JP2023179206A - Power supply device and image forming device - Google Patents

Abstract

To provide a power supply device to be protected by appropriately controlling discharge time of a gate of a first transistor when the first transistor is turned off.SOLUTION: A power supply device includes: a first converter unit that generates a first voltage according to an input voltage regardless of a first mode and a second mode; a first transistor that is turned on during the first mode to output the first voltage as a second voltage and is turned off during the second mode to stop the output from the second voltage; a second converter that generates a third voltage during the first mode and stops generating the third voltage during the second mode; and a gate control unit that turns off the first transistor by conducting a discharge path connected to the gate of the first transistor in response to a decrease in the third voltage during the second voltage is outputted and suppresses conduction of the discharge path in response to a decrease in the third voltage while the output of the second voltage is stopped.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power supply device and an image forming apparatus.

2. Description of the Related Art A power supply device is known that includes a semiconductor switch that is connected between a power supply and a load and turns on or off the power supplied to the load. In this type of power supply device, the semiconductor switch is protected by controlling the semiconductor switch according to the output current to the load and the elapsed time after the semiconductor switch is turned on (for example, see Patent Document 1).

However, depending on the gate discharge time required to set the gate voltage of the semiconductor switch to a level that turns off the semiconductor switch, there is a possibility that the power supply device including the semiconductor switch cannot be protected from malfunction or failure.

In view of the above problems, an object of the present invention is to protect a power supply device by appropriately controlling the discharge time of the gate of the first transistor when the first transistor is turned off.

In order to solve the above technical problem, a power supply device according to one embodiment of the present invention includes: a first converter section that generates a first voltage according to an input voltage regardless of the first mode and the second mode; a first transistor that is turned on during the mode to output the first voltage as a second voltage, and turned off during the second mode to stop outputting the second voltage; and a first transistor that outputs the first voltage as a second voltage during the second mode; a second converter unit that generates a third voltage and stops generating a third voltage during the second mode; and a second converter unit that is connected to the gate of the first transistor in response to a decrease in the third voltage while outputting the second voltage. and a gate control unit that makes the discharge path conductive, turns off the first transistor, and suppresses conduction of the discharge path in response to a decrease in the third voltage while outputting the second voltage is stopped. Features.

By appropriately controlling the discharge time of the gate of the first transistor when the first transistor is turned off, the power supply device can be protected.

FIG. 1 is a circuit block diagram showing an example of a power supply device according to an embodiment of the present invention. FIG. 2 is a circuit block diagram showing an example of a converter section in FIG. 1. FIG. FIG. 3 is a circuit block diagram showing an example of another power supply device. 4 is a timing chart showing an example of the operation of the power supply device of FIGS. 1 and 3. FIG. 2 is a timing chart showing another example of the operation of the power supply device of FIG. 1. FIG. FIG. 3 is a circuit block diagram showing an example of a power supply device according to another embodiment of the present invention. 7 is a timing chart showing an example of the operation of the power supply device of FIG. 6. FIG. 7 is an overall configuration diagram showing an example of an image forming apparatus in which the power supply device of FIGS. 1 and 6 is installed. FIG.

Hereinafter, embodiments will be described using the drawings. In the following, the same symbols as the voltage names are used for voltage lines through which voltages are transmitted, and the same symbols as the signal names are used for signal lines through which signals are transmitted. In each drawing, the same components are given the same reference numerals, and redundant explanations may be omitted.

FIG. 1 is a circuit block diagram showing an example of a power supply device according to an embodiment of the present invention. The power supply device 100 shown in FIG. 1 has a function of generating a plurality of types of DC voltages DC5X, DC5, and DC24 using an AC voltage Vin supplied from an AC power source AC such as a commercial power source, and outputting the generated DC voltages to a load. The direct current voltage DC5X is an example of the first voltage, and is, for example, 5V. The direct current voltage DC5 is an example of the second voltage, and is, for example, 5V. The direct current voltage DC24 is an example of the third voltage, and is, for example, 24V.
Power supply device 100 includes smoothing section 20, converter section 30, power supply section 40, converter section 50, discharge section 60, transistors Q1, Q2, resistance elements R1, R2, R3, diodes D1, D2, and capacitor C2. Although not particularly limited, for example, the transistors Q1 and Q2 are n-channel type insulated gate field effect transistors. Converter section 30 is an example of a first converter section, and converter section 50 is an example of a second converter section.

The smoothing unit 20 includes a diode bridge DB that performs full-wave rectification on the AC voltage Vin, and a capacitor C1 that smoothes the full-wave rectified voltage, and outputs a DC voltage generated by the smoothing. Converter unit 30 generates DC voltage DC5X from the DC voltage output from smoothing unit 20.

