JP2000232777A - Power supply device and its drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a power supply device that has a simple configuration and can suppress ringing for stabilizing output, and a drive circuit of the power supply device that has a simple configuration and can prevent errors in operation, when turning on an input voltage again. SOLUTION: A high-voltage power supply part 14 is provided with a booster transformer 20, a rectifier filter circuit 22, a switching circuit 24, a voltage detection circuit 26, a control circuit 28, a D/A conversion circuit 30, and an starter circuit 32. A tuning capacitor 44 is connected between the other terminal of a primary coil winding 36 and a terminal of a bias coil winding 38, while the starter circuit 32 is composed of an offset voltage power supply 66, a resistor 68, and a voltage level conversion circuit 74. When a PWM signal is outputted from a main control part 18, a transistor 42 is turned on by a start-up current from the starter circuit 32. When the transistor 42 is turned on, a rush current is suppressed by the tuning capacitor 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device and a drive circuit of the power supply device, and more particularly to a power supply device and a drive circuit of the power supply device which can be used in an electrophotographic printer, a copying machine, and the like.

[0002]

2. Description of the Related Art In an electrophotographic printer, a copying machine or the like, the output stability of a high voltage power supply for development affects the uniformity of image quality. In recent years, the demand for high image quality has increased, and a wide range of output control of a DC component is required in a high voltage power supply for development for functions such as environmental control, density control on a photoreceptor, and a photograph mode set by a user. I have. Similarly, the charging power supply device and the transfer power supply device also need to control the output of a wide range of DC components.

Conventionally, as such a power supply device, a self-excited RCC having a relatively simple circuit configuration and excellent in cost has been known.
(Ringing choke converter) circuit. FIG.
FIG. 1 shows an example of such a self-excited RCC circuit. As shown in FIG. 11, the self-excited RCC circuit includes a switching transistor 4 via a starting resistor 90 connected between the DC power supply 16 and a base terminal of the switching transistor 42.
When a start-up current flows through the base terminal of the switching transistor 42, a voltage is applied to the primary winding 36, and an induced voltage proportional to this voltage is generated in the bias winding 38. And the switching transistor 42 is turned on. When the induced voltage disappears, the switching transistor 4
2 is turned off, and thereafter, when all the excitation energy of the transformer 20 is released, a kick voltage is generated in a direction of forward biasing the base terminal of the switching transistor 42, and the switching transistor 42 is turned on again. In this way, self-oscillation generates a high voltage.

In such a self-excited RCC circuit, there is a problem that the turn-off operation becomes unstable due to the ringing of the current flowing through the primary winding 36 of the transformer 20. Techniques such as combining a regulation circuit, dividing the capacitance between the secondary windings to suppress ringing, inserting a diode, and delaying turn-on timing have been proposed (Japanese Patent Publication No. 3-57709). Etc.).

[0005]

However, the above-mentioned prior art has a problem that the number of parts increases and the cost increases. In addition, the current on the primary winding 36 side in the above-mentioned self-excited RCC circuit is determined by the capacitance between the secondary winding 40 side and
A rush current flowing through a so-called distributed capacitance due to the capacitance between the primary and secondary windings generated between the primary winding 36 and the secondary winding 40;
And the current flowing through the inductance component (so-called leakage inductance) of the primary winding 36. Ringing occurs because the leakage inductance resonates with the distributed capacitance.

In addition, such a drive circuit of the self-excited RCC circuit inputs an input voltage (for example, 24 V) to the transformer 20 to a base terminal of the switching transistor 42 through a starting resistor 90 as shown in FIG. Some include an on / off circuit 92 including a resistor, a diode, a transistor, and the like. When the power supply device is turned off, such a drive circuit operates the main control unit 1.
ON / OFF circuit 92 according to the ON / OFF signal output from
Is turned on to prevent the start-up current from flowing through the switching transistor 42. When the power supply is turned on, the transistor of the on / off circuit 92 is turned off, and the start-up current flows through the start resistor 90 to the base terminal of the switching transistor 42. So that it flows to

