JPH07213054A - Transformer-coupled switching power unit - Google Patents

Abstract

PURPOSE:To improve the stability grade of secondary DC power voltage and also, materialize the downsizing, the cost down, and the facilitation of changeover control by providing a stabilizing circuit with the second voltage detecting circuit and a changeover and connection element which connects this second voltage detection circuit to the secondary DC power circuit. CONSTITUTION:A stabilizing circuit 45, which is provided on the side of the secondary DC power unit 30 of a transformer-coupled switching power unit comprising a primary DC power circuit 10, a secondary DC power circuit 30, and a transformer 20, is provided with the second voltage detecting circuit and a changeover and connection circuit. And, The first voltage detection circuit and the second voltage detection circuit are selected and changed over with one changeover signal SGN, whereby the secondary DC power voltages V21 and V22 can be changed over. Hereby, downsizing and cost down can be materialized, and also both secondary DC power voltages V21 and V22 before and after changeover can be made stabilized high-grade power sources, and besides the changeover control can be facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer-coupled switching power supply device capable of switching a secondary DC power supply voltage in at least two stages.

[0002]

2. Description of the Related Art In FIG. 3, a primary DC power supply circuit 10 and a secondary DC power supply circuit 30 are connected and coupled via a transformer 20. The primary DC power supply circuit 10 is an AC power supply 1
1, switch 12, noise filter 13, rectifier circuit 1
4, a smoothing capacitor C10, a switching element (transistor) 15, a control circuit 40 including a PWM IC, and the like. The switching element 15 connects the primary winding L11 of the transformer 20 and the negative-side electric circuit Ln of the rectifier circuit 14. Is connected in between. The driving power (voltage Vd) is induced from the auxiliary winding L12 and is supplied via the diode D10.

The secondary DC power supply circuit 30 includes a diode D connected to the first secondary winding L21 of the transformer 20.
21 and smoothing capacitors C211 and C212 to form a stable power supply system 31, which is connected to a load (OUT). A stabilizing circuit 45 inputs a voltage detection signal to the photocoupler 46. As a result, the feedback signal f is input to the control circuit 40.

Thus, in the separately-excited flyback type frequency fixed type, the switching element 15 is provided in the control circuit 4.
Since the ON / OFF control is performed by the drive control signal S output from 0, when the load (OUT) is light, the current I flowing through the switching element 15 is reduced and the conduction time thereof is shortened. On the other hand, when the load (OUT) becomes heavy, the current I flowing through the switching element 15 increases, and the energization time becomes longer accordingly. This is because the oscillation frequency, that is, the period is constant.

In the secondary DC power supply circuit 30, the diode D
21 and rectifies and smoothing capacitors C211 and C212
To generate a secondary DC power supply (voltage V21) and supply it to the load (OUT). The fluctuation of the load (OUT) is detected by the stabilizing circuit 45 as the fluctuation of the secondary DC power supply voltage V21. As a result, the feedback signal f is input to the control circuit 40 via the photocoupler 46. Therefore,
The secondary DC power supply voltage V21 is stabilized.

Further, in the RCC type self-oscillation type (frequency fluctuation type) transformer coupling type secondary DC power supply generator, the control power supply voltage is changed by turning the control circuit (transistor 40) ON / OFF by the feedback signal f. ON-OFF control of the switching element 15 is performed using it, and electric power energy is supplied from the primary winding L11 to the secondary winding L21. The control power supply voltage is the drive power supply voltage Vd.
It is generated from the auxiliary winding L12 of the transformer 20 similarly to.

Therefore, when the load (OUT) is light, the current I flowing through the switching element 15 decreases and the oscillation frequency increases. On the other hand, when the load (OUT) becomes heavy, the current I flowing through the switching element 15 increases and the oscillation frequency decreases. This is because the ON duty of the switching element 15 by the control circuit (40) is constant.

Here, the stabilization circuit 45 on the secondary side (30)
Is a first voltage detection circuit (R48, R4
9), a resistor R46, a photocoupler 46, and a resistor R46 connected in series.
A voltage control element (shunt regulator) RG47 is formed, and the secondary DC power supply voltage V21 corresponds to the first set voltage value Vd1.
Based on the control signal CNT detected and output in the above case, the voltage control element RG 47 is drive-controlled to output the feedback signal f from the photocoupler 46. Therefore, the secondary DC power supply voltage V21 is set to the first
It can be stabilized to the first predetermined voltage value corresponding to the set voltage value Vd. The resistor R and the capacitor C are a phase adjustment circuit.

By the way, in addition to the secondary DC power supply voltage V21, a secondary DC power supply voltage V22 higher or lower than it.
There is a request to switch to. For example, when the load is the print head of the printer, it is necessary to increase the impact force corresponding to the print target paper.

