JPH0429562A - Switching power source device having standby power circuit - 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] [Industrial Application Field] This invention relates to a switching power supply device equipped with a standby power supply circuit that continues to supply power to some circuits for some kind of standby operation even after the power switch is turned off. In particular, the present invention relates to a switching power supply device having a resonant converter and a power-saving, small-sized standby power supply circuit.

[Summary of the invention]

The present invention relates to a switching power supply device having a standby power supply circuit, and in a switching power supply device having a resonant converter using a resonance frequency control method with a fixed switching frequency, a first resonant circuit for a main power supply section and a second resonant circuit for a standby power supply section are provided. 2 resonant circuits, the first and second resonant circuits are connected to a common switching circuit, and a connection point between the second resonant circuit and the switching circuit is connected to the first resonant circuit. This is a switching power supply device that has a standby power supply circuit equipped with a main power switch.

This improves the power conversion efficiency of the standby power supply circuit, reduces the size of the power supply cadence of the standby power supply circuit, eliminates the need for magnetic shielding, and allows mounting on a printed circuit board.

Furthermore, the inrush current when the main power switch is turned on is reduced, so
Power supply voltage drop and heat generation can be prevented by short-circuiting the inrush current limiting resistor.

[Conventional technology]

Some power supply devices include a standby power supply circuit that continues to supply voltage to some circuits for some kind of standby operation even after the power switch is turned off. For example, Figure 6 shows an example of a power supply circuit for a color television receiver.
V) Main power supply circuit for the receiver body, power supply circuit for the remote control device (remote control) receiver, and satellite broadcasting (
BS) The tuner and converter power supply circuits are provided separately.

The power supply circuit for the remote control receiving unit, which also operates the on/off of the main power switch of the TV receiver body, and the power supply circuit for the BS tuner and BS converter, in which reservation reception using a timer, etc., are performed, are used to receive TV images. Even if the main power switch for the main body of the machine is turned off, the power supply continues.

In the example shown in FIG. 6, the main power supply circuit for the main body of the TV receiver is a switching power supply using a current resonance converter of a type in which the switching frequency is fixed and the series resonance frequency is controlled. Switching transistors Q1 and Q2 alternately connect to a converter drive transformer (CDT).
), the high-frequency current generated by this automatic oscillation that repeatedly turns on and off at a cycle determined by the inductance of the secondary winding L8 and the capacitance of the capacitor C8 can be controlled by controlling the inductance by direct current flowing through the control winding. A sine wave is formed by a series resonant circuit constituted by the inductance of the negative winding N1 of the power output control transformer (PRT) and the capacitance of the capacitor CI connected in series thereto.

Since the switching transistors Q, , and Q are turned on and off near the zero cross of the sinusoidal current, the switching loss is small, and because of the high frequency, the power output control transformer (PRT) and converter drive transformer (CDT) are also used. It has become more compact, resulting in a compact and highly efficient switching power supply.

Note that the output voltage is made constant by magnetically controlling the series resonance frequency of the PRT so that, for example, the maximum output power can be obtained when the series resonance frequency of the PRT matches the switching frequency. .

In the example shown in Fig. 6, the standby power supply for the remote control device (remote control) receiving section is provided with a small power transformer PT-1, and is connected via a 3-terminal regulator, for example
A DC voltage of 2V is obtained.

Relay (RL) for driving main power switch 5w-1
) is also supplied with voltage from this power supply. Since this power supply is always energized, it is desirable that the power loss is as small as possible, but the power transformer PT-1 is made of silicon steel plate, etc.
．． The weight of the transformer required for 0W (watt) power transmission is, for example, about 100 grams, and the power conversion efficiency is, for example, 5.
It is low at around 0%.

In the example shown in Fig. 6, the standby power supply for the BS tuner and converter is a large power supply truss PT-2.
For example, four types of DC stabilizing voltages of ±5 volts, 12 V, and 15 volts are obtained through three-terminal regulators. Power transformer PT-2 is 12.0W (watt)
The weight of the transformer required for power transmission is, for example, about 1.2 kilograms, and the power conversion efficiency is, for example, about 60%.

As shown in the above example, the conventional technology in which a standby power transformer is provided separately from the power supply for the TV receiver body has the following problems.

First, since the power transformers PT-1 and PT-2 are excited at the frequency of the commercial input power source (50Hz or 60Hz), leakage magnetic flux is large, and in the case of a power supply for a TV receiver, this may cause mislanding of the picture tube. It was necessary to place the power transformers PT-1 and PT-2 in a location where there is no magnetic flux, or to provide sufficient magnetic shielding to the power transformers PT-1 and PT-2.

Secondly, the power transformers PT-1 and PT-2 are heavy and generate a lot of heat, so they cannot be mounted on a printed circuit board together with other circuit components.