The power supply section 40 supplies the constant voltage received from the converter section 30 to the converter section 50 when the energy saving signal ECO indicates the normal mode. When the energy saving signal ECO indicates the energy saving mode, the power supply section 40 stops supplying the constant voltage received from the converter section 30 to the converter section 50 . The normal mode is an example of the first mode, and the energy saving mode is an example of the second mode. For example, the energy saving signal ECO is set to low level during normal mode, and set to high level during energy saving mode. In the following, the energy saving mode is also referred to as energy saving mode.

Converter section 50 operates while receiving constant voltage from power supply section 40 and generates direct current voltage DC24 from the direct current voltage output from smoothing section 20. When converter section 50 does not receive constant voltage from power supply section 40, converter section 50 stops generating operation of direct current voltage DC24. That is, the converter section 50 generates the DC voltage DC24 during the normal mode, and stops generating the DC voltage DC24 during the energy saving mode.

The gate of transistor Q1 is connected to DC voltage line DC24 via resistance elements R1, R2 and diode D2. The diode D2 has an anode connected to the DC voltage line DC24 and a cathode connected to the resistance element R2. The drain of transistor Q1 is connected to DC voltage line DC5X, and the source of transistor Q1 is connected to DC voltage line DC5. Transistor Q1 turns on when receiving a high level at its gate, connects DC voltage line DC5X to DC voltage line DC5, and generates DC voltage DC5. For example, transistor Q1 is turned on based on converter section 50 generating direct current voltage DC24, and continues to be turned on while direct current voltage DC24 is being generated.

Transistor Q1 turns off when receiving a low level at its gate, cuts off the connection between DC voltage line DC5X and DC voltage line DC5, and stops generating DC voltage DC5. For example, transistor Q1 is turned off based on converter section 50 stopping generation of direct current voltage DC24, and continues to be turned off while generation of direct current voltage DC24 is stopped. Transistor Q1 is an example of a first transistor.

The power supply device 100 constantly outputs a direct current voltage DC5X while receiving the alternating current voltage Vin. The power supply device 100 outputs the DC voltage DC24 in the normal mode while receiving the AC voltage Vin, and outputs the DC voltage DC5 by turning on the transistor Q1. The power supply device 100 stops outputting the DC voltages DC24 and DC5 in the energy saving mode while receiving the AC voltage Vin.

In this manner, during the normal mode, power supply device 100 branches the DC voltage generated by converter section 30 into two systems and outputs them as DC voltages DC5X and DC5. For example, a load that receives direct current voltage DC5X as an operating power source has a control circuit that is constantly operating to control the operating mode. For example, a load that receives direct current voltage DC5 as its operating power source has a control circuit that operates only during normal mode. For example, a load that receives direct current voltage DC24 as an operating power source has a drive mechanism or the like that operates only in the normal mode.

Capacitor C2, resistance element R3, and transistor Q2 are connected in parallel between node ND1, which is a connection node between resistance elements R1 and R2, and ground line VSS. During the normal mode, transistor Q2 receives a low-level energy saving signal ECO at its gate and is turned off. During the energy saving mode, transistor Q2 is turned on upon receiving a high-level energy saving signal ECO at its gate, and connects node ND1 and the gate of transistor Q1 to ground line VSS.

For example, the energy saving signal ECO is generated by a control circuit that receives the direct current voltage DC5X and operates to control the operation mode, and is output to the power supply device 100. During the energy saving mode, power supply device 100 stops the operation of converter section 50 and stops supplying direct current voltage DC5 from converter section 30 to the load. Further, the system in which the power supply device 100 is installed stops the operation of the load receiving the direct current voltages DC5 and DC24 during the energy saving mode.

This reduces the power consumption of the power supply device 100 and the system during the energy saving mode. In this way, the power supply device 100 can operate in a low power consumption energy saving state in which only the DC voltage DC5X is output, and in a high power consumption operation state in which all of the DC voltages DC5X, DC5, and DC24 are output, depending on the logic level of the energy saving signal ECO. You can switch between states.

The discharge section 60 includes a diode D1 and a transistor Tr1 (NPN bipolar transistor) connected in series between the node ND1 and the DC voltage line DC24. The diode D1 has an anode connected to the node ND1 and a cathode connected to the collector of the transistor Tr1. Diode D1 and transistor Tr1 are an example of a discharge path formed between node ND1 (ie, the gate of transistor Q1) and DC voltage line DC24.

The base of the transistor Tr1 is connected to a DC voltage line DC5. The transistor Tr1 is turned on when the direct current voltage DC5 is a normal value (eg, 5V). As a result, the discharge path from the gate of transistor Q1 to DC voltage line DC24 is made conductive.

For example, when the converter unit 50 normally generates the direct current voltage DC24, the gate of the transistor Q1 and the node ND1 can be set by setting the resistance value of the resistance element R3 to be sufficiently larger than the resistance value of the resistance element R2. Since the direct current voltage is set to DC24, no discharge is performed by the discharge section 60.

