Linear power supply circuit

Abstract

The utility model relates to a linear power supply circuit, which comprises a power tube, a first switch tube, a first power supply circuit, a second switch tube, a first resistor and a second power supply circuit, the third end of the first switch tube is coupled to the first end of the power tube, the third end of the second switch tube is coupled to the second end of the first switch tube, the first power circuit is coupled to the first end of the first switch tube, and the second power circuit is coupled to the first end of the second switch tube; in the first mode, the second switching tube is completely switched on, the first power circuit controls the first switching tube to drive the power tube, and stable first output voltage is output; and in the second mode, the second power supply circuit takes the first resistor as a current detection resistor, controls the second switch tube to drive the power tube and adjusts the output voltage, so that the second output current flowing through the first resistor is constant. According to the circuit, the first switching tube, the second switching tube and the power tube work cooperatively, the constant-voltage and constant-current circuit is simplified, and free switching between a constant-voltage mode and a constant-current mode is achieved.

Description

Technical Field

[0001] This application relates to the field of power supply circuits, and in particular to a linear power supply circuit. Background Technology

[0002] Currently, common constant voltage and constant current circuits typically employ a completely separate design, with constant voltage and constant current operating independently. This requires two complete control loops, which not only increases the number of components but also makes the PCB layout more complex. Additionally, it may introduce extra noise and signal delay, affecting overall performance.

[0003] Since the two control loops are independent of each other, the discrete design makes it difficult to achieve a smooth transition when switching between constant voltage mode and constant current mode, which can easily lead to response lag or instantaneous fluctuations, resulting in poor circuit stability under dynamic load. Utility Model Content

[0004] To address the above problems, this application provides a linear power supply circuit with a voltage output terminal, the linear power supply circuit comprising:

[0005] Power transistor;

[0006] The third terminal of the first switching transistor is coupled to the first terminal of the power transistor.

[0007] A first power supply circuit, the output terminal of which is coupled to the first terminal of the first switching transistor, is used to control the first switching transistor to drive the second terminal of the power transistor to generate a first output voltage when receiving a first control signal.

[0008] The third terminal of the second switch is coupled to the second terminal of the first switch.

[0009] A first resistor, the first end of which is coupled to the second end of the power transistor, and the second end of which is coupled to the voltage output terminal; and

[0010] The second power supply circuit has its output terminal coupled to the first terminal of the second switching transistor. The second power supply circuit is used to control the second switching transistor to drive the power transistor to generate a second output current on the first resistor when receiving the second control signal.

[0011] In the first mode, the first power supply circuit receives the first control signal, the second switching transistor is fully turned on, and the first output voltage remains unchanged.

[0012] In the second mode, the second power supply circuit receives the second control signal, the first switching transistor is fully turned on, and the second output current remains unchanged.

[0013] Furthermore, the linear power supply circuit includes: a first voltage source, which is a voltage source that outputs a first negative voltage, the first negative voltage being applied to the third terminal of the power transistor.

[0014] Furthermore, the linear power supply circuit includes: a second voltage source and a switching circuit, wherein the positive terminal of the second voltage source is coupled to the feedback terminal of the switching circuit, the negative terminal of the second voltage source is grounded, the output terminal of the switching circuit is coupled to the third terminal of the power transistor, and the switching circuit is used to output a second negative voltage.

[0015] Furthermore, the first power supply circuit includes:

[0016] A first operational amplifier, the output terminal of which is coupled to the first terminal of the first switching transistor, and the inverting input terminal of which is coupled to the voltage output terminal;

[0017] The first power supply circuit has its output terminal coupled to the non-inverting input terminal of the first operational amplifier, and is used to output a first set voltage.

[0018] Furthermore, the first power supply circuit includes:

[0019] A third voltage source, wherein the third voltage source is used to output a first positive voltage;

[0020] The first inverting amplifier has its inverting input terminal coupled to the positive terminal of the third voltage source, and its output terminal coupled to the non-inverting input terminal of the first operational amplifier.

[0021] Furthermore, the linear power supply circuit is used to supply power to the first load, and the linear power supply circuit further includes:

[0022] The first follower has its input terminal coupled to the power supply terminal of the first load and its output terminal coupled to the inverting input terminal of the first operational amplifier.

