Discharging circuit, switching power supply and driving chip
By introducing bias units and control units into the integrated circuit and using mirror reference current to improve transistor matching, the problem of uncertain discharge voltage in switching power supplies is solved, enabling precise control of discharge terminal voltage and reduction of process angle.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-24
- Publication Date
- 2026-03-31
AI Technical Summary
In integrated circuits, when the output of a switching power supply switches from operating mode to sleep mode, the discharge voltage value is difficult to determine accurately and is greatly affected by process technology, resulting in significant differences in output voltage between different chips.
By employing a bias unit and a control unit, the voltage at the input terminal is converted into a second bias voltage to precisely control the voltage value at the discharge terminal after discharge is completed. Furthermore, the matching degree of the transistor is improved by mirroring the reference current, thereby reducing the impact of process corners.
It achieves precise control of the discharge terminal voltage, reduces the impact of process angle on the voltage value after discharge, and ensures that the discharge terminal voltage is close to the input terminal voltage and not less than the input terminal voltage.
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Figure CN224068539U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to integrated circuit technical field, especially a kind of discharge circuit, switching power supply and drive chip. BACKGROUND
[0002] In the chip integrated with switching power supply, when chip is switched from working mode to sleep mode, in order to reduce the power consumption of sleep mode and improve the service life of switching power supply, the output of switching power supply needs to be discharged. Take the drive chip in display device as an example, its inside usually includes two switching power supplies, one switching power supply is boost type switching power supply, and the other switching power supply is negative voltage type switching power supply.
[0003] Referring to Figure 1 , the input voltage Vin1 / Vin2 of switching power supply DC-DC_1 / DC-DC_2 is usually only ±5V~±6V, and the output voltage VGH / VGL may need to reach ±16V. After the work of drive chip ends, switching power supply DC-DC_1 and DC-DC_2 need to be discharged. Since the output voltage VGH is generally the highest voltage of chip, and the output voltage VGL is generally the lowest voltage of chip, in order to avoid leakage, the discharge circuit has the following requirements: when discharging the output end of switching power supply DC-DC_1, the final output voltage VGH should be as close to input voltage Vin1 as possible, but cannot be lower than input voltage Vin1; when discharging the output end of switching power supply DC-DC_2, the final output voltage VGL should be as close to input voltage Vin2 as possible, but cannot be higher than input voltage Vin2.
[0004] However, after the discharge of the output end of switching power supply DC-DC_1 and DC-DC_2 ends, the voltage value of the final output voltage VGH / VGL is not easy to determine, and is greatly affected by process angle, resulting in great difference in output voltage VGH / VGL of different chips after discharge ends. UTILITY MODEL CONTENTS
[0005] In view of the above problems, the purpose of the utility model is to provide a discharge circuit, switching power supply and drive chip, so that the voltage value of discharge end after discharge completion can be accurately determined.
[0006] According to an aspect of the utility model, a discharge circuit is provided, including bias unit, connected between input end and ground end, for generating first bias voltage according to the voltage of input end;Control unit, connected with the bias unit, for generating second bias voltage according to the voltage of input end and the first bias voltage;Discharge unit, connected with the control unit and discharge end, for discharging the discharge end according to the second bias voltage, wherein the voltage value of the second bias voltage.
[0007] Optionally, the control unit comprises a first resistor and a second resistor, which are connected in sequence between the input terminal and the first bias voltage, and a middle node of the first resistor and the second resistor provides the second bias voltage.
[0008] Optionally, the bias unit has a bias current, and the bias current is greater than a current flowing through the first resistor.
[0009] Optionally, the control unit is implemented by a digital-to-analog converter, and a voltage of the input terminal and the first bias voltage are taken as a high-level reference voltage and a low-level reference voltage of the digital-to-analog converter respectively, an output terminal of the digital-to-analog converter provides the second bias voltage, and a decoding coefficient of the digital-to-analog converter is set according to a requirement of the second bias voltage.
