JP2000050650A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply ensuring positive operation. SOLUTION: A secondary power supply circuit 6 has a resonance circuit configuration and a primary winding N1 of a transformer T in the secondary power supply circuit 6 is connected at the end thereof, with the trigger input terminal of a first power supply circuit via diodes D2, D3. A first power supply circuit 4a comprises a control transistor Q2 connected between the base and emitter of a switching transistor Q1, and a constant-voltage diode DZ1 connected between the base of the control transistor Q2 and the output terminal 2. A trigger signal having an AC full-wave rectified waveform is inputted to the base of the switching transistor Q1 via a trigger input terminal 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for causing a power supply circuit constituting a power supply device to perform a reliable operation.

[0002]

2. Description of the Related Art For example, in an electronic device equipped with a fluorescent display tube, a logic circuit or the like provided in a control system and a fluorescent display tube or the like provided in an output system may require different driving voltages. Here, when high stability is required for each drive voltage supplied to each circuit or component, or when independence of power supply is required, such as under different drive voltage supply conditions, the control system and output A power supply circuit is separately provided in the system. As an example of a power supply device having a plurality of power supply circuits as described above, there is a conventional power supply device as shown in FIG. The power supply device shown in FIG. 3 controls the first power supply circuit 4c and the second power supply circuit 12 to supply a drive signal to the first power supply circuit 4c and a trigger signal to the second power supply circuit. And a circuit 13.
Here, the first power supply circuit 4c has the following circuit configuration.

A collector of a switching transistor Q1 is connected to an input terminal 1 via a choke coil L1,
The emitter of the switching transistor Q1 is connected to the ground. The collector of the switching transistor Q1 is connected to the output terminal 2 via a rectifying diode D1, and a smoothing capacitor C is connected between the output terminal 2 and the ground.
1 is connected. The base of the switching transistor Q1 is connected to the trigger input terminal 3 via the resistor R1, and the control transistor Q2 is connected between the base of the switching transistor Q1 and the ground. A constant voltage diode DZ1 constituting a first feedback circuit is connected between the base of the control transistor Q2 and the output terminal 2, and a second diode is connected between the base of the control transistor Q2 and the collector of the switching transistor Q1. A series circuit of a resistor R6 and a capacitor C3 constituting a feedback circuit is connected, and a bias resistor R2 is connected between the base of the control transistor Q2 and the ground.

The first power supply circuit 4c having such a configuration
The operation was as follows. A trigger signal is applied from the control circuit 13 to the trigger input terminal 3, and the trigger input terminal 3
Is high, the switching transistor Q
1 is turned on. Then, a current that increases linearly with time flows from the choke coil L1 to the collector of the switching transistor Q1. Eventually, when the current flowing into the collector of the switching transistor Q1 becomes equal to the magnitude of the collector saturation current of the switching transistor Q1 at that time, the magnitude of the current becomes constant, and the voltage at the position of the collector of the switching transistor Q1 increases.

Then, a second feedback signal based on the voltage appearing at the collector of the switching transistor Q1 is connected to the base of the control transistor Q2 by a resistor R6 and a capacitor C3.
, And the control transistor Q2 is turned on. When the control transistor Q2 is turned on, the base and the emitter of the switching transistor Q1 are short-circuited, and as a result, the switching transistor Q1 is turned off. When the switching transistor Q1 is turned off, a flyback voltage is generated in the choke coil L1, and a high voltage including the input voltage and the flyback voltage is supplied to the capacitor C1 via the diode D1. As a result, the voltage generated at both ends of the capacitor C1 is supplied as an output voltage to an external load connected to the output terminal 2.

Here, a voltage appearing at the output terminal 2, that is, a first feedback signal corresponding to the output voltage is input to the base of the control transistor Q2 via the constant voltage diode DZ1. When the output voltage is higher than the Zener voltage of the constant voltage diode DZ1, the control transistor Q2 maintains the ON state. By supplying power to the load, the output voltage gradually decreases. When the output voltage becomes lower than the Zener voltage of the constant voltage diode DZ1, the control transistor Q2 shifts to the off state. When the control transistor Q2 is turned off, a trigger signal is input to the base of the switching transistor Q1 and turned on again. Thereafter, while the voltage at the position of the trigger input terminal 3 is high due to the trigger signal, the operation process described above is repeated to perform the self-excited oscillation operation.

