Power amplifier protection circuit and ink-jet printing equipment

Abstract

The utility model provides a power amplifier protection circuit and ink-jet printing equipment, the ink-jet printing equipment comprises a power amplifier circuit, the power supply end of the power amplifier circuit is electrically connected with a filter capacitor circuit, and the power amplifier protection circuit comprises a switching circuit, a voltage detection circuit and a power supply management circuit. The input end of the switching circuit is connected with the power access end, and the output end of the switching circuit is connected with the power end of the power amplifier circuit; the voltage detection circuit is connected with the power supply access end and is used for detecting power supply voltage accessed by the power supply access end and outputting a corresponding voltage detection signal; the power supply management circuit is respectively connected with the filter capacitor circuit, the output end of the voltage detection circuit and the controlled end of the switching circuit; the power supply management circuit charges the filter capacitor circuit and controls the working state of the switching circuit according to the voltage of the filter capacitor circuit and the voltage detection signal. According to the utility model, the problem of short circuit false alarm caused by large current generated when the power amplifier circuit is powered on and started is solved through the power supply management circuit.

Description

Technical Field

[0001] This utility model relates to the field of inkjet printing technology, and in particular to a power amplifier protection circuit and an inkjet printing device. Background Technology

[0002] In inkjet printers, short circuits can occur in the printhead during operation, leading to damage to the control board or triggering malfunctions. Currently, current detection is commonly used to detect printhead short circuits. However, the power amplifier circuits in inkjet printers have high power, requiring a large number of filter capacitors for power supply. When the inkjet printer is first powered on, current detection cannot determine whether the short circuit is in the power amplifier's downstream circuitry or due to capacitor charging requiring a large current. Excessive current limiting can easily damage the power amplifier circuit, while insufficient current limiting can easily generate false alarms. Utility Model Content

[0003] The main purpose of this invention is to propose a power amplifier protection circuit and an inkjet printing device, which aims to solve the problem of being unable to both protect the power amplifier circuit and prevent false alarms.

[0004] This utility model proposes a power amplifier protection circuit for use in an inkjet printer. The inkjet printer includes a power amplifier circuit and a filter capacitor circuit. The power amplifier protection circuit includes: a switching circuit, the input terminal of which is connected to a power input terminal, and the output terminal of which is connected to both the power amplifier circuit and the filter capacitor circuit; a voltage detection circuit, connected to the power input terminal, for detecting the supply voltage supplied to the power input terminal; and a power supply management circuit, connected to the output terminal of the voltage detection circuit, the controlled terminal of the switching circuit, and the output terminal of the switching circuit. The power supply management circuit is used to control the switching circuit to a first state based on the supply voltage when the power input terminal is powered on, supplying power to the power amplifier circuit and the filter capacitor circuit at a first power. After a first period of time, if the difference between the supply voltage and the voltage at the output terminal of the switching circuit meets a preset condition, the switching circuit is controlled to a second state, supplying power to the power amplifier circuit and the filter capacitor circuit at a second power. The first power is less than the second power.

[0005] In one embodiment, the power supply management circuit is specifically used to: after a first period of time, if the voltage difference between the output voltage of the switching circuit and the power supply voltage is less than a first preset voltage, control the switching circuit to be turned on in the second state; after the first period of power-on, if the voltage difference between the output voltage of the switching circuit and the power supply voltage is greater than the first preset voltage, output a power amplifier protection signal.

[0006] In one embodiment, the power supply management circuit is specifically used to: control the switching circuit to shut off the path between the power supply terminal and the power amplifier circuit when the power supply voltage exceeds a second preset voltage.

[0007] In one embodiment, the power management circuit includes a power control circuit, a power adjustment circuit, and a time adjustment circuit; the power control circuit is connected to the power adjustment circuit and the time adjustment circuit; the power control circuit is used to set the first power based on the power adjustment circuit and to set the first duration based on the time adjustment circuit.

[0008] In one embodiment, the power regulation circuit includes a power regulation resistor; and / or, the power regulation circuit includes a time regulation capacitor.

[0009] In one embodiment, the power supply control circuit includes a power supply control chip, the power supply management chip includes a voltage input pin, an output pin, a voltage detection pin, and a control pin, the power input terminal is connected to the voltage input pin, the output terminal is connected to the output terminal of the switching circuit, the voltage detection terminal is connected to the output terminal of the voltage detection circuit, and the control terminal is connected to the controlled terminal of the switching circuit.

[0010] In one embodiment, the power management chip further includes an enable pin and a signal output pin for connection to an external control circuit. The enable pin is used to receive an enable signal output by the external control circuit, and the signal output pin is used to output a power amplifier protection signal to the external control circuit. The power management circuit is used to start working when the enable pin receives the enable signal from the external control circuit, and to output a power amplifier protection signal to the external control circuit through the signal output pin when the current or voltage at the output terminal of the switching circuit is abnormal, so as to control the power management chip to shut down.