When the converter unit 50 stops operating when the DC voltage DC5 is at a normal value and the DC voltage DC24 decreases toward the ground voltage VSS, the gate voltage of the transistor Q1 rapidly decreases due to discharge through the discharge unit 60. (discharge function enabled state). As a result, transistor Q1 is turned off and generation of direct current voltage DC5 is stopped.

When the DC voltage line DC5 becomes 0V due to a short circuit, the transistor Tr1 is turned off, and the discharge path between the gate of the transistor Q1 and the DC voltage line DC24 by the discharge section 60 is cut off (the discharge function is disabled).

In this way, the discharge unit 60 has a function of switching the discharge path of the gate of the transistor Q1 between enabled and disabled depending on the generation state of the direct current voltage DC5. The discharge unit 60 is an example of a gate control unit that discharges the gate of the transistor Q1 and turns off the transistor Q1 in response to a decrease in the DC voltage DC24 while the DC voltage DC5 is being output. Further, the discharge unit 60 is an example of a gate control unit that suppresses discharge of the gate of the transistor Q1 in response to a decrease in the DC voltage DC24 while the output of the DC voltage DC5 is stopped.

FIG. 2 is a circuit block diagram showing an example of the converter sections 30 and 50 of FIG. 1. The converter section 30 includes a transformer T1, a transistor Q3, a control section 31 including a pulse width determining section 32 and a current detecting section 33, a constant voltage generating section 34, an output feedback section 35, and a smoothing section 36. , operates as a flyback converter.

The control unit 31 operates by receiving power from the auxiliary winding of the transformer T1. The current detection unit 33 of the control unit 31 detects the current on the primary side of the transformer T1. The output feedback section 35 feeds back the output voltage on the secondary side of the transformer T1 to the control section 31.

The control unit 31 uses the pulse width determining unit 32 to determine the pulse width of the voltage applied to the transistor Q3 based on the primary side current detection result and the secondary side output voltage feedback result. Further, when the current detection unit 33 detects a current exceeding the threshold value, the control unit 31 sets the pulse width to 0 to stop the switching operation of the transistor Q3. Further, the control unit 31 latches and stops when the current detection unit 33 detects a current exceeding the threshold value for a certain period of time.

Converter section 50 has a control section 51 and a main circuit 52. During the normal mode, the control section 51 operates by receiving power from the transformer auxiliary winding of the converter section 30 via the power supply section 40, and controls the operation of the main circuit 52. The main circuit 52 is controlled by the control unit 51 and generates a DC voltage DC24 using the DC voltage output from the smoothing unit 20.

For example, the control unit 51 performs feedback control on the main circuit 52 so that the voltage obtained by dividing the direct current voltage DC24 generated by the main circuit 52 approaches the reference voltage. Note that during the energy saving mode, the control unit 51, to which the power supply from the power supply unit 40 is stopped, stops operating. Therefore, during the energy saving mode, feedback control of the main circuit 52 by the control unit 51 is stopped, and generation of the direct current voltage DC24 by the main circuit 52 is stopped.

FIG. 3 is a circuit block diagram showing an example of another power supply device. Detailed description of elements that are the same or similar to those in FIG. 1 will be omitted. The power supply device 200 shown in FIG. 3 includes a smoothing section 20, a converter section 30, a power supply section 40, a converter section 50, transistors Q1, Q2, resistance elements R1, R2, R3, a diode D2, a capacitor C2, a current detection section 70, and It has a stop part 80. In the power supply device 200, the configuration and connection relationship excluding the current detection section 70 and the stop section 80 are the same as those of the power supply device 100 of FIG. 1, except that the discharge section 60 of FIG. 1 is not included.

The current detection section 70 is connected to the DC voltage line DC5 and detects the output current of the transistor Q1. The stop unit 80 has a function of suspending control of the gate voltage of the transistor Q1 until a predetermined time has elapsed after the transistor Q1 was turned on. However, the power supply device 200 does not control the discharge time of the gate of the transistor Q1 when the direct current voltage DC24 is stopped. Therefore, for example, if the gate voltage of the transistor Q1 cannot be lowered quickly when a momentary interruption of the AC voltage Vin occurs, there is a possibility that the converter section 30 will latch and stop.

FIG. 4 is a timing chart showing an example of the operation of the power supply device 100 of FIG. 1 and the power supply device 200 of FIG. 3. FIG. 4 shows the operation when a momentary interruption of the AC voltage Vin occurs.

In the power supply device 100, when a momentary interruption of the AC voltage Vin occurs, the DC voltage (input voltage) output from the smoothing section 20 decreases. Accordingly, the output of the DC voltage DC24 from the converter unit 50 is stopped, and the DC voltage DC24 decreases toward the ground voltage VSS (FIG. 4(a)).

