Soft start circuit with pre-bias voltage protection

Abstract

The invention discloses a soft start circuit with pre-bias voltage protection, which comprises a pre-bias voltage protection circuit and a start circuit, two ends of an MOS (Metal Oxide Semiconductor) tube M1 are in circuit connection with an MOS tube M2, one end of the MOS tube M1 and one end of the MOS tube M2 are in circuit connection with an MOS tube M9, the MOS tube M9 is connected in series with an MOS tube M10, and the MOS tube M3, the MOS tube M8 and the MOS tube M12 are sequentially connected in series. When the power supply is powered on, no matter whether the output voltage is zero or not, the output voltage can be slowly and monotonically increased, the hidden danger of chip damage caused by overshoot voltage and backward current is avoided, the circuit structure is simple and easy to implement, the area is small, the problem that small current and large capacitance are difficult to select is effectively solved, sufficient soft start time is guaranteed through periodic pulses, and the soft start efficiency is improved. The power tube can be accurately controlled to carry out switching work and is closed after soft start is completed, and power consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of soft start circuits, and in particular to a soft start circuit with pre-bias voltage protection. Background Art

[0002] With the widespread popularity of electronic devices, people's demand for high-performance portable electronic products has increased, and the research on smaller, more reliable, efficient and low-power switching power supply chips is of great significance. As an important switching power supply chip, the DC / DC converter has two hidden dangers when the power supply starts: first, due to the modulation of the loop, the switch tube is almost in a 100% duty cycle working state, which can easily cause voltage overshoot and damage the chip; second, in order to improve the conversion efficiency, the chip uses synchronous rectification technology. If there is residual charge (pre-bias voltage) at the output end, the duty cycle of the rectifier tube will become very large when the power supply is just started, forming a path from the output to the ground, generating backflow current, causing the circuit to restart or a large current to flow in and damage the chip. Therefore, a soft start circuit with pre-bias voltage protection is provided to solve the above problems. Summary of the invention

[0003] In order to solve the problems in the above background technology, the technical solution adopted by the present invention to solve the technical problems is: a soft start circuit with pre-bias voltage protection, which includes: a pre-bias voltage protection circuit and a start circuit, the pre-bias voltage protection circuit includes MOS tube M1, MOS tube M2, MOS tube M3, MOS tube M4, MOS tube M5, MOS tube M6, MOS tube M7, MOS tube M8, MOS tube M9, MOS tube M10, MOS tube M11, MOS tube M12, MOS tube M13, MOS tube M14, the two ends of the MOS tube M1 are connected to the MOS tube M2, the MOS tube M1 and the MOS tube M2 are connected to the MOS tube M9 at one end, the MOS tube M9 is connected in series with the MOS tube M10, and the MOS tube M3, MOS tube M8 and MOS tube M12 are connected in series in sequence.

[0004] As a preferred technical solution of the present invention, the MOS tube M4 and the MOS tube M5 are connected in parallel and then connected in series to one end of the MOS tube M13, the other end of the MOS tube M13 is connected to the MOS tube M12, one end of the MOS tube M4 and the MOS tube M5 is connected to the MOS tube M3, and the MOS tube M3 is connected to the MOS tube M2.

[0005] As a preferred technical solution of the present invention, the MOS tube M12 is connected in parallel with the MOS tube M11, one end of the MOS tube M11 is connected to the MOS tube M12a, and the MOS tube M12a is connected in parallel with the MOS tube M12d.

[0006] As a preferred technical solution of the present invention, one end of the MOS tube M12a, MOS tube M12d and MOS tube M11 is connected to the MOS tube M10, and the line between the MOS tube M12a and the MOS tube M11 is connected to a NOT gate.

[0007] As a preferred technical solution of the present invention, the MOS tube M6, MOS tube M17, and MOS tube M14 are connected in series, one end of the MOS tube M6 is connected to the MOS tube M5, and one end of the MOS tube M14 is connected to the MOS tube M13.

