Negative voltage-to-negative voltage circuit

Abstract

The invention discloses a negative voltage-to-negative voltage circuit, which belongs to the technical field of step-down circuits and comprises a step-down converter, an inductor, a first capacitor, a second capacitor, a first resistor and a second resistor. The buck converter comprises a first pin, a second pin, a third pin and a fourth pin; a first terminal of the inductor is connected with an external negative voltage input port, and a second terminal of the inductor is connected with the first pin; a first terminal of the first capacitor is connected with a series connection midpoint of the inductor and the external negative voltage input port, and a second terminal of the first capacitor is connected with a first terminal and a second pin of the second capacitor; the second terminal of the second capacitor is connected with the third pin, the third pin is connected with the negative voltage output port and the first terminal of the first resistor, and the second terminal of the third pin is connected with the fourth pin and the first terminal of the second resistor. By changing the connection mode of the peripheral circuit of the step-down converter, the negative voltage-to-negative voltage circuit of the step-down converter is realized, and the circuit is simple to realize, high in compatibility and good in reliability.

Description

Technical Field

[0001] The present application relates to the technical field of step-down circuits, and in particular to a negative voltage to negative voltage conversion circuit. Background Art

[0002] In the field of electronic circuits, power conversion circuits play a key role in the normal operation of various electronic devices. Among them, there is a widespread demand for the technology of converting one voltage to another.

[0003] At present, it is common to use a buck converter to realize a circuit that converts positive voltage to negative voltage or positive voltage to positive voltage. Conventional buck converters usually input a positive voltage through the IN pin, and through the circuit structure inside the buck converter and in conjunction with specific peripheral circuits, the voltage is stepped down and converted to a negative voltage or positive voltage output to meet the needs of different loads for negative voltage power supply. However, in some specific application scenarios, it is necessary to convert the negative voltage to another negative voltage of a different value. The existing circuit based on the buck converter to realize the positive voltage to negative voltage conversion cannot directly meet this demand.

[0004] If negative pressure is to be converted to negative pressure, the current solutions are often more complicated and may require redesigning the chip architecture or cascading multiple chips to achieve it. This not only increases the difficulty and cost of circuit design, but also increases the volume of the entire circuit system, reducing the integration and reliability of the circuit.

[0005] Therefore, how to improve these defects has become a technical problem to be solved urgently in this field. Summary of the invention

[0006] The present application aims to provide a negative voltage to negative voltage circuit implemented by a buck converter.

[0007] In order to achieve the above-mentioned purpose, the technical solution of this application is: A negative voltage to negative voltage circuit comprises: a buck converter, a first inductor, a first capacitor, a second capacitor, a first resistor and a second resistor; the buck converter comprises: a first pin, a second pin, a third pin and a fourth pin; The first terminal of the first inductor is connected to the external negative voltage input port, the second terminal of the first inductor is connected to the first pin, the first terminal of the first capacitor is connected to the series midpoint of the first inductor and the external negative voltage input port, the second terminal of the first capacitor is respectively connected to the first terminal and the second pin of the second capacitor, the second terminal of the second capacitor is connected to the third pin, the third pin is connected to the negative voltage output port and the first terminal of the first resistor, and the second terminal of the first resistor is connected to the fourth pin and the first terminal of the second resistor.

[0008] Optionally, the buck converter further includes: a first switch and a second switch, wherein the first terminal of the first switch is connected to the second pin, the second terminal of the first switch is connected to the first terminal of the second switch and the first pin, and the second terminal of the second switch is connected to the third pin.

[0009] Optionally, the second terminal of the first capacitor, the second pin, and the first terminal of the second capacitor are connected and grounded.

[0010] Optionally, the second terminal of the second resistor is connected to the first terminal of the first inductor.

[0011] Optionally, the second terminal of the second resistor is grounded.

[0012] Optionally, the first switch and the second switch are MOS tubes.

[0013] Optionally, the first pin is pin LX, the second pin is pin IN, the third pin is pin GND, and the fourth pin is pin FB.

[0014] Optionally, the step-down converter includes a Buck chip.

[0015] Optionally, the external negative pressure input port inputs external negative pressure, and the negative pressure output port outputs negative pressure.

