Negative-to-negative buck-boost sampling feedback circuit

Abstract

The embodiment of the invention discloses a negative-to-negative buck-boost sampling feedback circuit, which comprises a main power circuit, a control circuit and a sampling circuit connected with the main power circuit and the control circuit, the sampling circuit is used for sampling a negative output voltage and transmitting the negative output voltage to the control circuit, and the control circuit controls the output duty ratio of the main power circuit according to the negative output voltage so as to adjust the negative output voltage; the sampling circuit comprises a first switching tube and a voltage stabilizing circuit; the first end of the first switch tube is connected with the sampling circuit, the second end of the first switch tube is connected with the input end of the control circuit, and the third end of the first switch tube is grounded. By means of the mode, accurate voltage feedback can be obtained through sampling, and it is guaranteed that the negative input and negative output voltage conversion function is normal.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of switching power supplies, and in particular to a negative-to-negative buck-boost sampling feedback circuit. Background Art

[0002] In modern electronic systems, positive and negative working voltages are generally required. At present, there are many mature and optimized non-isolated conversion solutions for positive input and positive output voltage conversion; but there are not many studies on negative input and negative output voltage conversion. One is that the output voltage feedback method uses a method similar to that of an isolated power supply, using multiple devices such as optocouplers and references. The loop design of the power conversion is relatively complex, and the optocoupler itself also has life and reliability issues.

[0003] See also Figure 1 In the prior art, a transistor V2 and resistors R1 and R2 are used to form an output voltage detection feedback circuit, and a signal with Vin as the reference level is formed on the resistor R2 and input to the FB terminal of A1; the voltage sampling and feedback circuit formed by the reference regulator and its peripheral resistor-capacitor network optocoupler is replaced. Its disadvantage is that in order to ensure that the transistor V2 can work normally, the absolute value of the Vin voltage must be greater than the absolute value of the Vout voltage plus the FB comparison voltage value. When the absolute value of the output Vin voltage is lower than the absolute value of Vout plus the comparison voltage (Vref) value of FB, at this time, the Vout voltage may be normal, but FB detects a feedback of a low voltage, so that the conversion circuit adjusts the output to a value greater than the current Vout voltage, and the voltage detected by FB will be further reduced, and the circuit cannot work normally. Similarly, when a negative input negative output boost voltage needs to be output, that is, when the absolute value of Vout is greater than the absolute value of Vin, this feedback circuit is not applicable. This limits this solution to only be applied to negative input negative output buck conversion, and the application input voltage range is also limited. Summary of the invention

[0004] In view of the above problems, an embodiment of the present invention provides a negative-to-negative buck-boost sampling feedback circuit, which overcomes the above problems or at least partially solves the above problems.

[0005] According to one aspect of an embodiment of the present invention, a negative-to-negative buck-boost sampling feedback circuit is provided, comprising: a main power circuit, a control circuit, and a sampling circuit connected to the main power circuit and the control circuit; the sampling circuit is used to sample the negative output voltage and transmit it to the control circuit, and the control circuit controls the output duty cycle of the main power circuit according to the negative output voltage, thereby adjusting the negative output voltage; the sampling circuit comprises: a first switch tube and a voltage stabilizing circuit; the first end of the first switch tube is connected to the sampling circuit, the second end of the first switch tube is connected to the input end of the control circuit, and the third end of the first switch tube is grounded.

[0006] Optionally, the sampling circuit further includes a first resistor and a second resistor, the second end of the first switch tube is connected to a negative input voltage through the second resistor, and the third end of the first switch tube is grounded through the first resistor.

[0007] Optionally, the voltage stabilizing circuit includes: a voltage stabilizing tube, an anode of the voltage stabilizing tube is connected to the output end of the negative-to-negative buck-boost sampling feedback circuit, and a cathode of the voltage stabilizing tube is connected to the first end of the first switching tube.

[0008] Optionally, the voltage stabilizing circuit further includes: a third resistor, and the first end of the first switch tube is grounded through the third resistor.

