JPS5849108B2 - Dengen Sochi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device that supplies power to an AC load and a DC load using a common inverter.

An example of a power supply device that operates an AC load and a DC load is one used in a copying machine.

In this type of copying machine, constant current characteristics are applied to the AC load.
It is desirable to provide a DC load with constant voltage characteristics.

In order to satisfy the characteristics required for each of the AC load and the DC load, it is sufficient to prepare a constant voltage power supply device and a constant current power supply device for each load and operate them at predetermined timings.

However, it is clear that providing a power supply device for each load increases the cost and increases the size of the entire device.

This invention was made in consideration of these circumstances,
For AC loads and DC loads that require constant voltage characteristics and constant current characteristics, respectively, using a common inverter and one control unit, select constant current characteristics for one and constant voltage characteristics for the other. The purpose of this invention is to provide a power supply device that can be used for a long time.

This invention makes the output transformer of the inverter a leakage type transformer, so that the output voltage of this inverter has constant voltage characteristics, and for loads that require constant current, this load current is detected and negative feedback control is performed. This not only satisfies the constant current property, but also connects the low potential side of the DC load in common with one end of the AC load, which makes it possible to share part of the output winding for the DC load and the winding for the AC load. , it is possible to easily supply the edges between these two windings.

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

1 is a DC power supply, and an inverter 2 is connected to this DC power supply 1.

This inverter 2 has a leakage type output transformer 3, and a primary winding 4 with an intermediate tap of the output 1 and the lance 3.
both ends of which are commonly connected to one pole of the DC power supply 1 via switching elements 5 and 6 such as transistors, respectively,
The center tap is connected to the other pole of the DC power supply 1.

Then, the output g. of the output transformer 3. IJ? This is provided with an AC load 8 and a DC load 12 as in the copying machine described above.

That is, the intermediate tapped secondary winding 7 of the output transformer 3
Both ends S.

, 83, and one end S on the low potential side.

A DC load 12 is connected between the capacitor 10 and the intermediate tap S2 via a rectifier 9 in series and a parallel circuit consisting of a capacitor 10 and a resistor 11 in parallel.

In addition, the edge S.

A capacitor 13 is connected between the tap S1 and the intermediate tap S1.

A current detection circuit 14 detects the load current of either the AC load 8 or the DC load 12.

This detection circuit 14 includes the AC load 8 and the DC load 12.
and one end S of the secondary winding 7.

In this embodiment, the load current of the AC load 8 is detected.

Such a current detection circuit 14 includes, for example, a common connection point between the AC load 8 and the DC load 12 and one end S of the secondary winding 7, as shown in FIG.

A full-wave rectifier circuit 29 is connected between both terminals of this resistor 27 via a DC cut capacitor 28 in series, and a voltage dividing circuit is connected between the output terminals of this rectifier circuit 29. It is possible to use a configuration in which resistors 30 and 31 are provided in series and a capacitor 32 is connected to the resistor 30 in parallel.

In this current detection circuit 14, a current ic, which is the weight of the load current ia of the AC load 8 and the load current ib of the DC load 12, flows through the resistor 27.
8 and rectify only the AC load current ia, the magnitude of the AC load current ia is output in the form of a DC voltage.

Reference numeral 16 denotes a voltage detection circuit, which is connected to the other secondary winding 15 of the output transformer 7, but is not directly related to the present invention.

Each detection output of each of the detection circuits 14 and 16 is inverted 2.
It is supplied to the control circuit 17 of.

This JP circuit 11 triggers a flip-flop 19 with the output of the oscillator 18, and sends set and reset outputs from the set output terminal S and the reset output terminal R of the flip-flop 19 to the switching element of the inverter 2 via AND circuits 20 and 21. -f5 and f6 are applied as control signals.

Further, the output of the oscillator 18 is converted into a rectangular wave by a waveform conversion circuit 22, and the time width of the rectangular wave is controlled by a time width control circuit 23, and is inputted to an AND circuit 20, 21 and applied to the switching elements 5 and 6. The time width of the control signal is controlled.

A time width control circuit 23 controls the time width of the rectangular wave according to the output of an error amplifier 26 to which the outputs of the current detection circuit 14 and voltage detection circuit 16 are collectively supplied via diodes 24 and 25. It is something to do.

Note that the detection circuit 16 includes, for example, a full-wave rectifier 33 connected between the secondary windings 15 as shown in FIG. A capacitor 37 is connected in parallel to the series circuit of a resistor 34 and a resistor 36, and a detection output is outputted between both terminals of the resistor 34 via a constant voltage diode 38.

Therefore, this voltage detection circuit 16 generates an output only when the output voltage of the inverter 2 exceeds a certain set voltage.

However, this voltage detection circuit 16 is not essential as described above.

