JPH04368466A - Switching power source - Google Patents

Abstract

PURPOSE:To delay a rising time of a DC output voltage by suppressing a current flowing to a primary winding of a power transformer by a rectifier when a power switch is closed. CONSTITUTION:When a power source voltage is supplied to a television load, a relay drive transistor 51 is conducted by an ON signal from a remote control receiver, an electromagnetic power relay 50 is energized, and a relay contact 20 is closed. Thus, a current I'1 flows, and a resonance capacitor 21 is charged. A rectifier 60 becomes forward by the stored charge when the current I'1 is a negative cycle. That is, the charge stored in the capacitor 21 is discharged as the current I'1 in a circuit of a rectifying diode 61, a smoothing electrolytic capacitor 62, a winding 15c of a converter drive transformer 15 and the relay contact 20. Accordingly, a current flowing to the primary winding N1 of a power regulation transformer 22, is suppressed, and collector currents of switching transistors 9, 10 in a transient state, are suppressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply apparatus, and more particularly to a switching power supply apparatus having a switching power supply using a current resonant converter circuit of a fixed switching frequency series resonance frequency control type.

0002

[Prior Art] Recently, switching power supplies have been used in many consumer fields, such as large-sized televisions and satellite broadcast (BS) receivers, in response to demands for high efficiency, small size, light weight, and low noise. has been done. In addition, it can be used as a standby power supply (5V/10
0 mA). Here, remote control standby refers to a state in which, for example, due to the increasing popularity of color TVs with built-in BS tuners, an independent light load power (15W or less) is supplied only to the BS receiver for VTR recording mode. Say something.

[0003] As a switching power supply device used as a standby power supply when the remote controller is on standby in such a color television power supply, a switching power supply (so-called F-Z power supply) using a current resonant converter circuit with a fixed switching frequency and series resonance frequency control method is used. There is one that uses a system. Conventionally, this device has had the following problems because the primary and secondary windings of a power transformer made of silicon steel plates are insulated from the commercial AC power source. (a) The weight of the remote control power transformer is large. (b) There are drawbacks such as the need for magnetic shielding using permalloy as a countermeasure against leakage flux from the transformer.

[0004]Therefore, as a method for solving these problems, a method as shown in FIG. 4, for example, is known. This device is a switching power supply (
It is composed of a so-called F-Z power supply) and is combined with a standby power supply when the remote control is on standby. In the figure, reference numeral 1 denotes an AC power supply, which supplies a voltage of AC 80 to 144 V, for example, to a bridge circuit 3 via a resistor 2. The bridge circuit 3 is constructed by connecting four diodes 4 to 7 in a bridge manner. A capacitor 8 is connected to the output side of the bridge circuit 3.
are connected, and the switching transistor 9,
10 is connected to a half-bridge resonant converter including 10. The first half-bridge resonant converter includes a switching transistor 9, resistors 11, 12, a capacitor 13, a diode 14 and a converter drive transformer (CD
T) consists of a part of the winding 15a of 15. Further, the second half-bridge resonant converter includes a switching transistor 10, resistors 16 and 17, a capacitor 18,
Diode 19 and converter drive transformer (C
DT) 15 is constituted by a part of the winding 15b.

The converter drive transformer 15 has a primary
Insulation is ensured for both secondary and split bobbins. The transistor 9 is driven by a series resonant circuit consisting of a winding 15a, a resistor 12 and a capacitor 13, and similarly the transistor 10 is driven by a series resonant circuit consisting of a winding 15b, a resistor 17 and a capacitor 18. A portion of the winding 15c of the converter drive transformer 15 is connected to a primary winding N1 of a rectangular power regulation transformer (PRT) 22 via a relay contact 20 and a capacitor 21. Note that the current flowing through this primary winding N1 is I1.

[0006] Power regulation transformer 22-2
The next winding N3 is connected to a capacitor 24 via a bridge circuit 23.
The DC voltage of 15V/1.5A is taken out from here. Note that the middle point of this secondary winding N3 is grounded via the capacitor 25, and 7.
A DC voltage of 5V/1A is taken out. Further, the secondary winding N2 of the power regulation transformer 22 is connected to a capacitor 27 via a bridge circuit 26, from which a DC voltage Eo of 135V/0.8A is taken out, and this terminal is connected to a control circuit 28. ing. The control circuit 28 is composed of circuit elements including transistors, and is connected to the control winding N of the power regulation transformer 22.
Control the control current flowing through c. Furthermore, the secondary winding N4 of the power regulation transformer 18 is connected to a capacitor 31 via diodes 29 and 30,
A DC voltage of 24V/2A is taken out from here. Note that the middle point of this secondary winding N4 is a 0V terminal. Further, the winding ratio of the power regulation transformer 22 is N1/N2/N3/N4/Nc.