[0023] The second follower has its input terminal coupled to the ground terminal of the first load and its output terminal coupled to the non-inverting input terminal of the first operational amplifier.

[0024] Furthermore, the second power supply circuit includes:

[0025] The second operational amplifier has its output terminal coupled to the first terminal of the second switching transistor; its inverting input terminal is coupled to the first terminal of the first resistor, and its non-inverting input terminal is coupled to the second terminal of the first resistor.

[0026] The second power supply circuit has its output terminal coupled to the non-inverting input terminal of the second operational amplifier, and the second power supply circuit is used to output the second set voltage.

[0027] Furthermore, the second power supply circuit includes:

[0028] A fourth voltage source, which is used to output a second positive voltage;

[0029] The second inverting amplifier has its inverting input terminal coupled to the positive terminal of the fourth voltage source, and its output terminal coupled to the non-inverting input terminal of the second operational amplifier.

[0030] Furthermore, the second terminal of the second switch is grounded to enable the return of the second control signal.

[0031] Furthermore, the linear power supply circuit also includes:

[0032] The third follower has its non-inverting input coupled to the first terminal of the first resistor and its output coupled to the inverting input of the second operational amplifier.

[0033] The fourth follower has its non-inverting input coupled to the second end of the first resistor, and its output coupled to the non-inverting input of the second operational amplifier.

[0034] Compared with the prior art, this application has the following advantages: In constant voltage mode, the second switch is fully turned on, and the first power supply circuit controls the first switch to dynamically drive the power transistor, directly adjusting the stable first output voltage; while in constant current mode, the first switch is fully turned on, and the second power supply circuit uses the first resistor as a current sensing resistor, and directly adjusts the output voltage by controlling the second switch to dynamically drive the power transistor, so as to achieve a constant second output current flowing through the first resistor; thus, the circuit of this application utilizes the first switch, the second switch, and the power transistor to work together, simplifying the constant voltage and constant current circuit, and enabling free switching between constant voltage mode and constant current mode. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the linear power supply circuit framework structure of this application;

[0036] Figure 2 This is a schematic diagram of the specific structure of the linear power supply circuit in this application;

[0037] Figure 3 This is a schematic diagram of the second voltage source and switching circuit structure of this application.

[0038] Explanation of reference numerals in the attached figures

[0039] 1. First power supply circuit; 11. First power supply circuit; 2. Second power supply circuit; 21. Second power supply circuit; 3. Switching circuit. Detailed Implementation

[0040] To gain a more detailed understanding of the features and technical content of the embodiments disclosed herein, the following description is provided in conjunction with the accompanying drawings. Figure 1-3The implementation of the embodiments of this disclosure is described in detail. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, various details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other instances, well-known structures and apparatuses may be simplified in their depiction to simplify the drawings.

[0041] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0042] Furthermore, the terms "setup" and "coupled" should be interpreted broadly. For example, "coupled" can be a fixed coupling, a detachable coupling, or an integral structure; it can be a mechanical coupling or an electrical coupling; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0043] It should be noted that, unless otherwise specified, the embodiments and features described in the present disclosure can be combined with each other.

[0044] To provide a better understanding of the purpose, structure, features, and functions of this application, detailed descriptions are provided below with reference to specific embodiments.

[0045] To address the aforementioned issues, this application provides a linear power supply circuit with a voltage output terminal Vout. The linear power supply circuit includes a power transistor Q3, a first switching transistor Q1, a first power supply circuit 1, a second switching transistor Q2, a first resistor R1, and a second power supply circuit 2.

[0046] In this application, the first switch Q1, the second switch Q2, and the power transistor Q3 each include a first terminal, a second terminal, and a third terminal. To more clearly describe the solution of this application, in the following description, the first terminal of the first switch Q1, the second switch Q2, and the power transistor Q3 will be described as the base, the second terminal as the collector, and the third terminal as the emitter.