[0016] The present application provides a negative voltage to negative voltage circuit. Based on a conventional buck converter, the pin LX of the buck converter is connected to an external negative voltage input port. Through a negative feedback control loop, the application of negative voltage to negative voltage is realized. Even if an external disturbance is introduced, the negative voltage to negative voltage circuit provided by the present application will recover to a normal working state within a few cycles, and there is no risk of losing control. Each pin of the buck converter has no risk of negative voltage breakdown and has good reliability. Without modifying the conventional buck converter, the existing buck converter is directly used, and the common buck converter can be seamlessly adapted to cooperate with a variety of buck converter platforms without additional custom development, which greatly reduces the chip selection cost and development difficulty, and has strong compatibility. Only the connection mode of the peripheral circuit of the buck converter is changed, the circuit structure is simple, easy to understand and master, and also convenient for later maintenance and upgrading, and simple to implement. No expensive special devices are introduced, and the peripheral circuit is built based on common electronic components, which reduces the material cost, is low in cost, and because the circuit is simple, the failure rate in the production process is low, which further saves costs. After testing, the negative voltage to negative voltage circuit can stably achieve negative voltage to negative voltage conversion, has small output voltage ripple, can provide stable output negative voltage for the load, and can maintain good electrical performance under different working conditions, ensuring stable circuit operation and reliable performance.

[0017] In order to make the above features and advantages of the application more obvious and easy to understand, the following embodiments are specifically cited and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a negative pressure to negative pressure circuit diagram of the first specific embodiment provided in the present application.

[0019] Figure 2 4 is an equivalent circuit diagram of the negative pressure to negative pressure circuit in mode 1 in the first specific embodiment.

[0020] Figure 3 4 is an equivalent circuit diagram of the negative pressure to negative pressure circuit in mode 2 in the first specific embodiment.

[0021] Figure 4 A schematic diagram of startup waveforms of a negative voltage to negative voltage circuit according to the first specific embodiment provided in the present application.

[0022] Figure 5 A schematic diagram of the steady-state operating waveform of the negative-voltage-to-negative-voltage circuit of the first specific embodiment provided in the present application.

[0023] Figure 6 This is a negative pressure to negative pressure circuit diagram of the second specific embodiment provided in the present application.

[0024] In the drawings, like reference numerals refer to the same drawing elements. DETAILED DESCRIPTION

[0025] In order to make the purpose and technical solution of the embodiment of the present application clearer, the technical solution of the embodiment of the present application will be clearly and completely described in conjunction with the drawings of the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, not all of the embodiments. Based on the described embodiment of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] In a specific embodiment of the present application, please refer to Figure 1 , Figure 1 The negative voltage to negative voltage circuit diagram of the first specific embodiment provided in the present application, the negative voltage to negative voltage circuit comprises: a buck converter 1, an inductor L, a capacitor C IN , capacitor C OUT , resistor R H And the resistor R L The buck converter 1 comprises: a pin IN, a pin LX, a pin FB and a pin GND.

[0027] Among them, inductance L, capacitance C IN , capacitor C OUT , resistor R HAnd the resistor R L The peripheral circuits constituting the step-down converter 1.

[0028] As an example, the first terminal of the inductor L is connected to the external negative voltage input port V IN The second terminal of the inductor L is connected to the pin LX, and the capacitor C IN The first terminal of the inductor L and the external negative voltage input port V IN The midpoint of the series connection, capacitor C IN The second terminal of the capacitor C OUT The first terminal, pin IN and reference ground terminal PGND are connected, capacitor C OUT The second terminal is connected to the pin GND, and the pin GND is connected to the negative voltage output port V OUT And the resistor R L The first terminal is connected to the resistor R L The second terminal is connected to the pin FB and the resistor R H The first terminal is connected to the resistor R H The second terminal is grounded.

[0029] As an example, the buck converter 1 further includes: a switch S1 and a switch S2, wherein a first terminal of the switch S1 is connected to the pin IN, a second terminal of the switch S1 is connected to a first terminal of the switch S2 and the pin LX, and a second terminal of the switch S2 is connected to the pin GND.

[0030] As an example, pin IN is a power output pin, pin LX is a switch node, pin GND is a chip reference ground, and pin FB is an output voltage feedback pin.

[0031] Specifically, the buck converter 1 further includes: a frequency selection pin FS, a mode selection pin MODE, an internal LDO power supply pin VCC, a soft start configuration pin SS, etc. The reference grounds of these pins in actual applications need to be connected to the chip reference ground pin GND.