Here, in the prior art, the transformer 20 has a second
Secondary winding L22 and an unstable power supply system 32 connected to this
(Diode D22, smoothing capacitors C221, C22
2) is formed, and the switching element 55 provided in the stable power supply system 31 can be opened and closed by the first switching signal SGN1 and the switching element 56 provided in the unstable power supply system 32 can be opened and closed by the second switching signal SGN2. The stable DC power supply system 31 and the unstable DC power supply system 32 are switched between the secondary DC power supply voltage V21 and the secondary DC power supply voltage V22 and output to the load (OUT).

Therefore, the first switching signal SGN1 is output (H level) to turn on the switching element 55, and the second switching signal SGN2 is set to L level to turn off the switching element 56.
If so, the load is set to the secondary DC power supply voltage V of the stable power supply system 31.
It can be driven at 21 (for example, 24V). On the other hand, the first switching signal SGN2 is output (H level) to turn on the switching element 56.
If the switching element 55 is turned off by setting FF and setting the first switching signal SGN1 to L level, the secondary DC power supply voltage V22
The load can be driven at (eg, 30V).

[0012]

By the way, such a transformer coupling type switching power supply device is no exception, further reduction in size and weight, cost reduction, and further reduction of fluctuation of the switching secondary DC power supply voltage V22. There is a strong demand for improving the stability and quality of the product and expanding the appropriateness of selection of its absolute value (V22).

Here, the unstable power supply system 32 (second second power supply) is used.
Next winding L22, diode D22, smoothing capacitor C2
21, C222), the above requirements can be satisfied more than enough. Further, if the stable power supply system 31 can be constructed so that voltage values of two or more stages can be switched and generated and output, each voltage value can be stabilized together and high quality can be achieved. Further, by doing so, the switching elements 55, 5 for large current
I am convinced that the cost can be greatly reduced because the number 6 can be omitted and the switching control can be further facilitated. The above is a problem common to both fixed frequency type and frequency variable type transformer coupling type switching power supply devices.

An object of the present invention is that the secondary DC power supply voltage can be switched and the stability and quality of each secondary DC power supply voltage before and after the switching can be improved, the size and weight are low, the cost is low, and the switching control is easy. It is to provide a transformer coupling type switching power supply device.

[0015]

A transformer coupling type switching power supply device according to the present invention includes a primary DC power supply circuit having a rectifying circuit, a smoothing capacitor, a switching element and a control circuit, and a secondary DC power supply having a stabilizing circuit. A voltage control element and a photocoupler, in which the circuit is connected and coupled via a transformer, and the stabilizing circuit is connected in series with the first voltage detection circuit, and the value of the secondary DC power supply voltage becomes the first set voltage value. A feedback signal can be output from the photocoupler to the control circuit based on the control signal output from the first voltage detection circuit when the voltage becomes equal to or higher than the corresponding first predetermined voltage value, and the switching element is ON-OFF controlled. In a transformer coupling type switching device configured to generate a secondary DC power supply while being able to switch the value of the secondary DC power supply voltage in at least two stages A second voltage detection circuit configured to output the control signal to the stabilizing circuit when the value of the secondary DC power supply voltage is equal to or higher than a second predetermined voltage value corresponding to a second set voltage value. And a switching connection element that connects the second voltage detection circuit to the secondary DC power supply circuit when a switching signal is input.

[0016]

According to the present invention having the above structure, the control signal is output from the first voltage detection circuit when the value of the secondary DC power supply voltage becomes equal to or higher than the first predetermined voltage value corresponding to the first set voltage value. To be done. The control signal drives and controls the voltage control element to input a feedback signal from the photocoupler to the control circuit. Therefore, since the amount of power energy supplied from the primary side to the secondary side is adjusted by ON-OFF control of the switching element on the primary DC power supply circuit side, the secondary DC power supply voltage corresponds to the first set voltage value. Can be stabilized at a first predetermined voltage value.

When a switching signal is input here, the switching connection element is turned on to switch and connect the second voltage detection circuit to the secondary DC power supply circuit. Then, when the value of the secondary DC power supply voltage becomes equal to or higher than the second predetermined voltage value corresponding to the second set voltage value, the control signal is output from the second voltage detection circuit. Therefore, this time, the secondary DC power supply voltage is stabilized to the second predetermined voltage value value corresponding to the second set voltage value. That is, the secondary DC power supply voltage is switched from the first predetermined voltage value corresponding to the stabilized first set voltage value to the second predetermined voltage value corresponding to the second set voltage value. If the switching connection element is turned off by turning off the switching signal, the second set voltage value is switched to the first set voltage value. In addition, if the first and second set voltage values of the first and second voltage detection circuits are changed, the absolute values of the first predetermined voltage and the second predetermined voltage value of the secondary DC power supply voltage can be appropriately changed. It is possible to change.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. This transformer coupling type switching power supply device is shown in FIG.
As shown in FIG. 7, the basic configuration (10, 20, 30) is the conventional example (FIG. 3) and the non-stable power supply system 32 (D22, C221, C222) including the second secondary winding L22 of the transformer 20 and the switching element. 55 and 56 are wiped out, and the stabilization circuit 45 has a second voltage detection circuit (R51,
R48, R49) and the switching connection elements (Q51, Q52) are provided, and the first voltage detection circuit (R
48, R49, R52) and the second voltage detection circuit (R51,
R48 and R49) are selectively switched to switch the secondary current power supply voltage (V21, V22).