[0011] In one embodiment, the power amplifier protection circuit further includes: a current limiting circuit disposed between the power input terminal and the switching circuit, and connected to the power supply management circuit; the power supply management circuit is further configured to acquire the output current of the current limiting circuit when controlling the switching circuit to be in the second state, and output a power amplifier protection signal when the output current of the current limiting circuit is greater than a preset current.

[0012] In one embodiment, the switching circuit includes: a switching transistor, the input terminal of which is connected to the power input terminal, the output terminal of which is connected to the power supply terminal of the power amplifier circuit, and the controlled terminal of which is connected to the power supply management circuit; and / or, the voltage detection circuit includes: a first resistor and a second resistor, a first end of which is connected to the power input terminal, a second end of which is connected to the first end of which, the connection point between which is connected to the power supply management circuit, and a second end of which is grounded.

[0013] This utility model also proposes an inkjet printing device, which includes a power amplifier circuit, a filter capacitor circuit, and a power amplifier protection circuit. The output terminal of the power amplifier protection circuit is connected to the power amplifier circuit and the filter capacitor circuit, respectively.

[0014] This invention proposes a power amplifier protection circuit for use in inkjet printing equipment. The inkjet printing equipment includes a power amplifier circuit, and a filter capacitor circuit is electrically connected to the power supply terminal of the power amplifier circuit. The power amplifier protection circuit includes a switching circuit, a voltage detection circuit, and a power supply management circuit. The input terminal of the switching circuit is connected to the power supply terminal, and the output terminal of the switching circuit is connected to both the power amplifier circuit and the filter capacitor circuit. The voltage detection circuit is connected to the power supply terminal. The power supply management circuit is connected to the output terminal of the voltage detection circuit, the controlled terminal of the switching circuit, and the output terminal of the switching circuit. In practical applications, the voltage detection circuit detects the supply voltage connected to the power supply terminal. The power supply management circuit controls the switching circuit to a first state based on the supply voltage when the power supply terminal is powered on, supplying power to the power amplifier circuit and the filter capacitor circuit at a first power. After a first period of time, if the difference between the supply voltage and the voltage at the output terminal of the switching circuit meets a preset condition, the switching circuit is controlled to a second state, supplying power to the power amplifier circuit and the filter capacitor circuit at a second power. The first power is less than the second power. When powered on at the power input terminal, this invention can charge the power amplifier circuit and filter capacitor circuit with a relatively small initial power. This effectively reduces the risk of burning out the power amplifier circuit due to excessive power, and also avoids false alarms caused by the large current required to charge the filter capacitor circuit, thus ensuring the stable operation of the overall power amplifier protection circuit of the inkjet printer. After the first period, if the difference between the supply voltage and the voltage at the output terminal of the switching circuit meets the preset condition, the switching circuit is controlled to enter the second state, supplying power to the power amplifier circuit and filter capacitor circuit with a relatively large second power. This ensures the power supply to the power amplifier circuit, making the power supply to the power amplifier circuit more stable and the drive signal quality of the power amplifier circuit better. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a circuit functional block diagram of the power amplifier protection circuit and inkjet printing equipment of this utility model;

[0017] Figure 2 This is a circuit functional block diagram of another embodiment of the power amplifier protection circuit and inkjet printing equipment of this utility model;

[0018] Figure 3 This is a schematic diagram of the power amplifier protection circuit and the circuit structure of the inkjet printing device of this utility model;

[0019] Figure 4 This is a schematic diagram of the mechanical structure of the inkjet printing equipment of this utility model.

[0020] Explanation of icon numbers:

[0021] 1000 Inkjet printer; 100 Print head; 200 Print table; 300 Ink supply module; 400 Ink stack module; 500 Waste liquid container.

[0022] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0024] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0025] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, if the word "and / or" appears throughout the text, it means including three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0026] It is understandable that short circuits can occur in printheads during operation in existing inkjet printers, causing control boards to burn out or report abnormalities. To address printhead short circuits, most commercially available solutions employ current detection. However, the power amplifier circuit in an inkjet printer needs to provide sufficient energy to drive ink ejection from the printhead. Printheads typically contain multiple tiny nozzles; to ensure accurate and rapid ink ejection onto the printing medium, the power amplifier circuit needs to output significant power to generate sufficient pressure and driving force. Due to the high power of the power amplifier circuit, a large number of filter capacitors are required in the power supply. When the inkjet printer is first powered on, a large current is generated, making it impossible to determine whether the short circuit is due to a short circuit in the power amplifier stage or the large current required for capacitor charging, easily leading to false short circuit alarms.

[0027] Therefore, this utility model proposes a power amplifier protection circuit 70, applied to an inkjet printing device 1000, with reference to... Figure 1 and Figure 4 The inkjet printing device 1000 further includes a power amplifier circuit 60 and a filter capacitor circuit 40. The output terminal Vout of the power amplifier protection circuit 70 is connected to the power amplifier circuit 60 and the filter capacitor circuit 40. (Refer to...) Figure 1 and Figure 2 The power amplifier protection circuit 70 includes a switching circuit 10, a voltage detection circuit 20, and a power supply management circuit 30.