[0010] Optionally, the bias unit comprises a first high-voltage transistor, a third resistor, a first transistor and a second transistor, which are connected in sequence between the input terminal and a ground terminal, a control terminal of the first high-voltage transistor is connected to a second terminal thereof and provides the first bias voltage, a control terminal of the first transistor is connected to a second terminal thereof, and a control terminal of the second transistor receives a first control signal.
[0011] Optionally, the bias unit mirrors a reference current, and a mirrored current is taken as a bias current of the bias unit.
[0012] Optionally, the bias unit comprises a second high-voltage transistor, a third transistor and a fourth transistor, which are connected in sequence between the input terminal and the ground terminal, a control terminal of the second high-voltage transistor is connected to a second terminal thereof and provides the first bias voltage, a control terminal of the third transistor receives a second control signal, a fifth transistor is connected between the reference current and the ground terminal, and a control terminal of the fourth transistor is connected to a first terminal thereof and a control terminal of the fifth transistor.
[0013] Optionally, the discharge unit comprises a third high-voltage transistor, a fourth high-voltage transistor and a fourth resistor, which are connected in sequence between the discharge terminal and the ground terminal, a control terminal of the third high-voltage transistor receives the second bias voltage, and a control terminal of the fourth high-voltage transistor receives a third control voltage.
[0014] According to the second aspect of the utility model, a switching power supply is provided, comprising the discharge circuit as described above, the input terminal of the discharge circuit is connected to the input terminal of the switching power supply, the discharge terminal of the discharge circuit is connected to the output terminal of the switching power supply, and the discharge circuit discharges the output terminal of the switching power supply after starting.
[0015] According to the third aspect of the utility model, a driving chip is provided, comprising at least one switching power supply as described above.
[0016] The discharging circuit, the switching power supply and the driving chip provided by the utility model, through the control unit, the voltage of the input end and the first bias voltage provided by the bias unit are converted into the second bias voltage, so that the voltage value of the discharging end after the discharging is completed can be accurately determined.
[0017] In the preferred embodiment, the bias unit obtains the bias current through the mirror reference current, further reducing the influence of the process angle on the voltage of the discharging end after the discharging is completed. BRIEF DESCRIPTION OF DRAWINGS
[0018] The above and other objects, features and advantages of the utility model will become more apparent from the following description of the utility model embodiments with reference to the accompanying drawings, in which:
[0019] Figure 1 The structure schematic diagram of the switching power supply and the discharging circuit in the driving chip is shown;
[0020] Figure 2 The structure schematic diagram of a kind of discharging circuit is shown;
[0021] Figure 3 The structure schematic diagram of a kind of discharging circuit is shown; Figure 2 The circuit schematic diagram of the discharging circuit shown;
[0022] Figure 4 The timing schematic diagram of discharging end in discharging process when the discharging circuit shown is used is shown; Figure 3 The circuit schematic diagram of the discharging circuit shown;
[0023] Figure 5 The timing schematic diagram of discharging end in discharging process when the discharging circuit shown is used is shown; Figure 2 The circuit schematic diagram of the discharging circuit shown;
[0024] Figure 6 The timing schematic diagram of discharging end in discharging process when the discharging circuit shown is used is shown; Figure 5 The circuit schematic diagram of the discharging circuit shown;
[0025] Figure 7 The structure schematic diagram of the discharging circuit according to the utility model embodiment is shown;
[0026] Figure 8 The circuit schematic diagram of the discharging circuit according to the first embodiment of the utility model is shown;
[0027] Figure 9 The circuit schematic diagram of the discharging circuit according to the second embodiment of the utility model is shown;
[0028] Figure 10 The timing schematic diagram of discharging end in discharging process when the discharging circuit shown is used is shown; Figure 9The timing diagram of the discharge end during the discharging process is shown in the discharge circuit;
[0029] Figure 11 A circuit schematic diagram of the control unit according to an embodiment of the present application is shown;
[0030] Figure 12 Another structural schematic diagram of the control unit according to an embodiment of the present application is shown;
[0031] Figure 13 A connection schematic diagram when a digital-to-analog converter is used as the control unit according to an embodiment of the present application is shown;
[0032] Figure 14 Another connection schematic diagram when a digital-to-analog converter is used as the control unit according to an embodiment of the present application is shown. DETAILED DESCRIPTION
[0033] Various embodiments of the present application will be described hereinafter with reference to the accompanying drawings. In the drawings, like reference numerals are used to represent the same or similar elements throughout. For the purpose of clarity, not every component is drawn to scale.
