JPS61288730A - Power source unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply device, and more particularly to a power supply device that excites a converter transformer by a switching means and obtains a high voltage output on its secondary side.

[Summary of the Disclosure] This specification and drawings describe a switching means connected to the primary side of a converter transformer, a means for controlling the switching means, and a means for applying an alternating current signal to the primary side of the converter transformer. , a means for separating an AC component of a superimposed signal of AC and DC supplied to a DC load provided on the secondary side of the converter transformer and outputting it to another AC load; and power supply to the DC and AC loads. Stable supply of different electric power to a plurality of AC and DC loads by means of controlling the switching means according to the output and stabilizing the outputs for both DC and AC loads, This invention discloses a technology for configuring a power supply section in a simple, inexpensive, lightweight, and compact manner.

[Prior Art] In devices such as copying machines and laser beam printers, a high-voltage power source is used as a power source for a charger that charges a photoreceptor, and a direct current is superimposed on an alternating current to control the developing conditions of a developing device as desired. Requires power supply to obtain developing bias.

[Problems to be Solved by the Invention] This type of device generally converts and stabilizes the commercial power supply to a low voltage of about 24V, and then boosts the voltage by passing it through a high voltage power supply again.
A configuration for rectification is adopted.

Furthermore, in conventional devices, the high-voltage DC power supply for the charger and the power supply for producing an output of alternating current and direct current for the developing bias are constructed as separate independent units, and both are configured by boosting the low-voltage power supply to obtain the desired output. voltage was obtained. In particular, since the AC and DC power supplies for the developing device are generated separately using independent converters, the configuration of the power supply section tends to become complicated, making it extremely difficult to reduce the size and weight.

[Means for Solving the Problems] In order to solve the above problems, the present invention includes a switching means connected to the primary side of the converter transformer, a means for controlling the switching means, and a switching means connected to the primary side of the converter transformer. means for applying an alternating current signal to the primary side of the
Means for separating an AC signal from a signal obtained by superimposing AC and DC signals provided to a DC load provided on the secondary side of the converter transformer and outputting it to another AC load; and a power supply output for the DC and AC loads. A configuration is adopted in which means is provided to control the switching means according to the conditions and stabilize the outputs for both DC and AC loads.

[Function] In the basic circuit of the present invention, as shown in FIG.
The primary winding of the converter transformer T1 is a transistor Tr.
It is excited by i. The power generated on the secondary side is rectified and smoothed by the diode Di and the capacitor C3, and is then supplied to the load. The load current is detected as a voltage via the resistor R5, and the error amplifier 3 outputs P in response to this detection signal.
The output current is stabilized by changing the duty ratio of a switching signal generated by a WM (pulse width modulator).

The reference voltage of the error amplifier 3 is inputted via a resistor R7, and a relatively low frequency AC signal output from the oscillator 2 is added to this voltage via a resistor R6. Therefore, the output voltage level varies with the frequency of the oscillator 2. By taking out this exchange power through the coupling capacitor C2, power is supplied from the terminal 02 to other loads. In the case of FIG. 1, the DC bias generated by the DC bias generation circuit 1 is superimposed on the extracted exchange circuit and output.

In addition to the above configuration, an LPF (low pass filter) 6 is connected between the detection resistor R5 and the error amplifier 3 as shown in FIG. The output current can be stabilized according to the current. According to this configuration, it is possible to reduce the influence of the exchange input as a change in the input voltage on the primary side of the transformer by the transistors Tr2 and Tr3 on the loop response of the output control, and to apply the output of the terminal O1 to the developing bias of the copying machine. When used as a developer, it is possible to easily increase the frequency of the developing bias.

In addition, as shown in FIG. By adjusting the addition amount of AC,
AC and DC components can be stabilized independently.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a power supply circuit that uses a single transformer to supply power to a charger and a developer of an image forming apparatus.

A low power supply voltage V is applied to the primary winding 11 of the converter transformer T1 via a choke coil L1 and a capacitor C1.
cc is supplied, and the other end of the winding is connected to a transistor Tr.
It is designed to be interrupted by i. transistor T
A damper diode D2 and a resonance capacitor C4 are connected between the collector and emitter (ground) of ri.

