JPH044747A - Switching power supply - Google Patents

Abstract

PURPOSE:To eliminate driving transformer, sub-converter transformer or the like by providing a remote control circuit on the secondary and outputting a power ON/OFF signal in response to an input of a remote control signal. CONSTITUTION:Upon receiving a power ON/OFF signal, a control circuit 16 substantially interrupt power supply to a load 12 while simultaneously controls a switching element 20, with a second control signal, so that power is fed through a smoothing/rectifying circuit 8 to a remote control circuit 26. Consequently, power supply to the load 12 is substantially interrupted but driving power supply is provided through the smoothing/rectifying circuit 8 to the remote control circuit 26. At this time, the remote control circuit 26 turns a transistor TR ON in response to a remote control signals provided from remote control signal input terminals 28, 28 and provides a power ON/OFF signal to a photocoupler 32.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a switching power supply of a type in which an input side and an output side are electrically isolated using a converter transformer.

(Prior Art/Problems to be Solved by the Invention) First Conventional Example [Structure/Operation] A first conventional example switching power supply is shown in FIG. 7.

This switching power supply rectifies and smooths an AC input applied between input terminals 2 and 2 to convert it into a DC voltage using a rectifier and smoothing circuit 4, and supplies the DC voltage to the primary winding 6a of the main converter transformer 6. Main converter transformer 6
The voltage induced in the secondary winding 6b is rectified and smoothed by the rectifier and smoothing circuit 8 in accordance with the turns ratio between the primary winding 6a and the secondary winding 6b, and converted into a DC voltage, and then output. End 10,1
The DC voltage is supplied as an output voltage to a load 12 connected in parallel between the two terminals.

In this switching power supply, in order to make the output voltage between the output terminals 10 and 10 a constant voltage,
An output voltage detection circuit 14 is provided, and this output voltage detection circuit 1
4 is input to the control circuit 16, and in response to the input of the output voltage detection signal, the control circuit 16 sends a control signal for making the output voltage constant to the drive transformer 18. via switching element 2
Output to 0. The switching element 20 has its switching operation controlled by inputting a control signal, and thereby controls the on/off duty ratio of the current path 22 of the primary winding 6a of the converter transformer 6, thereby controlling the on/off duty ratio of the secondary winding 6b. The output voltage applied between the output terminals 10 and 10 via the rectifying and smoothing circuit 8 is made constant.

Here, the control circuit 16 is supplied with power from the auxiliary power supply circuit 24. The auxiliary power supply circuit 24 includes a switching element 24a1, an auxiliary converter transformer 24b, and a rectifying and smoothing circuit 24c.

In such a switching power supply, if the load 12 is, for example, a drive system such as a motor and a mechanical part driven by the motor, if a voltage is supplied to the motor and the motor is driven before the voltage to the motor rises. This could cause the drive system to malfunction, so in order to prevent malfunctions, the control system temporarily stops the voltage supply to the motor until the voltage rises. Is it necessary to release the stop control and supply voltage to the motor to drive it?

Therefore, the switching power supply shown in FIG. 7 has a remote control circuit 26 as its control system, which controls the voltage supply to the load 12 and the stoppage of the supply through the input terminals 28 and 28. By inputting a remote control signal to the remote control circuit 26, the control circuit 1 is transmitted from the remote control circuit 26.
6, it is possible to output power supply and a stop control signal for the supply.

〔assignment〕

By the way, in this switching power supply, each transformer 6.
18 and 24b electrically isolate the primary side and the secondary Ill. Here, the primary side circuit includes a rectifying and smoothing circuit 4 and a switching element 20.24a, and the secondary side circuit includes a rectifying and smoothing circuit 8.24c, an output voltage detection circuit 14, a control circuit 16, and a remote control circuit 26. The structure is expensive, requires a large installation space, and requires a heavy transformer to insulate and separate the primary and secondary circuits.

A switching power supply that requires such a transformer is difficult to incorporate into electronic equipment that needs to be inexpensive and compact, and is therefore difficult to employ.

Second Conventional Example [Configuration/Operation] The switching power supply of the second conventional example adopts the configuration shown in FIG. This eliminates the need to use .

In FIG. 8, parts corresponding to those in FIG. 7 are given the same reference numerals. And since the operation explanation of this switching power supply is basically the same as that in Fig. 7,
Its explanation here will be omitted.

