Power supply circuit and oscilloscope probe

Abstract

The present invention provides a power supply circuit, including a positive input node and a negative input node, a first startup module and a second startup module, a first filter capacitor and a second filter capacitor, a positive output node and a negative output node; the first startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a slowly increasing positive voltage according to the positive power signal and the negative power signal; the second startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a slowly increasing negative voltage according to the positive power signal and the negative power signal; the positive voltage is further provided to the positive output node after passing through the first filter capacitor; the negative voltage is further provided to the negative output node after passing through the second filter capacitor, thereby realizing soft starting of the electrical equipment, so that no impact current is generated when the electrical equipment is plugged into a power source.

Description

Technical Field

[0001] The invention relates to the field of electronic technology, and in particular to a power supply circuit and an oscilloscope probe. Background Art

[0002] Existing oscilloscope probes include active probes and passive probes. Among them, active probes mainly draw power from the oscilloscope. The oscilloscope can provide a set of positive and negative power supplies for active probes, such as ±12V or ±15V. However, there is a set of large filter capacitors in the power supply circuit of the existing active probe. When the oscilloscope is not inserted, the voltage value of this set of filter capacitors is 0. At the moment the oscilloscope is inserted, the voltage value of the filter capacitor immediately changes to ±12V or ±15V. The huge voltage change will generate a large impact current on the filter capacitor, which may easily cause the internal circuit of the oscilloscope to malfunction. The active probe includes a positive pin connected to the positive power supply and a negative pin connected to the negative power supply. In actual applications, due to different insertion angles and insertion forces, the positive pin and the negative pin cannot be inserted synchronously, and the positive power supply and the negative power supply cannot be powered on at the same time, causing the probe to malfunction. Summary of the invention

[0003] The invention provides a power supply circuit and an oscilloscope probe to solve the problems of impact current and simultaneous power-on of positive and negative electrodes generated when the existing equipment is plugged into a power supply.

[0004] The present invention is implemented in this way: a power supply circuit comprises:

[0005] A positive input node and a negative input node, a first startup module and a second startup module, a first filter capacitor and a second filter capacitor, a positive output node and a negative output node;

[0006] The first end of the first startup module and the second end of the second startup module are commonly connected to the positive input node;

[0007] The second end of the first startup module and the first end of the second startup module are commonly connected to the negative input node;

[0008] The third terminal of the first startup module and the positive electrode of the first filter capacitor are connected to the positive output node, and the negative electrode of the first filter capacitor is grounded;

[0009] The third terminal of the second startup module and the negative electrode of the second filter capacitor are connected to the negative electrode output node, and the positive electrode of the second filter capacitor is grounded;

[0010] The first startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a slowly increasing positive voltage according to the positive power signal and the negative power signal, and the positive voltage is provided to the positive output node after passing through the first filter capacitor;

[0011] The second startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a negative voltage with a slowly increasing absolute value according to the positive power signal and the negative power signal. The negative voltage is provided to the negative output node after passing through the second filter capacitor.

[0012] Optionally, the first startup module includes:

[0013] A first soft start unit and a first interlock unit;

[0014] The first end of the first soft start unit is connected to the positive input node, the second end is connected to the positive electrode of the first filter capacitor, and the third end is connected to the first end of the first interlocking unit;

[0015] The second end of the first interlocking unit is connected to the negative input node;

[0016] The first interlocking unit is used to receive a negative power signal from the negative input node, and enable the first soft start unit when the absolute value of the negative power signal is greater than or equal to a preset power threshold;

[0017] The first soft start unit is used to receive a positive power signal from the positive input node, and output a slowly increasing positive voltage according to the positive power signal when in an enabled state.

[0018] Optionally, the first interlocking unit includes a first voltage stabilizing diode;

[0019] The anode of the first voltage stabilizing diode is connected to the cathode input node, and the cathode is connected to the third end of the first soft start unit.

[0020] Optionally, the first soft start unit includes:

[0021] PMOS tube, first capacitor, first resistor, first diode, second resistor;

[0022] The source of the PMOS tube, the first end of the first capacitor, and the first end of the second resistor are commonly connected to the positive input node;

[0023] A common point between the gate of the PMOS tube and the second end of the first capacitor is connected to a common point between the cathode of the first diode and the first end of the first resistor;

[0024] The drain of the PMOS tube is connected to the positive electrode of the first filter capacitor;

[0025] A common point between the second end of the second resistor, the anode of the first diode and the second end of the first resistor is connected to the first end of the first interlocking unit.

