Buzzer drive device

Abstract

The buzzer sounds appropriately at the desired volume setting. [Solution] The buzzer drive device 20 provided in the printer 1 includes a control unit 17 that outputs a PWM-controlled drive signal 101 to sound the buzzer 19, a charge pump 21 that applies an output voltage to the buzzer 19, which is obtained by converting the positive voltage power supply voltage Vcc from the power supply unit 16 (power supply) into a negative voltage based on the drive signal 101, and a delay circuit 22 that delays the drive signal 101 and outputs it to the buzzer 19 while waiting for the negative voltage output voltage Vout from the charge pump 21 to be boosted.

Description

Technical Field

[0001] The present invention relates to a buzzer drive device that controls the ringing of a buzzer.

Background Art

[0002] Electronic devices such as image forming apparatuses are provided with a buzzer for notifying a user of status notifications such as transition to sleep, and are provided with a buzzer drive device that applies a voltage to the buzzer so as to make the buzzer ring at a desired volume.

[0003] For example, according to Patent Document 1, an audio and music playback device changes the parameter of the output voltage value of a power supply circuit that supplies power to an output amplifier, according to the volume of the audio or music signal to be played back.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A buzzer drive device applies a voltage of a voltage value corresponding to a desired set volume to a buzzer, and inputs a drive signal of a predetermined cycle to the buzzer. However, in the conventional buzzer drive device, since the drive signal is input to the buzzer before the voltage applied to the buzzer is boosted to the voltage value corresponding to the desired set volume, before the actual volume reaches the desired set volume, the buzzer may ring at a volume lower than the desired set volume, or the drive signal input to the buzzer may rise a plurality of times, causing the buzzer to ring a plurality of times. As described above, the conventional buzzer drive device may not be able to properly ring the buzzer at the desired set volume.

[0006] In view of the above circumstances, the present invention aims to properly ring the buzzer at a desired set volume. [Means for solving the problem]

[0007] The buzzer drive device of the present invention is characterized by comprising: a control unit that outputs a PWM-controlled drive signal to sound a buzzer; a charge pump that applies an output voltage obtained by converting a positive voltage from a power supply to a negative voltage based on the drive signal to the buzzer; and a delay circuit that delays the drive signal and outputs it to the buzzer while waiting for the output voltage to be boosted by the charge pump. [Effects of the Invention]

[0008] According to the present invention, the buzzer can be sounded appropriately at a desired set volume. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view illustrating an example of a printer according to one embodiment of the present invention. [Figure 2] This is a block diagram illustrating an example of a printer buzzer drive device according to one embodiment of the present invention. [Figure 3] This table shows the relationship between the buzzer level signal, volume level, and set voltage in a buzzer drive device for a printer according to one embodiment of the present invention. [Figure 4] This is a schematic circuit diagram showing an example of a charge pump in a printer buzzer drive device according to one embodiment of the present invention. [Figure 5] This is a schematic circuit diagram illustrating an example of a delay circuit in a printer buzzer drive device according to one embodiment of the present invention. [Figure 6] This graph shows examples of signals when a delay circuit in a printer buzzer drive device according to one embodiment of the present invention outputs an output signal that delays the drive signal. [Modes for carrying out the invention]

[0010] First, the overall configuration of the printer 1 (image forming apparatus) to which the buzzer drive device 20 according to an embodiment of the present invention is applied will be described with reference to Figure 1. For the sake of convenience in the following explanation, the front side of the paper in Figure 1 will be referred to as the front side of the printer 1. The arrows L, R, U, and Lo appropriately attached to each figure indicate the left, right, top, and bottom sides of the printer 1, respectively.

[0011] Printer 1 operates in either normal mode or sleep mode (power-saving mode), and in sleep mode it operates with less power consumption than in normal mode.

[0012] Printer 1 comprises a roughly box-shaped printer body 2, with a paper feed cassette 3 for storing paper located at the bottom of the printer body 2, and an output tray 4 located at the top of the printer body 2.