Further, in this embodiment, the conventional first voltage detecting circuit is formed of the resistors R48 and R49, whereas each of the resistors forming the first voltage detecting circuit and the second voltage detecting circuit is formed. The combination of R48, R49, R51, and R52 is formed to detect the first set voltage value Vd1 and the second set voltage value Vd2. This is to simplify the circuit.

The same parts as those of the conventional example (FIGS. 3 and 4) are designated by the same reference numerals, and the description thereof will be simplified or omitted.

In FIG. 2, in the conventional first voltage detection circuit (R48, R49), a resistor 51, a switching connection element Q51, a switching connection element Q52, and a resistance 52 connected in series are connected in parallel, and an electric line L is connected. Connected by. When the switching signal SGN is output (H level), the switching connection element Q51
Turns on and the switching connection element Q52 turns off. If the switching signal SGN is set to the L level, the opposite is true.

When the switching signal SGN is at L level, the resistor R52 is connected in parallel with the resistor R49, and these (R4
9, R52) is connected in series with the resistor R48 and the stable power supply system 31, and the secondary DC power supply voltage V21 is the first set voltage value Vd1.
The control signal CNT is output when the voltage becomes equal to or higher than the first predetermined voltage value (for example, 24 V) corresponding to the. That is, in this embodiment, this state is the first voltage detection circuit (R48, R
49, R52).

A switching signal SGN is output (H level).
Then, when the switching connection element Q51 is ON, the switching connection element Q51
Since 52 is turned off, the resistor R51 is connected in parallel with the resistor R48, and these (R51, R48) and the resistor R4 are connected.
9 is connected in series, and the secondary DC power supply voltage V22 corresponds to the second set voltage value Vd2 at a second predetermined voltage value (for example,
30 V) or more, the control signal CNT is output. That is, in this embodiment, this state is understood to constitute the second voltage detection circuit (R51, R48, R49). Further, the switching connection element Q51 is turned on, and the second voltage detection circuit (R51, R48, R49) is connected to the secondary DC power supply circuit 30 (31).

Next, the operation of this embodiment will be described. In the normal state in which the switching signal SGN is at the L level, the switching connection element Q51 is OFF and the switching connection element Q52 is ON, so the value of the secondary DC power supply voltage V21 is the first set voltage value Vd.
When the voltage becomes equal to or higher than the first predetermined voltage value (24V) corresponding to 1, the control signal CNT is output from the first voltage detection circuit (R48, R49, R52), the voltage control element RG47 is driven and controlled, and the photocoupler 46 is controlled. Feedback signal f
Is output. Therefore, the control circuit 40 adjusts the amount of power energy supplied to the secondary side (30) to be reduced by the ON-OFF control of the switching element 15, so that the secondary DC power supply voltage V21 is stabilized at the first predetermined voltage. Value (24
V) can be controlled. That is, load (OUT)
Can be driven with a first predetermined voltage value.

Here, the secondary DC power supply voltage is switched (V2
1 → V22), the switching signal SGN is output (H level). Then, the switching connection element Q51 is turned on and the switching connection element Q52 is turned off, so that the value of the secondary DC power supply voltage V22 becomes equal to or higher than the second predetermined voltage value (30V) corresponding to the second set voltage value Vd2. , The control signal CNT from the second voltage detection circuit (R51, R48, R49)
Is output. Therefore, the feedback signal f is fed back to the control circuit 40 and the amount of power energy supplied to the secondary side (30) is adjusted, so that the secondary DC power supply voltage V22.
Can be switched to the stabilized second predetermined voltage value (30 V) on the high voltage side.