Switching of transistor Tri is controlled by PWM5. The PWM 5 adjusts the duty ratio of the rectangular wave generated by the oscillator 4 according to the output of the error amplifier 3, and controls the output of the transformer. The high voltage output of the secondary winding J2 of the converter transformer TI is connected to the diode D1 and the capacitor C.
3, and is supplied from terminal 02 to the charger via resistor R3 for preventing sparks. A current corresponding to the load current flows through the resistor R4, and this current is detected as a voltage corresponding to the load current via the resistor R5.

A voltage corresponding to the detected load current is input to one input terminal of the error amplifier 3. A reference voltage corresponding to a predetermined load current is input to the other input of the error amplifier 3 via a resistor R7. Further, the output of an oscillator 2 that generates a rectangular wave is input to the same terminal via a capacitor C5 and a resistor R6. On the other hand, the rectified and smoothed output of the first winding J2 is taken out via the coupling capacitor C2, and the DC voltage generated by the DC bias generation circuit l under the control of the input terminal I2 is superimposed on this via the coupling resistor R1 for protection. Resistance R2
It is output from the terminal 02 via the terminal 02 as a bias for the developing roller.

Next, the operation of the above configuration will be explained with reference to the waveform diagram of FIG. 2. Figure 2 shows, from the top, the output of oscillator 2, the output of oscillator 4, and the secondary winding t2 of converter transformer TI.
The rectified and smoothed outputs of , and the developing bias output of terminal 02 are shown, respectively.

Power supply voltage Vc is applied to primary winding No. 1 of converter transformer T1.
c, and the oscillator 4 is set to 20 as shown in the second row of FIG.
When the transformer is started to be excited by oscillating with a waveform of about 100 KHz, an alternating current is generated in the secondary winding 2 in accordance with the winding ratio. This current is rectified and smoothed by the diode D1 and the capacitor C3, and is supplied to the charger of the load via the resistor R3. This load current is detected via the resistor R5 and applied to the error amplifier 3, so the error amplifier 3 controls the PWM 5 according to the other input value and controls the output current.

A voltage corresponding to a predetermined load current is input to the input terminal I2, and the output of the oscillator 2 is added to the input terminal I2 by resistors R6 and R7. Since the oscillator 2 outputs a frequency of 1 to 2 KHz, which is lower than the output of the oscillator 4 in the second stage of the figure, as shown in the upper stage of Fig. 2, the energization ratio of the converter transformer TI is controlled by the PWM 5 accordingly. As a result, the rectified output on the secondary side of the converter transformer Tl has a DC level of about 5 KV and a superimposed AC amplitude of 1.2 KVp-p, as shown in the third row of FIG. This high voltage output is supplied to a charger.

On the other hand, this output is taken out via capacitor C2,
The DC bias output from the DC bias generation circuit 1 is superimposed. The control input from terminal 1 of the DC bias generation circuit 1 is such that the output from terminal 02 is 2 as shown in the bottom row of Figure 2.
The amplitude is adjusted to be centered around 00V.

As described above, both the high-voltage direct current for the charger and the developing bias in which direct current is superimposed on alternating current can be outputted by a circuit using a single converter transformer. Therefore, in the conventional device, an alternating current using three independent transformers,
This has the advantage that the DC power supply circuit can be shared, the configuration of the power supply section can be made simple and inexpensive, and the entire device can be made smaller and lighter.

In the above embodiment, a configuration for stabilizing the load current to the charger was exemplified, but a configuration for stabilizing the load voltage as shown in FIG. 3 is also conceivable. In the case of FIG. 3, the rectified and smoothed output of the converter transformer Tl is divided by resistors R4 and R5 and returned to the input of the error amplifier 3. The other configurations are exactly the same as in the case of FIG. According to such a configuration, a value corresponding to the voltage applied to the charger of the load is extracted from the output terminal 02 as the terminal voltage of the resistor R5, and the PWM 5 controls oscillation based on this value. Constant voltage power supply can be performed.