[0009] Optionally, the control circuit includes an operational amplifier; the non-phase input terminal of the operational amplifier is connected to a reference voltage, the inverting input terminal of the operational amplifier is connected to the sampling circuit, and the output terminal of the operational amplifier is connected to the main power circuit via the logic control circuit and the drive circuit connected in series.

[0010] Optionally, the control circuit also includes a logic control circuit and a drive circuit; the output end of the operational amplifier is connected to the logic control circuit, and the logic control circuit is connected to the main power circuit via the drive circuit connected in series.

[0011] Optionally, the negative output voltage Vout=-[(1+1 / h FE )*(V ref / R2)*R1+V eb +V V3 ], where V ref is the reference voltage of the operational amplifier, h FE is the current amplification factor of the first switch tube, V eb is the voltage drop between the emitter and base of the first switch tube, V V3 is the voltage stabilization value of the voltage stabilization circuit, R1 is the resistance value of the first resistor, and R2 is the resistance value of the second resistor.

[0012] Optionally, the main power circuit includes: a second switch tube, an inductor, a diode, a first capacitor and a second capacitor; the first end of the second switch tube is connected to the control circuit, the second end of the second switch tube is connected to the negative input voltage, one end of the first capacitor is connected to the second end of the second switch tube, and the other end is grounded, the anode of the diode is connected to the third end of the second switch tube, the cathode of the diode is grounded, one end of the inductor is connected to the third end of the second switch tube, and the other end is the output end of the main power circuit, outputting the negative output voltage; one end of the second capacitor is connected to the output end of the main power circuit, and the other end is grounded.

[0013] Optionally, the main power circuit includes: a second switching tube, an inductor, a diode, a first capacitor and a second capacitor; the first end of the second switching tube is connected to the control circuit, the second end of the second switching tube is connected to the negative input voltage through the inductor, one end of the first capacitor is connected to one end of the inductor away from the second end of the second switching tube, and the other end is grounded, the second end of the second switching tube is also connected to the cathode of the diode, the anode of the diode is the output end of the main power circuit, and outputs the negative output voltage; one end of the second capacitor is connected to the anode of the diode, and the other end is grounded.

[0014] Optionally, the first switch tube is a triode, the first end is the base, the second end is the collector, and the third end is the emitter; the second switch tube is a MOS tube, the first end is the gate, the second end is the drain, and the third end is the source.

[0015] The negative-to-negative buck-boost sampling feedback circuit of an embodiment of the present invention comprises a main power circuit, a control circuit, and a sampling circuit connected to the main power circuit and the control circuit; the sampling circuit is used to sample the negative output voltage and transmit it to the control circuit, and the control circuit controls the output duty cycle of the main power circuit according to the negative output voltage, thereby adjusting the negative output voltage; the sampling circuit comprises: a first switch tube and a voltage stabilizing circuit; the first end of the first switch tube is connected to the sampling circuit, the second end of the first switch tube is connected to the input end of the control circuit, and the third end of the first switch tube is grounded, so that accurate voltage feedback can be obtained by sampling to ensure the normal function of the negative input to negative output voltage conversion.

[0016] The above description is only an overview of the technical solution of the embodiment of the present invention. In order to more clearly understand the technical means of the embodiment of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0018] Figure 1 A schematic diagram of a negative input and negative output sampling feedback circuit in the prior art is shown;

[0019] Figure 2 A schematic diagram of a negative-to-negative buck-boost sampling feedback circuit provided in an embodiment of the present invention is shown;