In such a configuration, when paper jam occurs in a printer or the like and paper is removed, the input power is once turned off, and the input power is turned on again when resuming. There has been a problem that the input voltage fluctuates and the drive circuit malfunctions. Also,
When the power supply device is off, a current flows to the transistor of the on / off circuit 92, so that not only wasteful power is consumed, but also the on / off circuit 92 includes the resistor, the diode, the transistor, and the like as described above. There has been a problem that the cost increases and the size of the circuit cannot be reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. A power supply device capable of suppressing ringing with a simple configuration and stabilizing an output voltage, and a power supply device having a simple configuration for re-inputting an input voltage. It is an object of the present invention to provide a drive circuit of a power supply device capable of preventing malfunction of the power supply device.

[0009]

According to a first aspect of the present invention, there is provided a power supply apparatus comprising: an input winding having one end inputting power; A transformer having a bias winding in which electric power is induced, and a transformer having an output winding; one end connected to the other end of the input winding, and a control input end connected to the bias winding; Switching means for switching the application of power to the input winding according to the power induced in the
And a current suppressing means connected between the other end of the input winding and the control input end of the bias winding, for suppressing a current flowing through the switching means and the control input end. I have.

According to the first aspect of the present invention, power corresponding to the power applied to the input winding is induced in the output winding and the bias winding, and the power induced in the bias winding is generated by the power induced in the bias winding. The switching means is turned on, and when the induced power disappears, the switching means is turned off. When all the excitation energy of the transformer is released, a kick voltage is generated in a direction of forward biasing the control input terminal of the switching means, and the switching means is turned on again. In this way, the switching means self-oscillates to switch the power applied to the input winding. As the switching means, for example, a transistor or a MOS-FET can be used.

Since the current suppressing means is connected between the other end of the input winding and the bias winding, the current to the control input terminal when the switching means is turned on is suppressed. For this reason, it is possible to prevent a rush current (inrush current) due to the distributed capacitance due to the output inter-winding-side capacitance and the input-output inter-winding capacitance generated between the input winding and the output winding from flowing to the switching means. it can. Therefore, occurrence of ringing can be prevented, and the output is stabilized. For example, a capacitor can be used as the current suppressing means.

According to a second aspect of the present invention, there is provided an input winding to which power is input to one end, a bias winding for inducing power according to the power applied to the input winding, and an output winding. And a control input terminal, one end of which is connected to the other end of the input winding and the control input end of which is connected to the bias winding, and which supplies power to the input winding in accordance with power induced in the bias winding. Switching means for switching the application;
In the drive circuit of the power supply device for starting the power supply device based on an external remote signal, the power supply device is started by inputting the external remote signal to a control input terminal of the switching means via at least a resistor. It is characterized by doing.

According to the second aspect of the present invention, the current caused by the external remote signal is suppressed by the resistor and becomes a starting current for starting the power supply device. As this external remote signal, for example, a PWM signal can be used. Therefore,
It is possible to prevent a malfunction of the drive circuit due to an input voltage fluctuation at the time of re-input of the input power, as in the case where the input voltage of several tens of volts is input to the switching means via the starting resistor as in the related art and the power supply is started. . In addition, since an on / off circuit is not required, current does not flow to a transistor of the on / off circuit when the power supply device is turned off as in the related art, so that useless power is not consumed. Further, the size of the apparatus can be reduced and the cost can be reduced.

According to a third aspect of the present invention, there is provided an input winding to which power is input at one end, a bias winding for inducing power according to the power applied to the input winding, and an output winding. And a control input terminal, one end of which is connected to the other end of the input winding and the control input end of which is connected to the bias winding, and which supplies power to the input winding in accordance with power induced in the bias winding. Switching means for switching the application;
Input means for inputting an external remote signal for starting to a control input terminal of the switching means via at least a resistor, and connected between the other end of the input winding and the control input end of the bias winding. And a current suppressing means for suppressing a current flowing through the switching means and the control input terminal.

