A positive and negative logic control circuit and a switching power supply circuit

Abstract

The present invention belongs to the technical field of analog circuit design, and relates to a positive and negative logic control circuit and a switching power supply circuit, including a positive logic control circuit unit, which is composed of a resistor R2 and a diode D1, one end of the resistor R2 is connected to a power control pin CTR, the other end of the resistor R2 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to a power enable pin EN1; a negative logic control circuit unit, which is composed of a resistor R1, a transistor Q1 and a resistor R2, one end of the resistor R1 is connected to a voltage input terminal, the other end of the resistor R1 is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the base of the transistor Q1, the emitter of the transistor Q1 is grounded, the collector of the transistor Q1 is connected to the power enable pin EN1, and the power control pin CTR is connected between the resistor R1 and the resistor R2. The present invention only uses one transistor that is not an electrostatic sensitive device, which reduces the area occupied by the PCB and improves the reliability of the circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuit design, and in particular to a positive and negative logic control circuit and a switching power supply circuit. Background Art

[0002] Switching power supplies have the advantages of high conversion efficiency, wide voltage regulation range, good voltage stabilization accuracy, energy saving, compact structure and environmental protection, and have been widely valued in recent years. Positive and negative logic control circuits are commonly used circuits in power supplies. If the power supply uses positive logic to control the power enable pin, then when the power enable pin is suspended or connected to a high level, the power supply works normally, and when the power enable pin is grounded, the power supply is turned off. If the power supply uses negative logic to control the power enable pin, then when the power enable pin is grounded, the power supply works normally, and when the power enable pin is suspended or connected to a high level, the power supply is turned off. However, the existing positive and negative logic control circuits use more components and occupy a large PCB area, and the MOS tubes in the positive and negative logic control circuits are electrostatically sensitive devices, which are easily damaged by static electricity, resulting in reduced power supply reliability.

[0003] In view of this, this application is hereby filed. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing positive and negative logic control circuits use many components, occupy a large PCB area, and the MOS tubes in the positive and negative logic control circuits are easily damaged by static electricity.

[0005] In order to solve the above technical problems, the present invention is implemented by the following technical solutions: In the first aspect, a positive and negative logic control circuit is proposed, including: a positive logic control circuit unit and a negative logic control circuit unit; the positive logic control circuit unit includes: a resistor R2 and a diode D1, one end of the resistor R2 is connected to a power control pin CTR, the other end of the resistor R2 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to a power enable pin EN1; the negative logic control circuit unit includes: a resistor R1, a transistor Q1 and the resistor R2, one end of the resistor R1 is connected to a voltage input end, the other end of the resistor R1 is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the base of the transistor Q1, the emitter of the transistor Q1 is grounded, the collector of the transistor Q1 is connected to the power enable pin EN1, and the power control pin CTR is connected between the resistor R1 and the resistor R2.

[0006] Furthermore, the transistor Q1 is an NPN transistor, a Darlington transistor or a field effect transistor.

[0007] In the second aspect, a switching power supply circuit is proposed, including: a control chip U1, a capacitor C1, a capacitor C2, a capacitor C3, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7 and an inductor L1; the control chip U1 is peripherally provided with a positive and negative logic control circuit as described in the first aspect; one end of the capacitor C1, one end of the resistor R3 and a power input pin VIN of the control chip U1 are all connected to a voltage input end; the other end of the resistor R3 is connected to one end of the resistor R4; the other end of the capacitor C3, the other end of the resistor R4 and a ground pin GND of the control chip U1 are all grounded; the power enable pin EN1 is connected between the resistor R3 and the resistor R4; one end of the resistor R5 is connected to the control chip The RT pin of U1, the other end of the resistor R5 is grounded; one end of the resistor R7 is connected to the FB pin of the control chip U1, and the other end of the resistor R7 is grounded; one end of the capacitor C2 is connected to the BOOT pin of the control chip U1, the other end of the capacitor C2 is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the voltage output terminal; one end of the resistor R6 is connected between the FB pin and the resistor R7, and the other end of the resistor R6 is connected between the inductor L1 and the voltage output terminal; one end of the capacitor C3 is connected between the inductor L1 and the voltage output terminal, and the other end of the capacitor C3 is grounded; the SW pin of the control chip U1 is connected between the capacitor C2 and the inductor L1.