[0020] Figure 3 A schematic diagram of another negative-to-negative buck-boost sampling feedback circuit according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0021] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0022] Figure 2 FIG. 2 shows a schematic diagram of a negative-to-negative buck-boost sampling feedback circuit according to an embodiment of the present invention. Figure 2 As shown, the negative-to-negative buck-boost sampling feedback circuit includes: a main power circuit, a control circuit, and a sampling circuit connected to the main power circuit and the control circuit; the sampling circuit is used to sample the negative output voltage and transmit it to the control circuit, and the control circuit controls the output duty cycle of the main power circuit according to the negative output voltage, thereby adjusting the negative output voltage; the sampling circuit includes: a first switch tube V2 and a voltage stabilizing circuit; the first end of the first switch tube V2 is connected to the sampling circuit, the second end of the first switch tube V2 is connected to the input end of the control circuit, and the third end of the first switch tube V2 is grounded. The first switch tube V2 is a triode, the first end is the base, the second end is the collector, and the third end is the emitter. The sampling circuit also includes a first resistor R1 and a second resistor R2, the second end of the first switch tube V2 is connected to the negative input voltage through the second resistor R2, and the third end of the first switch tube V2 is grounded GND through the first resistor R1.

[0023] In the embodiment of the present invention, a voltage with the negative input voltage Vin as the reference level is formed on the second resistor R2 and input to the inverting input terminal FB of the operational amplifier A1. The control circuit compares and amplifies the voltage obtained from the sampling circuit with the reference voltage, and outputs a DRIVE signal after being processed by the logic control circuit and the drive circuit, and adjusts the duty cycle of the main power circuit according to the DRIVE signal, thereby adjusting the output voltage Vout. The DRIVE signal is a PWM pulse signal.

[0024] The voltage stabilizing circuit includes: a voltage stabilizing tube V3, the anode of the voltage stabilizing tube V3 is connected to the output end of the negative-to-negative buck-boost sampling feedback circuit, and the cathode of the voltage stabilizing tube V3 is connected to the first end of the first switch tube V2. The voltage stabilizing circuit also includes: a third resistor R3, the first end of the first switch tube V2 is grounded GND through the third resistor R3.

[0025] The control circuit includes an operational amplifier A1; the non-inverting input terminal of the operational amplifier A1 is connected to a reference voltage, the inverting input terminal of the operational amplifier A1 is connected to the sampling circuit, and the output terminal of the operational amplifier A1 is connected to the main power circuit through the serially connected logic control circuit and the drive circuit. The control circuit also includes a logic control circuit and a drive circuit; the output terminal of the operational amplifier A1 is connected to the logic control circuit, and the logic control circuit is connected to the main power circuit through the serially connected drive circuit.

[0026] like Figure 2 As shown, the main power circuit includes: a second switch tube V1, an inductor L1, a diode D1, a first capacitor C1 and a second capacitor C2; the first end of the second switch tube V1 is connected to the control circuit, the second end of the second switch tube V1 is connected to the negative input voltage Vin, one end of the first capacitor C1 is connected to the second end of the second switch tube V1, and the other end is grounded GND, the anode of the diode D1 is connected to the third end of the second switch tube V1, the cathode of the diode D1 is grounded GND, one end of the inductor L1 is connected to the third end of the second switch tube V1, and the other end is the output end of the main power circuit, outputting the negative output voltage Vout; one end of the second capacitor C2 is connected to the output end of the main power circuit, and the other end is grounded GND. Figure 2 The negative-to-negative buck-boost sampling feedback circuit is a BUCK conversion topology, and the absolute value of the negative output voltage Vout is smaller than the absolute value of the negative input voltage Vin.

[0027] like Figure 3 As shown, the main power circuit includes: a second switch tube V1, an inductor L1, a diode D1, a first capacitor C1 and a second capacitor C2; the first end of the second switch tube V1 is connected to the control circuit, the second end of the second switch tube V1 is connected to the negative input voltage Vin through the inductor L1, one end of the first capacitor C1 is connected to one end of the inductor L1 away from the second end of the second switch tube V1, and the other end is grounded GND, the second end of the second switch tube V1 is also connected to the cathode of the diode D1, the anode of the diode D1 is the output end of the main power circuit, and outputs the negative output voltage Vout; one end of the second capacitor C2 is connected to the anode of the diode D1, and the other end is grounded GND. Figure 3 The negative-to-negative buck-boost sampling feedback circuit is a BOOST conversion topology, and the absolute value of the negative output voltage Vout is greater than the absolute value of the negative input voltage Vin.