[0047] The emitter of the first switching transistor Q1 is coupled to the base of the power transistor Q3; the output of the first power supply circuit 1 is coupled to the base of the first switching transistor Q1; the emitter of the second switching transistor Q2 is coupled to the collector of the first switching transistor Q1; the input of the first resistor R1 is coupled to the collector of the power transistor Q3, and the output of the first resistor R1 is coupled to the voltage output terminal Vout; the output of the second power supply circuit 2 is coupled to the base of the second switching transistor Q2.

[0048] In the first mode, the second switch Q2 is fully turned on, the first power supply circuit 1 receives the first control signal, controls the first switch Q1 to drive the collector of the power transistor Q3 to generate the first output voltage, and the first output voltage remains unchanged.

[0049] When the second switch Q2 is fully turned on, the first switch Q1 acts as an emitter follower, and its emitter current is only related to the voltage signal output by the first power supply circuit 1. The first switch Q1 converts the small voltage signal output by the first power supply circuit 1 into a large current signal, and uses it to drive the power transistor Q3 to generate a stable first output voltage at its collector.

[0050] In the second mode, the first switch Q1 is fully turned on, the second power supply circuit 2 receives the second control signal, and controls the second switch Q2 to drive the power transistor Q3 to generate a second output current across the first resistor R1, and the second output current remains unchanged.

[0051] When the first switch Q1 is fully turned on, the second switch Q2 acts as an emitter follower, and its emitter current is only related to the voltage signal output by the second power supply circuit 2. The second switch Q2 converts the small voltage signal output by the second power supply circuit 2 into a large current signal, and uses it to drive the power transistor Q3 to generate a stable second output current in the first resistor R1.

[0052] In this application, the first resistor R1 uses high-side current sensing, which avoids the impact of low-side current sensing on the grounding loop, which may lead to system instability.

[0053] In one embodiment, the linear power supply circuit includes a first voltage source V1, which is a negative voltage switching power supply that outputs a first negative voltage. The first negative voltage acts on the emitter of the power transistor Q3, and the ground terminal of the first voltage source V1 is coupled to a reference ground.

[0054] The first negative voltage output by the first voltage source V1 acts on the emitter of the power transistor Q3, causing electrons in the power transistor Q3 to flow from the collector of the power transistor Q3 through the base of the power transistor Q3 to the emitter of the power transistor Q3, generating a reverse current from the collector of the power transistor Q3 to ground.

[0055] A first voltage source V1 provides a power supply voltage, which is a first negative voltage, so that the first output voltage output by the voltage output terminal Vout of the linear power supply circuit is a negative voltage. The first voltage source V1 provides a negative voltage source for the voltage output terminal Vout, and the voltage range and power of the first voltage source V1 are both greater than the first output voltage of the voltage output terminal Vout, so that the first output voltage is output normally as a negative voltage.

[0056] In this embodiment, an NPN power transistor Q3 is used as the main power transistor of the linear power supply circuit. The power transistor Q3 is powered by the first voltage source V1. In the actual solution, if the load current is required to be in the mA level and the output range of the first output voltage is not large, after considering the power consumption of the power transistor, the first voltage source V1 can be considered to use a fixed negative power supply to output a fixed and unadjustable first negative voltage.

[0057] In another embodiment, the linear power supply circuit includes: a second voltage source V2 and a switching circuit 3, the positive terminal of the second voltage source V2 is coupled to the feedback terminal of the switching circuit 3, the negative terminal of the second voltage source V2 is grounded, the output terminal of the switching circuit 3 is coupled to the emitter of the power transistor Q3, and the switching circuit 3 is used to output a second negative voltage.

[0058] The negative terminal of the second voltage source V2 is grounded, providing an adjustment control signal to the switching circuit 3. By adjusting the output voltage of the second voltage source V2, the switching circuit 3 outputs an adjustable second negative voltage.

[0059] An adjustable second negative voltage is applied to the emitter of the power transistor Q3. Compared with a fixed first negative voltage applied to the power transistor Q3, this allows for a greater adjustment range in the potential of the emitter of the power transistor Q3, thereby enabling a greater range of adjustment for the first output voltage and the second output current generated by the collector of the power transistor Q3.

[0060] Among them, the second voltage source V2 adopts an adjustable DC / DC power supply, which is suitable for scenarios with a large output load current and a wide first output voltage range. Through the DAC control of the DC / DC power supply and the linear power supply, the voltage difference between the two power supplies is controlled within a small voltage range, usually controlled at about 1V. This ensures both the stability of the linear power supply and the low power consumption of the power transistor Q3, thereby improving the reliability of the linear power supply.