When the instantaneous interruption occurs, the transistor Q1 is outputting a direct current voltage DC5, and the transistor Tr1 of the discharge section 60 is turned on (FIG. 4(b)). Therefore, current can be caused to flow through the diode D1 following the decrease in the direct current voltage DC24, and the gate voltage of the transistor Q1 can be rapidly decreased to immediately turn off the transistor Q1 (FIG. 4(c)). By turning off the transistor Q1, the DC voltage DC5 decreases to the ground voltage VSS (FIG. 4(d)).

By turning off transistor Q1, the connection between the output of converter section 30 and DC voltage line DC5 is cut off, and the load connected to the output of converter section 30 becomes smaller. Therefore, the converter section 30 can continue to operate without being latched to a halt even in a state where a momentary interruption of the alternating current voltage Vin occurs. That is, the converter section 30 can continue to output the normal direct current voltage DC5X even when a momentary power outage occurs (FIG. 4(e)). The output current of the converter section 30 decreases because the load connected to the output of the converter section 30 becomes smaller (FIG. 4(f)).

As the instantaneous interruption is resolved, the amplitude of the alternating current voltage Vin returns to its original level, and the converter section 50 resumes generating the direct current voltage DC24 (FIG. 4(g)). As the direct current voltage DC24 rises, the gate voltage of the transistor Q1 rises, turning on the transistor Q1 (FIG. 4(h)). As a result, the output of the direct current voltage DC5 is restarted (FIG. 4(i)). By turning on the transistor Q1, the load connected to the output of the converter section 30 increases, so the output current of the converter section 30 increases (FIG. 4(j)). The converter section 30 then returns to its normal state.

In this way, by providing the power supply device 100 with the discharge section 60 including the transistor Tr1 that is turned on or off depending on the voltage value of the DC voltage DC5, the transistor Q1 can be quickly turned off when a momentary power outage occurs. As a result, the output load of the converter section 30 is reduced, so that excessive protection due to latch stop can be suppressed, and generation of the direct current voltages DC24 and DC5 can be restarted after the momentary interruption is resolved.

In the power supply device 200, similarly to the power supply device 100, when a momentary interruption of the AC voltage Vin occurs, the DC voltage (input voltage) output from the smoothing section 20 decreases. Accordingly, the converter unit 50 stops outputting the direct current voltage DC24, and the direct current voltage DC24 decreases to the ground voltage VSS (FIG. 4(k)).

Since the power supply device 200 does not have the discharge section 60 shown in FIG. 1, there is no discharge path that steeply lowers the gate voltage of the transistor Q1. Therefore, even if the direct current voltage DC24 drops to the ground voltage VSS, the gate voltage of the transistor Q1 gradually drops, and the transistor Q1 does not turn off during the momentary interruption (FIG. 4(l)).

Since the transistor Q1 is maintained in the on state, the converter section 30 continues to operate with a large load connected to the output and a low input voltage. Therefore, the current on the primary side of converter section 30 also increases, and converter section 30 latches to a halt.

Due to the latch stop, the converter unit 30 stops generating the direct current voltage DC5X (FIG. 4(m)). By stopping the generation of the DC voltage DC5, the output of the DC voltage DC5 is also stopped (FIG. 4(n)). Then, the output current of the converter section 30 becomes zero (FIG. 4(o)). Since the latch stop state continues even after the instantaneous power outage is resolved, the entire system of the power supply device 200 remains stopped.

In addition, in the power supply device 200, when the load connected to the output of the converter section 30 is light, the latching stop may not occur and the output of the DC voltages DC5X, DC24, and DC5 may be restored after the momentary interruption is resolved. However, since the transistor Q1 is maintained in the on state without being turned off when a momentary interruption occurs, the startup sequence after the momentary interruption is different from normal.

For example, in a normal startup sequence, output of DC voltages DC5X, DC24, and DC5 is started in this order, but after the momentary interruption is resolved, output is started in this order of DC voltages DC5X, DC5, and DC24. If the startup sequences are different, an unexpected error may occur in the system in which the power supply device 200 is installed.

FIG. 5 is a timing chart showing another example of the operation of the power supply device 100 of FIG. 1. FIG. 5 shows the operation when the discharge function of the discharge unit 60 is disabled when the DC voltage line DC5 is short-circuited. The operation timing shown in the square brackets in FIG. 5 indicates the operation when the discharge function of the discharge section 60 is in an effective state when the DC voltage line DC5 is short-circuited. For example, the portion in parentheses in FIG. 5 shows the operation when the discharge section 60 in FIG. 1 does not include the transistor Tr1.