[0028] The input terminal of the switching circuit 10 is connected to the power input terminal Vin, and the output terminal of the switching circuit 10 is connected to the power supply terminal of the power amplifier circuit 60 and the filter capacitor circuit 40, respectively. The voltage detection circuit 20 is connected to the power input terminal Vin and is used to detect the power supply voltage connected to the power input terminal Vin. The power supply management circuit 30 has a capacitor connection terminal for connecting to the filter capacitor circuit 40, and the power supply management circuit 30 is connected to the output terminal of the voltage detection circuit 20 and the controlled terminal of the switching circuit 10, respectively.

[0029] The power supply management circuit 30 is used to control the switching circuit 10 to be in a first state when powered on, based on the power supply voltage, to supply power to the power amplifier circuit 60 and the filter capacitor circuit 40 with a first power; after a first period of time, when the difference between the voltage of the voltage detection signal and the voltage of the power supply management circuit 30 meets a preset condition, the switching circuit 10 is controlled to be in a second state, to supply power to the power amplifier circuit 60 and the filter capacitor circuit 40 with a second power; wherein, the first power is less than the second power.

[0030] Upon initial power-on at the power input terminal, the power management circuit 30 controls the switching circuit 10 to be in the first state based on the power supply voltage detected by the voltage detection circuit 20. At this state, a relatively small initial power is supplied to the power amplifier circuit 60 and the filter capacitor circuit 40. This power is sufficient to safely pre-charge the subsequent circuits, effectively reducing the risk of the power amplifier burning out due to a sudden surge in current, and also preventing false alarms caused by excessive capacitor charging current. After the first duration, if the difference between the power supply voltage and the voltage at the output terminal of the switching circuit meets a preset condition, the power management circuit 30 controls the switching circuit 10 to switch to the second state, supplying the power amplifier circuit 60 and the filter capacitor circuit 40 with a larger initial power, ensuring normal and efficient circuit operation.

[0031] The first state can be a partially conducting state of the switch circuit 10, and the second state can be a fully conducting state of the switch circuit 10. Alternatively, the first state can be an open state of the switch circuit 10, and the second state can be a conducting state of the switch circuit 10.

[0032] It's understandable that when a 1000 inkjet printer uses a large number of filter capacitors in its power supply, these capacitors charge rapidly upon power-on. Since current short-circuit protection for power amplifier circuits typically relies on current sensing to determine if a circuit malfunction has occurred, the large current required for charging the filter capacitors during power-on can trigger the power amplifier's overcurrent protection mechanism, causing a false short-circuit alarm. For example, if the filter capacitor requires 1-2 amps to charge, and the current limit is set to 0.5 amps, it's impossible to distinguish between the capacitor charging current and the short-circuit current in the power amplifier's output stage. This can easily lead to a misjudgment of a short circuit, triggering the overcurrent protection mechanism and resulting in an alarm signal or circuit disconnection. In reality, the power amplifier circuit is not faulty, yet a false short-circuit alarm occurs. Therefore, in order to prevent the large current at the moment of power-on from falsely triggering the overcurrent protection mechanism, the power amplifier protection circuit 70 of this utility model is provided with a power supply management circuit 30. At the moment the inkjet printer 1000 is powered on, the power supply management circuit 30 charges the filter capacitor circuit 40 so that the charging current of the filter capacitor circuit 40 is limited to a safe range, preventing excessive fluctuations in the charging current and causing false short circuit alarms.

[0033] In this embodiment, the switching circuit 10 can be implemented using components such as transistors, transistor switches, or relays, and is used to control the connection and disconnection of the power supply from the power input terminal Vin to the filter capacitor circuit 40. The voltage detection circuit 20 can be implemented using components such as voltage divider resistors, and / or comparators, and / or capacitors, and is used to detect the supply voltage of the power input terminal Vin and output a corresponding voltage detection signal, thereby realizing the voltage detection function. The power management circuit 30 can be implemented using a power management chip, and is used to charge the filter capacitor circuit 40 according to certain current and voltage parameters. Specifically, the power management circuit 30 determines the voltage difference between the filter capacitor circuit 40 and the voltage detection signal based on the voltage of the filter capacitor circuit 40 and the voltage detection signal, and determines whether to control the switching circuit 10 to conduct the path between the power input terminal Vin and the filter capacitor circuit 40 based on the magnitude of the voltage difference. Since the power amplifier circuit 60 requires a stable voltage supply to operate normally, when the voltage difference between the power input terminal Vin and the filter capacitor circuit 40 is small, it can be considered that the filter capacitor circuit 40 has reached a suitable charging level and can provide a relatively stable voltage for the power amplifier circuit 60. In other words, when the voltage difference between the power input terminal Vin and the filter capacitor circuit 40 reaches the expected value, there is no need to limit the charging current of the filter capacitor circuit 40. The power management circuit 30 controls the switching circuit 10 to open the path between the power input terminal Vin and the filter capacitor circuit 40, so that the voltage of the power input terminal Vin is output to the filter capacitor circuit 40 through the switching circuit 10. Conversely, when the voltage difference between the power input terminal Vin and the filter capacitor circuit 40 is too large, if the power management circuit 30 controls the switching circuit 10 to open, it will cause a sudden large current to surge through the power amplifier circuit 60, damaging the electronic components of the power amplifier circuit 60, such as burning out the power amplifier chip, power transistors, and other components in the power amplifier circuit 60. In this embodiment, the power management circuit 30 sets a smaller discharge power to limit the charging current of the filter capacitor circuit 40, keeping the charging current of the filter capacitor circuit 40 within a safe range. This avoids being misjudged as a short circuit due to excessive charging current, thereby protecting the normal operation of the power amplifier circuit 60. On the other hand, the power supply management circuit 30 enables a soft-start function, allowing the voltage and current of the power amplifier circuit 60 to gradually rise to normal operating values ​​instead of reaching them instantaneously. This avoids the impact of sudden large current and voltage changes on the components in the power amplifier circuit 60, allowing the power amplifier circuit 60 to enter a more stable normal operating state.

