The circuit structure diagram of the isolated switch circuit 30 according to an embodiment of the present invention is shown. The isolated switch circuit 30 includes a noise control circuit 300. The noise control circuit 300 includes: a reverse noise circuit 301, a resistor R1 and a capacitor Cs. The reverse noise circuit 301 includes: a detection and adjustment circuit 3011, having an input end coupled to the resistor R1, outputting a pull-up voltage adjustment signal V1 at a first output end and outputting a pull-down voltage adjustment signal V2 at a second output end based on the resistance value of the resistor R1; a logic circuit 3012, having a power supply adjustment end receiving the pull-up voltage adjustment signal V1, a ground adjustment end receiving the pull-down voltage adjustment signal V2, having an input end receiving a noise signal Vn, and based on the pull-up voltage adjustment signal V1, the pull-down voltage adjustment signal V2 and the driving signal Vn, the logic circuit 3012 outputs a noise control signal Vp1 at an output end.

[0031] exist Figure 3In an embodiment, the logic circuit 3012 includes an inverter A1, a pull-up voltage source VS1, and a pull-down voltage source VS2. The pull-up voltage source VS1 has a control end for receiving a pull-up voltage adjustment signal V1, and an output end for outputting a pull-up voltage signal VH, and the value of the pull-up voltage signal VH is controlled by the pull-up voltage adjustment signal V1. The pull-down voltage source VS2 has a control end for receiving a pull-down voltage adjustment signal V2, and an output end for outputting a pull-down voltage signal VL, and the value of the pull-down voltage signal VL is controlled by the pull-down voltage adjustment signal V2. The inverter A1 has a power supply end for receiving a pull-up voltage signal VH, a ground end for receiving a pull-down voltage signal VL, an input end for receiving a noise signal Vn, and an output end for outputting a noise control signal Vp1. In one embodiment, when the voltage of the noise signal Vn is lower than the threshold value, the value of the noise control signal Vp1 output by the inverter A1 is the same as the value of the pull-up voltage signal VH, and when the voltage of the noise signal Vn is higher than the threshold value, the value of the noise control signal Vp1 output by the inverter A1 is the same as the value of the pull-down voltage signal VL. In some embodiments, the threshold value of the inverter A1 is a hysteresis threshold, that is, the threshold value includes an upper hysteresis limit and a lower hysteresis limit, that is, when the voltage of the noise signal Vn is lower than the lower hysteresis limit, the value of the noise control signal Vp1 output by the inverter A1 is the same as the value of the pull-up voltage signal VH, and when the voltage of the noise signal Vn is higher than the upper hysteresis limit, the value of the noise control signal Vp1 output by the inverter A1 is the same as the value of the pull-down voltage signal VL. It should be understood that placing an odd number of inverters before the inverter A1 can change the phase of the noise control signal Vp1, while placing an even number of inverters will keep the phase of the noise control signal Vp1 unchanged, and the phase of the noise control signal Vp1 is also related to the noise intensity of the primary and secondary sides, so whether the noise control signal Vp1 needs to be inverted depends on the actual application circuit. In some embodiments, the input end of the reverse noise circuit 301 can be coupled to the connection point between the primary power switch P1 and the primary winding Lp.

[0032] In some embodiments, the detection and adjustment circuit 3011 may be composed of a current source circuit and a reference circuit, wherein the current source circuit provides current to the resistor R1 to form an adjustment signal Vadj thereon, and the reference circuit outputs a pull-up voltage adjustment signal V1 and a pull-down voltage adjustment signal V2 based on the adjustment signal Vadj. In other words, by changing the resistance value of the resistor R1, the adjustment signal Vadj can be changed, thereby adjusting the values ​​of the pull-up voltage adjustment signal V1 and the pull-down voltage adjustment signal V2.

[0033] In some embodiments, the detection and adjustment circuit 3011 can be implemented by a digital circuit, such as a table lookup circuit. The detection and adjustment circuit 3011 detects the resistance of the resistor R1 and provides a pull-up voltage adjustment signal V1 and a pull-down voltage adjustment signal V2 with corresponding voltage values ​​according to the resistance.