[0026] Optionally, a resistance value of the second resistor is smaller than a resistance value of the first resistor.

[0027] Optionally, the second startup module includes:

[0028] a second soft start unit and a second interlock unit;

[0029] The first end of the second soft start unit is connected to the negative input node, the second end is connected to the negative electrode of the second filter capacitor, and the third end is connected to the first end of the second interlock unit;

[0030] The second end of the second interlocking unit is connected to the positive input node;

[0031] The second interlocking unit is used to receive a positive power signal from the positive input node, and enable the second soft start unit when the positive power signal is greater than or equal to a preset power threshold;

[0032] The second soft start unit is used to receive a negative power supply signal from the negative input node, and output a negative voltage whose absolute value increases slowly according to the negative power supply signal when in an enabled state.

[0033] Optionally, the second interlocking unit includes a second voltage stabilizing diode;

[0034] The cathode of the second voltage stabilizing diode is connected to the anode input node, and the anode is connected to the third end of the second soft start unit.

[0035] Optionally, the second soft start unit includes:

[0036] NMOS tube, second capacitor, third resistor, second diode, fourth resistor;

[0037] The source of the NMOS tube, the first end of the second capacitor, and the first end of the fourth resistor are commonly connected to the negative input node;

[0038] A common point between the gate of the NMOS tube and the second end of the second capacitor is connected to a common point between the anode of the second diode and the first end of the third resistor;

[0039] The drain of the NMOS tube is connected to the negative electrode of the second filter capacitor;

[0040] A common point among the second end of the third resistor, the cathode of the second diode and the second end of the fourth resistor is connected to the first end of the second interlocking unit.

[0041] Optionally, the resistance of the fourth resistor is smaller than the resistance of the third resistor.

[0042] An oscilloscope probe comprises a probe circuit and the power supply circuit as described above;

[0043] The positive electrode of the probe circuit is connected to the positive output node of the power supply circuit;

[0044] The cathode of the probe circuit is connected to the cathode output node of the power supply circuit.

[0045] The power supply circuit provided by the present invention includes a positive input node and a negative input node, a first startup module and a second startup module, a first filter capacitor and a second filter capacitor, a positive output node and a negative output node; the first startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a slowly increasing positive voltage according to the positive power signal and the negative power signal; the second startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a slowly increasing negative voltage according to the positive power signal and the negative power signal; the positive voltage is further provided to the positive output node after passing through the first filter capacitor; the negative voltage is further provided to the negative output node after passing through the second filter capacitor, thereby realizing soft starting of the electrical equipment, so that no impact current is generated when the electrical equipment is plugged into a power source. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, 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 these drawings without paying creative labor.

[0047] Figure 1 is a schematic diagram of a power supply circuit provided by an embodiment of the present invention;

[0048] Figure 2 is a schematic diagram of a power supply circuit provided by another embodiment of the present invention;

[0049] Figure 3 is a schematic diagram of a power supply circuit provided by another embodiment of the present invention;

[0050] Figure 4 Schematic diagram of an oscilloscope probe provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0052] The present invention provides a power supply circuit provided by the present invention, including a positive input node and a negative input node, a first startup module and a second startup module, a first filter capacitor and a second filter capacitor, a positive output node and a negative output node; the first startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a slowly increasing positive voltage according to the positive power signal and the negative power signal; the second startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a slowly increasing negative voltage according to the positive power signal and the negative power signal; the positive voltage is further provided to the positive output node after passing through the first filter capacitor to achieve the effect of slowly charging the first filter capacitor; the negative voltage is further provided to the negative output node after passing through the second filter capacitor to achieve the effect of slowly charging the second filter capacitor, thereby realizing the soft start process of the electrical equipment.