[0034] It should be understood that, in the following description, "circuitry" can include a single or multiple components of hardware, programmable circuitry, state machine circuitry, and / or elements storing instructions for execution by programmable circuitry. When an element or circuitry is referred to as being "connected to" another element, or "connected between" two nodes, it can be directly coupled or connected to the other element or can have intervening elements between the coupling or connection, and the connection between elements can be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled to" or "directly connected to" another element, it implies that there are no intervening elements between them.
[0035] Meanwhile, some terms are used in the present patent specification and claims to refer to certain components. It should be understood by those of ordinary skill in the art that hardware manufacturers can use different names to refer to the same component. The present patent specification and claims do not use the difference in name as a way to distinguish components, but rather use the difference in function of components as a criterion for distinction.
[0036] Furthermore, it is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology used herein is inclusive of numbers in a structure and / or instrumentalities that are equivalent to the numbers expressly listed. Additionally, where
[0037] Figure 2 A structure diagram of a discharge circuit is shown; Figure 3 A circuit diagram of the discharge circuit is shown. Figure 2 A circuit diagram of the discharge circuit is shown.
[0038] The discharge circuit 100 is used to discharge a circuit which needs to be discharged. For example, the discharge circuit 100 is used to discharge an output terminal of a switching power supply, the switching power supply has an input terminal and an output terminal, the input terminal receives an input voltage Vin, and the output terminal provides an output voltage Vout. The switching power supply can be a boost type switching power supply or a negative voltage type switching power supply whose absolute value of the output voltage Vout is greater than that of the input voltage Vin.
[0039] Referring to Figure 2 , the discharge circuit 100 includes a bias unit 110 and a discharge unit 120. The bias unit 110 is used to determine the voltage value of the discharge terminal after the discharge is completed. The discharge unit 120 is used to perform a discharge operation on the discharge terminal to discharge the charge stored on the energy storage element of the discharge terminal. When the discharge circuit 100 is used to discharge the output terminal of the switching power supply, the input terminal of the discharge circuit 100 is the input terminal of the switching power supply, and the discharge terminal of the discharge circuit 100 is the output terminal of the switching power supply.
[0040] Referring to Figure 3 , the bias unit 110 includes a transistor MP2, resistors R1 (number not limited), transistors MP1 (number not limited), and a transistor MN1 connected in sequence between the input terminal and the ground terminal of the discharge circuit 100. The discharge unit 120 includes a high-voltage transistor HP2, a high-voltage transistor HP3, and resistors R2 (number not limited) connected in sequence between the discharge terminal and the ground terminal.
[0041] In this circuit, high-voltage transistor HP2 is a bleeder, and resistor R2 is a bleeder resistor. Transistor MN1 and high-voltage transistor HP3 are control switches that control the start and stop of the discharge circuit, respectively controlled by control signals Ctrl1 and Ctrl2. Transistor MP1 and resistor R1 are used to adjust the bias current flowing through transistor MP2, thereby fine-tuning the bias voltage supplied to the gate terminal of transistor MP2.