Thirdly, the output voltage from the power transformers PT-1 and PT-2 changes with fluctuations in the input voltage of the commercial input power supply, so in order to maintain the output DC voltage at a constant voltage, the voltage at the three-terminal regulator must be adjusted. It was necessary to increase the drop (t-force loss), and a heat sink was required for this purpose.

Fourthly, the power transformers PT-1 and PT-2 are large in size, and are expensive because they require particularly high power conversion efficiency and magnetic shielding.

In addition to the above, in the example shown in Figure 6, when the load power of the power supply for the TV receiver main body is large, the power loss and heat generation of the inrush current limiting resistor Ri when the main power switch 5W-1 is turned on is caused. There was a problem with the amount being too large.

[Problems to be Solved by the Invention] The present invention solves the problems described in the prior art section, and provides a compact and lightweight standby power transformer that does not require magnetic shielding, has high power conversion efficiency, generates little heat, An object of the present invention is to obtain a power supply device having an inexpensive standby power supply circuit.

In addition, it is desirable to solve the problem of large power loss due to the inrush current limiting resistor when the power supplied by the main power supply is large.

(Means for Solving the Problems) In the present invention, the switching frequency of a switching circuit connected to a resonant circuit having a transformer that supplies power to a load is fixed, and the output voltage is controlled by controlling the resonant frequency of the resonant circuit. In a switching power supply device having a control type resonant converter, the first resonant circuit of the main power supply section to which a load is connected when the main power switch is turned on.
and a second resonant circuit, which is the resonant circuit of the standby power supply unit that supplies power to a predetermined load that is kept in standby operation even after the main power switch is opened, the first resonant circuit and the second resonant circuit. The standby power supply is connected to the switching circuit that is common to the circuit, and the main power switch is arranged between a connection point between the switching circuit and the second resonant circuit and the first resonant circuit. A switching power supply device having a circuit.

Furthermore, in the switching power supply device having this standby power supply circuit, a second power switch is provided that opens and closes in conjunction with the main power switch, and the second power switch limits the inrush current of the commercial input power supply. The switching power supply device may be characterized in that the inrush current limiting resistor can be short-circuited.

Further, the transformer of the second resonant circuit may be, for example, a power supply output transformer with a fixed inductance whose resonant frequency is approximately equal to the switching frequency; For example, a structure configured such that at least the inductance of the primary winding can be controlled by passing a direct current through the control winding may be used. Alternatively, the transformer of the second resonant circuit may be provided with a winding for driving a switching transistor of the switching circuit.

[Effect]

In the present invention, the alternating current power supplied to the second resonant circuit having the power output voltage of the standby power supply section is supplied as high frequency power from a switching circuit common to the main power supply section. Since the resonant frequency of the second resonant circuit is approximately matched to the frequency of the high-frequency power,
The power output transformer of the standby power supply section can be made smaller by using a ferrite core or the like to improve power conversion efficiency. Furthermore, since it handles high-frequency sinusoidal currents and leakage magnetic flux is small, a magnetic shield is not required, and as a result, it can be mounted on a printed circuit board.

Further, since the second resonant circuit converts the high frequency into a sine wave and switches the high frequency in the vicinity of zero voltage or current, there is little switching loss due to passing through the switching circuit.

In addition to the above, the present invention has a new effect by significantly changing the position of the main power switch compared to the conventional example. That is, by disposing the main power switch between the connection point between the switching circuit and the second resonant circuit and the first resonant circuit, in the present invention, the main power switch is connected after the smoothing capacitor after rectifying the commercial input power supply. There is a power switch, so the inrush current when the main power is turned on is extremely small. Therefore, in conjunction with turning on the main power switch, the inrush current limiting resistor to the commercial input power source can be short-circuited.

Thereby, a switching power supply device can be obtained in which voltage drop and heat generation at the inrush current limiting resistor due to large current during operation of the main power supply section are prevented.

Furthermore, in the present invention, in place of the power supply output transformer of the standby power supply section, a control winding is added that can control the inductance of the -order winding of the transformer by direct current (for example, a saturable reactor transformer). By adding a voltage stabilization function using a power supply output control transformer, it is possible to reduce cross regulation between each DC output voltage due to fluctuations in the input AC voltage. On the other hand, when a voltage drop type voltage stabilizing circuit (regulator) is used to stabilize the voltage, the internal drop voltage can be lowered, power loss is reduced, and a heat sink can be eliminated.

Furthermore, if a winding for driving the switching transistor of the switching circuit is provided in the power output transformer of the standby power supply section, a converter drive transformer (CDT) for driving the switching transistor can be eliminated, and the circuit can be simplified. can do.

〔Example〕

A first embodiment of the present invention will be described with reference to FIG.