Next, we will discuss the effect.

When the oscillator 18 of the control circuit 17 generates a pulse signal at a predetermined period as shown in FIG. As shown in d, outputs are generated alternately and input to AND circuits 20 and 21.

On the other hand, the output of the oscillator 18 is converted into a rectangular wave by the waveform conversion circuit 22, and the time width control circuit 23 outputs the time width t.
is controlled as shown in FIG. 3b, and the AND circuits 20, 2
input to the other input terminal of 1.

Therefore, as shown in FIG. 3e and f from the AND circuits 20 and 21, a control signal whose time width is controlled is applied to the output of the time width control circuit 23 to the switching elements -75 and -6, and -75, 6 are turned on alternately for times corresponding to the time width in synchronization with the oscillation synchronization of the oscillator 18.

As a result, currents of different polarities alternately flow through the primary winding 4 at the end t! The voltage becomes alternating as shown in FIG. The current is converted into a direct current and applied, so that load currents ia and ib flow through each load, respectively.

Therefore, the magnitude of this AC load current ia is controlled by the conduction time width of the switching element -F-5.6 of the inverter 2.

Now, if the AC load current ia increases or decreases from the rated value, the error is transmitted from the error amplifier 26 to the time width control circuit 2.
3 to control the opening time of the AND circuits 20 and 21, and control the time width of the rectangular wave that controls the time width of the control signal in the direction in which the AC load current ia returns to the rated value. Even if there is, the AC load current ia is kept at a constant rated value.

In other words, the AC load 8 can be provided with constant current characteristics.

Of course, since the output transformer 3 has a constant voltage property, the DC load 12 can be provided with a constant voltage property.

Further, if the capacitor 13 is provided as in this embodiment, the constant voltage property can be further improved.

Therefore, the load voltage characteristics with respect to the load current of the AC load 8 and the DC load 12 are as shown in FIG. 4, respectively.

Note that as the current detection circuit 14, one as shown in FIG. 5 may be used.

That is, the AC load current ia is a sine wave as shown in FIG. 6a, and the DC load current ib is a half wave as shown in FIG. As shown in FIG. 6C, the waveform of ic is a shadow of the DC load current ib superimposed on the positive side of the AC load current ia.

Therefore, if a diode 39 which is in the forward direction with respect to the DC load current ib is connected to the resistor 27 in parallel, the voltage at the end of the resistor 2γ will be only the negative side component of the AC load current ia, so it should be smoothed. For example, as shown in FIG. 6d, a detection output indicating the magnitude of the AC load current ia can be obtained.

Therefore, as shown in FIG.
Alternatively, a diode 39 may be connected in parallel with the resistor 2γ, and the terminal voltage of the resistor 2γ may be outputted via the smoothing circuit 40.

In addition, in the above embodiment, only the case where the AC load is given constant current characteristics by detecting the AC load current is shown, but in some cases, the DC load current is detected and the DC load is given constant current characteristics. Of course, it is also possible to do so.

In this case, it is easily understood that a well-known alternating current component cutting element may be used.

As described in detail above, the present invention uses a leakage type transformer having constant voltage as the output transformer of an inverter, and connects an AC load and a DC load to this output transformer, with the low potential side of the DC load being connected to one end of the AC load. A current detection circuit is provided between the common connection point and the output transformer to detect the load current of either the AC load or the DC load that requires a constant current. ,
Since the inverter is controlled by negative feedback according to the output of this detection circuit, it is possible to selectively supply constant current output to one of the AC load and DC load, and constant voltage output to the other. Since a common inverter and control circuit are used for the DC load and the AC load, the configuration is simple and inexpensive.

Further, a part of the output winding for the DC load and the output difference wire for the AC load can be shared, and the supply between these windings can be simplified.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing a current and voltage detection circuit of the embodiment, and Fig. 3 is a waveform diagram for understanding the operation of the embodiment. , Fig. 4 is a diagram showing the load voltage characteristics with respect to the load current of the same embodiment, Fig. 5 is a circuit diagram showing another example of the current detection circuit, and Fig. 6 is a waveform diagram to explain its operation. be. 1...DC wire, 2...Inverter circuit, 3...Output transformer, 8...AC load, 12...DC load, 14... Current detection circuit, 11... Control circuit.

Claims (1)

[Claims] 1. A town control type inverter formed by using a leakage type output transformer, and an output g41J of the output transformer. a DC load provided on the output side of the output transformer via a rectifier and whose low potential side is commonly connected to one end of the AC load; and a common connection between the AC load and the DC load. a current detection circuit inserted between the point and the output transformer to detect the load current of either the AC load or the DC load; and a current detection circuit that controls the inverter by negative feedback in response to the output of the detection circuit. A power supply device comprising: a control circuit for controlling;