[0013] Inside the printer body 2, an exposure unit 5 is provided below the paper output tray 4, and below the exposure unit 5, an image forming unit 6 is provided to form an image on the paper. The image forming unit 6 is rotatably mounted on a photoreceptor drum 7, which is an image carrier, and around the photoreceptor drum 7, a charging unit, a developing unit connected to a toner container, a transfer roller, and a cleaning unit are arranged along the rotation direction of the photoreceptor drum 7.

[0014] Furthermore, a paper transport path 10 is provided inside the printer body 2. A paper feed unit 11 is provided at the upstream end of the transport path 10 near the paper feed cassette 3, and a transfer unit 12, consisting of a photosensitive drum 7 and transfer rollers, is provided in the middle section of the transport path 10. A fuser unit 13 is provided at the downstream end of the transport path 10, and a paper discharge unit 14 is provided at the downstream end of the transport path 10 near the paper discharge tray 4.

[0015] The printer 1 is equipped with a buzzer 19 to notify the user of status changes such as the transition from normal mode to sleep mode, and a buzzer drive device 20 that drives the buzzer 19 to sound at a desired set volume.

[0016] Further, inside the printer main body 2, a power supply unit 16 that supplies power to each component of the printer 1, and a control unit 17 that controls each component of the printer 1 are provided.

[0017] The control unit 17 is composed of a CPU (Central Processing Unit) or the like, and is connected to a storage unit 18 configured with a ROM (Read Only Memory), a RAM (Random Access Memory) or the like. The control unit 17 is connected to each component of the printer 1, and controls each component by executing arithmetic processing based on control programs and control data stored in the storage unit 18.

[0018] Next, the image forming operation of the printer 1 will be described. The printer 1 starts an image forming operation when image data is input from an external computer or the like and a print start instruction is issued. In the image forming operation, first, after the charging unit of the image forming section 6 charges the photoreceptor drum 7, the exposure unit 5 exposes the photoreceptor drum 7 according to the image data, and an electrostatic latent image is formed on the photoreceptor drum 7. Then, the developing unit of the image forming section 6 develops the electrostatic latent image on the photoreceptor drum 7 with toner, and a toner image is formed on the photoreceptor drum 7.

[0019] Meanwhile, the sheet taken out from the paper feed cassette 3 by the paper feed unit 11 is conveyed on the conveyance path 10 to the transfer unit 12, and the toner image on the photoreceptor drum 7 is transferred to the sheet. The sheet to which the toner image has been transferred is conveyed to the fixing unit 13, and the toner image is fixed to the sheet. The sheet with the fixed toner image is discharged from the paper discharge unit 14 to the paper discharge tray 4.

[0020] Next, the configuration of the buzzer drive device 20 will be described with reference to Figure 2. As shown in Figure 2, the buzzer drive device 20 is connected to the power supply unit 16, and is configured to include the control unit 17, a charge pump 21, and a delay circuit 22.

[0021] The power supply unit 16 applies a power supply voltage Vcc of a predetermined voltage value to the charge pump 21 and the delay circuit 22 of the buzzer drive device 20. For example, the power supply unit 16 applies a 3.3V power supply voltage Vcc to the delay circuit 22.

[0022] When a state change such as a transition of the operation mode of the printer 1 occurs and the buzzer 19 is to be sounded, the control unit 17 generates a PWM-controlled drive signal 101 and outputs it to the charge pump 21 and the delay circuit 22 of the buzzer drive device 20. For example, the control unit 17 generates the drive signal 101 that is PWM-controlled at a frequency of 2 kHz.

[0023] Further, when sounding the buzzer 19, the control unit 17 generates a volume instruction signal 102 that instructs the volume of the buzzer 19 and outputs it to the charge pump 21. The control unit 17 sets the volume of the buzzer 19 in response to a state change such as a transition of the operation mode of the printer 1, and generates the volume instruction signal 102 corresponding to the set volume. For example, when the buzzer 19 sounds at a volume corresponding to the applied voltage, the control unit 17 outputs, as the volume instruction signal 102 for applying a voltage corresponding to the set volume to the buzzer 19, a first buzzer level signal 102a and a second buzzer level signal 102b indicating the volume level of the buzzer 19 to the charge pump 21 by a GPIO signal indicating H (High) level or L (Low) level, as shown in FIG. 3.