[0008] As a preferred technical solution of the present invention, the startup circuit includes a D trigger D1, an oscillator, an operational amplifier, a capacitor C1, a MOS tube M15, a MOS tube M16, a MOS tube M17, a MOS tube M18, a MOS tube M19, a MOS tube M20, and a MOS tube M21. The MOS tube M15 is connected in series with the MOS tube M17, one end of the MOS tube M17 is connected to the MOS tube M18, and the capacitor C1, the MOS tube M17, and the MOS tube M18 are connected in parallel.

[0009] As a preferred technical solution of the present invention, one end of the D flip-flop D1 is connected to a NOR gate, the D flip-flop D1 is connected to an oscillator through the NOR gate, a MOS tube M20 is connected between the oscillator and the NOR gate, one end of the oscillator is connected to an operational amplifier, and a MOS tube M19 is connected between the oscillator and the operational amplifier.

[0010] As a preferred technical solution of the present invention, the MOS tube M19 is connected to the MOS tube M20, one end of the operational amplifier is connected to the MOS tube M16, the MOS tube M16 is connected to the MOS tube M19, and one end of the MOS tube M16 is connected to the capacitor C1.

[0011] As a preferred technical solution of the present invention, one end of the MOS tube M15 is connected to the line between the MOS tube M7 and the MOS tube M14, the MOS tube M17 is connected to the line of the MOS tube M14, and one end of the MOS tube M16 is connected to the line of the MOS tube M6.

[0012] As a preferred technical solution of the present invention, the line between the MOS tube M6 and the MOS tube M16 is connected to the NOR gate, the NOR gate is connected to the NAND gate, the MOS tube M17 and the operational amplifier are connected to the NOR gate, the resistor R1, and the resistor C2, and one end of the resistor C2 is connected to the MOS tube M21.

[0013] The present invention has the following advantages: the present invention designs a soft start circuit with pre-bias voltage protection, so that when the power supply is powered on, no matter whether the output voltage is zero or not, the output voltage can rise smoothly and monotonically, avoiding the hidden danger of chip damage caused by overshoot voltage and backflow current. The circuit structure is simple and easy to implement, with a small area, and effectively solves the problem of difficulty in selecting small current and large capacitance. Sufficient soft start time is guaranteed through periodic pulses, and the power tube can be accurately controlled to switch, and closed after the soft start is completed, thereby reducing power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of a soft start circuit for pre-bias voltage protection according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present invention are described clearly and completely below. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Many specific details are explained in the following description to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0016] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Please refer to Figure 1 The present invention discloses a soft start circuit with pre-bias voltage protection, comprising: a pre-bias voltage protection circuit and a start circuit, wherein the pre-bias voltage protection circuit comprises a MOS tube M1, a MOS tube M2, a MOS tube M3, a MOS tube M4, a MOS tube M5, a MOS tube M6, a MOS tube M7, a MOS tube M8, a MOS tube M9, a MOS tube M10, a MOS tube M11, a MOS tube M12, a MOS tube M13, and a MOS tube M14, wherein two ends of the MOS tube M1 are connected to the MOS tube M2, one end of the MOS tube M1 and the MOS tube M2 are connected to the MOS tube M9, the MOS tube M9 is connected in series to the MOS tube M10, and the MOS tubes M3, M8, and M12 are connected in series in sequence.