Converter unit 30 detects the occurrence of a short circuit in DC voltage line DC5 by detecting, based on DC voltage DC5X, that DC voltage DC5 has decreased to ground voltage VSS or a voltage close to ground voltage VSS. When converter section 30 detects a short circuit, it stops the switching operation of transistor Q3 (FIG. 2) (FIG. 5(a)). As a result, the power supply from the converter section 30 to the converter section 50 is stopped, so the operation of the converter section 50 is stopped, and the direct current voltage DC24 decreases to the ground voltage VSS (FIG. 5(b)).

Due to the short circuit of the DC voltage line DC5, the transistor Tr1 of the discharge section 60 receives the DC voltage DC5 having a voltage value corresponding to the low level and is turned off, and the discharge function of the discharge section 60 becomes disabled. Therefore, when the DC voltage line DC5 is short-circuited, the gate of the transistor Q1 is not discharged even if the DC voltage DC24 decreases. The gate voltage of the transistor Q1 gradually decreases, for example, via a path from the resistors R1 and R3 to the ground line VSS (FIG. 5(c)).

The converter section 30 latches to a halt based on the fact that the low voltage (for example, the ground voltage VSS) of the DC voltage DC5X (that is, the DC voltage DC5) continues for a certain period of time until the transistor Q1 is turned off. That is, the power supply device 100 having the discharge section 60 whose discharge function can be set to an invalid state can activate the protection function of the power supply device 100 against short circuits. In this way, in addition to providing the discharge section 60 in the power supply device 100, by switching the discharge function between the valid state and the disabled state according to the output state of the direct current voltage DC5, the circuits such as the converter section 30 in the power supply device 100 can be can be properly protected.

On the other hand, as shown in the square brackets, when the discharge function by the discharge unit 60 is enabled when the DC voltage line DC5 is short-circuited, the gate voltage of the transistor Q1 immediately changes to the ground voltage when the DC voltage line DC5 is short-circuited. It decreases toward VSS (Fig. 5(d)). As a result, transistor Q1 is turned off before converter section 30 is latched to a halt.

When transistor Q1 is turned off, converter section 30 and the short-circuit location are cut off by transistor Q1. Therefore, the converter section 30 no longer detects the short circuit of the DC voltage line DC5, and resumes the switching operation of the transistor Q3 (FIG. 5(e)).

By restarting the switching operation of transistor Q3, generation of direct current voltage DC5X is restarted (FIG. 5(f)). Furthermore, the supply of power from converter section 30 to converter section 50 is restarted. Thereby, the converter section 50 restarts generation of the direct current voltage DC24 (FIG. 5(g)). By restarting the generation of the DC voltage DC24, the gate voltage of the transistor Q1 increases in accordance with the rise in the DC voltage DC24, and when it exceeds the threshold voltage VT of the transistor Q1, the transistor Q1 is turned on (FIG. 5 (h) ).

Turning on transistor Q1 connects converter section 30 and the short circuit via transistor Q1. As a result, the converter unit 30 detects the short circuit of the DC voltage line DC5 again and stops the switching operation of the transistor Q3 (FIG. 5(i)). Since the above operation is repeated, the converter unit 30 is repeatedly activated without being latched to a stop, and the protection function of the power supply device 100 against short circuits cannot be activated.

As described above, in this embodiment, the power supply device 100 is provided with the discharge section 60 including the transistor Tr1 that is turned on or off depending on the voltage value of the direct current voltage DC5. Thereby, the discharge function can be switched between a valid state and a disabled state, and the circuit within the power supply device 100 can be appropriately protected. That is, the power supply device 100 can be protected by appropriately controlling the discharge time of the gate of the transistor Q1 when the transistor Q1 is turned off.

For example, by providing the discharge section 60 in the power supply device 100, the transistor Q1 can be quickly turned off when a momentary power outage occurs. As a result, the output load of the converter section 30 is reduced, so that excessive protection due to latch stop can be suppressed, and generation of the direct current voltages DC24 and DC5 can be restarted after the momentary interruption is resolved.

When the DC voltage line DC5 is short-circuited, by disabling the discharge function of the discharge section 60, the converter section 30 can be latched stopped, and the protection function of the power supply device 100 against short circuits can be activated.

Furthermore, even when the power supply device 100 has a function of suspending control of the gate voltage of the transistor Q1 until a predetermined time has elapsed after the transistor Q1 is turned on, by providing the discharge section 60, it is possible to Transistor Q1 can be quickly turned off.

FIG. 6 is a circuit block diagram showing an example of a power supply device according to another embodiment of the present invention. Elements that are the same as or similar to those in the embodiment described above are given the same reference numerals, and detailed explanations are omitted. A power supply device 110 shown in FIG. 6 adds a voltage detection section 90 and a transistor Tr2 (NPN bipolar transistor) to the power supply device 100 shown in FIG. Transistor Tr2 is an example of a second transistor.