[0061] See Figure 3 , Figure 3 This is a schematic diagram of the second voltage source and switching circuit structure of this application. The second voltage source and switching circuit are used to generate a second negative voltage.

[0062] Specifically, it includes a 22nd resistor R22, a 23rd resistor R23, and a 24th resistor R24; the positive terminal of the second voltage source V2 is coupled to the feedback terminal of the switching circuit 3 through the 24th resistor R24, the output terminal of the switching circuit 3 is coupled to the first terminal of the 22nd resistor R22, the second terminal of the 22nd resistor R22 is coupled to both the feedback terminal of the switching circuit 3 and the first terminal of the 23rd resistor R23, and the second terminal of the 23rd resistor R23 is grounded.

[0063] The 22nd resistor R22 and the 23rd resistor R23 form a voltage divider network, which feeds back the second negative voltage at the output terminal of the switching circuit 3 to the feedback terminal, i.e., the FB terminal, of the switching circuit 3. By adjusting the voltage drop across the 24th resistor R24 ​​of the output voltage of the second voltage source V2, the voltage fed back to the switching circuit 3 is changed, so that the switching circuit 3 outputs an adjustable second negative voltage.

[0064] The switching circuit 3 is a DC / DC switching power supply with negative voltage output. When the negative voltage output of the DC / DC switching power supply is high power, the linear power supply circuit of this application can be applied to the test environment, such as aging test. The high power DC / DC switching power supply of this application can be used for 4 to 8 channels of linear power supply at the same time, without having to select an independent DC / DC switching power supply for each channel, which reduces the power consumption of the linear power supply circuit and also reduces the test cost.

[0065] The first power supply circuit 1 includes a first operational amplifier U1 and a first power supply circuit 11; the output terminal of the first operational amplifier U1 is coupled to the base of the first switching transistor Q1, and the inverting input terminal of the first operational amplifier U1 is coupled to the voltage output terminal Vout; the output terminal of the first power supply circuit 11 is coupled to the non-inverting input terminal of the first operational amplifier U1, and the first power supply circuit 11 is used to output a first set voltage.

[0066] The output signal of the first operational amplifier U1 is used to control the conduction state of the first switching transistor Q1. When the output voltage of the first operational amplifier U1 changes, it directly changes the on or off state of the first switching transistor Q1. The inverting input terminal of the first operational amplifier U1 is coupled to the voltage output terminal Vout to monitor and receive changes in the first output voltage in real time, so that the linear power supply circuit can automatically adjust according to the changes in the first output voltage output from the voltage output terminal Vout, thereby stabilizing the first output voltage.

[0067] In one embodiment, the first power supply circuit 1 further includes an eighth resistor R8 and a ninth resistor R9. The inverting input terminal of the first operational amplifier circuit is connected to the first terminal of the eighth resistor R8, and the second terminal of the eighth resistor R8 is coupled to the voltage output terminal Vout. The first terminal of the ninth resistor R9 is coupled to the first terminal of the eighth resistor, and the second terminal of the ninth resistor R9 is coupled to reference ground.

[0068] The first power supply circuit 11 includes a third voltage source V3, a second resistor R2, a third resistor R3, and a first inverting amplifier U3; the negative terminal of the third voltage source V3 is grounded, and the third voltage source V3 is used to output a first positive voltage; the first end of the second resistor R2 is coupled to the non-inverting input terminal of the first operational amplifier U1; the inverting input terminal of the first inverting amplifier U3 is coupled to the positive terminal of the third voltage source V3, and the output terminal of the first inverting amplifier U3 is coupled to the second end of the second resistor R2; the first end of the third resistor R3 is coupled to the non-inverting input terminal of the first operational amplifier U1, and the second end of the third resistor R3 is coupled to a reference ground.

[0069] The first inverting amplifier U3 amplifies the first positive voltage output from the third voltage source V3 in reverse phase and transmits it to the non-inverting input of the first operational amplifier U1 through the second resistor R2; the second resistor R2 and the third resistor R3 divide the output voltage of the first inverting amplifier U3 and transmit it to the non-inverting input of the first operational amplifier U1.