[0042] After discharge is complete, the voltage Vout_final at the discharge terminal can be expressed as:
[0043] Vout_final=Vin-Vth_mp2-Vod_mp2+Vth_hp2 (1),
[0044] Where Vth_mp2 represents the threshold voltage of transistor MP2, Vod_mp2 represents the overdrive voltage of transistor MP2, and Vth_hp2 represents the threshold voltage of high-voltage transistor HP2.
[0045] In the discharge circuit 100, due to the different withstand voltages of transistor HP2 and high-voltage transistor MP2, and the large difference in their threshold voltages, the change in process corner will cause the voltage Vout_final at the discharge terminal of different chips to vary greatly after the discharge is completed.
[0046] Figure 4 It shows the use of Figure 3 The diagram shows the timing sequence of the discharge terminal during the discharge process in the discharge circuit shown.
[0047] See Figure 4 The two curves define the voltage fluctuation range at the discharge terminal during the discharge process. The voltage fluctuation range at the discharge terminal is also relatively large due to the significant influence of the process angle.
[0048] To address the aforementioned issues, the applicant of this application attempted to replace transistor MP2 with a high-voltage transistor HP1 to improve transistor matching. The specific circuit diagram is shown below. Figure 5 As shown.
[0049] When using Figure 5 When the discharge circuit 200 is shown, after the discharge is complete, the voltage Vout_final at the discharge terminal can be expressed as:
[0050] Vout_final=Vin-Vth_hp1-Vod_hp1+Vth_hp2 (2),
[0051] Where Vth_hp1 represents the threshold voltage of high-voltage transistor HP1, and Vod_hp1 represents the overdrive voltage of high-voltage transistor HP1.
[0052] Since the threshold voltages of the high-voltage transistors HP1 and HP2 are basically the same, the voltage Vout_final of the discharge end after the discharge is completed can also be expressed as:
[0053] Vout_final=Vin-Vod_hp1(3).
[0054] As can be seen from the above formula (3), when the discharge circuit 200 shown in Figure 5 is used, the voltage Vout_final of the discharge end after the discharge is completed will be less than the input voltage Vin. Therefore, when the discharge circuit 200 is used, if the voltage Vout of the discharge end is required to be close to and not greater than the voltage Vin of the input end, the time of the discharge end needs to be controlled.
[0055] Figure 6 The time sequence diagram of the discharge end during the discharge process when the discharge circuit shown in Figure 5 is used is shown.
[0056] Referring to Figure 6 , the two curves therein define the voltage value fluctuation range of the discharge end during the discharge process of the discharge end. Since the voltage Vout_final of the discharge end after the discharge is completed will be less than the input voltage Vin, the time of the discharge end needs to be controlled.
[0057] Based on the above problems, the applicant of the present application has further improved the discharge circuit.
[0058] Figure 7 The structural schematic diagram of the discharge circuit according to the embodiment of the present application is shown.
[0059] The discharge circuit 300 is used for discharging the circuit which needs to be discharged. For example, the discharge circuit 300 is used for discharging the boost switching power supply or the negative voltage switching power supply whose absolute value of the output voltage Vout is greater than the absolute value of the input voltage Vin. The switching power supply has an input end and an output end, the input end receives the input voltage Vin, and the output end provides the output voltage Vout.
[0060] Referring to Figure 7 , the discharge circuit 300 includes a bias unit 310, a control unit 320, and a discharge unit 330. Taking the discharge of the output end of the switching power supply as an example, the input end of the discharge circuit 300 is the input end of the switching power supply, and the discharge end of the discharge circuit 300 is the output end of the switching power supply.
[0061] The bias unit 310 is connected between the input terminal and the ground terminal, and is configured to generate a bias voltage Vbias1 according to a voltage Vin of the input terminal. The control unit 320 is connected with the bias unit 310, and is configured to generate a bias voltage Vbias2 according to the voltage Vin of the input terminal and the bias voltage Vbias1, and a voltage value of the bias voltage Vbias2 determines a voltage value of the discharge terminal after the discharge is completed. The discharge unit 330 is connected between the discharge terminal and the ground terminal, and is configured to discharge the discharge terminal according to the bias voltage Vbias2.