[0034] This utility model proposes a power amplifier protection circuit 70, applied to an inkjet printer 1000. The inkjet printer 1000 includes a power amplifier circuit 60, the power supply terminal of which is electrically connected to a filter capacitor circuit 40. The power amplifier protection circuit 70 includes: a switching circuit 10, the input terminal of which is connected to a power input terminal Vin, and the output terminal of which is connected to the power supply terminal of the power amplifier circuit 60; a voltage detection circuit 20, which is connected to the power input terminal Vin and is used to detect the supply voltage connected to the power input terminal Vin and output a corresponding voltage detection signal; and a power supply management circuit 30, which has a capacitor connection terminal for connecting to the filter capacitor circuit 40, and is connected to the output terminal of the voltage detection circuit 20 and the controlled terminal of the switching circuit 10 respectively. The power supply management circuit 30 is used to charge the filter capacitor circuit 40 and control the working state of the switching circuit 10 according to the voltage of the filter capacitor circuit 40 and the voltage detection signal. This invention charges the filter capacitor circuit 40 through the power supply management circuit 30, so that the charging current of the filter capacitor circuit 40 is limited to a safe range, preventing excessive fluctuations in the charging current when the inkjet printer 1000 is powered on, which could cause a false short circuit alarm.

[0035] In one embodiment, the power supply management circuit 30 is specifically used to: after a first period of time, if the voltage difference between the output voltage of the switching circuit 10 and the power supply voltage is less than a first preset voltage, control the switching circuit 10 to be turned on in the second state; after the first period of power-on, if the voltage difference between the output voltage of the switching circuit 10 and the power supply voltage is greater than the first preset voltage, output a power amplifier protection signal.

[0036] The power amplifier protection signal is used to trigger the power supply management circuit 30 to disconnect or control the switching circuit 10 to disconnect, thereby protecting the power amplifier circuit 60. The preset conditions in the above embodiment include the voltage difference between the output voltage of the switching circuit 10 and the supply voltage being less than a first preset voltage.

[0037] In one embodiment, reference is made to Figure 1 , Figure 2 and Figure 3 The power supply management circuit 30 is also used to control the switching circuit 10 to shut off the path between the power input terminal Vin and the power amplifier circuit 60 when the voltage of the voltage detection signal exceeds the second preset voltage.

[0038] Understandably, the voltage detection circuit 20 is connected to the power input terminal to monitor the voltage at the power input terminal, providing accurate voltage information to the power management circuit 30, thereby protecting the power amplifier circuit 60. In one embodiment, the example is provided where the voltage at the power input terminal Vin is 24V, the voltage detection signal is 16V, and the second preset voltage is 18V. Specifically, since the voltage detection signal detected by the power management circuit 30 is 16V, which does not exceed the second preset voltage of 18V, the voltage at the power input terminal is within the normal range. The power management circuit 30 controls the switching circuit 10 to open the path between the power input terminal Vin and the power amplifier circuit 60. Conversely, when the voltage detection signal detected by the power management chip U1 is 19V, which exceeds the second preset voltage of 18V, the voltage at the power input terminal is within the abnormal range. The power management circuit 30 controls the switching circuit 10 to close the path between the power input terminal Vin and the power amplifier circuit 60, thereby protecting the power amplifier circuit 60 from excessive voltage.

[0039] like Figure 3 As shown, in one embodiment, the power management circuit includes a power control circuit 31, a power adjustment circuit 32, and a time adjustment circuit 33; the power control circuit 31 is connected to the power adjustment circuit 32 and the time adjustment circuit 33; the power control circuit is used to set the first power based on the power adjustment circuit 32 and to set the first duration based on the time adjustment circuit 33.

[0040] The power supply control circuit 31 can use a power supply control chip U1, which can be a chip with functions such as starting power limiting and operating current limiting. Alternatively, the power supply control circuit 31 can also be constructed using multiple discrete transistors, resistors, capacitors, and other components to implement the chip; these are related circuits in the prior art, and will not be elaborated here. The power adjustment circuit 32 can be a circuit composed of one or more resistors, and the time adjustment circuit 33 can be a circuit composed of one or more capacitors. The power adjustment circuit 32 is used to set the first power, and the time adjustment circuit 33 is used to set the first duration. Alternatively, the time adjustment circuit 33 and the power adjustment circuit 32 can also be similar circuits in the prior art, which will not be listed here.