In the switching power supply shown in FIG. 8, the control circuit 16 and remote control circuit 26, which were on the secondary side in FIG.
has become unnecessary. Note that 30 is a starting resistor for the control circuit 16, and 32 is a single photocoupler that outputs an output voltage detection signal from the output voltage detection circuit 14 to the control circuit 16.

〔assignment〕

However, since the remote control circuit 26 is on the secondary side in the conventional example shown in FIG. 7, the signal given to the remote control signal input terminal 28 is
For example, an electrical open/short circuit between the input terminals 28 and 28 using a relay contact or a manual switch can also be used to deal with the problem, whereas in FIG. 8, the remote control circuit 26 is on the primary side, and the remote Since the control signal input side is applied from the secondary side, it is necessary to electrically insulate and separate the remote control circuit 26 and the remote control signal input side. For that purpose, the remote control signal input terminal 28
．． A photocoupler 34 is connected between the remote control signal input side 28 and the remote control signal input side for electrically insulating and separating the two.

In such a structure, an expensive photocoupler 34 is required, and a current source for supplying light emitting current to the light emitting diode 34a of the photocoupler 34 is required, which not only complicates the structure, but also makes the structure complicated. Since it is necessary to apply an appropriate light emitting current to the light receiving transistor 34b to drive the light receiving transistor 34b, there remains a problem that it lacks versatility.

(Object of the invention) Therefore, in the present invention, in addition to the main converter transformer, there is no need for a drive transformer or a sub-converter transformer as shown in FIG. 7, and the remote control circuit is provided on the secondary side of the main converter transformer. Therefore, by eliminating the need for a photocoupler for insulation isolation on the remote control circuit side as shown in Figure 8, we aim to provide a switching power supply that is inexpensive and simple in configuration and has general versatility. There is.

(Means for solving the problem) In order to achieve such an object, claim (1) of the present invention
) has a converter transformer, a primary side circuit, a secondary side circuit, and a photocoupler, and the converter transformer has a primary side winding and a secondary side winding, and the switching power supply described in The side winding is connected to the input end side, the secondary winding is connected to the output end side, and the primary side circuit has a switching element and a control circuit, and the switching element is connected to the primary side. The circuit is inserted into and connected to the current path of the winding, and performs a switching operation in response to the input of a control signal to turn the current path on and off.The control circuit responds to the input of the output voltage detection signal. and outputs a first control signal to the switching element for making the output voltage a constant voltage, and a second control signal for substantially stopping the power supply to the load in response to the input of the power on/off signal. The secondary side circuit has a rectifying and smoothing circuit, an output voltage detection circuit, and a remote control circuit, and the rectifying and smoothing circuit outputs a control signal to the switching element. It rectifies and smoothes the voltage induced in the line and outputs it to the load and remote control circuit.The output voltage detection circuit detects the magnitude of the output voltage at the output terminal, and uses the detection result to detect the output voltage. The remote control circuit outputs a power on/off signal in response to the input of the remote control signal, and the photocoupler outputs an output voltage detection signal and a power on/off signal, respectively. It is characterized in that it outputs to a control circuit.

The switching power supply according to claim (2) is the switching power supply according to claim (1), wherein the remote control circuit has a switch driving means, and the switch driving means is configured to control the remote control, and the switching power supply according to claim (1). When the remote control circuit operates in response to the input of It is characterized by short-circuiting the ends.

The switching power supply according to claim (3) is the switching power supply according to claim (1).
), the switching power supply has a light emitting element and a light receiving element instead of a photocoupler, the output voltage detection circuit has the light emitting element, and the control circuit has the light receiving element. The light emitting element emits light in response to the output voltage detection operation by the output voltage detection circuit, and emits light in response to the input of a power on/off signal from the remote control circuit, and the light receiving element emits light in response to the input of a power on/off signal from the remote control circuit. , is characterized in that it responds to the reception of the light emission.

The switching power supply according to claim (4) is the switching power supply according to claim (3).
), wherein the remote control circuit has switch driving means, and the switch driving means receives a switch driving signal when the remote control circuit operates in response to input of the remote control signal. A switch is connected in parallel to the output end, and the switch short-circuits the output end in response to a switch drive signal.

The switching power supply according to claim (5) is the switching power supply according to claim (3).
), wherein the remote control circuit includes a photocoupler, the photocoupler includes a light emitting element and a light receiving element, and the remote control circuit responds to input of a remote control signal. The light emitting element is driven to emit light, and the light emitting element operates the light receiving element, and the light receiving element outputs a power on/off signal to the light emitting element in the output voltage detection circuit by the operation.