[0062] The bias voltage Vbias2 can be expressed as:
[0063] Vbias2=Vin+a(Vbias1-Vin) (4).
[0064] Figure 8 A circuit schematic diagram of the discharge circuit according to the first embodiment of the present application is shown.
[0065] Referring to Figure 8 The bias unit 310 includes a high voltage transistor HP1, a resistor R1, a transistor MP1 and a transistor MN1 connected in sequence between the input terminal and the ground terminal, a control terminal of the high voltage transistor HP1 is connected to the second terminal thereof and provides the bias voltage Vbias1, a control terminal of the transistor MP1 is connected to the second terminal thereof, and a control terminal of the transistor MN1 receives a control voltage Ctrl1. The bias unit 310 has a bias current, and the bias current flows through the high voltage transistor HP1.
[0066] The discharge unit 330 includes a high voltage transistor HP2, a high voltage transistor HP3 and a resistor R2 connected in sequence between the discharge terminal and the ground terminal, a control terminal of the high voltage transistor HP2 receives the bias voltage Vbias2, and a control terminal of the high voltage transistor HP3 receives a control voltage Ctrl2.
[0067] Two input terminals of the control unit 320 are connected to the input terminal and an output terminal of the bias voltage Vbias1 respectively, and an output terminal of the control unit 320 provides the bias voltage Vbias2. The bias voltage Vbias1 can be expressed as:
[0068] Vbias1=Vin-(Vth_hp1+Vod_hp1) (5),
[0069] Substituting formula (5) into formula (4), the bias voltage Vbias2 can also be expressed as:
[0070] Vbias2=Vin-a(Vth_hp1+Vod_hp1) (6).
[0071] When the discharge circuit 200 is used, after the discharge is completed, the voltage Vout_final of the discharge terminal can be expressed as:
[0072] Vout_final=Vbias2+Vth_hp1=Vin-a(Vth_hp1+Vod_hp1)+Vth_hp2(7),
[0073] It can be known from formula (7) that when a=Vth_hp2 / (Vth_hp1+Vod_hp1) is set, Vout_final=Vin. Considering the change of process angle, a can be set slightly smaller to ensure that Vout_final>=Vin. Therefore, a can be set as a≤Vth_hp2 / (Vth_hp1+Vod_hp1).
[0074] The applicant of the present application considers that the bias current of the bias unit 310 will fluctuate with the change of PVT (Process, Voltage, Temperature, that is, process, voltage, and temperature), which causes the change range of the overdrive voltage hp1_vod of the high-voltage transistor HP1 to increase, and then affects the voltage value range of the discharge end after the discharge is completed. Therefore, the bias unit 310 is improved.
[0075] Figure 9 A circuit schematic diagram of a discharge circuit according to a second embodiment of the present application is shown.
[0076] Referring to Figure 9 , the structures of the control unit 320 and the discharge unit 330 are the same as those in Figure 8 , and details are not repeated here. The bias unit 340 mirrors the reference current ibias and takes the mirrored current as the bias current of the bias unit 340. The reference current ibias can be the original reference current inside the chip. Since the reference current ibias changes less with PVT, the fluctuation range of the overdrive voltage hp1_vod of the high-voltage transistor HP1 is also smaller, and accordingly, the voltage Vout_final of the discharge end after the discharge is completed is less affected by the process angle.
[0077] Specifically, the bias unit 340 includes a high-voltage transistor HP4 and transistors MN2-MN4. The transistors MN2 and MN3 constitute a mirror circuit. The high-voltage transistor HP4, the transistor MN2, and the transistor MN4 are connected in sequence between an input end and a ground end, the transistor MN3 is connected between the reference current ibias and the ground end, the control end of the high-voltage transistor HP4 is connected to the second end thereof and provides a bias voltage Vbias2, the control end of the transistor MN2 receives a control voltage Ctrl3, the control end of the transistor MN4 is connected to the control end of the transistor MN3, and the control end of the transistor MN3 is connected to the first end thereof.