[0041] In one embodiment, reference is made to Figure 1 and Figure 3 The power supply control circuit 31 includes a power management chip U1. The power adjustment circuit 32 includes a power adjustment resistor R4. The time adjustment circuit 33 includes a time adjustment capacitor C3.

[0042] The power management chip U1 has a power adjustment pin PWR and a time adjustment pin TIMER. The power adjustment pin PWR of the power management chip U1 is connected to the power adjustment resistor R4, and the time adjustment pin TIMER of the power management chip U1 is connected to the time adjustment capacitor C3.

[0043] The power management chip U1 is used to charge the filter capacitor circuit 40 according to the conduction state of the switch circuit 10, and when the charging time of the filter capacitor circuit 40 reaches the charging time set by the time adjustment capacitor C3, it controls the working state of the switch circuit 10 according to the voltage of the filter capacitor circuit 40 and the voltage detection signal.

[0044] It is understood that in this embodiment, the power management circuit 30 includes a power management chip U1, a power adjustment resistor R4, and a time adjustment capacitor C3, and the filter capacitor circuit 40 includes a second capacitor C2. Furthermore, referring to... Figure 3 The inkjet printer 1000 also includes a first capacitor C1, which is connected to the power input terminal Vin. The first capacitor C1 is mainly used to smooth the power supply voltage at the power input terminal Vin and reduce voltage fluctuations. Simultaneously, it can filter out high-frequency noise in the power supply line, bypassing this noise to ground, improving power quality, and providing a more stable power supply for subsequent circuits. The power management chip U1 also has a voltage input pin VIN (i.e., the voltage input terminal of the power management circuit 30), a voltage output pin OUT (i.e., the voltage output terminal of the power management circuit 30), a control pin GATE (i.e., the control terminal of the power management circuit 30), a current detection pin SENSE (i.e., the current detection terminal of the power management circuit 30), a controlled pin UVLO / EN (i.e., the controlled terminal of the power management circuit 30), a voltage detection pin UVLO (i.e., the voltage detection terminal of the power management circuit 30), and a signal output pin PGD (i.e., the signal output terminal of the power management circuit 30).

[0045] The power management chip U1 has several key components: its voltage input pin VIN is connected to the power input terminal Vin and the third resistor R3, respectively, to receive the voltage at Vin and power the chip. Its voltage output pin OUT is connected to the source S of the first switching transistor Q1 and the power output Vout of the power amplifier circuit 60, respectively, to power the power amplifier circuit 60 and the filter capacitor circuit. Its control pin GATE is connected to the gate G of the first switching transistor Q1, controlling the switching on and off of Q1. Its current detection pin SENSE is connected between the third resistor R3 and the drain D of Q1, detecting the current in R3. Its controlled pin UVLO / EN receives the enable signal EN. Its voltage detection pin UVLO is connected between the first resistor R1 and the second resistor R2, detecting the voltage at Vin. Its signal output pin PGD outputs the power amplifier protection signal ERROR to the external control circuit.

[0046] In one embodiment, reference is made to Figure 1 , Figure 2 and Figure 3 The power management chip U1 is specifically used to control the switching circuit 10 to open the path between the power input terminal Vin and the power amplifier circuit 60 when the voltage difference between the voltage of the filter capacitor circuit 40 and the voltage of the voltage detection signal is less than a first preset voltage, and to output the power amplifier protection signal ERROR when the voltage difference between the voltage of the filter capacitor circuit 40 and the voltage of the voltage detection signal is not less than the first preset voltage.

[0047] Understandably, in this embodiment, when the voltage at the power input terminal Vin is 42V, the voltage at the filter capacitor circuit 40 is 50V, the voltage at the voltage detection signal is 2V, and the first preset voltage is 8V, the power management chip U1, after charging the second capacitor C2 for the time set by the time adjustment capacitor C3, will obtain the 2V voltage of the voltage detection signal through the voltage detection circuit 20 and obtain the 50V voltage of the second capacitor C2 from the capacitor connection terminal, thus calculating the voltage difference between the two as 50V - 2V = 48V. Since 48V is greater than the first preset voltage 8V, it indicates that the voltage difference between the power input terminal Vin and the second capacitor C2 is too large. If the path between the power input terminal Vin and the power amplifier circuit 60 is connected at this time, a large instantaneous current will impact the power amplifier circuit 60, which may very likely damage the electronic components in the power amplifier circuit 60. Therefore, the power management chip U1 controls the switching circuit 10 to cut off the path between the power input terminal Vin and the power amplifier circuit 60, and outputs the power amplifier protection signal ERROR to trigger the power amplifier protection mechanism.

[0048] Conversely, if the power management chip U1 calculates that the voltage difference between the voltage of the second capacitor C2 and the voltage of the voltage detection signal is 7V, since 7V is less than the first preset voltage of 8V, it means that the voltage difference between the power input terminal Vin and the second capacitor C2 is within an acceptable range. At this time, the power management chip U1 can control the switching circuit 10 to conduct the path between the power input terminal Vin and the power amplifier circuit 60, ensuring that the power amplifier circuit 60 works normally.