[0034] According to the needs of the subsequent circuit, the values ​​of the pull-up voltage regulation signal V1 and the pull-down voltage regulation signal V2 can be the same or different. The pull-up voltage regulation signal V1 is used to control the pull-up voltage signal VH output by the pull-up voltage source VS1, and the pull-down voltage regulation signal V2 is used to control the pull-down voltage signal VL output by the pull-down voltage source VS2, that is, the values ​​of the pull-up voltage signal VH and the pull-down voltage signal VL correspond to the pull-up voltage regulation signal V1 and the pull-down voltage regulation signal V2, respectively, that is, the values ​​of the pull-up voltage signal VH and the pull-down voltage signal VL are indirectly controlled by the resistor R1.

[0035] exist Figure 3 In the embodiment, the waveform of the noise control signal Vp1 is opposite to that of the noise signal Vn, and the amplitude is determined by the pull-up voltage signal VH and the pull-down voltage signal VL. The noise control signal Vp1 is coupled to the secondary ground SGND through the capacitor Cs. By detecting the noise at the power supply end of the isolated switch circuit 30 and adjusting the resistance value of the resistor R1 according to the noise detected at the power supply end, the noise pollution caused by the switching action of the isolated switch circuit 30 can be reduced to a lower level.

[0036] Figure 4 FIG. 4 is a schematic diagram of a circuit structure of an isolated switch circuit 40 according to an embodiment of the present invention. The isolated switch circuit 40 includes a noise control circuit 400. Figure 3 Compared with the isolated switch circuit 30 shown in FIG. Figure 4 In the embodiment, the auxiliary winding La replaces the capacitor Cs as a coupling device, one end of the auxiliary winding La is coupled to the output end of the reverse noise circuit 301 to receive the noise control signal Vp1, and the other end is suspended, and the parasitic capacitance between the auxiliary winding La and the secondary winding Ls is used to couple the noise control signal Vp1 to the secondary circuit. A person skilled in the art can make the coil direction of the auxiliary winding La consistent with or opposite to that of the primary winding Lp according to the specific circuit application. For example, in Figure 4 In the embodiment, the coil directions of the auxiliary winding La and the primary winding Lp are consistent.

[0037] Figure 5The circuit structure diagram of an isolated switch circuit 50 according to an embodiment of the present invention is shown. The isolated switch circuit 50 includes a noise control circuit 500. The noise control circuit 500 includes: a feedback circuit 503, having a first input terminal coupled to the secondary ground SGND of the isolated switch circuit 50, and a second input terminal coupled to the primary ground PGND of the isolated switch circuit 50. Based on the current flowing between the secondary ground SGND and the primary ground PGND, the feedback circuit 503 outputs a regulation signal Vadj at the output terminal; a reverse noise circuit 301, having a first input terminal receiving a noise signal Vn, a second input terminal receiving a regulation signal Vadj, and based on the noise signal Vn and the regulation signal Vadj, the reverse noise circuit 301 outputs a noise control signal Vp1 at the output terminal; and a coupling circuit 202, having a first terminal coupled to the output terminal of the reverse noise circuit 301 to receive the noise control signal Vp1, and having a second terminal coupled to the secondary ground SGND of the isolated switch circuit 50.

[0038] exist Figure 5 In an embodiment, the feedback circuit 503 outputs a regulation signal Vadj based on the current between the primary ground PGND and the secondary ground SGND of the isolation switch circuit 50. In an embodiment, the feedback circuit 503 includes a resistor, and the noise at the primary ground PGND and the secondary ground SGND flows through the resistor in the form of current, thereby generating a regulation signal Vadj on the resistor that represents the noise of the primary ground PGND and the secondary ground SGND. It should be understood that in some embodiments, the feedback circuit 503 can also be coupled to the non-grounded terminal B of the secondary winding, and output the regulation signal Vadj based on the signal at the non-grounded terminal B of the secondary winding.

[0039] Figure 6 The circuit structure diagram of an isolated switch circuit 60 according to an embodiment of the present invention is shown. The isolated switch circuit 60 includes a noise control circuit 600. The noise control circuit 600 includes: a reverse noise circuit 301, a capacitor Cs and a feedback circuit 603. The feedback circuit 603 includes a noise detection capacitor Cd, a noise detection resistor R2 and a differential circuit EA1. The noise detection capacitor Cd and the noise detection resistor R2 are coupled in series between the primary ground PGND and the secondary ground SGND, and the noise at the primary ground PGND and the secondary ground SGND is introduced into the feedback circuit 603 in the form of current, and a feedback signal Vfb is generated on the noise detection resistor R2. The input end of the differential circuit EA1 is coupled to the two ends of the noise detection resistor R2 to receive the feedback signal Vfb, and the adjustment signal Vadj is output based on the feedback signal Vfb. In one embodiment, the adjustment signal Vadj is an amplified signal of the feedback signal Vfb.