[0053] Figure 1 Schematic diagram of a power supply circuit provided by an embodiment of the present invention. Figure 1 As shown, the power supply circuit includes:

[0054] A positive input node Vin+ and a negative input node Vin-, a first startup module 10 and a second startup module 20, a first filter capacitor 30 and a second filter capacitor 40, a positive output node Vout+ and a negative output node Vout-;

[0055] The first end of the first startup module 10 and the second end of the second startup module 20 are commonly connected to the positive input node Vin+;

[0056] The second end of the first startup module 10 and the first end of the second startup module 20 are commonly connected to the negative input node Vin-;

[0057] The third terminal of the first startup module 10 and the positive electrode of the first filter capacitor 30 are connected to the positive output node Vout+, and the negative electrode of the first filter capacitor 30 is grounded;

[0058] The third terminal of the second startup module 20 and the negative electrode of the second filter capacitor 40 are connected to the negative electrode output node Vout-, and the positive electrode of the second filter capacitor 40 is grounded;

[0059] The first startup module 10 is used to receive a positive power signal from the positive input node Vin+ and a negative power signal from the negative input node Vin-, and output a slowly increasing positive voltage according to the positive power signal and the negative power signal, and the positive voltage is provided to the positive output node Vout+ after passing through the first filter capacitor 30;

[0060] The second startup module 20 is used to receive a positive power signal from the positive input node Vin+ and a negative power signal from the negative input node Vin-, and output a negative voltage with a slowly increasing absolute value according to the positive power signal and the negative power signal. The negative voltage is provided to the negative output node Vout- after passing through the second filter capacitor 40.

[0061] In an embodiment of the present invention, the positive input node Vin+ and the negative input node Vin- serve as signal input terminals of the power supply circuit and are connected to a power supply module, wherein the positive input node Vin+ is connected to the positive electrode of the power supply module, and the negative input node Vin- is connected to the negative electrode of the power supply module. The positive output node Vout+ and the negative output node Vout- serve as signal output terminals of the power supply circuit and are connected to an electrical device, wherein the positive output node Vout+ is connected to the positive electrode of the electrical device, and the negative output node Vout- is connected to the negative electrode of the electrical device.

[0062] The first startup module 10 receives a positive power signal from the positive input node Vin+ and a negative power signal from the negative input node Vin-, and then outputs a slowly increasing positive voltage according to the positive power signal and the negative power signal. The positive voltage passes through the first filter capacitor 30 and is then provided to the positive electrode of the electrical device through the positive output node Vout+, so that when the electrical device is plugged into a power source, the first filter capacitor 30 on the positive side will not produce a huge voltage change, and thus will not generate an impact current on the first filter capacitor 30; similarly, the second startup module 20 receives a positive power signal from the positive input node Vout+ and ... in+ receives a positive power signal and a negative power signal from the negative input node Vin-, and then outputs a negative voltage with a slowly increasing absolute value according to the positive power signal and the negative power signal. The negative voltage passes through the second filter capacitor 40 and is then provided to the negative electrode of the electrical device through the negative output node Vout-, so that when the electrical device is plugged into a power source, the second filter capacitor 40 on the negative electrode side will not produce a huge voltage change, and thus will not generate an impact current on the second filter capacitor 40; the soft start of the electrical device is realized, and the problem of impact current generated when the existing electrical device is plugged into a power source is effectively solved.

[0063] Optionally, as an application example of the present invention, when the power supply circuit is applied to an active probe, the power supply module is an oscilloscope, and the electrical equipment is a probe circuit. The power supply circuit realizes soft start of the active probe, effectively solving the problem of impact current generated when the existing active probe is inserted into the oscilloscope power supply, thereby ensuring the normal operation of the oscilloscope and the active probe.

[0064] Optionally, as a preferred example of the present invention, Figure 2 As shown, the first starting module 10 also includes:

[0065] A first soft start unit 101 and a first interlock unit 102;

[0066] The first end of the first soft start unit 101 is connected to the positive input node Vin+, the second end is connected to the positive electrode of the first filter capacitor 30, and the third end is connected to the first end of the first interlocking unit 102;

[0067] The second end of the first interlocking unit 102 is connected to the negative input node Vin-;

[0068] The first interlocking unit 102 is used to receive a negative power signal from the negative input node Vin-, and enable the first soft start unit 101 when the absolute value of the negative power signal is greater than or equal to a preset power threshold;

[0069] The first soft start unit 101 is used to receive a positive power signal from the positive input node Vin+, and output a slowly increasing positive voltage according to the positive power signal when in an enabled state.