[0078] Figure 10The discharge circuit is shown in Fig. 3. Figure 9 The timing diagram of the discharge end during the discharge process is shown in Fig. 4.
[0079] Referring to Fig. 3, Figure 10 When the discharge circuit 300 is shown in Fig. 3, Figure 9 When the discharge circuit 300 is shown in Fig. 3, the voltage value of the discharge end fluctuates in a small range due to the small influence of the process angle, and by adjusting the voltage value of the bias voltage Vbias2, the voltage Vout_final of the discharge end after the discharge is close to the voltage Vin of the input end but not less than the voltage Vin of the input end.
[0080] Figure 11 A circuit diagram of the control unit according to an embodiment of the utility model is shown in Fig. 5.
[0081] Referring to Fig. 3, Figure 11 The control unit 320 is implemented in the form of resistance voltage division. Specifically, the control unit 320 includes resistors Rx and Ry connected in sequence between the discharge end and the bias voltage Vbias1, and the middle node of the resistors Rx and Ry provides the bias voltage Vbias2. By adjusting the resistance values of the resistors Rx and Ry, the expected bias voltage Vbias2 can be obtained.
[0082] It can be understood that, Figure 11 The bias unit 340 in Fig. 3 can also be replaced by the bias unit 310. In order to avoid the fluctuation of the bias current in the bias unit 340 / 310, i.e. the current flowing through the high-voltage transistor HP4 / HP1, caused by the process angle change of the resistor, the bias current in the bias unit 340 / 310 can be greater than the current flowing through the resistors Rx and Ry. Since the discharge circuit 300 is only temporarily turned on when the switching power supply is switched from the working mode to the sleep mode, the excessive bias current of the bias unit 340 / 310 will not have a significant impact on the power consumption of the circuit.
[0083] Figure 12 Another structural diagram of the control unit according to an embodiment of the utility model is shown in Fig. 6.
[0084] Referring to Fig. 3, Figure 12, the control unit 320 can also be implemented by any digital-to-analog converter (DAC). When the control unit 300 is implemented by a digital-to-analog converter, the voltage Vin at the input end is the high-level reference voltage of the digital-to-analog converter, the bias voltage Vbias1 is the low-level reference voltage of the digital-to-analog converter, the output end of the digital-to-analog converter provides the bias voltage Vbias2, and the input end of the digital-to-analog converter receives the digital signal Data [0, N]. The number a in the above formula (4) is the decoding coefficient of the digital-to-analog converter, which is determined by the digital signal Data [0, N] and affects the voltage value of the bias voltage Vbias2. The decoding coefficient of the digital-to-analog converter can be set according to the demand of the bias voltage Vbias2.
[0085] Figure 13 and Figure 14 An exemplary schematic diagram showing the connection between the digital-to-analog converter and the input end of the discharge circuit 300, the output end of the bias voltage Vbias1, and the output end of the bias voltage Vbias2 when the control unit 320 is implemented by a digital-to-analog converter.
[0086] The discharge circuit, switching power supply and driving chip provided by the embodiments of the present application can convert the voltage at the input end and the first bias voltage provided by the bias unit into the second bias voltage by the control unit and provide the second bias voltage to the discharge unit, so that the voltage value at the discharge end after the discharge is completed can be accurately controlled by adjusting the second bias voltage (for example, the voltage at the discharge end after the discharge is completed is close to the voltage at the input end and is not less than the voltage at the input end). In addition, since the transistors in the bias unit and the discharge unit have high matching degree, the voltage at the discharge end after the discharge is completed is less affected by the process angle. The bias unit obtains the bias current by the mirror reference current, which further reduces the influence of the process angle on the voltage at the discharge end after the discharge is completed.