[0070] Meanwhile, the second end of the third resistor R3 is coupled to the reference ground, and the ground level is collected as the reference ground level for the output setting voltage signal of the first inverting amplifier U3, so as to stabilize the working state of the first operational amplifier U1.

[0071] The first power supply circuit 11 generates and outputs the first set voltage, which is used to set the voltage value required for the voltage output terminal Vout of the linear power supply circuit.

[0072] The voltage value Vout required for the voltage output terminal Vout of the linear power supply circuit satisfies:

[0073]

[0074] Wherein, V3 is the first positive voltage output by the third voltage source V3. The overall voltage is set to the first preset voltage.

[0075] The linear power supply circuit is used to supply power to the first load. The linear power supply circuit also includes a first follower U5 and a second follower U6. The input terminal of the first follower U5 is used to couple to the power supply terminal of the first load, and the output terminal of the first follower U5 is coupled to the inverting input terminal of the first operational amplifier U1. The input terminal of the second follower U6 is used to couple to the ground terminal of the first load, and the output terminal of the second follower U6 is coupled to the non-inverting input terminal of the first operational amplifier U1.

[0076] Specifically, the linear power supply circuit in this application includes a first sampling terminal Vout_S+ and a second sampling terminal Vout_S-. The first sampling terminal Vout_S+ is led out from the non-inverting input terminal of the first follower U5 and is used to couple to the power supply terminal of the first load. The second sampling terminal Vout_S- is led out from the non-inverting input terminal of the second follower U6 and is used to couple to the ground terminal of the first load. The first load is usually directly coupled to the reference ground.

[0077] The non-inverting input of the first follower U5 is coupled to the power supply terminal of the first load, and the voltage applied to the first load is fed back to the inverting input of the first operational amplifier U1 via its output terminal. The non-inverting input of the second follower U6 is coupled to the ground terminal of the first load, and its output terminal is fed back to the non-inverting input of the first operational amplifier U1. That is, the non-inverting inputs of the first follower U5 and the second follower U6 collect the far-end voltage of the first load and introduce it into the non-inverting and inverting inputs of the first operational amplifier U1, respectively, for line loss compensation of the far-end first load.

[0078] This application samples the voltage at the far end of the first load through the first sampling terminal Vout_S+ and the second sampling terminal Vout_S-, and introduces it into the feedback network of the operational amplifier U1 to perform line loss compensation at the far end. By using hardware line loss compensation, the voltage loss caused by the resistance of the connecting line can be quickly compensated. Compared with software reading the voltage across the first load and then adjusting the output voltage of the DAC to adjust the line loss compensation response, the response is faster.

[0079] A DAC is a digital-to-analog converter that converts received digital signals into analog voltage signals.

[0080] In one embodiment, the linear power supply circuit further includes a seventh resistor R7 and a tenth resistor R10. The first end of the seventh resistor R7 is coupled to the voltage output terminal Vout, and the second end of the seventh resistor R7 is coupled to the non-inverting input terminal of the first follower U5. The first end of the tenth resistor R10 is coupled to the non-inverting input terminal of the second follower U6, and the second end of the tenth resistor R10 is coupled to reference ground. When the first sampling terminal Vout_S+ and the second sampling terminal Vout_S- are not coupled to the first load, the power supply circuit is coupled to the voltage output terminal Vout and the reference ground respectively through the seventh resistor R7 and the tenth resistor R10. The seventh resistor R7 samples the voltage of the voltage output terminal Vout and feeds it back to the inverting input terminal of the first operational amplifier U1 via the first follower U5. The second end of the tenth resistor R10 is coupled to the reference ground, samples the ground level, and feeds it back to the non-inverting input terminal of the first operational amplifier U1 via the second follower U6, serving as the ground reference for the voltage signal output by the first power supply circuit 11 to the non-inverting input terminal of the first operational amplifier U1.