In the above-mentioned embodiment, the reference voltage of the error amplifier 3 is fluctuated by the output of the oscillator 2 to obtain a high voltage output with a superimposed exchange, but in the case of Fig. 4, the converter transformer T
The power supply side of 2 is controlled by an oscillator 2. The output of the oscillator 2 is connected to the base of the transistor Tr2 via a coupling capacitor C5 and a resistor R6. Resistors R6, R8, and R9 are constituted by transistors Tr2 and Tr3, and determine the amplification factor of the emitter follower circuit whose output is connected to winding -41.

With this configuration, AC superposition is performed, and in the embodiment shown in FIG. 4, an LPF (low-pass filter) 6 is connected between the resistor R5 that detects the load current of the charger and the error amplifier 3, and the AC component is removed. The resulting signal is fed back to the error amplifier 3.

With such a configuration, it is possible to stabilize the output current according to the DC component. According to this configuration, the influence of the alternating current inputted as a change in the input voltage on the primary side of the transformer by the transistors Tr2 and Tr3 on the output control loop response can be reduced, and the output of the terminal 01 can be applied to the developing bias of the copying machine. When used as a developer, it is possible to easily increase the frequency of the developing bias.

Furthermore, in order to also control the superimposed alternating current component, a configuration as shown in FIG. 5 can be considered.

In the case of FIG. 5, the error amplifier 3 is installed before the PWM 5.
The error signal output from the oscillator 2 and the AC component output from the oscillator 2 are added. The amount of addition of the output of the oscillator 2 is adjusted by a variable gain amplifier 9.

The variable gain amplifier 9 has its gain controlled by the error signal output from the error amplifier 8. A voltage corresponding to a predetermined AC output is applied to one input of the error amplifier 8 via a terminal I3, and a capacitor C6 is applied to the other input.
An amount corresponding to the amplitude of the alternating current signal which has been voltage-divided by resistors R9 and RIO and then rectified by a rectifier 7 is applied.

According to the configuration shown in FIG. 5, the DC load at terminal 02, the
The output for the AC load can be freely controlled independently to the desired value.

In the embodiment shown in FIG. 6, the configuration shown in FIG. 5 is changed so that the input voltage of the converter transformer TI is controlled by a variable gain amplifier 9 as shown in FIG. Similar effects can also be obtained with such a configuration.

[Effects of the Invention] As is clear from the above description, according to the present invention, the switching means connected to the primary side of the converter transformer;
means for controlling the switching means; means for applying an AC signal to the primary side of the converter transformer; A means for separating the alternating current component and outputting it to another alternating current load, and a means for controlling the switching means according to the power supply output to the direct current and alternating current loads to stabilize the output for both the direct current and alternating current loads. Since it adopts a configuration that allows various AC and DC power supplies, which were previously independent, to be shared by using one converter transformer, the power supply part can be made simple, inexpensive, small and lightweight, and the equipment used is easy to use. It is possible to provide an excellent power supply device that can be used to reduce the overall cost and size, and can independently control both AC and DC loads and stabilize the output.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a power supply device according to the present invention;
FIG. 2 is a waveform diagram showing voltages at various parts of the circuit of FIG. 1, and FIGS. 3 to 6 are circuit diagrams showing different embodiments of the power supply device. l... DC bias generation circuit 2.4... Oscillator 5... PWM6... LP
F 7... Rectifier 9... Variable gain amplifier T1, T2... Converter transformer Tri-Tr3... Transistor (smoking circuit ml) ゛Figure 6

Claims (1)

[Claims] A switching means connected to the primary side of the converter transformer, a means for controlling the switching means, a means for applying an AC signal to the primary side of the converter transformer, and a DC signal provided on the secondary side of the converter transformer. means for separating an alternating current component of a signal in which alternating current and direct current are superimposed to be supplied to a load and outputting the separated alternating current to another alternating current load; A power supply device characterized in that it is provided with means for stabilizing both outputs with respect to an AC load.