[0040] and Figure 3The working conditions in the embodiment are the same, the reverse noise circuit 301 receives the adjustment signal Vadj, and generates a noise control signal Vp1 based on the adjustment signal Vadj and the noise signal Vn. The noise control signal Vp1 is coupled to the secondary ground SGND through the capacitor Cs to offset the noise signal at the secondary ground SGND.

[0041] exist Figure 6 In the embodiment, it can also be understood that the noise control circuit 600 creates a loop for the noise at the secondary ground SGND, so that the noise cannot be transmitted to the power supply end of the isolation switch circuit 60 .

[0042] In one embodiment, the noise control signal Vp1 can be coupled to the non-grounded end B of the secondary winding Ls through the capacitor Cs to offset the noise of the non-grounded end B of the secondary winding Ls and prevent it from being transmitted to the power supply end of the isolation switch circuit 60 .

[0043] Figure 7 FIG. 2 shows a circuit structure diagram of an isolated switch circuit 70 according to an embodiment of the present invention. The isolated switch circuit 70 includes a noise control circuit 700. Figure 6 Compared with the isolated switch circuit 60 shown in FIG. Figure 7 In the embodiment, the auxiliary winding La replaces the capacitor Cs as a coupling device, one end of the auxiliary winding La is coupled to the output end of the reverse noise circuit 301 to receive the noise control signal Vp1, and the other end is suspended, and the parasitic capacitance between the auxiliary winding La and the primary winding Lp and the secondary winding Ls is used to couple the noise control signal Vp1 to the transformer T1. The noise signal flowing from the primary side to the secondary side is offset in the transformer T1, thereby reducing the noise level coupled to the power input end.

[0044] Figure 8 FIG. 8 is a schematic diagram showing a circuit structure of an isolated switch circuit 80 according to an embodiment of the present invention. Figure 8 As shown, the isolated switch circuit 80 includes a noise control circuit 800. The noise control circuit 800 includes a reverse noise circuit 801. The reverse noise circuit 801 has an input end coupled to the signal jump end of the secondary switch D1 of the isolated switch circuit 80, that is, the non-grounded end B of the secondary winding Ls, receives the noise signal Vn, has an adjustment end to receive the adjustment signal Vadj, has an output end to output the noise control signal Vp1, and is coupled to the primary ground PGND. Figure 8In an embodiment, the reverse noise circuit 801 includes a variable capacitor Ca and a detection and adjustment circuit 8011. The detection and adjustment circuit 8011 has an input terminal coupled to the resistor R1, and outputs a capacitance adjustment signal V3 at the output terminal based on the resistance of the resistor R1. One end of the variable capacitor Ca is coupled to the signal transition terminal B of the secondary switch D1, and the other end is coupled to the primary ground PGND. The control end receives the adjustment signal V3, and the capacitance adjustment signal V3 adjusts the capacitance of the variable capacitor Ca so that it couples the noise of the signal transition terminal B of the secondary switch D1 to the primary ground PGND, providing a suitable return path for the secondary noise to flow to the primary ground PGND, so as to achieve cancellation with the primary noise, so as to prevent the noise from coupling to the power supply end of the isolation switch circuit 80.

[0045] The detection and adjustment circuit 8011 may include a current source circuit and a reference circuit. The current source circuit provides current to the resistor R1 to form an adjustment signal Vadj thereon. Meanwhile, the reference circuit outputs a capacitance adjustment signal V3 based on the adjustment signal Vadj.

[0046] In some embodiments, the detection and adjustment circuit 8011 can be implemented by a digital circuit, such as a table lookup circuit. The detection and adjustment circuit 8011 detects the resistance of the resistor R3 and provides a corresponding capacitance adjustment signal V3 according to the resistance.

[0047] exist Figure 8 In the embodiment, the resistance of the resistor R1 is adjusted according to the noise level measured from the power supply end, and the capacitance of the variable capacitor Ca can be adjusted to an appropriate level, thereby coupling the noise of the signal jump end B of the secondary switch D1 to the primary ground PGND, and reducing the noise pollution caused by the circuit switching action of the isolation switch circuit 80 to a lower level.