According to the third aspect of the present invention, a current suppressing means for suppressing a current flowing through the switching means and the control input terminal, and an external remote signal for starting the control input terminal of the switching means via at least a resistor. Since the input means for inputting to the input circuit is provided, it is possible to prevent the occurrence of ringing and to stabilize the output, and also possible to prevent the malfunction of the drive circuit due to the fluctuation of the input voltage.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. In this embodiment, the present invention is applied to a developing bias power supply, a transfer bias power supply, and a charging bias power supply for a copying machine, a printer, or the like.

As shown in FIG. 2, a power supply device 10 according to the present embodiment includes a high-voltage power supply unit 14 for supplying high-voltage power for supplying to a load 12, a DC power supply 16 for generating a predetermined DC voltage, and A main control unit 18 is provided to control the operation of the entire apparatus.

The high-voltage power supply section 14 includes a step-up transformer 20, a rectifying / smoothing circuit 22, a switching circuit 24, a voltage detection circuit 26, a control circuit 28, a D / A conversion circuit 30, and a start-up circuit 32.

As shown in FIG. 1, the step-up transformer 20 includes an iron core 34, a primary winding 36, a bias winding 38, and a secondary winding 40. One terminal of the primary winding 36 is connected to the DC power source 16 is applied the generated DC voltage V _in (eg 24V) by the DC power source 16, power is the secondary winding 40 side and in accordance with this It is induced on the bias winding 38 side. The other terminal of the primary winding 36 is connected to the collector terminal of the transistor 42 of the switching circuit 24 and one terminal of the tuning capacitor 44. When the transistor 42 is turned on and off, the application of power to the primary winding 36 is switched.

One terminal of the secondary winding 40 is connected to the cathode terminal of the diode 46, and the other terminal is grounded. The anode terminal of the diode 46 is connected to one terminal of a capacitor 48 whose other terminal is grounded,
2 is connected to one terminal. The current induced on the secondary winding 40 side is rectified and smoothed by the diode 46 and the capacitor 48, and output to the load 40 via the resistor 52.

The other terminal of the resistor 50 is connected to the input terminal of the voltage detection circuit 26, and the output terminal of the voltage detection circuit 26 is connected to one input terminal of the comparison circuit 54 of the control circuit 28. . The voltage detection circuit 26 includes, for example, an operational amplifier, a resistor, and a capacitor, as shown in FIG. 3, detects a voltage output to the load 12, and outputs the voltage to the comparison circuit 54 as a voltage monitor value V _mon .

On the other hand, one terminal of the bias winding 38 is
The other terminal of the tuning capacitor 44 and the capacitor 56 are connected to the anode terminal of a diode 58 connected in parallel. The other terminal of the bias winding 38 is grounded. The cathode terminal of the diode 58 is connected to one terminal of the resistor 60, and the other terminal of the resistor 60
The transistor 42 is connected to a base terminal, and the emitter terminal of the transistor 42 is connected to one terminal of a resistor 64 to which a capacitor 62 is connected in parallel. The other terminal of the resistor 64 is grounded.

The base terminal of the transistor 42 is
The offset voltage power supply 66 of the starting circuit 32, one terminal of the resistor 68, and the anode terminal of the diode 70 are connected. . The offset voltage power supply 66 includes, as an example, a resistor, a zener diode, and a capacitor, as shown in FIG. The other terminal of the resistor 68 is connected to the cathode terminal of the diode 72, and the anode terminal of the diode 72 is connected to the output terminal of the voltage level conversion circuit 74. The input terminal of the voltage level conversion circuit 74 is connected to the output terminal of the main controller 18.

The main control unit 18 includes, for example, a CPU, a ROM,
A RAM, an input / output (I / O) circuit, and the like are each configured by a microcomputer or the like connected by a bus. An output terminal of the main control unit 18 is also connected to an input terminal of the D / A conversion circuit 30, and outputs a PWM signal corresponding to a voltage to be supplied to the load 12. For example, if the duty value of the PWM signal increases, the output voltage to the load 12 increases, and if the duty value decreases, the output voltage decreases.