[0028] The second switch tube V1 is a MOS tube, the first end of which is a gate, the second end is a drain, and the third end is a source.

[0029] In the embodiment of the present invention, based on the working characteristics of the operational amplifier, the voltage of the inverting input terminal FB is equal to the internal reference voltage Vref, that is, the voltage applied to the second resistor R2 is Vref, then the current flowing through the second resistor R2, that is, the collector current of the first switch tube V2 is:

[0030] Ic=Vref / R2

[0031] The current gain factor h of the first switch tube V2 FE , its emitter current can be calculated as:

[0032] Ie=(1+1 / h FE )*Ic=(1+1 / h FE )*(V ref / R2)

[0033] Then the voltage drop across the first resistor R1 is:

[0034] V R1 =Ie*R1=(1+1 / h FE )*(V ref / R2)*R1

[0035] Thus, the emitter voltage of the first switch tube V2 can be obtained. Furthermore, the negative output voltage Vout is obtained by subtracting the emitter voltage of the first switch tube V2 from its eb inter-electrode voltage and the voltage drop of the voltage regulator tube V3:

[0036] Vout=0-V R1 -V eb -V V3

[0037] =-[(1+1 / h FE )*(V ref / R2)*R1+V eb +V V3 ]

[0038] Among them, V ref is the reference voltage of operational amplifier A1, h FE is the current amplification factor of the first switch tube V2, V eb is the voltage drop between the emitter and base of the first switch tube V2, V V3 is the voltage stabilization value of the voltage stabilization circuit, R1 is the resistance value of the first resistor, and R2 is the resistance value of the second resistor. The first switch tube V2 should be a triode that is less affected by temperature.

[0039] In the above formula, V ref 、h FE 、V eb 、V V3They are all fixed values, so the required negative output voltage Vout can be obtained by selecting the resistance values ​​of the first resistor R1 and the second resistor R2.

[0040] The negative-to-negative buck-boost sampling feedback circuit of the embodiment of the present invention realizes negative-to-negative voltage sampling feedback by using devices such as triodes and voltage regulators in a negative input and negative output power supply. The number of devices is small and the implementation method is simple. When the absolute value of the negative input voltage Vin is close to the absolute value of the negative output voltage Vout, it can ensure that the sampling circuit obtains normal voltage feedback and the control and adjustment function of the voltage conversion is normal. It can be applied to any negative input and negative output boost voltage power supply conversion.

[0041] To summarize, the negative-to-negative buck-boost sampling feedback circuit of an embodiment of the present invention includes: a main power circuit, a control circuit, and a sampling circuit connected to the main power circuit and the control circuit; the sampling circuit is used to sample the negative output voltage and transmit it to the control circuit, and the control circuit controls the output duty cycle of the main power circuit according to the negative output voltage, thereby adjusting the negative output voltage; the sampling circuit includes: a first switch tube and a voltage stabilizing circuit; the first end of the first switch tube is connected to the sampling circuit, the second end of the first switch tube is connected to the input end of the control circuit, and the third end of the first switch tube is grounded, so that accurate voltage feedback can be obtained by sampling to ensure the normal function of the negative input to negative output voltage conversion.

[0042] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure is limited to these examples. Based on the concept of the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0043] This application is intended to cover all such substitutions, modifications and variations that fall within the broad scope of all embodiments. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the scope of protection of this disclosure.

Claims

1. A negative-to-negative buck-boost sampling feedback circuit, characterized in that: The negative-to-negative buck-boost sampling feedback circuit includes: a main power circuit, a control circuit, and a sampling circuit connected to the main power circuit and the control circuit; the sampling circuit is used to sample the negative output voltage and transmit it to the control circuit, and the control circuit controls the output duty cycle of the main power circuit according to the negative output voltage, thereby adjusting the negative output voltage; the sampling circuit includes: a first switch tube and a voltage stabilizing circuit; the first end of the first switch tube is connected to the sampling circuit, the second end of the first switch tube is connected to the input end of the control circuit, and the third end of the first switch tube is grounded.

