Undervoltage protection circuit

Abstract

The utility model relates to an under-voltage protection circuit. The under-voltage protection circuit comprises a starting end, an operational amplifier module and an adjusting module, the operational amplifier module comprises an operational amplifier, a time delay unit, a resistor R14 and an MOS tube Q3, the time delay unit is electrically connected with the operational amplifier, a first end of the resistor R14 is electrically connected with the time delay unit, and a second end of the resistor R14 is electrically connected with the MOS tube Q3; the adjusting module is electrically connected with the first end of the resistor R14, and the starting end is electrically connected with the adjusting module. According to the scheme provided by the invention, the level output by the operational amplifier can be instantly lowered, so that the laser printer is normally started.

Description

Technical Field

[0001] The utility model relates to the technical field of circuits, in particular to an undervoltage protection circuit. Background Art

[0002] At present, it is usually required to set an undervoltage protection circuit on the power board of a laser printer to protect the circuit.

[0003] In the related art, Figure 1 U1B, Q3, etc. shown. Specifically, the inverting input of the op amp is connected to the Vref voltage, which is the reference voltage and continuously outputs a high level. The non-inverting input of the op amp is connected to the Vos voltage. When the Vos voltage is low, the op amp outputs a high level, which turns on Q3 and pulls down the VOFF drive voltage to enter a protection state. However, when the VO-ON / OFF signal is input at a high level to turn on the power, due to the timing difference between the Vos voltage and the Vref voltage, the Vos voltage is not quickly established and is still at a low level, while the Vref voltage reference is at a high level and continuously output. Therefore, the op amp output is at a high level at the moment of power on, causing Q3 to still be turned on, thereby pulling down the VOFF level, and the power supply enters a protection state, causing the laser printer to fail to turn on. Utility Model Content

[0004] The utility model aims to overcome the shortcomings of the prior art and provide an undervoltage protection circuit which can instantly lower the level of an operational amplifier output so that a laser printer can start normally.

[0005] The purpose of this utility model is achieved through the following technical solutions:

[0006] In a first aspect, the present application provides an undervoltage protection circuit, comprising: a starting end; an operational amplifier module, the operational amplifier module comprising an operational amplifier, a delay unit, a resistor R14 and a MOS tube Q3, the delay unit is electrically connected to the operational amplifier, the first end of the resistor R14 is electrically connected to the delay unit, and the second end of the resistor R14 is electrically connected to the MOS tube Q3; and an adjustment module, the adjustment module is electrically connected to the first end of the resistor R14, and the starting end is electrically connected to the adjustment module.

[0007] The regulating module includes a capacitor C18, and a first end of the capacitor C18 is electrically connected to the starting end.

[0008] The regulating module further includes a resistor R19 and a diode D10. The first end of the resistor R19 is electrically connected to the second end of the capacitor C18. The second end of the resistor R19 is electrically connected to the first end of the diode D10. The second end of the diode D10 is grounded.

[0009] The regulating module further includes a transistor Q4, a first end of the transistor Q4 is electrically connected to the second end of the resistor R19, a second end of the transistor Q4 is electrically connected to the first end of the resistor R14, and a third end of the transistor Q4 is grounded.

[0010] The operational amplifier module further includes a first voltage input terminal, which is electrically connected to the operational amplifier.

[0011] The operational amplifier module further includes a second voltage input terminal and a resistor R16, wherein a first terminal of the resistor R16 is electrically connected to the second voltage input terminal, and a second terminal of the resistor R16 is electrically connected to the operational amplifier.

[0012] The delay unit includes a resistor R17, and a first end of the resistor R17 is electrically connected to the operational amplifier.

[0013] The delay unit further includes a capacitor C16, a first end of the capacitor C16 is electrically connected to the second end of the resistor R17, and a second end of the capacitor C16 is grounded.

[0014] It also includes a boost module, which is electrically connected to the MOS tube Q3.

[0015] It also includes an output end, which is electrically connected to the boost module.