The PWM signal is supplied to a voltage level conversion circuit 7.
4 and converted to a predetermined voltage level by the voltage level conversion circuit 74, and then input to the base terminal of the transistor 42 via the diode 72 and the resistor 68 as a starting current. The voltage input to the base terminal of the transistor 42 is offset by a voltage equal to or lower than a predetermined voltage (for example, 2.5 V) by an offset voltage power supply 66 for stabilization. The voltage level conversion circuit 74 is unnecessary depending on the voltage level of the PWM signal. In addition, the voltage level conversion circuit 74 and the D / A conversion circuit 30 include, for example, a transistor, a resistor, and a capacitor as shown in FIG.

The output terminal of the D / A conversion circuit 30 is
4 is connected to the other input terminal. D / A conversion circuit 3
0 indicates that the PWM signal output from the main control unit 18 is D / A
Convert the analog signal (target voltage value) to the comparison circuit 5
Output to 4. The comparison circuit 54 is connected to the base terminal of the transistor 76 and to the voltage detection circuit 26. The emitter terminal of the transistor 76 is grounded, and the collector terminal is connected to the cathode terminal of the diode 70. As an example, as shown in FIG. 3, the comparison circuit 54 includes an operational amplifier, a capacitor, and a resistor, and outputs the voltage monitor value V _mon output from the voltage detection circuit 26 and the D / A conversion circuit 30. The base voltage of the transistor 42 is controlled by comparing the target voltage value and controlling the on / off of the transistor 76 so that the output voltage to the load 12 substantially matches the target voltage.

Next, the operation of this embodiment will be described.

When the main controller 18 outputs a PWM signal as shown in FIG.
The voltage level is converted to a predetermined voltage by the
A starting current flows to the base terminal of the transistor 42 via the resistor 2 and the resistor 68. The voltage level conversion circuit 7 at this time
4 (voltage output to the point a in FIG. 3) the output voltage V _a of the (voltage output to the point b in FIG. 3) the voltage V _b applied to the base terminal of the transistor 42, the base current I _b of the waveform Have waveforms as shown in FIGS. 4B, 4C, and 4D, respectively. The voltage V _b applied to the base terminal of the transistor 42 a predetermined voltage (for example, 2.
5V) offset.

The starting current causes a collector current I _{C of the} transistor 42 as shown in FIG. 4E to flow, and a voltage is applied to the primary winding 36. Then, as shown in FIG. 5 (E), the induced voltage V _X which is proportional to the voltage applied to the primary winding 36 is generated in the bias winding 38.

The induced voltage V _X generated in the bias winding 38
Since the current is further supplied to the base terminal of the transistor 42 through the resistor 60 to increase the base current, the transistor 42 is turned on, and the on period starts.

At the time of the turn-on, a rush current I _X (portion a in FIG. 5) due to the distributed capacitance as shown in FIG. 5D flows through the tuning capacitor 44, so that the base current I _b of the transistor 42 is suppressed. It is possible to sufficiently suppress the occurrence of the ringing of the collector current I _C as in the prior art shown in FIG. 12 (B), and to minimize the change in the ringing amplitude with respect to the change in the output voltage to the load 12. And the turn-on operation can be stabilized. Incidentally, FIG. 12 (A), (C) the collector of the transistor 42 in the prior - respectively show emitter voltage V _ce and the base current I _b.

[0032] In the on period, the current flowing through the primary winding 36, that is, the collector current I _C of the transistor 42 to excite the transformer 20 increases almost linearly with the ringing, the base current I _b by resistor 60 It is suppressed and gradually decreases. Therefore, the current flowing through the input winding,
That is, the collector current I _C is saturated at the value represented by the following equation (1), the induced voltage V _X of the bias winding 38 disappears, the transistor 42 is turned off, and the off period starts.

I _C = H _fe × I _b (1) where H _fe is the current amplification factor of the transistor 42.

At the time of this turn-off, the tuning capacitor 4
4, the supply of the base current Ib can be gently stopped by the current _IX (portion _{b in} the figure), so that the collector-emitter voltage V of the transistor 42 shown in FIG. It is possible to prevent a surge voltage from being generated in _CE . Therefore, noise is reduced and the output voltage can be stabilized. In addition, transistor 4
2 and the voltage stress on elements such as the transformer 20 are reduced.