[0032] As an example, the resistor R H The upper feedback resistor of pin FB, resistor R L is the lower feedback resistor of pin FB.

[0033] As an example, the external negative pressure input port V IN Input external negative pressure, negative pressure output port V OUT Output negative pressure.

[0034] As an example, a conventional buck converter is a step-down DC-DC converter, which can only input a positive voltage and then perform a step-down conversion on the positive voltage, but cannot directly input a negative voltage for step-down conversion.

[0035] Furthermore, the negative voltage-to-negative voltage circuit designed in the present application is adopted to change the connection mode of the peripheral circuit of the buck converter 1 to realize the application of negative voltage-to-negative voltage.

[0036] Next, continue to combine Figure 1 Describes how this application works.

[0037] As an example, the internal reference voltage of pin FB of buck converter 1 is V REF External negative pressure input port V IN The inductor L, the pin LX of the buck converter 1 and the midpoint of the series connection of the switch S1 and the switch S2 are connected in sequence. When the external negative voltage input port V IN When an external negative voltage is input to the negative voltage conversion circuit, the external negative voltage is input to the buck converter 1 through the inductor L. The external negative voltage is converted to the required negative voltage through the switching action of the switch S1 and the switch S2, and then the negative voltage is output through the capacitor C on the output side. OUT Filter out the AC component and get a stable DC negative voltage. H , lower feedback resistor R L The voltage divider circuit is formed to sample the output negative voltage and feed the sampled output negative voltage back to pin FB. REF The comparison result is the preset output negative pressure.

[0038] The output negative pressure setting formula is expressed as: As an example, in order to make the negative voltage to negative voltage circuit run smoothly, the peripheral circuit is connected to the reference ground terminal PGND for the power loop to withstand a large current; the buck converter 1 sets the pin GND as the chip ground and the negative voltage output port V OUT , reducing the interference of the power circuit to the signal circuit, making the buck converter 1 run more smoothly.

[0039] As an example, the inductor L is a power inductor that can pass a large current. At the same time, due to the characteristic that the inductor current cannot change suddenly, setting the inductor L can smooth the current waveform, reduce the current fluctuation, and make the output current more stable, thereby helping to stabilize the output negative voltage. IN It is an input filter capacitor that filters out high-frequency noise in the input external negative voltage, stabilizes the input external negative voltage, provides instantaneous large current, and reduces the impact of voltage fluctuations on the chip on the power supply line. Capacitor C OUT It is an output filter capacitor that filters the output negative voltage to make the output negative voltage smoother, reduce ripple and maintain the stability of the output voltage.

[0040] As an example, the step-down converter 1 is a Buck chip. All Buck chips can be used in the negative voltage to negative voltage circuit of the present application, including: Buck chips of model TPS548D26, model TPS62873, model LTC7151S, etc.

[0041] As an example, the switch S1 and the switch S2 are MOS tubes.

[0042] As an example, the negative voltage to negative voltage circuit enters mode 1, that is, when switch S1 is turned on and switch S2 is turned off, the external negative voltage input port V IN Input external negative voltage to the negative voltage to negative voltage circuit, the conduction time is recorded as D*T, and the external negative voltage current flows from the reference ground terminal PGND through the switch S1 and the inductor L to the external negative voltage input port V IN , the inductor L stores energy, and the voltage across the inductor L is V IN , the voltage stress of switch S1 is |V OUT |.

[0043] For further information, please refer to Figure 2 In mode 1, switch S1 is turned on and switch S2 is turned off, and the negative voltage to negative voltage circuit is equivalent to the following: Figure 2 In the boost circuit shown in the figure, the external negative voltage current flows from the reference ground terminal PGND through the switch S1 and the inductor L to the external negative voltage input port V IN , inductor L stores energy.

[0044] When the negative voltage to negative voltage circuit enters mode 2, that is, switch S1 is turned off and switch S2 is turned on, the on time is recorded as (1-D)*T, the inductor L is discharged, and the inductor current flows to the external negative voltage input port V through switch S2. IN , at this time the voltage across the inductor L = V IN -V OUT , the voltage stress of switch S2 is |V OUT |.

[0045] For further information, please refer to Figure 3 In mode 2, switch S1 is turned off and switch S2 is turned on, and the negative voltage to negative voltage circuit is equivalent to the following: Figure 3 In the boost circuit shown in the figure, the discharge current of the inductor L is freewheeled through the switch S2 and flows to the external negative voltage input port V IN .