[0048] Fig. 9 FIG. 2 shows a schematic diagram of a circuit structure of an isolated switch circuit 90 according to an embodiment of the present invention. Fig. 9 As shown, the isolated switch circuit 90 includes a noise control circuit 900. The noise control circuit 900 includes a reverse noise circuit 801 and a feedback circuit 503, and the reverse noise circuit 801 includes a variable capacitor Ca. As mentioned above, the feedback circuit 503 detects the noise signal between the primary side PGND and the secondary side SGND, and outputs a regulation signal Vadj representing the noise amplitude. Fig. 9 In the embodiment, the adjustment signal Vadj is used to adjust the capacitance of the variable capacitor Ca so that it couples the noise of the signal jump end B of the secondary switch D1 to the primary ground PGND, providing a return path for the secondary noise to flow to the primary ground PGND, so as to achieve mutual cancellation with the primary noise, so as to prevent the noise of the switching circuit from being coupled to the power supply end of the isolated switching circuit 90.

[0049] exist Fig. 9 In the embodiment, the capacitance of the variable capacitor Ca can be adjusted to an appropriate level based on the adjustment voltage Vadj obtained according to the noise detected between the primary ground PGND and the secondary ground SGND, thereby coupling the noise of the non-grounded end B of the secondary winding Ls to the primary ground PGND, thereby reducing the noise pollution caused by the circuit switching action of the isolated switching circuit 90 to a lower level.

[0050] exist Figure 8 and Fig. 9 In the embodiment, the other end of the variable capacitor Ca is coupled to the primary ground PGND. In other embodiments, one end of the variable capacitor Ca is coupled to the non-grounded end B of the secondary winding Ls, and the other end can be coupled to any end of the primary circuit, such as the power supply end A, the connection point C between the primary winding Lp and the primary power switch P1, etc.

[0051] In the embodiment of the present invention, the variable capacitor Ca may be a discrete component, or may be integrated with the detection and adjustment circuit 8011 or the feedback circuit 503 .

[0052] Although the present invention has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present invention can be embodied in a variety of forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A noise control circuit for an isolated switching circuit, comprising: A reverse noise circuit having a first input terminal coupled to a signal jump terminal of a primary power switch of the isolation switch circuit to receive a noise signal, and a second input terminal to receive an adjustment signal. Based on the noise signal and the adjustment signal, the reverse noise circuit outputs a noise control signal at an output terminal; The reverse noise circuit comprises: A detection regulation circuit receives a regulation signal and outputs a pull-up voltage regulation signal and a pull-down voltage regulation signal based on the regulation signal; and a logic circuit having a power regulation terminal receiving a pull-up voltage regulation signal, having a ground regulation terminal receiving a pull-down voltage regulation signal, having an input terminal receiving a noise signal, and outputting a noise control signal at an output terminal based on the pull-up voltage regulation signal, the pull-down voltage regulation signal and the noise signal; and The noise control signal is coupled to one end of the secondary winding of the isolated switch circuit through a coupling circuit, and the signal jump end of the primary power switch is any end of the primary power switch except the end coupled to the primary ground.

2. The noise control circuit according to claim 1, further comprising: The regulating circuit has a first end coupled to the second input end of the reverse noise circuit to provide a regulating signal, and a second end coupled to the primary ground of the isolation switch circuit.

3. The noise control circuit of claim 2, wherein the adjustment circuit comprises a resistor.

4. The noise control circuit of claim 2, wherein the adjustment circuit comprises a capacitor.

5. The noise control circuit according to claim 1, further comprising: The coupling circuit includes a capacitor having a first end coupled to the output end of the reverse noise circuit and a second end coupled to any end of the secondary winding of the isolation switch circuit.

6. The noise control circuit according to claim 1, further comprising: The coupling circuit includes an auxiliary winding having a first end coupled to the output end of the reverse noise circuit and a second end suspended.

7. A noise control circuit for an isolated switching circuit, comprising: A reverse noise circuit having a first input terminal coupled to a signal jump terminal of a primary power switch of the isolation switch circuit to receive a noise signal, and a second input terminal to receive an adjustment signal. Based on the noise signal and the adjustment signal, the reverse noise circuit outputs a noise control signal at an output terminal; as well as A feedback circuit having a first input terminal coupled to the secondary ground of the isolated switch circuit, a second input terminal coupled to the primary ground of the isolated switch circuit, and an output terminal providing a regulating signal to the second input terminal of the reverse noise circuit; The noise control signal is coupled to one end of the secondary winding of the isolated switch circuit through a coupling circuit, and the signal jump end of the primary power switch is any end of the primary power switch except the end coupled to the primary ground.