On the other hand, the winding 15c of the converter drive transformer 15 described above is connected to the primary winding N1' of the standby transformer 41 via a capacitor 40, and the voltage induced in the secondary winding N2' of the standby transformer 41 is The secondary voltage is rectified by diodes 42 and 43, and the rectified voltage is a 12V three-terminal series regulator IC4.
4. Note that the current flowing through the primary winding N1' is I2. Further, capacitors 45 and 46 are inserted on the secondary side of the standby transformer 41. Furthermore, the secondary side voltage of the standby transformer 41 is connected to a capacitor 45,
46, and its divided voltage output is 5V.
3-terminal series regulator IC47. A capacitor 48 is connected to the secondary side of this 5V three-terminal series regulator IC47.

[0008] As a result, a standby power of 5V/100mA is taken out based on the AC input power. Furthermore, 12V 3-terminal series regulator IC44
A capacitor 49 is connected to the secondary side of the capacitor 49, and is also connected to a transistor 51 via an electromagnetic power relay 50. When the electromagnetic power relay 50 is activated, the relay contact 2
0 is closed. An on/off signal for turning on/off the main load is supplied to the base of the transistor 51 via a resistor 52, and the electromagnetic power relay 5
A diode 53 is inserted at both ends of 0. In addition,
54 is a resistor connected to the base circuit of the transistor 51. The level of the on/off signal is es.

[0009] Such a power supply device uses a switching power supply (F-Z power supply) using a current resonant converter circuit with a fixed switching frequency series resonance frequency control system, and when an AC voltage is supplied from the AC power supply 1, After being rectified by the bridge circuit 3, the switching transistor 9,
10 alternately turns on/off at a predetermined switching frequency.
Due to the switching operation with the polarity repeating OFF, a resonant current flows through the standby transformer 41, and an alternating current voltage is generated on the secondary side of the standby transformer 41.
A voltage of V is supplied to the series regulator IC44. Then, when the relay drive transistor 51 is turned on by the on/off signal, the electromagnetic power relay 50 is turned on and its relay contact 20 is closed, and the main current flows to the power regulation transformer 22, and the second
The next-side voltage is rectified, resulting in 7.5V, 15V, 24V,
DC voltages of V and 135V are respectively taken out and supplied to the large-capacity main electronic equipment.

On the other hand, when the remote control is on standby, a standby power of 5V/100mA is taken out from the 5V three-terminal series regulator IC47 through the standby transformer 44.

[0011]

However, since such a power supply device includes a resonant capacitor 40, a standby transformer 41, and an electromagnetic power relay 50, when the electromagnetic power relay 50 is off, the standby transformer 41 is turned off. 150KH as switching frequency
It operates with a resonant current of However, there were new problems as follows.

(a) When the electromagnetic power relay 50 is turned on, the switching transistors 9,
An excessive collector current flows through 10. Therefore, the maximum rating of the transistor increases, making it larger and increasing cost. (b) The rise time of the 135V DC voltage Eo is fast;
For example, when applied to television broadcasting, the desirable characteristic of soft start cannot be obtained.

[0013] These drawbacks will now be explained with reference to the operating waveform diagram shown in FIG. First, during standby before t=t1, the half-bridge configuration switching transistors 9 and 10 are determined by the resistors 12 and 17, capacitors 13 and 18, and the winding of the converter drive transformer 15, which are part of the self-oscillation drive circuit, respectively. The switching frequency Fs is 15 as expressed by the following formula.
Switching operation is performed by alternating on/off polarity at 0KHz. Fs=1/2πLb・Cb However, Lb: Value of resistors 12 and 17 Cb: Value of capacitors 13 and 18

[0014] A resonance current I2 for the standby transformer 41 is determined by the resonance capacitor 40 and the inductance of the primary winding N1' of the standby transformer 41.
flows by 1Ap-p (P-P: peak-to-peak value), and as a result, the secondary winding N of the standby transformer 41
An alternating current voltage is generated at 2', and a direct current output voltage of 15 V for the power drive and 7.5 V for the remote control receiver is obtained.