[0024] Specifically, the printer 1 normally sets a medium level volume, accepts a change to any of a low level, medium level, and high level volume level in response to a user operation, and the control unit 17 outputs the volume instruction signal 102 indicating the volume level corresponding to the user operation.

[0025] Figure 3 is a table showing the relationship between the volume instruction signal 102 (first buzzer level signal 102a and second buzzer level signal 102b), the volume level, and the set voltage. When setting a low volume level, the control unit 17 outputs the H-level first buzzer level signal 102a and the H-level or L-level second buzzer level signal 102b to the charge pump 21 in order to apply a set voltage of 5V to the buzzer 19. When setting a medium volume level, the control unit 17 outputs the L-level first buzzer level signal 102a and the H-level second buzzer level signal 102b to the charge pump 21 in order to apply a set voltage of 10V to the buzzer 19. When setting a high volume level, the control unit 17 outputs the L-level first buzzer level signal 102a and the L-level second buzzer level signal 102b to the charge pump 21 in order to apply a set voltage of 15V to the buzzer 19.

[0026] The charge pump 21 converts the positive voltage power supply voltage Vcc from the power supply unit 16 into a negative voltage output voltage based on the drive signal 101 from the control unit 17 and applies it to the buzzer 19. At this time, the charge pump 21 boosts the output voltage to a set voltage corresponding to the volume instruction signal 102 from the control unit 17.

[0027] As shown in Figure 4, the charge pump 21 has a boost circuit 25 connected to the power supply unit 16 and a transistor circuit 26 that receives a drive signal 101 from the control unit 17. When a drive signal 101 of a predetermined voltage value or higher is input to the transistor circuit 26, the power supply voltage Vcc from the power supply unit 16 is energized through the boost circuit 25, boosted, and output. The charge pump 21 applies a volume instruction signal 102 (first buzzer level signal 102a and second buzzer level signal 102b) from the control unit 17 to the output voltage Vout output from the boost circuit 25 to the buzzer 19, so that the voltage boosted by the boost circuit 25 becomes the set voltage corresponding to the volume instruction signal 102.

[0028] The boost circuit 25 of the charge pump 21 has one or more combinations of diodes 28 and capacitors 29, and is configured to use the capacitors 29 as energy storage elements to increase the voltage level. The boost circuit 25 takes time to store energy and raise the voltage from 0V to a voltage level corresponding to the desired set volume (for example, one of three levels: 5V, 10V, or 15V), and the higher the voltage level, the longer the boost time from 0V.

[0029] In the boost circuit 25, if the value of capacitor 29 is relatively small, the charging and discharging of capacitor 29 is limited, limiting the boost, and the voltage boosted by the boost circuit 25 becomes small. As a result, the output voltage Vout from the charge pump 21 to the buzzer 19 becomes small, and the actual volume of the buzzer 19 does not reach the set volume. On the other hand, in the boost circuit 25, if the value of capacitor 29 is relatively large, the output voltage Vout from the charge pump 21 to the buzzer 19 becomes large, but the time it takes for capacitor 29 to boost to the maximum voltage becomes longer, so it takes time for the actual volume of the buzzer 19 to reach the set volume. Assuming that the boost time is approximately 60ms when the capacitance of capacitor 29 is 1μF, the boost circuit 25 is configured with a capacitor 29 such that the desired boost time can be obtained for the set volume of the buzzer 19.

[0030] In this manner, the charge pump 21 outputs a negative voltage output voltage Vout that has been boosted to a set voltage corresponding to the volume instruction signal 102, and the buzzer 19 sounds at a volume corresponding to the output voltage Vout applied from the charge pump 21.