[0070] The second starting module 20 includes:

[0071] A second soft start unit 201 and a second interlock unit 202;

[0072] The first end of the second soft start unit 201 is connected to the negative input node Vin-, the second end is connected to the negative electrode of the second filter capacitor 40, and the third end is connected to the first end of the second interlock unit 202;

[0073] The second end of the second interlocking unit 202 is connected to the positive input node Vin+;

[0074] The second interlocking unit 202 is used to receive a positive power signal from the positive input node Vin+, and enable the second soft start unit 201 when the positive power signal is greater than or equal to a preset power threshold;

[0075] The second soft start unit 201 is used for receiving a negative power signal from the negative input node Vin-, and outputting a negative voltage with a slowly increasing absolute value according to the negative power signal when in an enabled state.

[0076] Here, in order to solve the problem that the positive and negative poles cannot be inserted synchronously and the positive power supply and the negative power supply cannot be powered on at the same time due to different insertion angles and insertion forces in actual applications, the embodiment of the present invention adds a first interlocking unit 102 and a second interlocking unit 202 to the first starting module 10 and the second starting module 20 respectively.

[0077] On the positive input side of the power supply, the first soft start unit 101 receives a positive power signal from the positive input node Vin+, and then connects to the negative input node Vin- through the first interlock unit 102. The first interlock unit 102 receives a negative power signal from the negative input node Vin-, and when the absolute value of the negative power signal is greater than or equal to a preset power threshold, the first interlock unit 102 is turned on, thereby enabling the first soft start unit 101. The first soft start unit 101 outputs a slowly increasing positive voltage according to the positive power signal when in the enabled state. The positive voltage passes through the first filter capacitor 30 and is then provided to the positive electrode of the electrical device through the positive output node Vout+, so that when the electrical device is plugged into the power supply, no huge voltage change will occur on the positive side, and thus no impact current will be generated on the first filter capacitor 30.

[0078] Similarly, on the negative input side of the power supply, the second soft start unit 201 receives a negative power signal from the negative input node Vin-, and then connects to the positive input node Vin+ through the second interlock unit 202. The second interlock unit 202 receives a positive power signal from the positive input node Vin+, and when the positive power signal is greater than or equal to a preset power threshold, the second interlock unit 202 is turned on, thereby enabling the second soft start unit 201. When the second soft start unit 201 is in the enabled state, it outputs a negative voltage whose absolute value increases slowly according to the negative power signal. The negative voltage passes through the second filter capacitor 40 and is then provided to the negative electrode of the electrical device through the negative output node Vout-, so that when the electrical device is plugged into the power supply, no huge voltage change will occur on the negative side, and thus no impact current will be generated on the second filter capacitor 30.

[0079] In this embodiment, through a preset power threshold, the first startup module 10 and the second startup module 20 are started only when and only when the absolute value of the voltage received by the positive input node Vin+ and the negative input node Vin- is greater than or equal to the preset power threshold, thereby realizing that the positive input node Vin+ and the negative input node Vin- of the power supply circuit are powered on at the same time, that is, the positive and negative electrodes of the electrical device are powered on at the same time, and effectively solving the problem of malfunction of the electrical device when the positive and negative electrodes of the electrical device are powered on asynchronously.

[0080] Optionally, as a preferred example of the present invention, a circuit diagram of a power supply circuit provided by the present invention is given below. Figure 3 As shown, the first interlocking unit 102 includes a first voltage zener diode DZ1; the anode of the first voltage zener diode DZ1 is connected to the cathode input node Vin-, and the cathode is connected to the third end of the first soft start unit 101. The second interlocking unit 202 includes a second voltage zener diode DZ2. The cathode of the second voltage zener diode DZ2 is connected to the cathode input node Vin+, and the anode is connected to the third end of the second soft start unit 201.

[0081] Here, for the positive power supply side, only when the absolute value of the negative power supply signal is greater than or equal to the preset power supply threshold, the first voltage zener diode DZ1 can be broken down and turned on to form a current, thereby enabling the first soft start unit 101. If the absolute value of the negative power supply signal is less than the preset power supply threshold, the first voltage zener diode DZ1 is not broken down, and a current cannot be formed, and the first soft start unit 101 is not enabled.

[0082] Similarly, on the negative power supply side, only when the absolute value of the positive power supply signal is greater than or equal to the preset power supply threshold, the second voltage zener diode DZ2 can be broken down and turned on to form a current, thereby enabling the second soft start unit 201. If the absolute value of the positive power supply signal is less than the preset power supply threshold, the second voltage zener diode DZ2 is not broken down, and a current cannot be formed, and the second soft start unit 201 is not enabled.