[0087] Further, the present application also provides a switching power supply, which comprises the discharge circuit 300 as described above. The input end of the discharge circuit 300 is connected to the input end of the switching power supply, the discharge end of the discharge circuit 300 is connected to the output end of the switching power supply, and the discharge circuit 300 discharges the output end of the switching power supply after being started.
[0088] Further, the present application also provides a driving chip, which comprises at least one switching power supply as described above.
[0089] The embodiments of this utility model described above are examples of specific examples, and do not exhaustively describe all details, nor do they limit the utility model to only specific embodiments. Obviously, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this utility model, thereby enabling those skilled in the art to make good use of this utility model and its modifications. The scope of protection of this utility model should be determined by the scope defined by the claims of this utility model and their equivalents.
Claims
1. A discharge circuit, characterized by comprising: The discharge circuit comprises: a bias unit connected between an input terminal and a ground terminal, for generating a first bias voltage according to a voltage of the input terminal; a control unit connected with the bias unit, for generating a second bias voltage according to the voltage of the input terminal and the first bias voltage; a discharge unit connected with the control unit and a discharge terminal, for discharging the discharge terminal according to the second bias voltage, wherein a voltage value of the second bias voltage determines a voltage value of the discharge terminal after the discharging is completed.
2. The discharge circuit according to claim 1, characterized by The control unit comprises: a first resistor and a second resistor connected between the input terminal and the first bias voltage in sequence, and a middle node of the first resistor and the second resistor providing the second bias voltage.
3. The discharge circuit according to claim 2, characterized by The bias unit has a bias current, and the bias current is greater than a current flowing through the first resistor.
4. The discharge circuit of claim 1, wherein The control unit is implemented by a digital-to-analog converter, and the voltage of the input terminal and the first bias voltage are respectively used as a high-level reference voltage and a low-level reference voltage of the digital-to-analog converter, an output terminal of the digital-to-analog converter providing the second bias voltage, and a decoding coefficient of the digital-to-analog converter being set according to a requirement of the second bias voltage.
5. The discharge circuit of claim 1, wherein The bias unit comprises: a first high-voltage transistor, a third resistor, a first transistor and a second transistor connected between the input terminal and the ground terminal in sequence, a control terminal of the first high-voltage transistor being connected with a second terminal thereof and providing the first bias voltage, a control terminal of the first transistor being connected with a second terminal thereof, and a control terminal of the second transistor receiving a first control signal.
6. The discharge circuit of claim 1, wherein The bias unit mirrors a reference current, and the mirrored current is used as a bias current of the bias unit.
7. The discharge circuit of claim 6, wherein The bias unit comprises: a second high-voltage transistor, a third transistor and a fourth transistor connected between the input terminal and the ground terminal in sequence, a control terminal of the second high-voltage transistor being connected with a second terminal thereof and providing the first bias voltage, a control terminal of the third transistor receiving a second control signal, a fifth transistor connected between the reference current and the ground terminal, and a control terminal of the fourth transistor being connected with a first terminal thereof and a control terminal of the fifth transistor.
8. The discharge circuit according to claim 5 or 7, characterized by The discharge unit comprises: a third high-voltage transistor, a fourth high-voltage transistor and a fourth resistor connected between the discharge terminal and the ground terminal in sequence, a control terminal of the third high-voltage transistor receiving the second bias voltage, and a control terminal of the fourth high-voltage transistor receiving a third control voltage.
9. A switching power supply, characterized by The discharge circuit comprises: The discharge circuit according to any one of claims 1-8, an input terminal of the discharge circuit being connected with an input terminal of the switching power supply, a discharge terminal of the discharge circuit being connected with an output terminal of the switching power supply, and the discharge circuit discharging the output terminal of the switching power supply after being started.
10. A driving chip, characterized in that, The switching power supply comprises: at least one switching power supply according to claim 9.