[0008] Furthermore, the model of the control chip U1 is LMR38025-Q1.

[0009] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The positive and negative logic control circuit does not use the electrostatic sensitive device MOS tube, but only uses one transistor that is not an electrostatic sensitive device, thereby improving the reliability of the circuit; when the positive logic is controlled, only two components, a resistor and a diode, are used; when the negative logic is controlled, only three components, two resistors and a transistor, are used, thereby reducing the overall PCB area occupied. 2. The positive and negative logic control circuit can be used not only for power supply matching, but also for other circuits or components matching, such as digital circuits, analog circuits, functional modules, subsystems and systems, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 A schematic diagram of the principles of an existing positive and negative logic control circuit provided by an embodiment of the present invention; Figure 2 A schematic diagram of the principle of a positive and negative logic control circuit provided by an embodiment of the present invention; Figure 3 A schematic diagram of the principle of a positive logic control circuit unit provided by an embodiment of the present invention; Figure 4 A schematic diagram of the principle of a negative logic control circuit unit provided by an embodiment of the present invention; Figure 5 A schematic diagram of the principle of a switching power supply circuit provided by an embodiment of the present invention; Figure 6 This is an enable control level data diagram of the LMR38025-Q1 control chip provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0012] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0013] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other embodiments, in order to avoid obscuring the present invention, well-known structures, circuits, materials, or methods are not specifically described.

[0014] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0015] In the description of the present invention, the directions or positional relationships indicated by terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “vertical”, “horizontal”, “high”, “low”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the scope of protection of the present invention.

[0016] Embodiment: Before describing in detail the specific circuit structure of the positive and negative logic control circuit, this embodiment first describes the existing positive and negative logic control circuit.

[0017] Existing positive and negative logic control circuits such as Figure 1 As shown in the figure, a total of 6 components are used to implement it, including 3 resistors (resistors R8, R9 and R10), two MOS tubes (MOS tube Q2 and MOS tube Q3), and 1 diode D2. When the level of the power control pin CTR is high, or the CTR pin is suspended, the connection point of resistor R8 and resistor R9 is high level, the gate (pin 1) of MOS tube Q2 is high level to ground, MOS tube Q2 is turned on, and the drain (pin 2) of MOS tube Q2 is low level to ground, that is, the gate (pin 1) of MOS tube Q3 is low level to ground, MOS tube Q3 is turned off, and the power enable pin EN1 is not pulled down to ground through MOS tube Q3. Therefore, as long as the power input voltage is normal, the power supply works normally. When the power control pin CTR is low, or the power control pin CTR is grounded, the connection point of resistors R8 and R9 is low, the gate (pin 1) of MOS tube Q2 is low to ground, MOS tube Q2 is turned off, the drain (pin 2) of MOS tube Q2 is high to ground, that is, the gate (pin 1) of MOS tube Q3 is high to ground, MOS tube Q3 is turned on, and the power enable pin EN1 network is pulled down to ground. Therefore, at this time, regardless of whether the power input voltage is normal, the power supply stops working.

[0018] It should be noted that: Figure 1 In the figure, the number "1" corresponds to the gate of the MOS tube, the number "2" corresponds to the drain of the MOS tube, and the number "3" corresponds to the source of the MOS tube.

[0019] The disadvantages of the above-mentioned existing positive and negative logic control circuits are that they use more components, occupy a larger PCB area, and the MOS tube is an electrostatically sensitive device. The MOS tube may be damaged by static electricity, which will reduce the reliability of the power supply.

[0020] In view of the above defects of the existing positive and negative logic control circuit, the positive and negative logic control circuit proposed in this embodiment is as follows: Figure 2 As shown, it includes a positive logic control circuit unit and a negative logic control circuit unit.