[0049] In one embodiment, reference is made to Figure 1 , Figure 2 and Figure 3 The power supply management circuit 30 has a controlled terminal and a signal output terminal for connection to an external control circuit;

[0050] The power supply management circuit 30 is used to start working when the enable signal EN of the external control circuit is connected through the controlled terminal, and to output the power amplifier protection signal ERROR to the external control circuit through the signal output terminal so that the external control circuit stops outputting the enable signal EN.

[0051] It is understood that in this embodiment, the power management circuit 30 is connected to the external control circuit through both the controlled terminal and the signal output terminal. In practical applications, the external control circuit outputs an enable signal EN. The power management circuit 30 receives the enable signal EN through the controlled terminal and begins to operate, charging the filter capacitor circuit 40 according to the preset discharge power. When the power amplifier circuit 60 malfunctions, the power management circuit 30 outputs a power amplifier protection signal ERROR to the external control circuit through the signal output terminal. The external control circuit then shuts down the output of the enable signal EN based on the received power amplifier protection signal ERROR. At this time, the power management circuit 30 does not receive the enable signal EN, and it shuts down, stopping the supply of power to the power amplifier circuit 60. Consequently, the components in the power amplifier circuit 60 will not continue to be damaged due to abnormal conditions such as overcurrent or overvoltage, thus providing power amplifier protection. Abnormalities in the power amplifier circuit 60 include an unexpected voltage difference between the power input terminal and the filter capacitor circuit 40, and the current in the current limiting circuit reaching the current threshold.

[0052] In one embodiment, reference is made to Figure 1 , Figure 2 and Figure 3 The power amplifier protection circuit 70 further includes:

[0053] A current limiting circuit 50 is disposed between the power input terminal Vin and the switching circuit 10;

[0054] The power supply management circuit 30 has a current detection terminal for connection with the current limiting circuit 50; the power supply management circuit 30 is also used to detect the current of the current limiting circuit 50 when controlling the switching circuit 10 to turn off, and to output a power amplifier protection signal ERROR when the current of the current limiting circuit 50 is abnormal.

[0055] Understandably, in this embodiment, when the voltage difference between the voltage of the second capacitor C2 and the voltage of the voltage detection signal meets expectations, the power management chip U1 disables the power limiting function of the power regulation resistor R4 and enters the current limiting mode set by the current limiting circuit 50. When operating in the current limiting mode, the power management chip U1 detects the current of the current limiting circuit 50 and outputs a power amplifier protection signal ERROR when the current of the current limiting circuit 50 exceeds its current threshold, thereby triggering the power amplifier protection mechanism. When the power amplifier protection mechanism is triggered, the power amplifier protection effect can be achieved by shutting down the power management chip U1.

[0056] In one embodiment, reference is made to Figure 1 , Figure 2 and Figure 3 The current limiting circuit 50 includes a current limiting resistor R3. The first end of the current limiting resistor R3 is connected to the power input terminal Vin, and the second end of the current limiting resistor R3 is connected to the current detection terminals of the switching circuit 10 and the power management circuit 30, respectively.

[0057] It is understood that in this embodiment, the current limiting circuit 50 includes a current limiting resistor R3, and the current threshold of the current limiting resistor R3 is set to 3A as an example for explanation. Specifically, when the power management chip U1 operates in the current limiting mode, it detects the current of the current limiting circuit 50. When the detected current of the current limiting circuit 50 is 4A, 4A is greater than the current threshold of the current limiting circuit 50, 3A. At this time, the power management chip U1 will output a power amplifier protection signal ERROR to trigger the power amplifier protection mechanism.

[0058] In other embodiments, the current limiting circuit can also use other circuits, not limited to current limiting resistors, such as transistor current limiting circuits, MOSFET current limiting circuits, current transformer current limiting circuits, current chips, etc., or multiple current limiting resistors R3 can be used, with multiple current limiting resistors R3 connected in parallel or in series, which will not be elaborated here.

[0059] In one embodiment, reference is made to Figure 1 , Figure 2 and Figure 3 The switching circuit 10 includes:

[0060] The switching transistor Q1 has its input terminal connected to the power input terminal Vin, its output terminal connected to the power supply terminal of the power amplifier circuit 60, and its controlled terminal connected to the power supply management circuit 30.

[0061] It is understood that in this embodiment, the switching circuit 10 is implemented using a switching transistor Q1. In one embodiment, the switching transistor Q1 is a MOSFET. The gate G of the MOSFET is connected to the control pin GATE of the power management chip U1, the drain D of the MOSFET is connected to the third resistor R3, and the source of the MOSFET is connected to the power amplifier circuit 60 and the filter capacitor circuit 40. During the startup process of the power amplifier circuit 60, if the voltage directly connected to the power input terminal is applied, the components in the power amplifier circuit 60 may be damaged due to the instantaneous high voltage or large current. The switching transistor Q1 can be turned on at an appropriate time. For example, when the voltage difference between the power input terminal Vin and the filter capacitor circuit 40 is small, the switching transistor Q1 is controlled to open the path between the power input terminal Vin and the filter capacitor circuit 40 to connect the power to the power amplifier circuit 60, preventing unstable voltage from damaging the power management chip U1 and other components, thereby playing a role in power amplifier protection.