[0031] The delay circuit 22 delays the drive signal 101 to the buzzer 19, waiting for the output voltage Vout at the charge pump 21 to increase. At this time, the delay circuit 22 outputs the drive signal 101 to the buzzer 19 when the voltage of the drive signal 101 (input voltage Vin) reaches a predetermined threshold (reference voltage Vref).

[0032] As shown in Figure 5, the delay circuit 22 includes a comparator 30 (operational amplifier) ​​connected to the power supply unit 16 and an AND circuit 31 (logical AND circuit) that outputs a drive signal 101 based on the processing result of the comparator 30. Figure 6 is a graph showing examples of each signal when the output signal 106, which is the drive signal 101 delayed by the delay circuit 22, is output.

[0033] The delay circuit 22 inputs the drive signal 101 to the comparator 30 as an input voltage Vin that gradually increases in voltage by passing it through a delay resistor 33 and a delay capacitor 34. The delay circuit 22 also has a grounded first adjustment resistor 36 and a second adjustment resistor 37 connected to the power supply unit 16, and inputs a reference voltage Vref, obtained by adjusting the power supply voltage Vcc from the power supply unit 16, to the comparator 30.

[0034] For example, in the delay circuit 22, with respect to a power supply voltage Vcc of 3.3V, the reference voltage Vref is calculated as Vref = (R2 / (R2+R3)) × 3.3 based on the first adjustment resistor 36 and the second adjustment resistor 37, and a first adjustment resistor of 6.3kΩ 36 and a second adjustment resistor of 2.7kΩ 37 are installed.

[0035] The comparator 30 receives a reference voltage Vref based on the power supply voltage Vcc from the power supply unit 16 and an input voltage Vin based on the drive signal 101. As shown in Figure 6, it outputs an L (Low) level output signal 105 when the input voltage Vin is less than the reference voltage Vref, and an H (High) level output signal 105 when the input voltage Vin is equal to or greater than the reference voltage Vref.

[0036] The time it takes for the input voltage Vin, based on the drive signal 101, to rise from 0V to an H level corresponding to the reference voltage Vref is determined by the resistance value of the delay resistor 33 and the capacitance of the delay capacitor 34 that generate the input voltage Vin.

[0037] The AND circuit 31 receives the output signal 105 from the comparator 30 and the drive signal 101 from the control unit 17 as input and outputs their logical AND. The AND circuit 31 outputs an output signal 106 (an output signal 106 with the same period as the drive signal 101) that is at an H level when the comparator 30 outputs an H level output signal 105 and the drive signal 101, which is PWM controlled at a predetermined period, is at an H level. As shown in Figure 6, the drive signal 101 is at an H level periodically, so the AND circuit 31 outputs an output signal 106 corresponding to the drive signal 101 when the output signal 105 from the comparator 30 is at an H level, that is, when the input voltage Vin of the drive signal 101 reaches the reference voltage Vref.

[0038] The delay circuit 22 is configured to have a delay resistor 33 and a delay capacitor 34 such that a desired rise time can be obtained for the input voltage Vin of the drive signal 101.

[0039] Thus, when the input voltage Vin of the drive signal 101 reaches the reference voltage Vref, the delay circuit 22 outputs the drive signal 101 (output signal 106 with the same period as the drive signal 101), and the buzzer 19 sounds when it receives the drive signal 101 from the delay circuit 22.

[0040] In the buzzer drive device 20 of this embodiment, the charge pump 21 and the delay circuit 22 are configured such that the time it takes for the input voltage Vin to reach the reference voltage Vref in the delay circuit 22 (comparator 30) is equal to the time it takes for the charge pump 21 (boost circuit 25) to reach the set volume. For example, the delay circuit 22 is configured to have a 10kΩ delay resistor 33 and an 18μF delay capacitor 34.

[0041] In this embodiment, as described above, the buzzer drive device 20 provided in the printer 1 includes a control unit 17 that outputs a PWM-controlled drive signal 101 to sound the buzzer 19, a charge pump 21 that applies an output voltage obtained by converting the positive voltage power supply voltage Vcc from the power supply unit 16 (power supply) to a negative voltage based on the drive signal 101 to the buzzer 19, and a delay circuit 22 that delays the drive signal 101 and outputs it to the buzzer 19 while waiting for the negative voltage output voltage Vout from the charge pump 21 to be boosted.