(Function) In the switching power supply according to claim (1), when power is not supplied to the load connected to the output terminal, a remote control signal is output to the remote control circuit. The remote control circuit outputs a power on/off signal to the control circuit via the photocoupler in response to the input of the remote control signal. In response to the input of the power on/off signal, the control circuit outputs a second control signal to the switching element so that the output voltage is such that power is not substantially supplied to the load. This effectively de-energizes the load.

For example, when the power supply to the load starts up and becomes stable, if you stop inputting the remote control signal,
While the power on/off signal is no longer input to the control circuit via the photocoupler, the output voltage detection signal is given to the control circuit from the output voltage detection circuit via the photocoupler. In response to the detection signal, a second control signal for making the output voltage to the load constant voltage is output to the switching element. As a result, the output voltage to the load is controlled to a constant voltage.

In the switching power supply according to claim (2), the switch driving means of the remote control circuit outputs the switch driving signal when the remote control circuit operates in response to the input of the remote control signal. In the switching power supply according to claim (3), wherein the switch is turned on and the output terminal is turned on by this switch drive signal, the light emitting element in the output voltage detection circuit detects the output voltage of the output voltage detection circuit. It emits light in response to a detection operation, and emits light in response to input of a power on/off signal from a remote control circuit. Then, a light receiving element in the control circuit responds to the reception of the light emission.

In the switching power supply according to claim (4), the switch driving means of the remote control circuit outputs the switch driving signal when the remote control circuit operates in response to input of the remote control signal. The switching power supply according to claim 5, wherein the switch connected in parallel to the output terminal is turned on and the output terminal is turned on by this, is characterized in that the remote control circuit responds to the input of the remote control signal to The light emitting element is driven to emit light, and the light emission causes the light receiving element in the circuit to operate.

Then, the light receiving element outputs a power on/off signal to the light emitting element in the output voltage detection circuit by this operation.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

First Embodiment FIG. 1 is a circuit diagram of a switching power supply according to the first embodiment, and parts corresponding to those in FIGS. 7 and 8 are given the same reference numerals.

In the switching power supply of this embodiment, 2.2 is an input terminal of the AC power supply, 4 is a rectifying and smoothing circuit for the AC power supply, 6 is a converter transformer, 8 is a rectifying and smoothing circuit, 1010 is an output terminal to which a load is connected, and 12 is a rectifying and smoothing circuit. Load, 14 is an output voltage detection circuit, 16 is a control circuit, 20 is a switching element, 22 is a current path of the primary winding 6a, 26 is a remote control circuit, 28, 28 is a remote control signal input terminal, 30 is a starting resistor It is.

In the above configuration, the primary side circuit A of the converter transformer 6 includes the rectifying and smoothing circuit 4, the control circuit 16, and the switching element 20, and the secondary side circuit B thereof includes the rectifying and smoothing circuit 8 and the output voltage detection circuit. 14 is the same as that shown in FIG. 8, so a detailed explanation will be omitted here.

In the switching power supply of this embodiment, a remote control circuit 26 is provided on the secondary side of the converter transformer 6, and the photocoupler 32 receives not only the output voltage detection signal from the output voltage detection circuit I4 but also the remote control circuit 26. It is characterized in that it outputs a power on/off signal from.

The control circuit 16 controls the switching element 20 in response to the output voltage detection signal provided from the output voltage detection circuit 14 and the power on/off signal provided from the remote control circuit 26 via the photocoupler 32. First and second control signals are output to control the operation of the switching element 20.

In this case, in response to the input of the output voltage detection signal, the control circuit 16 outputs a first control signal to the switching element 20 and controls the operation of the switching element 20 so that a constant voltage is supplied to the load 12. However, in response to the input of the power on/off signal, the operation of the switching element 20 is controlled by the second control signal as follows.

That is, when the control circuit 16 receives the power on/off signal, the rectifying and smoothing circuit 8 substantially stops power supply to the load 12, while supplying the remote control circuit 26 with its driving power. The switching element 20 is driven and controlled by the second control signal so that power is supplied to it via the second control signal.

As a result, the power supply to the load 12 is substantially stopped, or the driving power is supplied to the remote control circuit 26 via the rectifying and smoothing circuit 8.

In this case, the remote control circuit 26 outputs a power on/off signal to the photocoupler 32 by turning on the transistor TR in response to the remote control signal input from the remote control signal input terminals 28 and 28.