[0083] If neither the positive input node Vin+ nor the negative input node Vin- is connected to a power source, and neither the first soft start unit 101 nor the second soft start unit 102 is enabled, the electrical device cannot form a conductive path. Only when the positive input node Vin+ and the negative input node Vin- of the power circuit are powered on at the same time, can the electrical device form a conductive path, thereby achieving simultaneous power-on of the positive and negative electrodes of the electrical device, effectively solving the problem of electrical device failure caused by asynchronous power-on of the positive and negative electrodes of the electrical device.

[0084] Alternatively, if Figure 3As shown, the first soft start unit 101 also includes:

[0085] PMOS tube Q1, first capacitor C1, first resistor R1, first diode D1, second resistor R2;

[0086] The source electrode S of the PMOS tube Q1, the first end of the first capacitor C1, and the first end of the second resistor R2 are commonly connected to the positive input node Vin+;

[0087] A common point between the gate G of the PMOS transistor Q1 and the second end of the first capacitor C1 is connected to a common point between the cathode of the first diode D1 and the first end of the first resistor R1;

[0088] The drain electrode D of the PMOS tube Q1 is connected to the positive electrode of the first filter capacitor 30;

[0089] A common point between the second end of the second resistor R2 , the anode of the first diode D1 , and the second end of the first resistor R1 is connected to the first end of the first interlocking unit 102 .

[0090] Here, when the positive input node Vin+ receives a positive power supply voltage and the negative input node Vin- receives a negative power supply voltage, and the absolute values ​​of the positive and negative power supply voltages are greater than or equal to the preset power supply threshold, the first voltage regulator diode DZ1 in the first interlocking unit 102 is turned on, enabling the first soft start unit 101. At this time, the first capacitor C1 is charged through the first resistor R1 and the first voltage regulator diode DZ1. The voltage of the first capacitor C1 gradually rises, so that the voltage V between the gate and the source of the PMOS tube Q1 GS The voltage of the first filter capacitor 30 increases gradually, and the PMOS tube Q1 is slowly turned on to output a slowly increasing positive voltage. Since the positive voltage increases slowly, the voltage change on the first filter capacitor 30 is greatly reduced, so that the current flowing through the first filter capacitor 30 will not generate a surge current due to the huge voltage change, effectively ensuring the normal operation of the electrical equipment.

[0091] Optionally, as a preferred example of the present invention, the first capacitor C1 may be a capacitor with a size of 2 μF, and the first resistor R1 may be a resistor with a size of 100 KΩ.

[0092] Furthermore, when the positive input node Vin+ is disconnected from the power supply, the first capacitor C1 is discharged through the second resistor R2 and the first diode D1. The embodiment of the present invention utilizes the unidirectional conductive characteristics of the first diode D1, and at the same time sets the resistance value of the second resistor R2 to be smaller than the resistance value of the first resistor R1, so that the time constant of the charge and discharge circuit of the first capacitor C1 is different, charging is slow, and discharging is fast. In the process of the positive input node Vin+ being connected to the power supply, a jumping state of contacting and disconnecting may occur. When the contact is made, the first capacitor C1 is fully charged. When the contact is disconnected, the embodiment of the present invention realizes the rapid discharge of the first capacitor C1 until the discharge is completed through the second resistor R2 and the first diode D1. When the positive input node Vin+ is connected to the positive pole of the power supply again, soft start can be performed again, thereby effectively avoiding the problem of being unable to soft start and generating impact current due to the first capacitor C1 not being fully discharged when contacted again.

[0093] Optionally, when the first resistor R1 is selected to be a resistor with a value of 100KΩ, the second resistor R2 can be selected to be a resistor with a value of 10KΩ. Since the resistance value of the second resistor R2 is much smaller than the resistance value of the first resistor R1, the discharge speed is much greater than the charging speed.

[0094] Alternatively, if Figure 3 As shown, the second soft start unit 201 also includes:

[0095] NMOS tube Q2, second capacitor C2, third resistor R3, second diode D2, fourth resistor R4;

[0096] The source electrode S of the NMOS transistor Q2, the first end of the second capacitor C2, and the first end of the fourth resistor R4 are commonly connected to the negative input node Vin-;

[0097] A common point between the gate G of the NMOS transistor Q2 and the second end of the second capacitor C2 is connected to a common point between the anode of the second diode D2 and the first end of the third resistor R3;

[0098] The drain electrode D of the NMOS tube Q2 is connected to the negative electrode of the second filter capacitor 40;

[0099] A common point among the second end of the third resistor R3 , the cathode of the second diode D2 , and the second end of the fourth resistor R4 is connected to the first end of the second interlocking unit 202 .