Next, when the relay drive transistor 51 is made conductive by the on/off signal at timing t=t1, the electromagnetic power relay 50 is turned on, its relay contact 20 is closed, and the main resonant current I1 is transferred to the series resonant capacitor 21. A sinusoidal resonant current flows due to the resonance caused by the inductance in the primary winding N1 of the power regulation transformer 22.
Immediately after t=t1, 4
A sinusoidal current with a value of 0 Ap-p drops to a steady 10 Ap-p in a few cycles.

At this time, the switching transistors 9,
As shown in Fig. 2, the collector currents Icp1 and Icp2 of No. 10 are excessive values as the main resonance current is superimposed on the collector current 0.5Ap-p during standby, and the steady collector current 5.5Ap-p at maximum load. 20.
A transistor having a maximum rated current of 5 Ap-p or more is required. Therefore, it is necessary to use a large transistor, which increases the cost.

Furthermore, as shown in FIG. 2, the DC output voltage Eo
The rise characteristic after the timing of t=t1 is fast, and the steady state is reached in 50ms, so the load digital IC
This may cause malfunction, so it is necessary to provide a soft start function.

The present invention has been made in view of the above-mentioned circumstances, and reduces the maximum rating of the switching transistor to enable miniaturization and cost reduction, and also slows down the rise time of the DC output voltage to achieve soft start. The purpose of this invention is to provide a power supply device that can be given specific characteristics.

[0019]

[Means for Solving the Problems] In order to solve the above-mentioned problems, a switching power supply device according to the present invention uses a switching power supply (F-Z power supply) using a current resonant converter circuit of a fixed switching frequency series resonance frequency control system. The switching power supply has a transistor drive transformer that drives the switching transistor, and a standby transformer that outputs a predetermined small-capacity standby output voltage and a power supply that outputs a predetermined large-capacity output voltage are installed downstream of the switching power supply. A power supply device in which a power switch is inserted between the transistor drive transformer and the power transformer, and an output of a switching power supply system is supplied to the power transformer by the power switch. A rectifier circuit is provided to be connected to the primary winding of the transformer, and the rectifier circuit supplies current in a direction that suppresses the current flowing to the primary winding of the power transformer when the power switch is turned on. It is characterized by being configured to flow.

[0020]

According to the present invention, when the power switch is turned on, the rectifier circuit suppresses the current flowing through the primary winding of the power transformer, and as a result, the collector current of the switching transistor in a transient state is suppressed. therefore,
The maximum rating of the switching transistor is reduced, resulting in smaller size and lower cost. Furthermore, the rise time of the DC output voltage is delayed, making it possible to provide soft start characteristics.

[0021]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention, and is an example in which the present invention is applied to a power supply device for a color television. In explaining FIG. 1, FIG. 4 is shown as a conventional example.
The same components are given the same reference numerals, and redundant explanation will be omitted. The difference between this embodiment and the configuration shown in FIG. 4 is that the converter drive transformer (equivalent to a transistor drive transformer)
15 and power regulation transformer (PRT) 22
The rectifier circuit 60 is connected to the primary winding N1 of
The point is that this is provided.

The rectifier circuit 60 includes a rectifier diode 61, a smoothing electrolytic capacitor 62, and a discharge resistor 63.
The rectifier diode 61 is connected in series with a smoothing electrolytic capacitor 62 with the forward direction being from the power regulation transformer 22 to the converter drive transformer 15, and a discharging resistor 6 is connected to the smoothing electrolytic capacitor 62.
3 are connected in parallel. The rectifier circuit 60 is connected to the connection point between the winding 15c and the emitter of the switching transistor 9 on the converter drive transformer 15 side, and is connected to the connection point between the primary winding N1 and the resonant capacitor 21 on the power regulation transformer 22 side. ing. When the electromagnetic power relay 50 is turned on and its relay contact 20 (corresponding to a power switch) is closed, the rectifier circuit 60 suppresses the current flowing through the primary winding N1 of the power regulation transformer 22, resulting in The collector currents of the switching transistors 9 and 10 in a transient state are suppressed.