[0042] As a result, when the buzzer drive device 20 is instructed to sound the buzzer 19 at a desired volume when a change in the state of the printer 1 occurs, it can input a drive signal 101 to the buzzer 19 to sound when the output voltage Vout applied to the buzzer 19 is increased to a set voltage corresponding to the set volume, thus enabling the buzzer 19 to sound appropriately at the desired volume.

[0043] Furthermore, in this embodiment, in the buzzer drive device 20, the control unit 17 outputs a volume instruction signal 102 that instructs the volume of the buzzer 19, and the charge pump 21 boosts the output voltage Vout, which is a negative voltage, to a voltage corresponding to the volume instruction signal 102.

[0044] As a result, the buzzer drive device 20 can boost the output voltage Vout applied to the buzzer 19 to a set voltage corresponding to the set volume by utilizing the volume instruction signal 102 corresponding to the desired set volume.

[0045] Furthermore, in this embodiment, the buzzer drive device 20 outputs the drive signal 101 to the buzzer 19 when the input voltage Vin of the drive signal 101 reaches a predetermined threshold reference voltage Vref.

[0046] As a result, the buzzer drive device 20 can adjust the rise time at which the input voltage Vin of the drive signal 101 reaches the reference voltage Vref, thereby outputting the drive signal 101 to the buzzer 19 at a desired timing that matches the voltage boost time at which the charge pump 21 reaches the set volume (set voltage).

[0047] Furthermore, in this embodiment, the buzzer drive device 20 has a control unit 17 that sets the volume of the buzzer 19 according to the transition of the operating mode and outputs a volume instruction signal 102 corresponding to this set volume.

[0048] As a result, the buzzer drive unit 20 can appropriately sound the buzzer 19 at the desired set volume when a transition in the operating mode of the printer 1 occurs.

[0049] In this embodiment, the case in which the configuration of the present invention is applied to a monochrome printer 1 has been described, but in other different embodiments, the configuration of the present invention can also be applied to other image forming devices equipped with a buzzer, such as color printers, copiers, facsimile machines, and multifunction devices, or to other electronic devices equipped with a buzzer. [Explanation of Symbols]

[0050] 1. Printer (image forming apparatus) 2. Printer body 3. Paper feed cassette 4. Paper output tray 5. Exposure area 6 Image forming unit 7. Photoconductor drum 10. Transport Route 11 Paper feed section 12 Transfer section 13 Fixing section 14 Paper output section 16 Power supply section (power supply) 17 Control Unit 18 Memory section 19 Buzzer 20 Buzzer drive device 21 Charge pump 22 Delay Circuit 25 Boost Circuit 26 Transistor Circuits 28 diodes 29 Capacitors 30 comparators 31 AND gate 33 Delay resistor 34 Delay capacitor 36 1st adjustment resistor 37 Second adjustment resistor

Claims

1. A control unit that outputs a PWM-controlled drive signal to sound the buzzer, A charge pump that applies an output voltage obtained by converting a positive voltage from a power supply to a negative voltage based on the drive signal to the buzzer, A delay circuit that delays the drive signal and outputs it to the buzzer while waiting for the output voltage to be increased in the charge pump, A buzzer drive device characterized by being equipped with the following features.

2. The control unit outputs a volume instruction signal that instructs the volume of the buzzer, The buzzer drive device according to claim 1, characterized in that the charge pump increases the output voltage to a voltage corresponding to the volume instruction signal.

3. The buzzer drive device according to claim 1, characterized in that the delay circuit outputs the drive signal to the buzzer when the voltage of the drive signal reaches a predetermined threshold.

4. The buzzer drive device according to claim 2, characterized in that the control unit sets the volume of the buzzer according to the transition of the operating mode and outputs the volume instruction signal corresponding to this volume.

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