Note that since the basic operation of the switching power supply is the same as in each of the above-mentioned conventional examples, detailed explanation thereof will be omitted.

Second Embodiment FIG. 2 is a circuit diagram of a switching power supply according to a second embodiment, and parts corresponding to those in FIG. 1 are given the same reference numerals. A feature of the switching power supply in the second embodiment is that a relay coil RL as a switch driving means is connected to the collector of the transistor TR.
A relay contact RC as a switch that turns on and off when energized is connected in parallel to the output terminals 10 and 10, and when the transistor TR is turned on by inputting a remote control signal, the relay coil RL is energized and the relay contact RC is turned on. This short-circuits the output end 10.10 to ensure that no power is supplied to the load 12.

Third Embodiment FIG. 3 is a circuit diagram of a switching power supply according to a third embodiment, and the same reference numerals are given to parts corresponding to those in the previous figures. The switching power supply in the third embodiment differs from that in the first embodiment in that the photocoupler 32 of the first embodiment is omitted, and instead, the photocoupler 32 has a light emitting diode and a light receiving transistor. However, in the third embodiment, they are provided inside the output voltage detection circuit 14 and the control circuit 16, respectively.

The output voltage detection circuit 14 includes a light emitting diode DI, a Zener diode D2, and resistors R3 to R5, and each of these elements performs an output voltage detection operation.

The control circuit 16 includes a light receiving transistor TRI, a transistor TR2, and a resistor R6R7.

Then, the light emitting diode DI in the output voltage detection circuit 14
emits light in response to the output voltage detection signal of the output voltage detection circuit 14 and the power on/off signal which is the output of the remote control circuit 26, and the light receiving transistor TRI in the control circuit 16 responds to the input of each of the signals described above. Perform each operation.

Fourth Embodiment FIG. 4 is a circuit diagram of a switching power supply according to a fourth embodiment, in which parts corresponding to those in each of the figures described above are given the same reference numerals. The fourth embodiment is a combination of the relay coil RL and relay contact RC of the second embodiment and the third embodiment, and its configuration and operation are clear from the second and third embodiments. Therefore, its explanation will be omitted.

Fifth Embodiment FIG. 5 is a circuit diagram of a switching power supply according to a fifth embodiment, in which the same reference numerals are given to parts corresponding to those in the previous figures. In the fifth embodiment, in contrast to the third embodiment, a photocoupler consisting of a light emitting diode D3 and a light receiving transistor TR3 is provided in the remote control circuit 26, and a remote control signal is applied to the input terminal 28. When TR is turned on, the light emitting diode D3 is made to emit light and the light receiving transistor TR3 is operated, thereby causing the light emitting diode DI of the output voltage detection circuit 140 to emit light.

The output of the power on/off signal accompanying the light emission of the light emitting diode D3 and the associated operation have been described above, so their explanation will be omitted.

Sixth Embodiment FIG. 6 is a circuit diagram of a switching power supply according to a sixth embodiment, and the same reference numerals are given to parts corresponding to those in the previous figures. The feature of the configuration of the sixth embodiment is that the remote control circuit 26 is the same as that of the fifth embodiment;
The control circuit 16 is an ICI 6 for PWM (pulse width control).
a and a light-receiving transistor TRI.

The switching power supplies of the first to fifth embodiments are RoCC
(ringing choke converter) method,
The sixth embodiment is a P, P, C (feed forward converter) type, and the IC 16a has a pulse width modulator, an oscillator, and a feedback amplifier, and the feedback amplifier converts the output of the light receiving transistor TRI. is compared with a reference value, amplified, synchronized with the oscillation frequency of the oscillator, and a pulse width modulator performs operations such as widening the pulse width when the output voltage is low and narrowing the pulse width when the output voltage is high. The output voltage is controlled to be constant, and the power supply to the load is stopped.

(Effects of the Invention) As is clear from the above explanation, according to the present invention,
A switching element and a control circuit are provided on the primary side of the converter transformer, and a rectifying and smoothing circuit is provided on the secondary side of the converter transformer.
Since an output voltage detection circuit and a remote control circuit are provided, there is no need for a drive transformer or a sub-converter transformer, which was required because a control circuit was provided on the secondary side of the converter transformer as in the first conventional example mentioned above. Furthermore, since the remote control circuit is provided on the secondary side of the converter transformer, there is no need for a photocoupler for driving the remote control circuit as in the second conventional example. Therefore, since this photocoupler is not required, the configuration is inexpensive and simple, and the remote control signal can be input to the remote control circuit by using a relay contact or a manual switch. Current control for photocouplers as in the conventional example is no longer necessary, and a versatile switching power supply can be provided.