[0100] The same is true for the first soft start unit 101. Here, when the positive input node Vin+ receives a positive power supply voltage and the negative input node Vin- receives a negative power supply voltage, and the absolute values ​​of the positive and negative power supply voltages are greater than or equal to the preset power supply threshold, the second voltage zener diode DZ2 in the second interlocking unit 202 is turned on, enabling the second soft start unit 201. At this time, the second capacitor C2 is charged through the third resistor R3 and the second voltage zener diode DZ2. The absolute value of the voltage of the second capacitor C2 gradually increases, so that the voltage V between the gate and the source of the NMOS tube Q2 GS The absolute value of gradually increases, and the NMOS tube Q2 is slowly turned on to output a negative voltage with a slowly increasing absolute value. Since the absolute value of the negative voltage increases slowly, the voltage change of the second filter capacitor 40 is greatly reduced, so that the current flowing through the second filter capacitor 40 will not generate a surge current due to the huge voltage change, effectively ensuring the normal operation of the electrical equipment.

[0101] Optionally, as a preferred example of the present invention, the second capacitor C2 may be a capacitor with a size of 2 μF, and the third resistor R3 may be a resistor with a size of 100 KΩ.

[0102] Further, when the positive input node Vin+ is disconnected from the power supply, the second capacitor C2 is discharged through the fourth resistor R4 and the second diode D2. The embodiment of the present invention utilizes the unidirectional conductive characteristics of the second diode D2, and at the same time sets the resistance of the fourth resistor R4 to be less than the resistance of the third resistor R3, so that the time constant of the charge and discharge circuit of the second capacitor C2 is different, charging is slow, and discharging is fast. In the process of the negative input node Vin- being connected to the power supply, a beating state of contacting and disconnecting may occur. When the contact is made, the second capacitor C2 is fully charged. When the contact is disconnected, the embodiment of the present invention realizes the rapid discharge of the second capacitor C2 until the discharge is completed through the fourth resistor R4 and the second diode D2. When the negative input node Vin- is connected to the negative pole of the power supply again, soft start can be restarted, thereby effectively avoiding the problem of being unable to soft start and generating impact current due to the second capacitor C2 not being fully discharged when contacted again.

[0103] Optionally, when the third resistor R3 is selected to be a resistor with a value of 100KΩ, the fourth resistor R4 can be selected to be a resistor with a value of 10KΩ. Since the resistance value of the fourth resistor R4 is much smaller than the resistance value of the third resistor R3, the discharge speed is much greater than the charging speed.

[0104] Optionally, as a preferred example of the present invention, an embodiment of the present invention further provides an oscilloscope probe. Figure 4As shown, the oscilloscope probe includes a probe circuit 2 and the power supply circuit 1 as described above;

[0105] The positive electrode of the probe circuit 2 is connected to the positive output node Vout+ of the power supply circuit 1;

[0106] The cathode of the probe circuit 2 is connected to the cathode output node Vout- of the power supply circuit 1 .

[0107] Among them, the circuit structure and function of the power supply circuit 1 are specifically described in the above embodiment, which will not be repeated here. In the embodiment of the present invention, the positive input node Vin+ in the power supply circuit 1 is connected to the positive pole of the power supply module in the oscilloscope, and the negative input node Vin- in the power supply circuit 1 is connected to the negative pole of the power supply module in the oscilloscope. The first soft start unit 101 in the power supply circuit outputs a slowly changing positive voltage to the positive pole of the probe circuit 2, and the second soft start unit 201 outputs a slowly changing negative voltage to the negative pole of the probe circuit 2, which effectively avoids the impact current generated by the oscilloscope on the first filter capacitor 30 and the second filter capacitor 40 when the existing probe circuit is inserted into the oscilloscope, ensuring the normal use of the oscilloscope; and through the first interlocking unit 102 and the second interlocking unit 202 in the power supply circuit 1, the positive and negative pins of the probe circuit 2 are powered on at the same time, avoiding the problem of failure of the probe circuit 2 caused by the positive and negative pins not being powered on at the same time.