[0021] When positive logic control is required, the resistor R1 and transistor Q1 are not welded. At this time, the equivalent circuit diagram of the positive logic control circuit unit is as follows: Figure 3 As shown, it includes: a resistor R2 and a diode D1, one end of the resistor R2 is connected to the power control pin CTR, the other end of the resistor R2 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the power enable pin EN1. When CTR is at a high level or suspended, no current flows through the diode D1, and the power enable pin EN1 is not pulled down. As long as the input voltage is normal, the power enable pin EN1 is at a high level and the power supply works normally. When the power control pin CTR is grounded, the network level of the power enable pin EN1 is pulled down to the ground through D1 and R2. As long as the power enable pin EN1 level is lower than the specified voltage (such as 1.1V), the power is turned off. Thereby realizing the positive logic control function. The diode D1 plays a unidirectional conduction role to prevent high voltage input to the power enable pin EN1 from damaging the power chip.

[0022] When negative logic control is required, diode D1 is not welded. At this time, the equivalent circuit schematic diagram of the negative logic control circuit unit is as follows: Figure 4 As shown, it includes: a resistor R1, a transistor Q1 and the resistor R2, and the transistor Q1 can be an NPN transistor, a Darlington transistor or a field effect transistor. One end of the resistor R1 is connected to the voltage input end, the other end of the resistor R1 is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the base of the transistor Q1, the emitter of the transistor Q1 is grounded, the collector of the transistor Q1 is connected to the power enable pin EN1, and the power control pin CTR is connected between the resistor R1 and the resistor R2. When the power control pin CTR is suspended, the current flows through the resistor R1 and the resistor R2 in sequence, flows into the base of the transistor Q1, the transistor Q1 is turned on, and the power enable pin EN1 is pulled down to the ground. When the power control pin CTR is at a high level, the same applies. As long as the level of the power enable pin EN1 is lower than the specified voltage (such as 1.1V), the power is turned off. When the power control pin CTR is grounded, no current flows into the base of transistor Q1, transistor Q1 is turned off, and the power enable pin EN1 is not pulled down to ground. As long as the input voltage is normal, the level of the power enable pin EN1 is higher than the specified voltage (such as 1.25V), and the power supply works normally, thereby realizing the negative logic control function.

[0023] Based on the above positive and negative logic control circuit, this embodiment also provides a switching power supply circuit, such as Figure 5As shown, it includes: a control chip U1 (model LMR38025-Q1), a capacitor C1, a capacitor C2, a capacitor C3, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7 and an inductor L1; the periphery of the control chip U1 has a positive and negative logic control circuit as described in the first aspect; one end of the capacitor C1, one end of the resistor R3 and the power input pin VIN of the control chip U1 are all connected to the voltage input end; the other end of the resistor R3 is connected to one end of the resistor R4; the other end of the capacitor C3, the other end of the resistor R4 and the ground pin GND of the control chip U1 are all grounded; the power enable pin EN1 is connected between the resistor R3 and the resistor R4; one end of the resistor R5 is connected to the control The RT pin of the chip U1, the other end of the resistor R5 is grounded; one end of the resistor R7 is connected to the FB pin of the control chip U1, and the other end of the resistor R7 is grounded; one end of the capacitor C2 is connected to the BOOT pin of the control chip U1, the other end of the capacitor C2 is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the voltage output terminal; one end of the resistor R6 is connected between the FB pin and the resistor R7, and the other end of the resistor R6 is connected between the inductor L1 and the voltage output terminal; one end of the capacitor C3 is connected between the inductor L1 and the voltage output terminal, and the other end of the capacitor C3 is grounded; the SW pin of the control chip U1 is connected between the capacitor C2 and the inductor L1. It should be noted that: Figure 5 In the figure, the numbers "1" and "2" correspond to the GND pin (ground pin) of the control chip U1, the number "3" corresponds to the EN pin (enable pin) of the control chip U1, the number "4" corresponds to the NC pin of the control chip U1 (the NC pin indicates that the pin is not connected to any circuit inside the chip), the numbers "5" and "6" correspond to the VIN pin (power input pin) of the control chip U1, the number "7" corresponds to the RT pin (function pin) of the control chip U1, and the number "8" corresponds to the FB pin of the control chip U1 (used to monitor the output voltage and provide feedback). Feedback signal to achieve stable and precise control of the output voltage), the number "9" corresponds to the PG pin of the control chip U1 (used to indicate whether the output voltage has reached and remained within the normal operating range), the number "10" corresponds to the BOOT pin of the control chip U1 (used to control the startup mode), the numbers "11" and "12" correspond to the SW pin (switch pin) of the control chip U1, the number "13" corresponds to the GND pin (ground pin) of the control chip U1, "24VIN" indicates 24V input voltage, and "12VOUT" indicates 12V output voltage.