When the voltage at the trigger input terminal 3 is low, for example, at the same voltage as the ground potential, a forward bias cannot be supplied between the base and the emitter of the switching transistor Q1. . Therefore, the switching transistor Q1 maintains the off state regardless of the state of the control transistor Q2. That is, the first power supply circuit 4c enters an operation stop state. The first power supply circuit 4c constituting the power supply device in this manner
Has performed a self-excited oscillation operation according to the signal level of a trigger signal.

In the power supply device shown in FIG. 3, a trigger signal supplied from the control circuit 13 to the first power supply circuit is based on a clock pulse generated in a process of generating a drive signal supplied to the second power supply circuit 12. You are using If any failure occurs in the second power supply circuit 12, the control circuit 13 stops supplying the drive signal to the second power supply circuit 12, and stops the operation of the second power supply circuit 12. At this time, the supply of the trigger signal from the control circuit 13 to the first power supply circuit 4c is also stopped at the same time. As a result, in the power supply device of FIG.
The operation state of the first power supply circuit is automatically switched in accordance with the state of No. 2, and a highly reliable power supply device can be constructed with a simple circuit configuration.

[0009]

The first problem shown in FIG.
The power supply circuit 4c is a circuit which is sensitive to an input voltage, a signal level of a trigger signal, a change in a load state, and the like due to its simple circuit configuration. Therefore, when the bad factors overlap at the time of startup, stable self-excited oscillation may not be performed. Then, while the trigger signal is in a high voltage state, there is a possibility that the switching transistor Q1 may remain in the on state, and there is a problem in safety of the device. Therefore, an object of the present invention is to provide a power supply device capable of reliably performing an operation.

[0010]

According to the present invention, there is provided a first power supply circuit in which a switching element performs a switching operation in response to a trigger signal supplied from the outside, and a second power supply circuit for generating an alternating voltage in the circuit. Wherein the full-wave rectified voltage of the alternating voltage generated in the second power supply circuit is supplied as a trigger signal to the first power supply circuit. Specifically, the first power supply circuit includes a series circuit of an inductance device and a switching element connected to an input terminal, a rectifying and smoothing circuit connected between the inductance device and an output terminal, and a control terminal of the switching element. A control transistor whose main current path is connected between the output terminal and one end of the main current path; and a feedback signal that is connected between the output terminal and the control terminal of the control transistor and corresponds to the difference between the output voltage and the reference voltage. And a feedback circuit that generates the trigger signal, and supplies the trigger signal to the control terminal of the switching element.

Alternatively, the first power supply circuit includes a series circuit of an inductance device and a switching element connected to the input terminal, a rectifying and smoothing circuit connected between the inductance device and the output terminal, A comparator having an output terminal connected to the control terminal, and a comparator of the first power supply circuit is supplied with a detection signal corresponding to the output voltage, a reference voltage signal, and a trigger signal. Configuration. Here, the second power supply circuit is constituted by a resonance type power supply,
The trigger signal is obtained by full-wave rectification of the resonance voltage generated there.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A winding end of a predetermined winding provided in a second power supply circuit is connected to a trigger input terminal of a first power supply circuit through two rectifying elements to form an AC full-wave waveform. The trigger signal is supplied by the voltage of. Here, a resonance type is used as the second power supply circuit. In the first embodiment of the present invention, a control transistor is connected between a base and an emitter of a switching transistor, and a constant voltage element is connected between a base of the control transistor and an output terminal of the power circuit. The trigger signal is input to the base of the switching transistor. In the second embodiment of the present invention, the first power supply circuit has a configuration of a separately excited PWM control system having a comparator, an error amplifier and a reference voltage source, and the trigger signal is input to the comparator instead of the triangular wave voltage. I do.