[0046] As an example, the negative voltage to negative voltage circuit provided in this embodiment obtains the following formula in two modes through the principle of volt-second balance across the inductor L: Simplified to: From the simplified formula, it can be obtained that the main switch of the negative voltage to negative voltage circuit provided in this embodiment and the main switch of the Boost circuit are the same switch. Therefore, the negative voltage to negative voltage circuit provided in this embodiment can be equivalent to the following in two modes: Figure 2 and Figure 3 The Boost circuit shown in the figure further realizes negative feedback control of the negative voltage to negative voltage circuit provided in this embodiment by controlling the duty cycle D of the switch S1, that is, the switch S1 can adjust the duty cycle D by itself to meet the set output negative voltage V OUT .

[0047] Specifically, the negative voltage-to-negative voltage circuit of the present application can be equivalent to a Boost circuit. When the switch S1 and the switch S2 perform switching actions crosswise, the main switch in the circuit is switch S1, and the voltage stress of the switch S1 and the switch S2 is |VOUT|. The preset output negative voltage is obtained through negative feedback; after the output negative voltage VOUT is established, each pin in the buck converter 1 is a positive voltage relative to the chip reference ground pin GND, and there is no risk of negative voltage. Combined with the above analysis, the control loop of the negative voltage-to-negative voltage circuit provided in this embodiment belongs to negative feedback. Even if there is an external disturbance, the negative voltage-to-negative voltage circuit provided in this embodiment will return to normal working state within a few cycles, and there is no risk of loss of control. Furthermore, there is no negative voltage risk on each pin of the buck converter 1, indicating that the negative voltage-to-negative voltage circuit provided in this embodiment has good reliability and no risk of negative voltage breakdown.

[0048] As an example, assume that the internal reference voltage V of the selected Buck chip pin FB is REF =0.6V, the upper feedback resistor R H =100kΩ, lower feedback resistor R L =5.1kΩ. According to the output negative voltage setting formula, the output negative voltage setting is calculated to be approximately 12.4V.

[0049] For further information, see Figure 4 and Figure 5 , set the external negative pressure input port V IN =6V, inductor L=1uH, the working waveform of the negative voltage to negative voltage circuit is as follows Figure 4 and Figure 5 As shown, Figure 4 This is a schematic diagram of the startup waveform of the negative voltage to negative voltage circuit of the first specific embodiment provided in the present application, Figure 5 The schematic diagram of the steady-state working waveform of the negative-voltage-to-negative-voltage circuit of the first specific embodiment provided in the present application is composed of Figure 4 It can be seen that when the negative pressure to negative pressure circuit is started, the external negative pressure input port V IN The negative pressure is quickly established, causing the voltage to drop rapidly to a certain value; the negative pressure output port V OUTThe output negative voltage gradually drops to the target negative voltage value, but due to the charging and discharging characteristics of the capacitor, its change is relatively slow; the voltage at the pin LX changes significantly due to the start of the switch tube and the change of the inductor current. Figure 5 It can be seen that after the negative pressure to negative pressure circuit has been running stably for a period of time, the external negative pressure input port V IN The external input negative pressure waveform is relatively stable with small fluctuations, indicating that the external input negative pressure has stabilized at this time, providing a stable energy source for the circuit; the negative pressure output port V OUT The output negative voltage waveform is also very stable, basically maintained near a certain fixed value, indicating that the output negative voltage has stabilized at the target negative voltage value, the circuit has entered a normal working state, and outputs a stable negative voltage; the voltage at the pin LX presents a periodic pulse waveform, indicating that the switch is periodically turned on and off, maintaining the normal step-down conversion of the negative voltage to negative voltage circuit, thereby achieving a stable negative voltage output. From the analysis of the operating results, it can be seen that the parameters of the negative voltage to negative voltage circuit proposed in this application undergo a rapid change and adjustment process at startup, and finally enter a stable operating state, and can stably output the target negative voltage to achieve normal operation.