[0035] In the off period, the induced voltage V _X of the bias winding 38 for reverse biasing the base terminal of the transistor 42 to a negative voltage, the excitation energy of the transformer 20 is released from the secondary winding 34 to the load 12 side Until the off period is maintained.

[0036] When the exciting energy of the transformer 20 is released to all load 12 side, rapidly although the induced voltage V _X of the bias winding 38 disappears, the base terminal of the transistor 42 by the leakage inductance and distributed capacitance of the transformer 20 Ringing occurs in the direction of forward biasing, and the transistor 42 is turned on again. In this manner, the transistor 42 keeps oscillating by repeating the on / off operation. As a result, a high voltage of several kV (for example, 1 kV) is supplied to the load 12. When the voltage value supplied to the load 12 is higher than the target voltage value, the comparison circuit 54 turns on the transistor 76 to draw in the base current flowing to the transistor 42. Thereby, the voltage value supplied to the load 12 is maintained at the target voltage value. When the supply of the high voltage to the load 12 is stopped, the duty value of the PWM signal output from the main control unit 18 is set to 0.

As described above, the tuning capacitor 44
Because the operation at the time of turn-on and turn-off is stable,
Output voltage can be stabilized, so development, transfer,
In addition, charge supply such as charging is stabilized, and uniformity of image quality can be maintained. In addition, a circuit for suppressing snubber energy at the time of turn-off, which was required in the past, becomes unnecessary,
The device can be downsized.

Further, since the transistor 42 is activated by the PWM signal whose voltage level has been converted, it is possible to prevent a malfunction of the activation circuit when the power is turned on again as in the prior art. ,
Cost can be reduced.

Next, another example of the power supply device 10 will be described with reference to FIG.
This will be described with reference to FIGS. In addition, the power supply device 1 of FIG.
The same reference numerals are given to the same portions as 0, and the detailed description thereof will be omitted.

The power supply device 10 shown in FIG. 6 is the same as the power supply device 10 shown in FIG. 1 except that a MOS-FET 42 is used instead of the transistor 42 shown in FIG.

In the power supply device 10 shown in FIG. 7, one terminal of the tuning capacitors 44A and 44B is connected to the other terminal of the primary winding 36. One terminal of the tuning capacitor 44A is connected to the anode terminal of the diode 80, and the cathode terminal of the diode 80 is connected to one terminal of the bias winding 38. Capacitor 44B
Is connected to the cathode terminal of the diode 82, and the anode terminal of the diode 82 is connected to one terminal of the bias winding 38. The rest is the same as the power supply device 10 shown in FIG.

The power supply device 10 shown in FIG.
Is connected to one terminal of a tuning capacitor 44, and the other terminal of the tuning capacitor 44 is connected to one terminal of a resistor 84. The other terminal of the resistor 84 is connected to one terminal of the bias winding 38. The rest is the same as the power supply device 10 shown in FIG.
The power supply device shown in FIGS. 6 to 8 operates almost in the same manner as the power supply device 10 shown in FIG.

Next, another example of the starting circuit 32 of the power supply device 10 will be described with reference to FIGS. In addition,
The same parts as those of the activation circuit 32 of FIG.
Detailed description is omitted.

The starting circuit 32 shown in FIG. 9 is the same as the starting circuit 32 shown in FIG. 1 except that the offset voltage power supply 66 and the diode 72 are not provided. The starting circuit 32 shown in FIG. 10 is the same as the starting circuit 32 shown in FIG. 1 except that the diode 72 is not provided. Such an activation circuit 32 shown in FIGS. 9 and 10 operates almost in the same manner as the activation circuit 32 shown in FIG.

In the present embodiment, the power supply device 10 applied to the self-excited RCC circuit by combining the tuning capacitor 44 and the starting circuit 32 using an external remote signal has been described. May be applied. Further, in this embodiment, the power supply device that generates a high voltage of several kV has been described.
It goes without saying that the present invention is also applicable to a power supply device that outputs a voltage of about 0 V to several 100 V.