[0081] The second power supply circuit 2 includes a second operational amplifier U2 and a second power supply circuit 21; the output terminal of the second operational amplifier U2 is coupled to the base of the second switching transistor Q2; the inverting input terminal of the second operational amplifier U2 is coupled to the first terminal of the first resistor R1, and the non-inverting input terminal of the second operational amplifier U2 is coupled to the second terminal of the first resistor R1; the output terminal of the second power supply circuit 21 is coupled to the non-inverting input terminal of the second operational amplifier U2, and the second power supply circuit 21 is used to output a second set voltage.

[0082] The output signal of the second operational amplifier U2 is used to control the conduction state of the second switch Q2. When the output voltage of the second operational amplifier U2 changes, the degree of turn-on or conduction of the second switch Q2 is changed.

[0083] The first resistor R1 is the current sensing resistor for the voltage output terminal Vout of the linear power supply circuit. The inverting input terminal of the second operational amplifier U2 is coupled to the first terminal of the first resistor R1 to obtain the potential of the first terminal of the first resistor R1. The non-inverting input terminal of the second operational amplifier U2 is coupled to the second terminal of the first resistor R1 to obtain the potential of the second terminal of the first resistor R1. The second operational amplifier U2 compares the changes in the potential signals of its non-inverting input terminal and its inverting input terminal and generates a corresponding output signal to control the degree of opening or conduction of the second switching transistor Q2, thereby adjusting the output voltage of the power transistor Q3 in the linear power supply circuit to stabilize the second output current flowing through the first resistor R1.

[0084] Specifically, the second power supply circuit 2 further includes a fourteenth resistor R14 and a fifteenth resistor R15. The inverting input terminal of the second operational amplifier U2 is simultaneously coupled to the first terminal of the fourteenth resistor R14 and the first terminal of the fifteenth resistor R15. The second terminal of the fourteenth resistor R14 is coupled to the first terminal of the first resistor R1, and the second terminal of the fifteenth resistor R15 is coupled to ground.

[0085] The second power supply circuit 21 includes a fourth voltage source V4, a fifth resistor R5, a sixth resistor R6, and a second inverting amplifier U4; the negative terminal of the fourth voltage source V4 is grounded, and the fourth voltage source V4 is used to output a second positive voltage; the first end of the fifth resistor R5 is coupled to the non-inverting input terminal of the second operational amplifier U2; the inverting input terminal of the second inverting amplifier U4 is coupled to the positive terminal of the fourth voltage source V4, and the output terminal of the second inverting amplifier U4 is coupled to the second end of the fifth resistor R5; the first end of the sixth resistor R6 is coupled to the non-inverting input terminal of the second operational amplifier U2, and the second end of the sixth resistor R6 is coupled to the voltage output terminal Vout.

[0086] The second inverting amplifier U4 inverts and amplifies the second positive voltage output from the fourth voltage source V4, and transmits it to the non-inverting input of the second operational amplifier U2 through the fifth resistor R5; the fifth resistor R5 and the sixth resistor R6 divide the output voltage of the second inverting amplifier U4 and transmit it to the non-inverting input of the second operational amplifier U2.

[0087] In one embodiment, the second power supply circuit 2 further includes a third follower U7 and a fourth follower U8. The output terminal of the third follower U7 is connected to the second terminal of the fourteenth resistor R14, and the non-inverting input terminal of the third follower U7 is connected to the first terminal of the first resistor R1. The output terminal of the fourth follower U8 is connected to the second terminal of the sixth resistor R6, and the non-inverting input terminal of the fourth follower U8 is connected to the second terminal of the first resistor R1.

[0088] The second power supply circuit 21 generates and outputs a second set voltage to the non-inverting input terminal of the second operational amplifier U2. The second set voltage is used to set the required current value flowing through the first resistor R1, i.e., the second output current.

[0089] If the required second output current is set to Iset, then:

[0090] The voltage at the inverting input of the second operational amplifier U2 is

[0091] The voltage at the non-inverting input of the second operational amplifier U2 is

[0092] Based on the virtual short characteristic of the second operational amplifier U2, we have

[0093] After sorting, we get

[0094] Wherein, V4 is the second positive voltage output by the fourth voltage source V4. The overall voltage is set as the second set voltage.