[0016] Compared with the prior art, the utility model has at least the following advantages:

[0017] By setting up the adjustment module, the output level of the operational amplifier can be lowered at the moment of starting the startup end, thereby providing time for the VOS voltage to build up. After the VOS voltage is built up, it is ensured that the output of the operational amplifier is always at a low level, so that the MOS tube Q3 will not be turned on, allowing the laser printer to start up normally. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for use in the embodiments are briefly introduced below.

[0019] Figure 1 A circuit diagram of the prior art;

[0020] Figure 2 This is a functional module diagram of an undervoltage protection circuit in an embodiment of the present utility model;

[0021] Figure 3 2 is a circuit diagram of an undervoltage protection circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0023] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0024] Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0025] See also Figure 1 An undervoltage protection circuit includes: a starting end 100, an operational amplifier module 200 and an adjustment module 300, the operational amplifier module 200 includes an operational amplifier, a delay unit, a resistor R14 and a MOS tube Q3, the delay unit is electrically connected to the operational amplifier, the first end of the resistor R14 is electrically connected to the delay unit, and the second end of the resistor R14 is electrically connected to the MOS tube Q3; the adjustment module 300 is electrically connected to the first end of the resistor R14, and the starting end 100 is electrically connected to the adjustment module 300.

[0026] It should be noted that the start-up terminal 100 is VO-ON / OFF, which is used to input a high level to start up, the delay unit plays a delay role, the resistor R14 is a current limiting resistor, and the MOS tube Q3 plays a switch role. By setting the adjustment module 300, the level of the output of the operational amplifier can be pulled down at the moment of starting up the start-up terminal, thereby providing time for the VOS voltage to be established. After the VOS voltage is established, it is ensured that the output of the operational amplifier is always at a low level, so that the MOS tube Q3 will not be turned on, so that the laser printer can start up normally.

[0027] See also Figure 1In one embodiment, the operational amplifier module 200 further includes a first voltage input terminal, which is electrically connected to the operational amplifier. Specifically, the operational amplifier module 200 further includes a second voltage input terminal and a resistor R16, wherein a first terminal of the resistor R16 is electrically connected to the second voltage input terminal, and a second terminal of the resistor R16 is electrically connected to the operational amplifier.

[0028] It should be noted that the first voltage input terminal is a negative input terminal for inputting a VOS voltage, and the second voltage input terminal is a positive input terminal for inputting a Vref voltage, and the reference of the Vref voltage is a high level.

[0029] See also Figure 1 In one embodiment, the regulating module includes a capacitor C18, and the first end of the capacitor C18 is electrically connected to the start end. Specifically, the regulating module 300 also includes a resistor R19 and a diode D10, the first end of the resistor R19 is electrically connected to the second end of the capacitor C18, the second end of the resistor R19 is electrically connected to the first end of the diode D10, and the second end of the diode D10 is grounded. Specifically, the regulating module 300 also includes a transistor Q4, the first end of the transistor Q4 is electrically connected to the second end of the resistor R19, the second end of the transistor Q4 is electrically connected to the first end of the resistor R14, and the third end of the transistor Q4 is grounded.

[0030] It should be noted that the first end of the transistor Q4 is the base, the second end is the collector, and the third end is the emitter. The capacitor C18 plays the role of isolating direct current and passing alternating current. Specifically, at the moment when the start-up end 100 is started, part of the alternating current signal will be generated. By utilizing the characteristics of the capacitor C18 isolating direct current and passing alternating current, the regulating module 300 can only be turned on at the moment of starting up, that is, the transistor Q4 will be turned on at the moment of starting up, that is, when the base is at a high level, the current flows from the base to the emitter to form a base current, and at the same time, the collector current flows to the emitter. This current is relatively large, and the collector and the emitter can be regarded as a short circuit. At this time, the transistor Q4 is equivalent to a switch, and then outputs a low level to the MOS tube Q3, and the MOS tube Q3 is cut off. After the VOS voltage is established, the printer starts up normally. In addition, when the start-up end is started, direct current will be provided, so the regulating module 300 is only turned on at an instant, and will not be continuously turned on after starting up, which ensures that the output of the operational amplifier is always at a low level, and the protection circuit will not fail after starting up, which solves the problem of starting up without affecting the protection function. The resistor R19 serves as a current limiter, and the diode D10 serves as an electrostatic protection device.