[0013]

FIG. 1 shows a circuit of a power supply device according to a first embodiment of the present invention which can be reliably operated. In the power supply device of FIG. 1, the first power supply circuit 4a is different from the conventional circuit of FIG. 3 in that a series circuit of a resistor R6 and a capacitor C3 connected to the base of a control transistor Q2 is omitted, and other circuits are omitted. The configuration is the same. On the other hand, in the second power supply circuit, the resonance capacitor C2 is connected in parallel to the primary winding N1 of the transformer T, the intermediate tap of the primary winding N1 is connected to the input terminal 1, and the primary winding N1
Are connected to the ground via transistors Q3 or Q4, respectively, so that an AC output voltage can be obtained from the secondary winding N2 of the transformer T via the terminals 5a, 5b and 5c. I have. The base side circuit of the transistors Q3 and Q4 of the second power supply circuit 6 is not shown.

In the power supply device of the present invention shown in FIG. 1, the trigger input terminal 3 of the first power supply circuit 4a is connected to the second power supply circuit 6a.
Are connected to one end and the other end of the primary winding N1 via a diode D2 and a diode D3, respectively. In the case of such a circuit configuration, first, the second power supply circuit 6 generates an alternating voltage in each winding of the transformer T when the transistors Q2 and Q3 are complementarily turned on or off. Here, when the switching frequency of the transistors Q2 and Q3 is substantially the same as the resonance frequency due to the inductance appearing in the primary winding N1 of the transformer T and the capacitance of the resonance capacitor C2, the alternating voltage becomes a resonance voltage and changes in a substantially sinusoidal manner. The resonance voltage generated in the secondary winding N2 of the transformer T is supplied as output voltage to the outside via the terminals 5a to 5c, while the resonance voltage generated in the primary winding N1 is full-wave by the diodes D2 and D3. Rectified,
It is supplied to the trigger input terminal 3.

The switching transistor Q1 in the first power supply circuit 4a is turned on or off according to a trigger signal in the form of an AC full-wave rectified waveform supplied via the trigger input terminal 3. That is, the switching transistor Q1 does not perform the self-excited oscillation operation as in the first power supply circuit 4c shown in FIG. 3, and the voltage value of the trigger signal supplied to the base via the resistor R1 becomes the threshold value between the base and the emitter. A simple switching operation of turning on when the voltage is higher than the voltage and turning off when the voltage is lower than the voltage is performed. Note that this switching operation appears at the time of start-up. During a steady operation, the switching transistor Q1 is turned off by the action of the control transistor Q2 even during a period when the voltage value of the trigger signal is high,
The switching operation is performed with the on-duty corresponding to the output voltage.

As described above, the first power supply circuit 4a shown in FIG.
Since the switching operation does not depend on self-excited oscillation,
The operation can be reliably performed. Additionally, according to the circuit configuration shown in FIG. 1, a special circuit is not required to obtain a trigger signal, and a power supply device can be constructed with a simple configuration.
In addition, the first operation which is performed by the trigger signal of the full-wave rectified waveform.
The power supply circuit 4a operates at twice the switching frequency of the second power supply circuit 6. Therefore, although the effect of the first power supply circuit 4c of FIG. 3 performing the self-excited oscillation operation is not obtained, the switching transistor Q1 is driven by at least the trigger signal itself by the clock pulse as shown in FIG. Also, an effect that the circuit can be downsized by increasing the switching frequency can be obtained.

FIG. 2 shows a circuit of a power supply device according to a second embodiment of the present invention. The circuit configuration of the power supply device shown in FIG. 2 is the same as that of the power supply device of FIG. 1 except that the configuration of the first power supply circuit 4b is as follows, and the other circuit portions are the same. Choke coil L1, switching transistor Q1, diode D1, and capacitor C1
Are connected to form a circuit configuration of a boost chopper converter as in FIG. A resistor R1 for bias supply is connected between the base of the switching transistor Q1 and the input terminal 1, and the output terminal of the comparator 7 is connected to the base of the switching transistor Q1. The trigger input terminal 3, the reference voltage source 8, and the output terminal of the error amplifier 9 are connected to the three input terminals of the comparator 7, respectively. Error amplifier 9-2
The two input terminals are connected to a reference voltage source 10 and a connection point of resistors R4 and R5 provided in series between the output terminal 2 and the ground.