2. The negative-to-negative buck-boost sampling feedback circuit according to claim 1, characterized in that: The sampling circuit further includes a first resistor and a second resistor. The second end of the first switch tube is connected to a negative input voltage through the second resistor, and the third end of the first switch tube is grounded through the first resistor.

3. The negative-to-negative buck-boost sampling feedback circuit according to claim 2, characterized in that: The voltage stabilizing circuit comprises: a voltage stabilizing tube, an anode of the voltage stabilizing tube is connected to the output end of the negative-to-negative buck-boost sampling feedback circuit, and a cathode of the voltage stabilizing tube is connected to the first end of the first switch tube.

4. The negative-to-negative buck-boost sampling feedback circuit according to claim 3, characterized in that: The voltage stabilizing circuit further includes: a third resistor, and the first end of the first switch tube is grounded through the third resistor.

5. The negative-to-negative buck-boost sampling feedback circuit according to claim 3, characterized in that: The control circuit includes an operational amplifier; the non-phase input terminal of the operational amplifier is connected to a reference voltage, the inverting input terminal of the operational amplifier is connected to the sampling circuit, and the output terminal of the operational amplifier is connected to the main power circuit through the logic control circuit and the drive circuit connected in series.

6. The negative-to-negative buck-boost sampling feedback circuit according to claim 5, characterized in that: The control circuit also includes a logic control circuit and a drive circuit; the output end of the operational amplifier is connected to the logic control circuit, and the logic control circuit is connected to the main power circuit via the drive circuit connected in series.

7. The negative-to-negative buck-boost sampling feedback circuit according to claim 5, characterized in that: The negative output voltage Vout = -[(1+1 / h FE )*(V ref / R2)*R1+V eb +V V3 ], where V ref is the reference voltage of the operational amplifier, h FE is the current amplification factor of the first switch tube, V eb is the voltage drop between the emitter and base of the first switch tube, V V3 is the voltage stabilization value of the voltage stabilization circuit, R1 is the resistance value of the first resistor, and R2 is the resistance value of the second resistor.

8. The negative-to-negative buck-boost sampling feedback circuit according to claim 1, characterized in that: The main power circuit includes: a second switch tube, an inductor, a diode, a first capacitor and a second capacitor; the first end of the second switch tube is connected to the control circuit, the second end of the second switch tube is connected to the negative input voltage, one end of the first capacitor is connected to the second end of the second switch tube, and the other end is grounded, the anode of the diode is connected to the third end of the second switch tube, the cathode of the diode is grounded, one end of the inductor is connected to the third end of the second switch tube, and the other end is the output end of the main power circuit, outputting the negative output voltage; one end of the second capacitor is connected to the output end of the main power circuit, and the other end is grounded.

9. The negative-to-negative buck-boost sampling feedback circuit according to claim 1, characterized in that: The main power circuit includes: a second switch tube, an inductor, a diode, a first capacitor and a second capacitor; the first end of the second switch tube is connected to the control circuit, the second end of the second switch tube is connected to the negative input voltage through the inductor, one end of the first capacitor is connected to the end of the inductor away from the second end of the second switch tube, and the other end is grounded, the second end of the second switch tube is also connected to the cathode of the diode, the anode of the diode is the output end of the main power circuit, and outputs the negative output voltage; one end of the second capacitor is connected to the anode of the diode, and the other end is grounded.

10. The negative-to-negative buck-boost sampling feedback circuit according to claim 8 or 9, characterized in that: The first switch tube is a triode, the first end is the base, the second end is the collector, and the third end is the emitter; the second switch tube is a MOS tube, the first end is the gate, the second end is the drain, and the third end is the source.

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