Therefore, according to this embodiment, in the stabilizing circuit 45 on the secondary DC power supply circuit 30 side, the value of the secondary DC power supply voltage (V22) corresponds to the second set voltage value Vd2.
Of the second voltage detection circuit (R51, R48, R49) formed to be able to output the control signal CNT to the voltage control element RG47 when the voltage becomes equal to or higher than the predetermined voltage value (30V). Switch connection element Q51 for connecting the second voltage detection circuit (R51, R48, R49) to the secondary DC power supply circuit 30 (31) instead of the first voltage detection circuit (R48, R49, R52) , Q52 are provided, and the secondary DC power supply voltage is set from the stabilized first predetermined voltage value (24V) corresponding to the first set voltage value Vd1 to the second setting only by inputting the switching signal SGN (H level). Since it is configured to be able to automatically switch to the stabilized second predetermined voltage value (30 V) corresponding to the voltage value Vd2, the unstable power supply system 32 (L22, D22, C221, C222)
In comparison with the conventional example (FIG. 3) in which switching elements 55 and 56 of large capacity are provided and switching is performed using two switching signals SGN1 and SGN2, significant reduction in size and weight and cost reduction are achieved. In addition, both of the secondary DC power supply voltages V21 and V22 before and after switching can be stabilized to be a high-quality power supply, and switching is possible with one switching signal S, so switching control is very easy. Is.

Further, the stabilizing circuit 45 has two resistors R5.
1, R52 and two switching connection elements Q51, Q52 only need to be provided, and the cost can be further reduced from this point as well.

Further, since the first voltage setting circuit and the second voltage setting circuit are integrally formed as a combination of the four resistors R48, R49, R51 and R52, the first setting voltage value Vd1 and the second voltage setting circuit The degree of freedom of selection with respect to the set voltage value Vd2 is expanded, and the selectivity of each absolute value of the secondary DC power supply voltages V21 and V22 before and after switching can be greatly expanded.

[0029]

According to the present invention, when the value of the secondary DC power supply voltage becomes equal to or higher than the second predetermined voltage value corresponding to the second set voltage value in the stabilization circuit on the secondary DC power supply circuit side. And a second voltage detection circuit formed to be able to output a control signal to the voltage control element, and a second DC detection circuit instead of the first voltage detection circuit when a switching signal is input to the secondary DC power supply circuit. A switching connection element to be connected is provided, and the secondary DC power supply voltage is stabilized from the stabilized first predetermined voltage value corresponding to the first set voltage value to the second set voltage value only by inputting the switching signal. Since it is configured such that it can be automatically switched to the second predetermined voltage value that is realized, it is possible to use a conventional example in which an unstable power supply system and a large-capacity switching element are provided and switching is performed using two switching signals. In comparison, it is possible to reduce the size and weight significantly and reduce the cost. Replacement can be a high quality power supply together stabilize both of the two secondary DC power supply voltage of about and 1
The switching control is very easy because it is configured to be switchable with one control signal.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is likewise a diagram for explaining a stabilizing circuit.

FIG. 3 is a circuit diagram for explaining a conventional example.

FIG. 4 is a diagram for explaining a conventional stabilizing circuit.

[Explanation of symbols]

 10 Primary DC Power Supply Circuit 14 Rectifier Circuit C10 Smoothing Capacitor 15 Switching Element 20 Transformer L11 Primary Winding L12 Auxiliary Winding L21 First Secondary Winding L22 Second Secondary Winding 30 Secondary DC Power Supply Circuit 31 Stable Power supply system V21, V22 Secondary DC power supply voltage D21 Diode C211, C212 Smoothing capacitor 32 Unstable power supply system 40 Control circuit 45 Stabilization circuit R46 Resistance 46 Photocoupler RG47 Voltage control element R48 (First voltage detection circuit, second voltage detection) Circuit) R49 (first voltage detection circuit, second voltage detection circuit) R51 (second voltage detection circuit) R52 (first voltage detection circuit) Vd1 first set voltage value Vd2 second set voltage value Q51, Q52 switching connection element SGN switching signal CNT control signal V21, V22 secondary DC power supply voltage f feed Back signal

Claims (1)

[Claims] 1. A primary DC power supply circuit having a rectifying circuit, a smoothing capacitor, a switching element, and a control circuit, and a secondary DC power supply circuit having a stabilizing circuit are connected and coupled via a transformer to form the stabilizing circuit. A first voltage detection circuit including a voltage control element and a photocoupler connected in series, wherein the first direct current power supply voltage is equal to or higher than a first predetermined voltage value corresponding to the first set voltage value; A feedback signal can be output from the photocoupler to the control circuit based on the control signal output from the voltage detection circuit, and a secondary DC power supply can be generated while ON-OFF control of the switching element and a secondary DC power supply voltage. In the transformer coupling type switching device configured to be able to switch the value of at least in two steps, the stabilization circuit is configured such that the value of the secondary DC power supply voltage corresponds to the second set voltage value. And a second voltage detection circuit configured to output the control signal when the voltage exceeds a second predetermined voltage value, and a second voltage detection circuit when the switching signal is input. And a switching connection element connected to the transformer coupling type switching power supply device.