[0108] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A power supply circuit, characterized in that: include: A positive input node and a negative input node, a first startup module and a second startup module, a first filter capacitor and a second filter capacitor, a positive output node and a negative output node; The first end of the first startup module and the second end of the second startup module are commonly connected to the positive input node; The second end of the first startup module and the first end of the second startup module are commonly connected to the negative input node; The third terminal of the first startup module and the positive electrode of the first filter capacitor are connected to the positive output node, and the negative electrode of the first filter capacitor is grounded; The third terminal of the second startup module and the negative electrode of the second filter capacitor are connected to the negative electrode output node, and the positive electrode of the second filter capacitor is grounded; The first startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a slowly increasing positive voltage according to the positive power signal and the negative power signal, and the positive voltage is provided to the positive output node after passing through the first filter capacitor; The second startup module is used to receive a positive power signal from the positive input node and a negative power signal from the negative input node, and output a negative voltage with a slowly increasing absolute value according to the positive power signal and the negative power signal, and the negative voltage is provided to the negative output node after passing through the second filter capacitor; Wherein, the first startup module includes a first soft start unit and a first interlock unit, and the second startup module includes a second soft start unit and a second interlock unit; The first end of the first soft start unit is connected to the positive input node, the second end is connected to the positive electrode of the first filter capacitor, and the third end is connected to the first end of the first interlocking unit; The second end of the first interlocking unit is connected to the negative input node; The first interlocking unit is used to receive a negative power signal from the negative input node, and enable the first soft start unit when the absolute value of the negative power signal is greater than or equal to a preset power threshold; The first soft start unit is used to receive a positive power supply signal from the positive input node, and output a slowly increasing positive voltage according to the positive power supply signal when in an enabled state; The first end of the second soft start unit is connected to the negative input node, the second end is connected to the negative electrode of the second filter capacitor, and the third end is connected to the first end of the second interlock unit; The second end of the second interlocking unit is connected to the positive input node; The second interlocking unit is used to receive a positive power signal from the positive input node, and enable the second soft start unit when the positive power signal is greater than or equal to a preset power threshold; The second soft start unit is used to receive a negative power supply signal from the negative input node, and output a negative voltage whose absolute value increases slowly according to the negative power supply signal when in an enabled state; The first soft start unit includes a PMOS tube, a first capacitor, a first resistor, a first diode, and a second resistor, and the second soft start unit includes an NMOS tube, a second capacitor, a third resistor, a second diode, and a fourth resistor; The source of the PMOS tube, the first end of the first capacitor, and the first end of the second resistor are commonly connected to the positive input node; A common point between the gate of the PMOS tube and the second end of the first capacitor is connected to a common point between the cathode of the first diode and the first end of the first resistor; The drain of the PMOS tube is connected to the positive electrode of the first filter capacitor; A common point between the second end of the second resistor, the anode of the first diode and the second end of the first resistor is connected to the first end of the first interlocking unit; The source of the NMOS tube, the first end of the second capacitor, and the first end of the fourth resistor are commonly connected to the negative input node; A common point between the gate of the NMOS tube and the second end of the second capacitor is connected to a common point between the anode of the second diode and the first end of the third resistor; The drain of the NMOS tube is connected to the negative electrode of the second filter capacitor; A common point among the second end of the third resistor, the cathode of the second diode and the second end of the fourth resistor is connected to the first end of the second interlocking unit.

2. The power supply circuit according to claim 1, characterized in that The first interlocking unit includes a first voltage stabilizing diode; The anode of the first voltage stabilizing diode is connected to the cathode input node, and the cathode is connected to the third end of the first soft start unit.

3. The power supply circuit according to claim 1, characterized in that The resistance of the second resistor is smaller than the resistance of the first resistor.

4. The power supply circuit according to claim 1, characterized in that: The second interlocking unit includes a second voltage stabilizing diode; The cathode of the second voltage stabilizing diode is connected to the anode input node, and the anode is connected to the third end of the second soft start unit.

5. The power supply circuit according to claim 1, characterized in that: The resistance of the fourth resistor is smaller than the resistance of the third resistor.

6. An oscilloscope probe, characterized in that: The oscilloscope probe comprises a probe circuit and a power supply circuit as claimed in any one of claims 1 to 5; The positive electrode of the probe circuit is connected to the positive output node of the power supply circuit; The cathode of the probe circuit is connected to the cathode output node of the power supply circuit.

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