[0095] When the linear power supply circuit needs to operate in the first mode, the fourth voltage source V4 is set to output the maximum negative current value flowing through the first load and / or the first resistor at the voltage output terminal Vout of the linear power supply circuit, so that the second switch Q2 is in a fully conducting state, and then the first output voltage required by the voltage output terminal Vout is set by the third voltage source V3 and kept stable.

[0096] When the linear power supply circuit needs to operate in the second mode, the third voltage source V3 is set to output the minimum negative voltage value at the voltage output terminal Vout of the linear power supply circuit, so that the first switching transistor Q1 is in a fully conducting state. Then, the fourth voltage source V4 sets the voltage output terminal Vout of the linear power supply circuit to output the required second output current flowing through the first load and / or the first resistor, and keeps it stable.

[0097] The linear power supply circuit also includes a fourth resistor R4, the first end of which is coupled to the emitter of the power transistor Q3, and the second end of which is coupled to the emitter of the first switching transistor Q1.

[0098] The fourth resistor R4 is connected between the emitter of the first switching transistor Q1 and the emitter of the power transistor Q3, forming an effective local feedback network. When the operating state of the power transistor Q3 changes due to load variations, this change is fed back to the emitter of the first switching transistor Q1 through the fourth resistor R4. The first switching transistor Q1 automatically adjusts its conduction level based on the feedback signal received at its emitter, thereby adjusting the base current of the power transistor Q3, thus maintaining the stability of the operating point of the power transistor Q3 and effectively improving the stability and reliability of the linear power supply circuit.

[0099] In one embodiment, the linear power supply circuit further includes an eleventh resistor R11, the first end of which is coupled to the emitter of the first switching transistor Q1, and the second end of which is coupled to the base of the power transistor Q3.

[0100] The eleventh resistor R11 is used to limit the base current of the power transistor Q3.

[0101] The collector of the second switch Q2 is grounded to enable the return of the second control signal.

[0102] In this application, the linear power supply circuit further includes a first capacitor C1 and a second capacitor C2. The first capacitor C1 is connected in parallel to the inverting input terminal and the output terminal of the first operational amplifier U1; the second capacitor C2 is connected in parallel to the inverting input terminal and the output terminal of the second operational amplifier U2.

[0103] The first capacitor C1 is used to provide frequency compensation and stabilization for the first operational amplifier U1; the second capacitor C2 is used to provide frequency compensation and stabilization for the second operational amplifier U2.

[0104] Furthermore, the small-signal bandwidth of the in-phase amplifier depends on the gain of the circuit and the gain-bandwidth product of the amplifier. Adding a sixth capacitor C6 in parallel with the eighth resistor R8 is used to achieve additional filtering. If the eighth resistor R8 is a high-value resistor, the sixth capacitor C6 can also improve the stability of the circuit. Similarly, the third capacitor C3 and the fourth capacitor C4 have the same function as the sixth capacitor C6.

[0105] Both the first switching transistor Q1 and the second switching transistor Q2 are PNP type transistors, and can typically be bipolar transistors or MOSFETs.

[0106] The power transistor Q3 is an NPN transistor, which can typically be a bipolar transistor or a MOSFET.

[0107] In this application, the first voltage source V1 is a negative voltage switching power supply, and the second voltage source V2, the third voltage source V3, and the fourth voltage source V4 are all DACs, and their output voltages are controlled by an MCU.

[0108] Compared with the prior art, this application has the following advantages: In constant voltage mode, the second switch Q2 is fully turned on, and the first power supply circuit 1 controls the first switch Q1 to dynamically drive the power transistor Q3, directly adjusting the stable first output voltage; while in constant current mode, the first switch Q1 is fully turned on, and the second power supply circuit 2 uses the first resistor R1 as a current sensing resistor, and controls the second switch Q2 to dynamically drive the power transistor Q3, directly adjusting the output voltage, so as to achieve a constant second output current flowing through the first resistor R1; thus, the circuit of this application utilizes the first switch Q1, the second switch Q2 and the power transistor Q3 to work together, simplifying the constant voltage and constant current circuit, and achieving free switching between constant voltage mode and constant current mode.