When the voltage detection unit 90 detects that the DC voltage DC5 is lower than a predetermined voltage higher than 0V (that is, when detecting a low voltage that is not a short circuit), the voltage detection unit 90 supplies a base current that turns on the transistor Tr2 to the base of the transistor Tr2. Output.

The transistor Tr2 has a collector connected to the gate of the transistor Q1 via the node ND1 and the resistive element R1, and an emitter that is grounded. Therefore, when the direct current voltage DC5 becomes equal to or less than a predetermined voltage value higher than 0V, the gate of the transistor Q1 is grounded, and the transistor Q1 is turned off.

FIG. 7 is a timing diagram showing an example of the operation of the power supply device 110 of FIG. 6. FIG. 7 shows the operation when an abnormality in the output of the converter section 50 occurs due to an abnormality in a feedback system circuit such as the control section 51 of the converter section 50 in FIG. 2, for example. Before the output abnormality occurs, the DC voltages DC24 and DC5 (DC5X) are normally output (FIGS. 7(a) and (b)). Further, in order to detect the normal DC voltage DC5, the voltage detection unit 90 does not output a base current to the base of the transistor Tr2, and the transistor Tr2 is turned off (FIG. 7(c)).

After this, an abnormal output of the converter section 50 occurs, and, for example, the direct current voltage DC24 decreases to an intermediate value between the normal value and the ground voltage VSS (FIG. 7(d)). As the direct current voltage DC24 decreases, a current flows from the gate of the transistor Q1 to the direct current voltage line DC24 via the discharge section 60. As a result, the gate voltage of the transistor Q1 decreases toward the voltage value of the direct current voltage DC24 (FIG. 7(e)).

Due to the decrease in the gate voltage of transistor Q1, transistor Q1 operates in a non-saturation region (FIG. 7(f)). As a result, the voltage drop between the drain and source of the transistor Q1 becomes large, so that the direct current voltage DC5 decreases (FIG. 7(g)). The voltage detection unit 90 detects a decrease (not a short circuit) in the direct current voltage DC5. Then, the voltage detection unit 90 outputs a base current to the base of the transistor Tr2, turning on the transistor Tr2 (FIG. 7(h)).

By turning on the transistor Tr2, the gate voltage of the transistor Q1 decreases toward the ground voltage VSS, and the transistor Q1 turns off (FIG. 7(i)). By turning off the transistor Q1, the output of the direct current voltage DC5 is stopped (FIG. 7(j)). Thereby, it is possible to prevent the transistor Q1 from continuing to operate in a non-saturated state, and it is possible to protect the transistor Q1 from failure or damage.

On the other hand, when the power supply device 110 does not include the voltage detection section 90 and the transistor Tr2, if the DC voltage DC24 continues to decrease due to an abnormality in the feedback system of the converter section 50, the gate voltage of the transistor Q1 decreases. There is a risk that this will continue. In this case, there is a possibility that the transistor Q1 continues to operate in the non-saturation region. Further, while the transistor Q1 is operating in the non-saturation region, the DC voltage DC5 also decreases due to the voltage drop between the drain and source of the transistor Q1. In this case, the loss of transistor Q1 increases, and there is a risk that transistor Q1 will fail or be damaged.

As described above, in this embodiment as well, the same effects as in the above-described embodiment can be obtained. For example, by providing the power supply device 110 with a discharge section 60 including a transistor Tr1 that is turned on or off depending on the voltage value of the direct current voltage DC5, the discharge function can be switched between a valid state and a disabled state, and the The circuit can be properly protected.

Furthermore, in this embodiment, the voltage detection section 90 and the transistor Tr2 are provided in the power supply device 110. Thereby, for example, when an abnormality in the output of the converter section 50 occurs, it is possible to prevent the transistor Q1 from continuing to operate in a non-saturated state, and it is possible to protect the transistor Q1 from failure or damage.

FIG. 8 is an overall configuration diagram showing an example of an image forming apparatus in which the power supply device 100 of FIG. 1 and the power supply device 110 of FIG. 6 are installed. The image forming apparatus 1 shown in FIG. 8 is, for example, a digital multi-function printer (MFP) having a copy function, a print function, a scanner function, a facsimile function, and the like. The image forming apparatus 1 can mutually switch between operation modes for realizing a copy function, a print function, a scanner function, and a facsimile function by using an application switching key or the like on an operation unit of the image forming apparatus 1. The image forming apparatus 1 enters a copy mode when a copy function is selected, a print mode when a print function is selected, a scanner mode when a scanner function is selected, and a facsimile mode when a facsimile function is selected.

Further, the internal state of the image forming apparatus 1 is switched to a normal mode, an energy saving mode (power saving mode), etc. depending on the state of the internal circuit. For example, the normal mode includes an operating mode (operating state) and a standby mode (standby state).