[0062] In other embodiments, the switching circuit 10 may also include multiple switching transistors, each of which can control the state of its respective transistor, thus placing the switching circuit 10 in various different states. Furthermore, the switching transistor Q1 may also be a transistor, etc.

[0063] In one embodiment, reference is made to Figure 1 , Figure 2 and Figure 3 The voltage detection circuit 20 includes:

[0064] A first resistor R1 and a second resistor R2 are connected. The first end of the first resistor R1 is connected to the power input terminal Vin, and the second end of the first resistor R1 is connected to the first end of the second resistor R2. The connection point between the first resistor R1 and the second resistor R2 is connected to the power management circuit 30, and the second end of the second resistor R2 is grounded.

[0065] It is understood that in this embodiment, the voltage detection circuit 20 consists of a first resistor R1 and a second resistor R2. The connection point between the first resistor R1 and the second resistor R2 is used to output a voltage detection signal to the power management chip U1, so as to provide the power management chip U1 with accurate voltage information. The explanation is further elaborated using an example where the voltage of the filter capacitor circuit 40 is 22V, the voltage of the voltage detection signal is 16V, and the first preset voltage is 2V. Specifically, since the voltage difference of 6V between the filter capacitor circuit 40 and the power input terminal is greater than the first preset voltage of 2V, the power management chip U1 controls the switch circuit 10 to shut off the path between the power input terminal Vin and the power amplifier circuit 60, and outputs a power amplifier protection signal ERROR to trigger the power amplifier protection mechanism. On the other hand, by monitoring the voltage at the power input terminal through the first resistor R1 and the second resistor R2, the power amplifier circuit 60 can be protected from the influence of excessive voltage. The explanation is further elaborated using an example where the voltage of the power input terminal Vin is 24V, the voltage of the voltage detection signal is 19V, and the second preset voltage is 18V. Specifically, since the voltage detection signal detected by the power management chip U1 is 19V, which exceeds the second preset voltage of 18V, the voltage at the power input terminal is in an abnormal range. The power management chip U1 controls the switch circuit 10 to shut off the path between the power input terminal Vin and the power amplifier circuit 60, thereby protecting the power amplifier circuit 60 from the influence of excessive voltage.

[0066] In other embodiments, the voltage detection circuit 20 may also be other circuits, such as an ADC chip, a capacitor voltage divider sampling circuit, a voltage transformer-based sampling circuit, or a follower isolation sampling circuit, etc.

[0067] Reference Figure 1 , Figure 2 and Figure 3 The power amplifier protection circuit 70 also includes a pull-up resistor R5. One end of the pull-up resistor R5 is connected to Vcc, and the other end is connected to the signal output terminal. The pull-up resistor R5 is used to pull the level of the signal output terminal high. When the signal output terminal is in a high impedance state, the pull-up resistor R5 can keep the signal output terminal in a stable high level state, ensuring that the power amplifier protection signal ERROR can be correctly output to the external control circuit and avoiding errors caused by uncertain states.

[0068] like Figure 3As shown, the power management circuit 30 includes a power management chip U1, a power adjustment resistor R4, and a time adjustment capacitor C3. The power management chip U1 has a power adjustment pin PWR and a time adjustment pin TIMER. The power adjustment pin PWR of the power management chip U1 is connected to the power adjustment resistor R4, and the time adjustment pin TIMER of the power management chip U1 is connected to the time adjustment capacitor C3. The power management chip U1 also has a voltage input pin VIN, a voltage output pin OUT, a control pin GATE, a current detection pin SENSE, a controlled pin UVLO / EN, a voltage detection pin UVLO, and a signal output pin PGD. The power management chip U1 has several key components: its voltage input pin VIN is connected to the power input terminal Vin and the third resistor R3 to receive the voltage at Vin; its voltage output pin OUT is connected to the source S of the first switching transistor Q1 and the power output Vout of the power amplifier circuit 60 to supply power to the power amplifier circuit 60 and the filter capacitor circuit; its control pin GATE is connected to the gate G of the first switching transistor Q1 to control the switching on and off of Q1; its current detection pin SENSE is connected between the third resistor R3 and the drain D of the first switching transistor Q1 to detect the current in the third resistor R3; its controlled pin UVLO / EN is used to receive the enable signal EN; its voltage detection pin UVLO is connected between the first resistor R1 and the second resistor R2 to detect the voltage at Vin; and its signal output pin PGD is connected to the pull-up resistor R5 to output the power amplifier protection signal ERROR to the external control circuit.

[0069] This utility model proposes an inkjet printing device 1000, which includes a power amplifier circuit 60, a filter capacitor circuit 40, and a power amplifier protection circuit 70 as described in the above embodiments. The specific structure of the inkjet printing device 1000 is as described in the above embodiments. Since the inkjet printing device 1000 adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated further here.