[0018] Among them, the MOS tube M4 is connected in parallel with the MOS tube M5 and then connected in series with one end of the MOS tube M13, the other end of the MOS tube M13 is connected to the MOS tube M12 by a line, one end of the MOS tube M4 and the MOS tube M5 is connected to the MOS tube M3 by a line, the MOS tube M3 is connected to the MOS tube M2 by a line, the MOS tube M12 is connected in parallel with the MOS tube M11, one end of the MOS tube M11 is connected to the MOS tube M12a by a line, the MOS tube M12a is connected in parallel with the MOS tube M12d, one end of the MOS tube M12a, the MOS tube M12d and the MOS tube M11 are connected to the MOS tube M10 by a line, the MOS tube M12a and the MOS tube M11 are connected to a NOT gate by a line, the MOS tube M6, the MOS tube M17 and the MOS tube M14 are connected in series, one end of the MOS tube M6 is connected to the MOS tube M5 by a line, and one end of the MOS tube M14 is connected to the MOS tube M13 by a line. In order to ensure sufficient soft-start time, the mirror ratio of the current mirror structure and the width-to-length ratio of MOS tube M14 and MOS tube M15 are adjusted to obtain a suitable Ic, solving the problem of difficult small current selection. The pulse signal of the oscillator in the DC / DC chip is used to control the on and off of the branch where Ic is located, so that the capacitor is periodically charged and the soft-start time is doubled. As the capacitor is charged, the soft-start voltage Vss and the output voltage Vout rise smoothly until Vss rises to VREF1 , the operational amplifier output flips to a low level, so SoftStart flips to a high level, and the soft start is completed, and Vss is quickly charged to V IN , the system enters a stable working state. With the completion of the soft start, signals S1 and S2 turn off the bias circuit, the capacitor charging and discharging part, and the operational amplifier part, and only use the output signal of the D flip-flop D1 to indicate whether the soft start is completed, which ensures accuracy and reduces system power consumption.

[0019] The startup circuit includes a D trigger D1, an oscillator, an operational amplifier, a capacitor C1, a MOS tube M15, a MOS tube M16, a MOS tube M17, a MOS tube M18, a MOS tube M19, a MOS tube M20, and a MOS tube M21. The MOS tube M15 is connected in series with the MOS tube M17, one end of the MOS tube M17 is connected to the MOS tube M18, the capacitor C1, the MOS tube M17, and the MOS tube M18 are connected in parallel, one end of the D trigger D1 is connected to the NOR gate, the D trigger D1 is connected to the oscillator through the NOR gate, the MOS tube M20 is connected between the oscillator and the NOR gate, one end of the oscillator is connected to the operational amplifier, and the line between the oscillator and the operational amplifier is connected to the MOS tube M1. 9, the MOS tube M19 is connected to the MOS tube M20, one end of the operational amplifier is connected to the MOS tube M16, the MOS tube M16 is connected to the MOS tube M19, one end of the MOS tube M16 is connected to the capacitor C1, one end of the MOS tube M15 is connected to the line between the MOS tube M7 and the MOS tube M14, the MOS tube M17 is connected to the MOS tube M14, one end of the MOS tube M16 is connected to the MOS tube M6, the line between the MOS tube M6 and the MOS tube M16 is connected to the NOR gate, the NOR gate is connected to the NAND gate, the MOS tube M17 and the operational amplifier are connected to the NOR gate, the resistor R1, and the resistor C2, and one end of the resistor C2 is connected to the MOS tube M21. When SS_EN is low, the circuit does not work, the MOS tube M17 is turned on, the capacitor C2 is pulled to the ground and discharged to zero, and the soft start module is initialized and waits for startup; when SS_EN jumps to a high level, the circuit starts to work. MOS tube M17 is turned off, and D flip-flop D1 is enabled. Since the soft start voltage Vss is less than the reference voltage V EEF , the operational amplifier outputs a high level, the soft start completion signal SoftStart port remains at a low level, the bias circuit is turned on, so that the output part of the operational amplifier is turned on after the bias circuit, and enters the soft start. The depletion MOS tube M9 generates a bias current I BIAS1 ;

[0020] Through MOS tube M2 tube I BIAS1 Convert to V BIAS1 , to provide bias voltage for the operational amplifier. To ensure the accuracy of the current and avoid interference caused by direct mirroring, the current mirror structure composed of MOS tubes M2 and M3, MOS tubes M12 and M13, MOS tubes M5 and MOS tubes M6 is used to copy the reduced current step by step. While obtaining a smaller current, the power consumption is reduced. Although a large deviation value of the bias current is generated, I is obtained after mirroring. BIAS2 .

[0021] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0022] Other parts of the present invention not described in detail belong to the prior art and will not be described in detail here.