For example, the active mode includes a copy mode or a print mode in which images, text data, etc. are printed on a paper medium or the like. The print mode includes an operation of printing received data on a paper medium or the like in the facsimile mode. Furthermore, the active mode includes transmission and reception operations in a scanner mode for scanning a document or the like or in a facsimile mode. The state of the internal circuit is switched by the user's operation of the operating unit or by control within the image forming apparatus 1.

For example, the image forming apparatus 1 includes an automatic document feeder (ADF) 2, an image reading device 3, a writing unit 4, a printer unit 5, an operation panel 11, a control device 12, and a power supply device 13.

The power supply device 13 is the power supply device 100 in FIG. 1 or the power supply device 110 in FIG. The power supply device 13 supplies the generated direct current voltage DC24 to various loads such as the printer unit 5. For example, the loads include various motors, a charger that charges the photosensitive drum 6, a developing roller of the developing device 7, and the like.

The power supply device 13 supplies the generated direct current voltage DC5 to the control device 12 as an operating power source for the CPU, memory, etc. mounted on the control device 12. The power supply device 13 constantly supplies the generated direct current voltage DC5X to the control board as an operating power source for a CPU (Central Processing Unit), memory, etc. mounted on the control board to which the operation panel 11 is connected.

The printer unit 5 includes a photosensitive drum 6, a developing device 7, a conveyor belt 8, a fixing device 9, and a storage space in which a paper feed tray 10 is stored. The automatic document feeder 2, image reading device 3, writing unit 4, printer unit 5, and operation panel 11 are examples of a main body that forms images.

The printer unit 5 creates a toner image to be transferred onto a paper medium or the like based on the image information. The printer unit 5 is an example of an image forming section that forms an image. Hereinafter, as an example of the flow of image formation in the image forming apparatus 1, a case where the operation mode is set to copy mode will be briefly described.

In the copy mode, a plurality of documents to be copied are set on the automatic document feeder 2, or a document to be copied is set on the image reading device 3. When the start button displayed on the operation panel 11 is pressed, the automatic document feeder 2 feeds the documents one by one to the image reading device 3. The image reading device 3 reads image information of each document sequentially sent from the automatic document feeder 2 or the document set in the image reading device 3. The image information read by the image reading device 3 is processed by, for example, an image processing section installed in the control device 12.

The writing unit 4 converts the image information processed by the image processing section into optical information. The photoreceptor drum 6 is uniformly charged by a charger placed opposite the photoreceptor drum 6, and then exposed to laser light containing converted optical information by the writing unit 4. An electrostatic latent image is formed on the photoreceptor drum 6 by exposure. The developing device 7 develops the electrostatic latent image on the photoreceptor drum 6 and forms a toner image on the photoreceptor drum 6 . The conveyor belt 8 transfers the toner image onto a paper medium or the like. The fixing device 9 fixes the toner image onto a paper medium or the like. Then, the transfer paper on which the original image has been copied is discharged from the discharge section.

For example, the standby mode (=normal mode) mentioned above is the state until the start button is pressed in copy mode, and the operating mode (=normal mode) is the state from when the start button is pressed until paper media etc. are ejected. This is the state until the In the normal mode in which the power supply device 13 generates the DC voltages DC24, DC5, and DC5X, a load such as a motor operates or can operate upon receiving the DC voltage DC24.

After the active mode ends, the state of the image forming apparatus 1 returns to the standby mode, and when the standby mode continues for a predetermined period of time, the image forming apparatus 1 enters the energy saving mode (sleep state). Then, upon receiving the high-level energy saving signal ECO, the power supply device 13 stops generating the direct current voltages DC24 and DC5. If the operation panel 11 is operated during the energy saving mode, the state of the image forming apparatus 1 returns to the standby mode. In this case, the power supply device 13 receives the low-level energy saving signal ECO and restarts generation of the direct current voltages DC24 and DC5.

The operation panel 11 receives various inputs according to user operations, and displays various information on the display section of the operation panel 11. For example, the information displayed on the operation panel 11 is information indicating the operation for which the input has been accepted, information indicating the operating status of the image forming apparatus 1, information indicating the setting state of the image forming apparatus 1, or the like. The control board to which the operation panel 11 is connected operates constantly by receiving the direct current voltage DC5X. Therefore, the operation panel 11 can accept various inputs not only during the normal mode but also during the energy saving mode. The operation panel 11 is an example of an external interface section that accepts operations from the outside.

The control device 12 controls the overall operation of the image forming apparatus 1, such as controlling the printer unit 5, controlling communication, and controlling input to the operation panel 11, by causing a built-in controller such as a CPU to execute a control program. do. Then, the control device 12 performs image processing or data processing by executing an image processing program or a data processing program, and forms an image to be transferred to a paper medium or the like. Since the control device 12 operates in response to the direct current voltage DC5, it stops operating during the energy saving mode.