[0070] Reference Figure 4 In some embodiments, the inkjet printing device 1000 also includes a printhead 100, a print table 200, an ink supply module 300, an ink stack module 400, and a waste liquid container 500, etc., which will not be listed here. Among them, the power amplifier circuit 60, the filter capacitor circuit 40, and the power amplifier protection circuit 70 can be located inside the printhead 100 and electrically connected to the printhead inside the printhead 100.

[0071] The above embodiments are merely preferred embodiments of this utility model and do not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made based on the content of this utility model specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. A power amplifier protection circuit, applied in an inkjet printing device, the inkjet printing device comprising a power amplifier circuit and a filter capacitor circuit, characterized in that, The power amplifier protection circuit includes: A switching circuit, wherein the input terminal of the switching circuit is connected to the power supply terminal, and the output terminal of the switching circuit is connected to the power amplifier circuit and the filter capacitor circuit respectively. A voltage detection circuit is connected to the power input terminal and is used to detect the supply voltage connected to the power input terminal. A power supply management circuit is connected to the output terminal of the voltage detection circuit, the controlled terminal of the switching circuit, and the output terminal of the switching circuit, respectively. The power supply management circuit is used to control the switching circuit to be in a first state according to the power supply voltage when the power input terminal is powered on, so as to supply power to the power amplifier circuit and the filter capacitor circuit with a first power; after a first period of time, if the difference between the power supply voltage and the voltage at the output terminal of the switching circuit meets a preset condition, the circuit is controlled to be in a second state, so as to supply power to the power amplifier circuit and the filter capacitor circuit with a second power. Wherein, the first power is less than the second power.

2. The power amplifier protection circuit as described in claim 1, characterized in that, The power management circuit is specifically used for: After a first duration, if the voltage difference between the output voltage of the switching circuit and the supply voltage is less than a first preset voltage, the switching circuit is controlled to conduct in the second state. After the first power-on period, if the voltage difference between the output voltage of the switching circuit and the supply voltage is greater than the first preset voltage, a power amplifier protection signal is output.

3. The power amplifier protection circuit as described in claim 1, characterized in that, The power supply management circuit is specifically used to: control the switching circuit to shut off the path between the power supply terminal and the power amplifier circuit when the power supply voltage exceeds the second preset voltage.

4. The power amplifier protection circuit as described in any one of claims 1 to 3, characterized in that, The power management circuit includes a power control circuit, a power regulation circuit, and a time regulation circuit; The power supply control circuit is connected to the power adjustment circuit and the time adjustment circuit; The power supply control circuit is used to set the first power based on the power adjustment circuit and to set the first duration based on the time adjustment circuit.

5. The power amplifier protection circuit as described in claim 4, characterized in that, The power regulation circuit includes a power regulation resistor; and / or, The time adjustment circuit includes a time adjustment capacitor.

6. The power amplifier protection circuit as described in claim 4, characterized in that, The power supply control circuit includes a power management chip, which includes a voltage input pin, a voltage output pin, a voltage detection pin, and a control pin. The power input pin is connected to the voltage input pin, the voltage output pin is connected to the output of the switching circuit, the voltage detection pin is connected to the output of the voltage detection circuit, and the control pin is connected to the controlled terminal of the switching circuit.

7. The power amplifier protection circuit as described in claim 6, characterized in that, The power management chip also has an enable pin and a signal output pin for connecting to an external control circuit. The enable pin is used to receive an enable signal output by the external control circuit, and the signal output pin is used to output a power amplifier protection signal to the external control circuit. The power management circuit is configured to start working when the enable pin receives the enable signal from the external control circuit, and to output a power amplifier protection signal to the external control circuit through the signal output pin when the current or voltage at the output terminal of the switching circuit is abnormal, so as to control the power management chip to shut down.

8. The power amplifier protection circuit as described in any one of claims 1 to 3, characterized in that, The power amplifier protection circuit also includes: A current limiting circuit is disposed between the power input terminal and the switching circuit, and is connected to the power management circuit; The power supply management circuit is also used to acquire the output current of the current limiting circuit when the switching circuit is in the second state, and to output a power amplifier protection signal when the output current of the current limiting circuit is greater than a preset current.

9. The power amplifier protection circuit as described in any one of claims 1 to 3, characterized in that, The switching circuit includes: A switching transistor, wherein the input terminal of the switching transistor is connected to the power supply terminal, the output terminal of the switching transistor is connected to the power supply terminal of the power amplifier circuit, and the controlled terminal of the switching transistor is connected to the power supply management circuit; and / or, The voltage detection circuit includes: A first resistor and a second resistor, wherein the first end of the first resistor is connected to the power input terminal, the second end of the first resistor is connected to the first end of the second resistor, the connection point between the first resistor and the second resistor is connected to the power management circuit, and the second end of the second resistor is grounded.

10. An inkjet printing device, characterized in that, The inkjet printing device includes a power amplifier circuit, a filter capacitor circuit, and a power amplifier protection circuit as described in any one of claims 1 to 9, wherein the output terminal of the power amplifier protection circuit is connected to the power amplifier circuit and the filter capacitor circuit respectively.

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