First power supply circuit 4 in power supply device of FIG.
In short, b is such that a trigger signal in the form of an AC full-wave rectified wave is used instead of the triangular wave voltage required in general separately-excited PWM control. Therefore, the operation of the first power supply circuit 4b is the same as that of a boost chopper converter employing general separately-excited PWM control. That is, the error amplifier 9 generates an error signal corresponding to the difference between the detection signal corresponding to the output voltage obtained at the connection point between the resistors R4 and R5 and the reference voltage supplied from the reference voltage source 10. The comparator 7 compares the trigger signal with the error signal,
An on-duty drive signal corresponding to the output voltage is supplied to the switching transistor Q1. The reference voltage source 8
Is provided for setting the dead time of the switching transistor Q1.

In the power supply device of FIG. 2 having such a configuration, a separate oscillation circuit is not required for the first power supply circuit 4b, and the configuration of the power supply device can be simplified. Further, by using the resonance voltage obtained by full-wave rectification as a trigger signal, it is possible to reliably operate the first power supply circuit 4b, and at the same time, to use the first power supply circuit 4b and the second power supply circuit 6b. Operation and stop can be linked without using a special logic circuit. In the power supply device according to the embodiment of the present invention shown in FIGS. 1 and 2, the first power supply circuit (4a, 4b) is a non-insulated power supply circuit using a choke coil L1 as an inductance device. Alternatively, an insulation type power supply circuit using a transformer for the inductance device may be used.

[0020]

As described above, according to the present invention, the alternating voltage generated in the second power supply circuit is full-wave rectified, and the full-wave rectified voltage is supplied to the first power supply circuit as a trigger signal. It is characterized by doing. According to the present invention, it is possible to obtain a power supply device having a simple configuration, in which the operation states of the first and second power supply circuits cooperate with each other without providing a special circuit, and in which the power supply circuit operates reliably. Will be able to do it.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of a power supply device according to the present invention.

FIG. 2 is a circuit diagram of a power supply device according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a conventional power supply device.

[Description of Signs] 1 input terminal 2 output terminal (first power supply circuit) 3 trigger input terminal 4a, 4b first power supply circuit 5a to 5c output terminal (second power supply circuit) 6 second using resonance type power supply Power supply circuit 7 Comparator 8, 10 Reference voltage source 9 Error amplifier Q1 Switching transistor Q2 Control transistor

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference)

Claims (5)

[Claims] A first power supply circuit in which a switching element performs a switching operation in response to a trigger signal supplied from the outside; and a second power supply circuit that generates an alternating voltage in the circuit. A power supply device, wherein a full-wave rectified voltage of an alternating voltage generated in a power supply circuit is supplied to the first power supply circuit as a trigger signal. 2. The circuit of claim 1, wherein the first power supply circuit includes a series circuit of an inductance device and a switching element connected to an input terminal, a rectifying and smoothing circuit connected between the inductance device and an output terminal, and the switching device. A control transistor whose main current path is connected between the control terminal of the element and one end of the main current path; and a control transistor connected between the output terminal and the control terminal of the control transistor, the output voltage and the reference voltage. A feedback circuit for generating a feedback signal corresponding to the difference, wherein a full-wave rectified voltage of the alternating voltage generated in the second power supply circuit is used as a trigger signal to control the switching element of the first power supply circuit. Being supplied to the terminal.
The power supply device according to claim 1. 3. The power supply according to claim 2, wherein the feedback circuit comprises a constant voltage diode, and the inductance device comprises a choke coil. 4. A first power supply circuit comprising: a series circuit of an inductance device and a switching element connected to an input terminal; a rectifying and smoothing circuit connected between the inductance device and an output terminal; A comparator having an output terminal connected to a control terminal of the element, wherein the comparator of the first power supply circuit corresponds to a difference between a detection signal corresponding to an output voltage and a reference voltage signal. An error signal;
The power supply device according to claim 1, wherein a trigger signal obtained by full-wave rectifying the alternating voltage generated in the second power supply circuit is supplied. 5. The power supply device according to claim 1, wherein the second power supply circuit is a resonance-type power supply circuit, and the alternating voltage is a resonance voltage. .