[0109] In the description of this specification, references to terms such as "an embodiment," "some embodiments," "specifically," or "optional embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0110] This application has been described with reference to the above-mentioned embodiments; however, the above embodiments are merely examples for implementing this application. It must be noted that the disclosed embodiments do not limit the scope of this application. On the contrary, any modifications and refinements made without departing from the spirit and scope of this application are within the scope of patent protection of this application.

Claims

1. A linear power supply circuit, characterized in that, The linear power supply circuit, having a voltage output terminal, includes: Power transistor; The third terminal of the first switching transistor is coupled to the first terminal of the power transistor. A first power supply circuit, the output terminal of which is coupled to the first terminal of the first switching transistor, is used to control the first switching transistor to drive the second terminal of the power transistor to generate a first output voltage when receiving a first control signal. The third terminal of the second switch is coupled to the second terminal of the first switch. A first resistor, the first end of which is coupled to the second end of the power transistor, and the second end of which is coupled to the voltage output terminal; and The second power supply circuit has its output terminal coupled to the first terminal of the second switching transistor. The second power supply circuit is used to control the second switching transistor to drive the power transistor to generate a second output current on the first resistor when receiving the second control signal. In the first mode, the first power supply circuit receives the first control signal, the second switching transistor is fully turned on, and the first output voltage remains unchanged. In the second mode, the second power supply circuit receives the second control signal, the first switching transistor is fully turned on, and the second output current remains unchanged.

2. The linear power supply circuit according to claim 1, characterized in that, Also includes: The first voltage source is a voltage source that outputs a first negative voltage, which is applied to the third terminal of the power transistor.

3. The linear power supply circuit according to claim 1, characterized in that, include: A second voltage source and a switching circuit are provided. The positive terminal of the second voltage source is coupled to the feedback terminal of the switching circuit, and the negative terminal of the second voltage source is grounded. The output terminal of the switching circuit is coupled to the third terminal of the power transistor. The switching circuit is used to output a second negative voltage.

4. The linear power supply circuit according to claim 1, characterized in that, The first power supply circuit includes: A first operational amplifier, the output terminal of which is coupled to the first terminal of the first switching transistor, and the inverting input terminal of which is coupled to the voltage output terminal; The first power supply circuit has its output terminal coupled to the non-inverting input terminal of the first operational amplifier, and is used to output a first set voltage.

5. The linear power supply circuit according to claim 4, characterized in that, The first power supply circuit includes: A third voltage source, wherein the third voltage source is used to output a first positive voltage; The first inverting amplifier has its inverting input terminal coupled to the positive terminal of the third voltage source, and its output terminal coupled to the non-inverting input terminal of the first operational amplifier.

6. The linear power supply circuit according to claim 4, characterized in that, The linear power supply circuit is used to supply power to the first load, and the linear power supply circuit further includes: The first follower has its input terminal coupled to the power supply terminal of the first load and its output terminal coupled to the inverting input terminal of the first operational amplifier. The second follower has its input terminal coupled to the ground terminal of the first load and its output terminal coupled to the non-inverting input terminal of the first operational amplifier.

7. The linear power supply circuit according to claim 1, characterized in that, The second power supply circuit includes: The second operational amplifier has its output terminal coupled to the first terminal of the second switching transistor; its inverting input terminal is coupled to the first terminal of the first resistor, and its non-inverting input terminal is coupled to the second terminal of the first resistor. The second power supply circuit has its output terminal coupled to the non-inverting input terminal of the second operational amplifier, and the second power supply circuit is used to output the second set voltage.

8. The linear power supply circuit according to claim 7, characterized in that, The second power supply circuit includes: A fourth voltage source, which is used to output a second positive voltage; The second inverting amplifier has its inverting input terminal coupled to the positive terminal of the fourth voltage source, and its output terminal coupled to the non-inverting input terminal of the second operational amplifier.

9. The linear power supply circuit according to claim 1, characterized in that, The second terminal of the second switch is grounded to enable the return of the second control signal.

10. The linear power supply circuit according to claim 7, characterized in that, The linear power supply circuit also includes: The third follower has its non-inverting input coupled to the first terminal of the first resistor and its output coupled to the inverting input of the second operational amplifier. The fourth follower has its non-inverting input coupled to the second end of the first resistor, and its output coupled to the non-inverting input of the second operational amplifier.

Images