[0031] See also Figure 1 In one embodiment, the delay unit includes a resistor R17, a first end of which is electrically connected to the operational amplifier. Specifically, the delay unit also includes a capacitor C16, a first end of which is electrically connected to a second end of the resistor R17, and a second end of the capacitor C16 is grounded.

[0032] It should be noted that the resistance of the resistor R17 is relatively large, the capacitor C16 is a charging capacitor, and the resistor R17 serves to delay the charging time of the capacitor C16.

[0033] See also Figure 3 In one embodiment, a boost module is also included, and the boost module is electrically connected to the MOS tube Q3.

[0034] It should be noted that the boost module is used to increase the voltage to 6600V.

[0035] See also Figure 3 In one embodiment, it also includes an output end, which is electrically connected to the boost module.

[0036] It should be noted that the output terminal is Vout, which is used to output 660V to the laser printer.

[0037] The scheme of the present application has been described in detail above with reference to the accompanying drawings. In the above embodiments, the descriptions of the various embodiments have their own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments. Those skilled in the art should also be aware that the actions and modules involved in the specification are not necessarily required for the present application. In addition, it can be understood that the steps in the method of the embodiment of the present application can be adjusted in order, merged and deleted according to actual needs, and the modules in the device of the embodiment of the present application can be merged, divided and deleted according to actual needs.

[0038] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. An undervoltage protection circuit, characterized in that: include: Start-up terminal; An operational amplifier module, the operational amplifier module comprising an operational amplifier, a delay unit, a resistor R14 and a MOS tube Q3, the delay unit is electrically connected to the operational amplifier, a first end of the resistor R14 is electrically connected to the delay unit, and a second end of the resistor R14 is electrically connected to the MOS tube Q3; and The regulating module is electrically connected to the first end of the resistor R14, and the starting end is electrically connected to the regulating module.

2. The undervoltage protection circuit according to claim 1, characterized in that: The regulating module includes a capacitor C18, and a first end of the capacitor C18 is electrically connected to the starting end.

3. The undervoltage protection circuit according to claim 2, characterized in that: The regulating module further includes a resistor R19 and a diode D10. The first end of the resistor R19 is electrically connected to the second end of the capacitor C18. The second end of the resistor R19 is electrically connected to the first end of the diode D10. The second end of the diode D10 is grounded.

4. The undervoltage protection circuit according to claim 3, characterized in that: The regulating module further includes a transistor Q4, a first end of the transistor Q4 is electrically connected to the second end of the resistor R19, a second end of the transistor Q4 is electrically connected to the first end of the resistor R14, and a third end of the transistor Q4 is grounded.

5. The undervoltage protection circuit according to claim 1, characterized in that: The operational amplifier module further includes a first voltage input terminal, which is electrically connected to the operational amplifier.

6. The undervoltage protection circuit according to claim 5, characterized in that: The operational amplifier module further includes a second voltage input terminal and a resistor R16, wherein a first terminal of the resistor R16 is electrically connected to the second voltage input terminal, and a second terminal of the resistor R16 is electrically connected to the operational amplifier.

7. The undervoltage protection circuit according to claim 1, characterized in that: The delay unit includes a resistor R17, and a first end of the resistor R17 is electrically connected to the operational amplifier.

8. The undervoltage protection circuit according to claim 7, characterized in that: The delay unit further includes a capacitor C16, a first end of the capacitor C16 is electrically connected to the second end of the resistor R17, and a second end of the capacitor C16 is grounded.

9. The undervoltage protection circuit according to claim 1, characterized in that: It also includes a boost module, which is electrically connected to the MOS tube Q3.

10. The undervoltage protection circuit according to claim 9, characterized in that: It also includes an output end, which is electrically connected to the boost module.

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