[0024] The basic principle of the above-mentioned switching power supply circuit is: the control chip U1, model LMR38025-Q1, has a positive and negative logic control circuit as described in the first aspect on the periphery, which controls the normal startup and normal operation of the power supply. Capacitor C1 is used for energy storage and input filtering, resistors R3 and R4 are used to set the power supply startup voltage, resistor R5 is used to set the power supply switching frequency, resistors R6 and R7 are used to set the output voltage, capacitor C2 is a bootstrap capacitor, and inductor L1 and capacitor C3 form an LC filter for output filtering. According to the technical specification of LMR38025-Q1, during the power-on process, when the voltage of the EN pin of the control chip U1 reaches 1.25V, the power supply starts and outputs the voltage. During the power-off process, when the voltage of the EN pin of the control chip U1 drops to 1.1V, the power supply is turned off. For detailed data, see Figure 6 (From the LMR38025-Q1 datasheet).

[0025] Combined with the above Figures 1 to 4 It can be seen that the positive and negative logic control circuit and the switching power supply circuit provided in this embodiment do not use the electrostatic sensitive device MOS tube, but only use one transistor Q1 which is not an electrostatic sensitive device, thereby improving reliability. During positive logic control, only two components, the resistor R2 and the diode D1, are used, which is 67% less than the original six components. During negative logic control, only three components, the resistor R1, the resistor R2 and the transistor Q1, are used, which is 50% less than the original six components. The PCB occupied area is reduced, the reliability of the control circuit is effectively improved, and it has practical value.

[0026] In addition, positive and negative logic control circuits can be used not only for power supply matching, but also for other circuits or components matching, such as digital circuits, analog circuits, functional modules, subsystems and systems, etc.

[0027] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A positive and negative logic control circuit, characterized in that: include: A positive logic control circuit unit and a negative logic control circuit unit; The positive logic control circuit unit includes: a resistor R2 and a diode D1, one end of the resistor R2 is connected to the power control pin CTR, the other end of the resistor R2 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the power enable pin EN1; the negative logic control circuit unit includes: a resistor R1, a transistor Q1 and the resistor R2, one end of the resistor R1 is connected to the voltage input end, the other end of the resistor R1 is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the base of the transistor Q1, the emitter of the transistor Q1 is grounded, the collector of the transistor Q1 is connected to the power enable pin EN1, and the power control pin CTR is connected between the resistor R1 and the resistor R2.

2. A positive and negative logic control circuit according to claim 1, characterized in that: The transistor Q1 is an NPN transistor, a Darlington transistor or a field effect transistor.

3. A switching power supply circuit, characterized in that: include: Control chip U1, capacitor C1, capacitor C2, capacitor C3, resistor R3, resistor R4, resistor R5, resistor R6, resistor R7 and inductor L1; the control chip U1 peripheral A positive and negative logic control circuit as described in claim 1 or 2; one end of the capacitor C1, one end of the resistor R3 and the power input pin VIN of the control chip U1 are all connected to the voltage input end; the other end of the resistor R3 is connected to one end of the resistor R4; the other end of the capacitor C3, the other end of the resistor R4 and the ground pin GND of the control chip U1 are all grounded; the power enable pin EN1 is connected between the resistor R3 and the resistor R4; one end of the resistor R5 is connected to the RT pin of the control chip U1, and the other end of the resistor R5 is grounded; one end of the resistor R7 is connected to the control chip U 1, and the other end of the resistor R7 is grounded; one end of the capacitor C2 is connected to the BOOT pin of the control chip U1, the other end of the capacitor C2 is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the voltage output terminal; one end of the resistor R6 is connected between the FB pin and the resistor R7, and the other end of the resistor R6 is connected between the inductor L1 and the voltage output terminal; one end of the capacitor C3 is connected between the inductor L1 and the voltage output terminal, and the other end of the capacitor C3 is grounded; the SW pin of the control chip U1 is connected between the capacitor C2 and the inductor L1.

4. A switching power supply circuit according to claim 3, characterized in that: The model of the control chip U1 is LMR38025-Q1.

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