First, a commercial input power source is passed through an inrush current limiting resistor Ri, a rectifier circuit with a diode bridge, and a smoothing circuit with a smoothing capacitor to obtain a DC input voltage, which is supplied to the switching circuit.

Then, from the resonant circuit connection point d (hereinafter referred to as connection point a) on the switching circuit, a power output control transformer for the main power supply part, which is opened and closed by the main power switch 5W-IA, is connected via the main power switch 5W-IA. (PRT) - next winding N1
and a capacitor C2, and rectifies the voltage from the secondary winding of the PRT to obtain a DC output voltage E ON for the main power supply section. The above configuration differs from the conventional main power supply unit shown in Fig. 6 mainly in that the main power switch 5W-IA is inserted between connection point a and PRT, and the symbols are also the same. It shows.

On the other hand, in the first embodiment, the secondary winding N of the power supply quadrence (SET) of the standby power supply circuit continues to be energized from the connection point a even if the main power switch 5W-IA is in the open state. A second resonant circuit consisting of a capacitor C0 is connected.

The resonant frequency of the second resonant circuit is determined by the inductance of the secondary winding of the converter drive transformer (CDT) on the switching circuit and the capacitance of the capacitor C1 connected in series with it. The current ICP+ flowing through the switching transistor Q and the current rcr□ flowing through the switching transistor Q2 alternately flow into the second resonant circuit, and the resonance of the second resonant circuit is made almost equal to the frequency. Current I11 is sinusoidal. Since the transistors Q, , and Q repeat switching alternately near zero current, switching loss can be made extremely small. This operating waveform diagram is shown in FIG. 3(a).

Next, when the main power switch 5W-IA is closed, the switching frequency remains fixed and the switching current flowing through the first resonant circuit is added. The resonant current flowing through the first resonant circuit is also sinusoidal. This operating waveform diagram is shown in FIG. 3(b).

By the way, the switching frequency can be set to a high frequency of, for example, 100 kHz or more, since the switching loss is small. Therefore, the standby power supply ratio quadrance (SET) can be a small transformer using a ferrite core, such as the EE type (Japanese Industrial Standard JIS C2514) shown in FIG. 2, for example. Further, because of the sinusoidal current having a high frequency of, for example, 100 KHz or more, leakage magnetic flux is reduced, a magnetic shield is not required, and the device can be mounted as is on a printed circuit board.

Incidentally, according to a specific design example in the first embodiment, when the switching frequency is 150 KHz and the DC output of the standby power supply is 13 W, the weight of the SBT using the EE type roughherite core is only 6 grams. Power conversion efficiency during standby was 70%. At this time,
Commercial AC input power is 18.6W for DC output 13W
This is a reduction of 3.4W compared to 22W in the conventional example shown in FIG. This is an extremely large effect in reducing power consumption during standby.

Furthermore, in the first embodiment, when the main power switch is turned on, the inrush current limiting resistor Ri is also short-circuited to reduce power loss during operation of the main power supply section. For example, when the main power supply output is 200W, this effect reduces power consumption by about 5W, and the inrush current limiting resistor Ri can be changed from a cement resistor of 1Ω/20W to a wire-wound resistor of 4.7Ω/3W, for example. It becomes smaller. In addition, in the first embodiment, the main power switch is inserted in the circuit after the smoothing capacitor after rectifying the commercial input power supply and before the first resonant circuit, so compared to the conventional example, when the main power switch is turned on, The rush current is small, and the second power switch 5W-2 may be closed simultaneously with the main power switch 5W-LA using a two-circuit, one-contact relay RL.

Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment.
The difference is that a small power output control transformer (PRT) is used in place of the SBT that constitutes the resonant circuit to stabilize the voltage. As the PRT, for example, an orthogonal saturable reactor transformer as shown in FIG. 7 can be used, in which the magnetic fields generated by the primary and secondary windings and the magnetic field generated by the control winding are orthogonal to each other. A configuration in which the PRT for the main power supply section is made smaller may be sufficient. DC output voltage E. , select one voltage that you want to stabilize at the AC voltage stage, compare that voltage with the reference value, obtain a DC current for the control winding drive according to the error signal, and then By passing a DC current through the wire, the inductance of the -order winding and the secondary winding is controlled, and the resonant frequency of the second resonant circuit is controlled to change the magnitude of the deviation from the switching frequency, and the load or The output voltage is stabilized against fluctuations in the input voltage.

With this configuration, the cross regulation of each DC output voltage is also greatly improved, so the drop voltage of the voltage drop type constant voltage circuit (for example, a 3-terminal regulator) used in the second embodiment can be reduced. Since the heat generation is reduced, there is an effect that the heat sink of the three-terminal regulator is not required.