With the above configuration, the operation of this apparatus will be explained with reference to the operational waveform diagram shown in FIG. First, when trying to supply power to a TV load, when a level es is applied to the base of the relay drive transistor 51 by an on signal from the remote control receiver at timing t=t1, this relay drive transistor 51 becomes conductive. When the electromagnetic power relay 50 turns on, its relay contact 2
0 closes. This causes the relay contact 20 to receive a current I1'
flows and is accumulated in the resonant capacitor 21, but this accumulated charge is transferred to the rectifier circuit 6 during the negative cycle of the current I1'.
Since 0 is the forward direction, the current flows through the rectifier circuit 60. That is, the charge accumulated in the resonant capacitor 21 during the negative cycle is discharged as a current I1' through the path of the rectifier diode 61 -> the smoothing electrolytic capacitor 62 -> the winding 15c of the converter drive transformer 15 -> the relay contact 20. Therefore, no current flows through the primary winding N1 on the power regulation transformer 22 side.

During the next positive half cycle, the charge in the smoothing electrolytic capacitor 62 is discharged via the discharging resistor 63 according to the time constant of the smoothing electrolytic capacitor 62 and the discharging resistor 63. The rectifier diode 6 is charged by the amount that the smoothing electrolytic capacitor 62 is discharged in half a cycle.
1 from the smoothing electrolytic capacitor 62. Since such operations are repeated, the capacitance of the DC output smoothing electrolytic capacitors 24, 25, 27, and 31 on the secondary side of the power regulation transformer 22 is determined by the magnitude of the load power.

Here, for example, capacitor 27=100μ
F, capacitor 25=2200μF, capacitor 24=
When the capacitor 31 is selected to have a capacity of 1000 μF and a capacitance of 2200 μF, the charging inrush current is significantly suppressed by adding the rectifier circuit 60. For example, as the constant of each element of the rectifier circuit 60, the smoothing electrolytic capacitor 62=4.7μ
F, when the value of discharge resistor 63 = 68KΩ is selected, the current flowing through each part in FIG. 1, that is, the current I1' flowing through relay contact 20 and switching transistors 9, 1
As shown in FIG. 2, the collector currents Icp1' and Icp2' at 0 are significantly reduced compared to the conventional case, and are approximately 1/2 of the conventional value. Therefore, switching transistor 9
, 10 is reduced to about twice the steady current, it becomes possible to use a small switching transistor in a TO-220 package, for example, and cost reduction can be achieved.

Furthermore, regarding the 135V DC output voltage Eo supplied to the television, t=
The rise characteristic after the timing t1 can be delayed, and a soft start characteristic can be provided. As a result, the possibility of malfunction of the load digital IC can be eliminated.

Next, FIG. 3 is a diagram showing the configuration of a second embodiment of the present invention. In the first embodiment, the switching transistor has a half-bridge configuration and one set of rectifier circuits is provided, but in this second embodiment, the switching transistor has a full-bridge configuration and two sets of rectifier circuits are provided. . Portions different from the configuration in FIG. 4 will be explained. In FIG. 3, a capacitor 70 is connected to the output side of the bridge circuit, and switching transistors 71 and 72 are connected to the output side of the bridge circuit.
connected to two sets of half-bridge resonant converters, including: The first half-bridge resonant converter includes a switching transistor 71, resistors 73 and 74, and a capacitor 75.
, diode 76 and converter drive transformer (
CDT) 77 and a part of the winding 77a. Further, the second half-bridge resonant converter includes a switching transistor 72, resistors 78 and 79, and a capacitor 8.
0, a diode 81, and a part of the winding 77b of the converter drive transformer (CDT) 77.

The converter drive transformer 77 has a primary
Insulation is ensured for both secondary and split bobbins. The transistor 71 is driven by a series resonant circuit consisting of a winding 77a, a resistor 74, and a capacitor 75.
Similarly, transistor 72 is driven by a series resonant circuit consisting of winding 77b, resistor 79 and capacitor 80. The secondary side of the converter drive transformer 77 also constitutes a half-bridge resonant converter including its winding. That is, the third half-bridge resonant converter includes a switching transistor 82, resistors 83, 8
4, a capacitor 85, a diode 86, and a part of the winding 77c of the converter drive transformer 77. Further, the fourth half-bridge resonant converter is constituted by a switching transistor 87, resistors 88 and 89, a capacitor 90, a diode 91, and a part of the winding 77d of the converter drive transformer 77. Transistor 82 is driven by a series resonant circuit consisting of winding 77c, resistor 84 and capacitor 85, and transistor 87 is similarly driven by a series resonant circuit consisting of winding 77d, resistor 89 and capacitor 90. Note that the collector currents flowing through the transistors 71 and 82 are Icp1' and Icp2', respectively.