[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A soft start circuit with pre-bias voltage protection, characterized in that: include: A pre-bias voltage protection circuit and a startup circuit, wherein the pre-bias voltage protection circuit comprises a MOS tube M1, a MOS tube M2, a MOS tube M3, a MOS tube M4, a MOS tube M5, a MOS tube M6, a MOS tube M7, a MOS tube M8, a MOS tube M9, a MOS tube M10, a MOS tube M11, a MOS tube M12, a MOS tube M13, and a MOS tube M14, wherein two ends of the MOS tube M1 are connected to the MOS tube M2, one end of the MOS tube M1 and the MOS tube M2 are connected to the MOS tube M9, the MOS tube M9 is connected in series to the MOS tube M10, and the MOS tubes M3, M8, and M12 are connected in series in sequence.

2. A soft start circuit with pre-bias voltage protection as claimed in claim 1, characterized in that: The MOS tube M4 and the MOS tube M5 are connected in parallel and then connected in series to one end of the MOS tube M13. The other end of the MOS tube M13 is connected to the MOS tube M12. One end of the MOS tube M4 and the MOS tube M5 is connected to the MOS tube M3. The MOS tube M3 is connected to the MOS tube M2.

3. A soft start circuit with pre-bias voltage protection as claimed in claim 1, characterized in that: The MOS transistor M12 is connected in parallel with the MOS transistor M11. One end of the MOS transistor M11 is connected to the MOS transistor M12a. The MOS transistor M12a is connected in parallel with the MOS transistor M12d.

4. A soft start circuit with pre-bias voltage protection as claimed in claim 3, characterized in that: One end of the MOS tube M12a, the MOS tube M12d and the MOS tube M11 is connected to the MOS tube M10 by lines, and the line between the MOS tube M12a and the MOS tube M11 is connected to a NOR gate.

5. A soft start circuit with pre-bias voltage protection as claimed in claim 1, characterized in that: The MOS tube M6, the MOS tube M17, and the MOS tube M14 are connected in series, one end of the MOS tube M6 is connected to the MOS tube M5, and one end of the MOS tube M14 is connected to the MOS tube M13.

6. A soft start circuit with pre-bias voltage protection as claimed in claim 1, characterized in that: The startup circuit includes a D trigger D1, an oscillator, an operational amplifier, a capacitor C1, a MOS tube M15, a MOS tube M16, a MOS tube M17, a MOS tube M18, a MOS tube M19, a MOS tube M20, and a MOS tube M21. The MOS tube M15 is connected in series with the MOS tube M17, one end of the MOS tube M17 is connected to the MOS tube M18, and the capacitor C1, the MOS tube M17, and the MOS tube M18 are connected in parallel.

7. A soft start circuit with pre-bias voltage protection as claimed in claim 6, characterized in that: One end of the D flip-flop D1 is connected to the NOR gate, the D flip-flop D1 is connected to the oscillator through the NOR gate, a MOS tube M20 is connected between the oscillator and the NOR gate, one end of the oscillator is connected to the operational amplifier, and a MOS tube M19 is connected between the oscillator and the operational amplifier.

8. A soft start circuit with pre-bias voltage protection as claimed in claim 6, characterized in that: The MOS tube M19 is connected to the MOS tube M20, one end of the operational amplifier is connected to the MOS tube M16, the MOS tube M16 is connected to the MOS tube M19, and one end of the MOS tube M16 is connected to the capacitor C1.

9. A soft start circuit with pre-bias voltage protection as claimed in claim 6, characterized in that: One end of the MOS tube M15 is connected to the line between the MOS tube M7 and the MOS tube M14, the MOS tube M17 is connected to the line of the MOS tube M14, and one end of the MOS tube M16 is connected to the line of the MOS tube M6.

10. A soft start circuit with pre-bias voltage protection as claimed in claim 1, characterized in that: The line between the MOS tube M6 and the MOS tube M16 is connected to the NOR gate, the NOR gate is connected to the NAND gate, the MOS tube M17 and the operational amplifier are connected to the NOR gate, the resistor R1, and the resistor C2, and one end of the resistor C2 is connected to the MOS tube M21.

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