Note that FIG. 8 shows an example in which the power supply device 100 shown in FIG. 1 or the power supply device 110 shown in FIG. 6 is installed in the image forming apparatus 1 as the power supply device 13. However, the power supply device 100 shown in FIG. 1 or the power supply device 110 shown in FIG. 6 is supplied with multiple types of DC voltages DC24, DC5, and DC5X, and can be installed in electronic equipment in which the DC voltages DC24 and DC5 are not used during energy saving mode. It is.

Aspects of the present invention are, for example, as follows.
<1>
A first converter section that generates a first voltage according to an input voltage regardless of the first mode or the second mode;
a first transistor that is turned on during the first mode to output the first voltage as a second voltage, and turned off during the second mode to stop outputting the second voltage;
a second converter unit that generates a third voltage during the first mode and stops generating the third voltage during the second mode;
While outputting the second voltage, a discharge path connected to the gate of the first transistor is turned on to turn off the first transistor in response to a decrease in the third voltage, and while outputting the second voltage is stopped. , a gate control unit that suppresses turning on of the discharge path in response to a decrease in the third voltage;
A power supply device comprising:
<2>
The power supply according to <1>, wherein the gate control unit suppresses turning on of the discharge path in response to a decrease in the third voltage when a voltage line that outputs the second voltage is short-circuited. Device.
<3>
The first voltage decreases together with the second voltage through the first transistor, which remains on due to suppression of turning on of the discharge path,
The power supply device according to <2>, wherein the first converter unit latches and stops based on the fact that the first voltage continues to decrease for a certain period of time.
<4>
a voltage detection unit that detects the voltage value of the second voltage;
is connected between the gate of the first transistor and a ground line, and when the voltage detection unit detects that the second voltage has decreased to a predetermined voltage higher than the ground voltage, the gate of the first transistor is grounded. The power supply device according to any one of <1> to <3>, further comprising a second transistor.
<5>
The power supply device according to any one of <1> to <4> above,
an image forming unit that forms an image using the second voltage and the third voltage during the first mode;
an external interface unit that receives an external operation using the first voltage during the second mode;
An image forming apparatus comprising:

Although the present invention has been described above based on each embodiment, the present invention is not limited to the requirements shown in the above embodiments. These points can be changed without detracting from the gist of the present invention, and can be determined appropriately depending on the application thereof.

1 Image forming device 2 Automatic document feeder 3 Image reading device 4 Writing unit 5 Printer unit 6 Photosensitive drum 7 Developing device 8 Conveyance belt 9 Fixing device 10 Paper feed tray 11 Operation panel 12 Control device 13 Power supply device 20 Smoothing section 30 Converter Section 31 Control section 32 Pulse width determination section 33 Current detection section 34 Constant voltage generation section 35 Output feedback section 36 Smoothing section 40 Power supply section 50 Converter section 51 Control section 52 Main circuit 60 Discharge section 70 Current detection section 80 Stop section 90 Voltage Detection unit 100, 110, 200 Power supply AC AC power supply D1, D2 Diode DB Diode bridge DC5, DC5X, DC24 DC voltage ECO Energy saving signal Q1, Q2, Q3 Transistor T1 Transformer Tr1, Tr2 Transistor Vin AC voltage

JP2019-62657A

Claims (5)

a first converter section that generates a first voltage according to an input voltage regardless of the first mode and the second mode;
a first transistor that is turned on during the first mode to output the first voltage as a second voltage, and turned off during the second mode to stop outputting the second voltage;
a second converter unit that generates a third voltage during the first mode and stops generating the third voltage during the second mode;
While outputting the second voltage, a discharge path connected to the gate of the first transistor is made conductive in response to a decrease in the third voltage to turn off the first transistor, and while outputting the second voltage is stopped. , a gate control unit that suppresses conduction of the discharge path in response to a decrease in the third voltage;
A power supply device comprising: The power supply device according to claim 1, wherein the gate control unit suppresses conduction of the discharge path according to a decrease in the third voltage when a voltage line that outputs the second voltage is short-circuited. . The first voltage decreases together with the second voltage through the first transistor that remains on due to suppression of conduction of the discharge path,
The power supply device according to claim 2, wherein the first converter unit latches and stops based on the fact that the first voltage continues to decrease for a certain period of time. a voltage detection unit that detects the voltage value of the second voltage;
a second transistor connected to the gate of the first transistor, which grounds the gate of the first transistor when the voltage detection section detects that the second voltage has decreased to a predetermined voltage higher than a ground voltage; The power supply device according to claim 1, further comprising a power supply device. The power supply device according to any one of claims 1 to 4,
an image forming unit that forms an image using the second voltage and the third voltage during the first mode;
an external interface unit that receives an external operation using the first voltage during the second mode;
An image forming apparatus comprising:

Images