A part of the winding 77e of the converter drive transformer 77 is connected to a rectangular power regulation transformer (PRT) via a relay contact 92 and a capacitor 93.
22 primary winding N1. Note that the current flowing through this primary winding N1 is I1'. In addition, the same winding 7
7e is connected via a capacitor 94 to the primary winding N1' of a standby transformer 41 similar to the first embodiment. Note that the current flowing through the primary winding N1' is I2. Relay contacts 92 are actuated by electromagnetic power relay 50.

Next, the rectifier circuit, which is a feature of this embodiment, will be explained. The converter drive transformer 77
winding 77e and power regulation transformer (PR
A rectifier circuit 100 is provided so as to be connected to the primary winding N1 of T) 22 via a relay contact 92. The rectifier circuit 100 includes two sets of rectifier diodes 101 and 102.
, smoothing electrolytic capacitors 103, 104, and discharge resistors 105, 106. rectifier diode 10
1. Smoothing electrolytic capacitor 103 and discharge resistor 10
5 is a set of power regulation transformer 22
The rectifying diode 102, the smoothing electrolytic capacitor 104, and the discharging resistor 106 are arranged as the other pair, and the direction from the power regulation transformer 22 to the converter drive transformer 77 is the forward direction. It is placed in the opposite direction.

In the second embodiment having such a configuration, especially when the load power is 200 W or more, the current resonant converter circuit has four switching transistors 71, 72, 82.
. Similarly, the charging inrush current is significantly suppressed by adding the rectifier circuit 100. Therefore, the switching transistors 71, 7 in the transient state when the power switch is turned on.
The collector current of the switching transistors 71, 72, 82, and 91 can be suppressed, and the maximum rating of the switching transistors 71, 72, 82, and 91 can be reduced to reduce the size and cost, and it also has soft start characteristics. can be set.

Although the above embodiment is an example in which the present invention is applied to a power supply device for a television, the present invention is not limited to this and can be applied to other electronic devices.

[0033]

[Effects of the Invention] As explained above, according to the present invention,
The collector current of the switching transistor in a transient state when the power switch is turned on can be suppressed, and the maximum rating of the switching transistor can be reduced to achieve miniaturization and cost reduction. Further, the rise time of the DC output voltage can be delayed, and the possibility of malfunction of the load digital IC can be eliminated by providing a soft start characteristic.

[Brief explanation of drawings]

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

FIG. 2 is a waveform diagram illustrating the operation of the same embodiment.

FIG. 3 is a circuit diagram showing the configuration of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional power supply device.

[Explanation of symbols]

1: AC power supply 15, 77: Converter drive transformer (CDT) 2
2: Orthogonal power regulation transformer (PRT) 41: Standby transformer 50: Electromagnetic power relay 60, 100: Rectifier circuit 61, 101, 102: Rectifier diode 62, 103,
104: Smoothing electrolytic capacitor 63, 105, 106:
Discharge resistance

Claims (1)

[Claims] 1. A switching power supply (F-Z power supply) using a current resonant converter circuit with a fixed switching frequency and series resonance frequency control method, the switching power supply having a transistor drive transformer for driving a switching transistor, A standby transformer that takes out a predetermined small-capacity standby output voltage and a power transformer that takes out a predetermined large-capacity output voltage are arranged at the subsequent stage, and a power switch is inserted between the transistor drive transformer and the power transformer. in a switching power supply device in which the output of the switching power supply is supplied to the power transformer by the power switch,
A rectifier circuit is provided to connect the transistor drive transformer and the primary winding of the power transformer, and the rectifier circuit controls the current flowing through the primary winding of the power transformer when the power switch is turned on. A switching power supply device characterized in that it is configured to allow current to flow in a direction to be suppressed.