8. The noise control circuit as claimed in claim 7, wherein the feedback circuit comprises: Noise detection capacitor; A noise detection resistor is coupled in series with a noise detection capacitor between a primary ground and a secondary ground of the isolated switch circuit; as well as The differential circuit has a differential input terminal coupled to both ends of the noise detection resistor. Based on the voltage across the noise detection resistor, the differential circuit outputs the adjustment signal at the output terminal.

9. The noise control circuit according to claim 7, further comprising: The coupling circuit includes a capacitor having a first end coupled to the output end of the reverse noise circuit and a second end coupled to any end of the secondary winding of the isolation switch circuit.

10. The noise control circuit according to claim 7, further comprising: The coupling circuit includes an auxiliary winding having a first end coupled to the output end of the reverse noise circuit and a second end suspended.

11. A noise control circuit for an isolated switch circuit, comprising: A reverse noise circuit, having an input end coupled to a signal jump end of a secondary switch of an isolated switch circuit to receive a noise signal, and a control end to receive an adjustment signal. Based on the noise signal and the adjustment signal, the reverse noise circuit outputs a noise control signal at an output end, and couples the noise control signal to any end of a primary circuit of the isolated switch circuit; The reverse noise circuit comprises: A detection adjustment circuit receives an adjustment signal and outputs a capacitance adjustment signal based on the adjustment signal; as well as The variable capacitor has a first end coupled to a signal jump end of a secondary switch of an isolation switch circuit, a second end coupled to any end of a primary circuit of the isolation switch circuit, and an adjustment end for receiving a capacitance adjustment signal.

12. The noise control circuit of claim 11, further comprising: The regulating circuit has a first end coupled to the control end of the reverse noise circuit and a second end coupled to the primary ground of the isolation switch circuit.

13. The noise control circuit of claim 12, wherein the adjustment circuit comprises a resistor.

14. The noise control circuit of claim 12, wherein the regulating circuit comprises a capacitor.

15. A noise control circuit for an isolated switch circuit, comprising: A reverse noise circuit, having an input end coupled to a signal jump end of a secondary switch of an isolated switch circuit to receive a noise signal, and a control end to receive an adjustment signal. Based on the noise signal and the adjustment signal, the reverse noise circuit outputs a noise control signal at an output end, and couples the noise control signal to any end of a primary circuit of the isolated switch circuit; The reverse noise circuit comprises: The variable capacitor has a first end coupled to the signal jump end of the secondary switch of the isolation switch circuit, a second end coupled to any end of the primary circuit of the isolation switch circuit, and a control end for receiving a regulating signal.

16. The noise control circuit of claim 15, further comprising: The feedback circuit has a first input terminal coupled to the secondary ground of the isolation switch circuit, a second input terminal coupled to the primary ground of the isolation switch circuit, and an output terminal providing a regulating signal to the control terminal of the reverse noise circuit.

17. The noise control circuit according to claim 16, wherein the feedback circuit comprises: Noise detection capacitor; A noise detection resistor is coupled in series with a noise detection capacitor between a primary ground and a secondary ground of the isolated switch circuit; as well as The differential circuit has a differential input terminal coupled to both ends of the noise detection resistor. Based on the voltage across the noise detection resistor, the differential circuit outputs the adjustment signal at the output terminal.

18. An isolated switch circuit, comprising the noise control circuit according to any one of claims 1 to 17, further comprising: A primary power switch has a first end, a second end and a control end, wherein the first end is coupled to an energy storage device of an isolated switch circuit, the second end is coupled to a primary ground, and the control end receives a switch control signal, wherein the first end and the control end are signal jump ends of the primary power switch. 19 . The isolated switch circuit of claim 18 , further comprising an energy storage device, wherein the energy storage device comprises a transformer having a primary winding and a secondary winding, wherein the primary winding is coupled to the primary power switch. 20 . The isolated switch circuit as claimed in claim 19 , further comprising a secondary switch coupled to the secondary winding of the energy storage device, wherein a connection point between the secondary switch and the secondary winding of the energy storage device is a signal jump end of the secondary switch.

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