[0050] In the second specific embodiment of this application, please refer to Figure 6 , Figure 6 The negative voltage to negative voltage circuit diagram of the second specific embodiment provided in the present application, the first terminal of the inductor L and the external negative voltage input port V IN The second terminal of the inductor L is connected to the pin LX, and the capacitor C IN The first terminal of the inductor L and the external negative voltage input port V IN The midpoint of the series connection, capacitor C IN The second terminal of the capacitor C OUT The first terminal, pin IN and reference ground terminal PGND are connected, capacitor C OUT The second terminal is connected to the pin GND, and the pin GND is connected to the negative voltage output port V OUT And the resistor R L The first terminal is connected to the resistor R L The second terminal is connected to the pin FB and the resistor R H The first terminal is connected to the resistor R H The second terminal of is connected to the first terminal of the inductor L. The output negative pressure setting formula is expressed as: As an example, Figure 6 The internal circuit connection mode of the buck converter 1 and the working state of the negative voltage to negative voltage circuit are Figure 1 The circuit is the same and will not be described again here.

[0051] In summary, the negative voltage to negative voltage circuit provided in the present application is based on the buck converter 1, and the pin LX of the buck converter 1 is connected to the external negative voltage input port V IN , through the negative feedback control loop, the application of negative voltage to negative voltage is realized. Even if there is external disturbance, the negative voltage to negative voltage circuit provided by the present application will restore the normal working state within several cycles, and there is no risk of loss of control. Each pin of the buck converter 1 has no risk of negative voltage breakdown and has good reliability. The buck converter 1 is not modified, and the existing buck converter is directly used. It can seamlessly adapt to common buck converters and cooperate with a variety of buck converter platforms without additional customized development, which greatly reduces the chip selection cost and development difficulty, and has strong compatibility. Only the connection method of the peripheral circuit of the buck converter 1 is changed, the circuit structure is simple, easy to understand and master, and it is also convenient for later maintenance and upgrading, and the implementation is simple. Expensive special devices are not introduced, and the peripheral circuit is built based on common electronic components, which reduces the material cost and is low in cost. Moreover, due to the simplicity of the circuit, the failure rate in the production process is low, which further saves costs. After testing, the negative voltage to negative voltage circuit can stably realize negative voltage to negative voltage, the output voltage ripple is small, and a stable output negative voltage can be provided for the load. Under different working conditions, good electrical performance can be maintained to ensure stable operation of the circuit and reliable performance.

[0052] Although the present application has been disclosed as above with the embodiments, it is not intended to limit the present application. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be determined by the scope of the attached patent application.

Claims

1. A negative voltage to negative voltage circuit, characterized in that: include: A buck converter, a first inductor, a first capacitor, a second capacitor, a first resistor and a second resistor; the buck converter comprises: a first pin, a second pin, a third pin and a fourth pin; The first terminal of the first inductor is connected to the external negative voltage input port, the second terminal of the first inductor is connected to the first pin, the first terminal of the first capacitor is connected to the series midpoint of the first inductor and the external negative voltage input port, the second terminal of the first capacitor is respectively connected to the first terminal of the second capacitor and the second pin, the second terminal of the second capacitor is connected to the third pin, the third pin is connected to the negative voltage output port and the first terminal of the first resistor, and the second terminal of the first resistor is connected to the fourth pin and the first terminal of the second resistor.

2. A negative voltage to negative voltage circuit as claimed in claim 1, characterized in that: The buck converter further includes: a first switch and a second switch, wherein the first terminal of the first switch is connected to the second pin, the second terminal of the first switch is connected to the first terminal of the second switch and the first pin, and the second terminal of the second switch is connected to the third pin.

3. A negative voltage to negative voltage circuit as claimed in claim 1, characterized in that: The second terminal of the first capacitor, the second pin, and the first terminal of the second capacitor are connected and grounded.

4. A negative voltage to negative voltage circuit as claimed in claim 1, characterized in that: A second terminal of the second resistor is grounded.

5. A negative voltage to negative voltage circuit as claimed in claim 1, characterized in that: The second terminal of the second resistor is connected to the first terminal of the first inductor.

6. A negative voltage to negative voltage circuit as claimed in claim 2, characterized in that: The first switch and the second switch are MOS tubes.

7. A negative voltage to negative voltage circuit as claimed in claim 1, characterized in that: The first pin is a pin LX, the second pin is a pin IN, the third pin is a pin GND, and the fourth pin is a pin FB.

8. The negative voltage to negative voltage circuit according to claim 1, characterized in that: The step-down converter includes a Buck chip.

9. The negative voltage to negative voltage circuit according to claim 1, characterized in that: The external negative pressure input port inputs external negative pressure, and the negative pressure output port outputs negative pressure.

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