[Brief explanation of the drawing]

1 to 6 are circuit diagrams of switching power supplies according to embodiments of the present invention, in which FIG. 1 is a first embodiment, FIG. 2 is a second embodiment, FIG. 3 is a third embodiment, FIG. 4 is a circuit diagram of a switching power supply of a fourth embodiment, FIG. 5 is a fifth embodiment, and FIG. 6 is a circuit diagram of a switching power supply of a sixth embodiment. Figure 7 is a circuit diagram of the first conventional switching power supply;
The figure is a circuit diagram of a second conventional switching power supply. 6...Converter transformer, 6a...Primary winding, 6
b... Secondary winding, 8... Rectifier smoothing circuit, 10 10
... Output end, 14... Output voltage detection circuit, 16...
Control circuit, 20 - Switching element, 26 - Remote control circuit, 28... Remote control signal input terminal, 32 - Photocoupler.

Claims (5)

[Claims] (1) Converter transformer (6), primary side circuit (A),
It has a secondary side circuit (B) and a photocoupler (32), and the converter transformer (6) has a primary side winding (6a) and a secondary side winding (6b). Winding wire (6
a) is connected to the input end (2) side, and the secondary winding (6b)
is connected to the output end (10) side, the primary side circuit (A) has a switching element (20) and a control circuit (16), and the switching element (20) is connected to the primary side winding. It is inserted and connected to the current path (22) of the wire (6a),
The control circuit (16) performs a switching operation to turn on and off the current path (22) in response to the input of the control signal, and the control circuit (16) makes the output voltage a constant voltage in response to the input of the output voltage detection signal. a first control signal to the switching element (29), and a second control signal for substantially stopping the power supply to the load (12) in response to the input of the power on/off signal. The secondary circuit (B) includes a rectifying and smoothing circuit (8), an output voltage detection circuit (14), and a remote control circuit (20).
6), the rectifying and smoothing circuit (8) rectifies and smoothes the voltage induced in the secondary winding (6b) of the converter transformer (6), and supplies the voltage to the load (12) and the remote control circuit (26). ), and the output voltage detection circuit (14) detects the magnitude of the output voltage at the output terminals (10, 10), and outputs the detection result to the control circuit (16) as an output voltage detection signal. The remote control circuit (26) outputs a power on/off signal in response to the input of the remote control signal, and the photocoupler (32) outputs an output voltage detection signal and a power on/off signal. A switching power supply characterized in that the switching power supply outputs each of the following to a control circuit (16). (2) The switching power supply according to claim (1), wherein the remote control circuit (26) has a switch drive means (RL), and the switch drive means (RL) receives a remote control signal. It outputs a switch drive signal when the remote control circuit (26) operates in response to the switch (RC), and a switch (RC) is connected in parallel to the output terminals (10, 10). RC) is a switching power supply characterized in that the output terminals (10, 10) are short-circuited in response to a switch drive signal. (3) The switching power supply according to claim (1), which has a light emitting element (D1) and a light receiving element (TR1) instead of the photocoupler (32), and has an output voltage detection circuit (14). ) has the light emitting element (D1), the control circuit (16) has the light receiving element (TR1), and the light emitting element (D1) detects the output voltage by the output voltage detection circuit (14). The light receiving element (TR1) emits light in response to the detection operation of the light emitting device, and emits light in response to the input of a power on/off signal from the remote control circuit (26), and the light receiving element (TR1) responds to the reception of the light emitted. A switching power supply characterized by: (4) The switching power supply according to claim (3), wherein the remote control circuit (26) has a switch drive means (RL), and the switch drive means (RL) is adapted to input a remote control signal. When the remote control circuit (26) operates in response, it outputs a switch drive signal, and a switch (RC) is connected in parallel to the output terminals (10, 10). ) is a switching power supply characterized in that the output terminals (10, 10) are short-circuited in response to a switch drive signal. (5) The switching power supply according to claim (3), wherein the remote control circuit (26) includes a photocoupler, and the photocoupler includes a light emitting element (D3) and a light receiving element (TR3). The remote control circuit (26) drives the light emitting element (D3) to emit light in response to the input of the remote control signal, and also causes the light emitting element (D3) to emit light.
) is operated, and the light receiving element (TR3) outputs a power on/off signal to the light emitting element (D1) in the output voltage detection circuit (14) by the operation.