[0046]

As described above, according to the first aspect of the present invention, between the other end of the input winding and the bias winding,
Since the switching means and the current suppressing means for suppressing the current flowing to the control input terminal of the switching means are provided, the capacity between the output winding and the capacity between the input and output windings generated between the input winding and the output winding are reduced. As a result, the rush current due to the distributed capacitance can be suppressed, so that the occurrence of ringing can be prevented, and the output voltage is stabilized.

According to the second aspect of the present invention, the current due to the external remote signal is suppressed by the resistance and becomes the starting current for starting the power supply device. Therefore, the drive circuit due to the input voltage fluctuation when the input power is turned on again. Can be prevented from malfunctioning, and an on / off circuit is not required, so that the device can be downsized and cost can be reduced.
It has the effect of.

According to the third aspect of the present invention, the switching means and the current suppressing means for suppressing the current flowing to the control input terminal and the external remote signal for starting the control input terminal of the switching means via at least a resistor. Since the input means for inputting to the input circuit is provided, it is possible to prevent the occurrence of ringing and to stabilize the output, and to prevent malfunction of the drive circuit due to input voltage fluctuation.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an example of a circuit configuration of a high-voltage power supply unit of a power supply device.

FIG. 2 is a block diagram illustrating a schematic configuration of a power supply device.

FIG. 3 is a circuit diagram illustrating an example of a detailed circuit configuration of a high-voltage power supply unit of the power supply device.

FIG. 4 is a waveform diagram showing operation waveforms of each part of the high-voltage power supply unit at the time of startup.

FIG. 5 is a waveform diagram showing operation waveforms of each unit of the high-voltage power supply unit at a regular time.

FIG. 6 is a circuit diagram showing another example of the circuit configuration of the high-voltage power supply unit of the power supply device.

FIG. 7 is a circuit diagram showing another example of the circuit configuration of the high-voltage power supply unit of the power supply device.

FIG. 8 is a circuit diagram showing another example of the circuit configuration of the high-voltage power supply unit of the power supply device.

FIG. 9 is a circuit diagram showing another example of the circuit configuration of the high-voltage power supply unit of the power supply device.

FIG. 10 is a circuit diagram showing another example of the circuit configuration of the high-voltage power supply unit of the power supply device.

FIG. 11 is a circuit diagram showing an example of a circuit configuration of a conventional power supply device.

FIG. 12 is a waveform diagram showing operation waveforms of various parts of a conventional high-voltage power supply unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 power supply device 12 load 14 high-voltage power supply unit 16 DC power supply 18 main control unit 20 step-up transformer 22 rectifying and smoothing circuit 26 voltage detection circuit 28 control circuit 30 D / A conversion circuit 32 start-up circuit (drive circuit) 34 secondary winding (output) Winding) 36 primary winding (input winding) 38 bias winding 42 transistor 44 tuning capacitor (current suppressing means) 68 resistor

Claims (3)

[Claims] A transformer having an input winding to which power is input to one end, a bias winding in which power according to the power applied to the input winding is induced, and an output winding; A switching means connected to the other end of the input winding and a control input end connected to the bias winding, for switching application of power to the input winding in accordance with power induced in the bias winding; And a current suppressing means connected between the other end of the input winding and the control input end of the bias winding, for suppressing a current flowing through the switching means and the control input end. A transformer having an input winding to which power is input to one end, a bias winding for inducing power according to the power applied to the input winding, and an output winding; A switching means connected to the other end of the input winding and a control input end connected to the bias winding, for switching application of power to the input winding in accordance with power induced in the bias winding; And a drive circuit for the power supply device that starts up the power supply device based on an external remote signal, comprising: inputting the external remote signal to a control input terminal of the switching unit via at least a resistor. A drive circuit of a power supply device, which is activated. A transformer having an input winding to which power is input to one end, a bias winding for inducing power according to the power applied to the input winding, and an output winding; A switching means connected to the other end of the input winding and a control input end connected to the bias winding, for switching application of power to the input winding in accordance with power induced in the bias winding; An input means for inputting an external remote signal for starting to a control input terminal of the switching means via at least a resistor; and a connection between the other end of the input winding and the control input end of the bias winding. And a current suppressing means for suppressing a current flowing through the switching means and the control input terminal.