Note that the standby power output control transformer PRT-2 has the configuration shown in FIG. 7, for example, and has a switching frequency of 150KH2.
In the case of a standby power supply with a DC output of 13W, the total weight is only about 22 grams, and the power conversion efficiency during standby is further improved than the first embodiment, reaching 75%, and is 4.5% lower than the conventional example shown in FIG. This results in a 7W reduction in power consumption.

Next, a third embodiment of the present invention will be described based on FIG. 5.

In the third embodiment, the converter drive transformer (CDT) on the switching circuit is omitted from the second embodiment, and two sets of drive windings N are wound around the PRT-2. This simplifies and reduces costs.

Although not shown, it is clear that in the second and third embodiments, the inrush current limiting resistor can be short-circuited when the main power switch is turned on, similarly to the first embodiment.

〔Effect of the invention〕

By implementing the present invention, it is possible to obtain a switching power supply device having a resonant converter in which the switching circuit of the main power supply unit is also used in the standby power supply circuit. This improves the power conversion efficiency of the standby power supply circuit, reduces the size of the power output transformer of the standby power supply circuit, eliminates the need for a magnetic shield, and provides a switching power supply device having a standby circuit that can be mounted on a printed circuit board.

Furthermore, it is possible to obtain a switching power supply device in which the inrush current when the main power switch is turned on is reduced, and the inrush current limiting resistor is short-circuited in conjunction with the main power switch on, and the power consumption when the main power supply section is operated is also reduced. I can do it.

Furthermore, the power conversion efficiency can be further improved by using a power output control transformer such as a saturation reactor transformer having a control winding capable of controlling inductance as the power output transformer of the standby power supply circuit.

Further, by providing a winding for driving the switching transistor of the switching circuit in the power output transformer of the standby power supply circuit, it is possible to obtain a switching power supply device with a simple configuration in which a converter drive transformer for driving the switching transistor is omitted.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, and FIG. 2 is a standby power supply output voltage (SB) used in the first embodiment.
This is an example of the structure of T). FIG. 3 is an operating waveform diagram of the first embodiment, and (a) is 5W-
When IA and 5W-2 are open, (b) is 5W-IA and 5W
-2 indicates occlusion. FIG. 4 is a circuit diagram of a main part of a second embodiment of the invention, and FIG. 5 is a circuit diagram of a main part of a third embodiment of the invention. FIG. 6 is a circuit diagram of a conventional example, and FIG. 7 is a structural example of a power output control transformer (PRT). Soil---------------1-------Switching circuit 2----------------1--
-----First resonant circuit U----1~------
----------Second resonant circuit SW -2---
------ To the second power switch Ri----
−・−−−−−−−−・Inrush current limiting resistor CD T−
-1- to -----11--Converter drive transformer Nc, Nc+-.-1--Control winding S B
T---------------Standby power output transformer N21 Fig. 2 Structure example of standby power output quadrant 7, (SBT) used in the first implementation (η) Fig. 3 Fig. 4 Rhyme circuit diagram of the second embodiment of the present invention (11) Fig. 5 Key circuit diagram of the third embodiment of the present invention

Claims (1)

[Claims] 1. A resonant converter in which the switching frequency of a switching circuit connected to a resonant circuit having a transformer that supplies power to a load is fixed, and the output voltage is controlled by controlling the resonant frequency of the resonant circuit. In the switching power supply device, power is supplied to the first resonant circuit, which is the resonant circuit of the main power supply unit to which the load is connected when the main power switch is turned on, and to a predetermined load that is kept in standby operation even after the main power switch is opened. a second resonant circuit that is the resonant circuit of a standby power supply section, the first resonant circuit and the second resonant circuit are connected to the common switching circuit, and the switching circuit and the second resonant circuit A switching power supply device having a standby power supply circuit, characterized in that the main power switch is disposed between a connection point between the main power supply circuit and the first resonant circuit. 2. The switching power supply device having a standby power supply circuit according to claim 1, further comprising a second power switch that opens and closes in conjunction with the main power switch, and the second power switch limits inrush current of the commercial input power supply. A switching power supply device characterized in that an inrush current limiting resistor can be short-circuited. 3. The switching power supply device having a standby circuit according to claim 1, wherein the transformer of the second resonant circuit has a control winding for controlling the inductance of the transformer. 4. The switching power supply device having a standby circuit according to claim 1, wherein the transformer of the second resonant circuit is provided with a winding for driving a switching transistor of the switching circuit. 5. The switching power supply device according to claim 2, wherein the transformer of the second resonant circuit is provided with a control winding for controlling the inductance of the transformer. 6. The switching power supply device according to claim 2, wherein the transformer of the second resonant circuit is provided with a winding for driving a switching transistor of the switching circuit.