JPH1028376A - Switching power supply and television receiver using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the stability of an outputted DC voltage which conventionally has been unstable under a widely fluctuating load in a switching power supply which supplies a stabilized DC voltage. SOLUTION: The stability of a second DC voltage, outputted by a secondary winding 3c, a diode 7 and a capacitor 8 is improved by a voltage detecting circuit 10, a control circuit 11 and a control circuit 13; the voltage detecting circuit 10 detects a first DC voltage outputted by a secondary winding 3b, a switching means 4 and a capacitor 5. The control circuit 11 turns on a switching means 2 on the primary winding side, after the switching means 4 has been turned off and turns off the switching means 2, so as to stabilize the first outputted DC voltage with the data from the voltage-detecting circuit 10. The control circuit 13 turns on the switching means 2 after the switching means 2 is turned off and turns off the second switching means 4, when the current value of the secondary winding 3b reaches the one which is adapted to be changed by a signal, corresponding to a load from a control signal-inputting terminal 14, based on the data, from a switching current-detecting circuit 12 which detects the current of the secondary winding 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply for supplying a stabilized DC voltage to various industrial and consumer electronic devices.

[0002]

2. Description of the Related Art In recent years, switching power supply devices have been used to reduce the cost, size, and performance of various electronic devices for industrial and consumer use.
Along with energy saving, there is a strong demand for smaller, low-noise, high-stability output and high-efficiency devices, and various systems have been proposed. Hereinafter, a conventional switching power supply device will be described.

Conventionally, as such a switching power supply, there is a switching power supply disclosed in, for example, Japanese Patent Application Laid-Open No. 7-67329 as shown in FIG. In FIG. 9, reference numeral 1 denotes an input DC voltage source, which is assumed to be an input DC voltage Vin. Reference numeral 2 denotes first switching means, which includes a first switching element 2a and a first diode 2b.
Reference numeral 3 denotes a transformer having a primary winding 3a and a (first) secondary winding 3b, and an input DC voltage Vin is converted into a high-frequency AC voltage by a first switching means 2 as a high-frequency AC voltage.
Input to the next winding 3a. Reference numeral 4 denotes second switching means, which includes a second switching element 4a and a second diode 4
b. 5 is the first output capacitor, 6-
Reference numeral 6 'denotes a first output terminal.
The flyback voltage generated at b is supplied to the load via the second switching means 4 and the first output capacitor 5 as the first output DC voltage Vout1. 10 is the first
And detects the first output DC voltage. Reference numeral 11 denotes a first control circuit, which turns on the first switching element 2a after the second switching means 4 is turned off, receives information from the first voltage detection circuit 10, and outputs a first output DC voltage Vout1. Is determined so as to stabilize the ON period of the first switching element 2a. A switching current detection circuit 12 detects a switching current flowing through the secondary winding 3b. Reference numeral 13 denotes a second control circuit, which turns on the second switching element 4a after the first switching means 2 is turned off, receives information from the switching current detection circuit 12, and changes the switching current Io1 to a predetermined value Io1th. When it reaches, the second switching element 4a
Has the function of turning off.

FIG. 10 is an operation waveform diagram of the switching power supply device. FIG. 10A shows the case of a heavy load state, and FIG. 10B shows the case of a light load state. It shows the voltage Vd across the element 2a, the current Id flowing through the primary winding 3a, and the current Io1 flowing through the secondary winding 3b.
The operation of the switching power supply device configured as described above will be described with reference to FIGS. 9 and 10. First, when the first switching means 2 is on, the input DC voltage Vin is input to the primary winding 3a, and the primary current I
d excites the transformer 3 while increasing linearly. First
When the switching means 2 is turned off, each winding voltage of the transformer 3 is inverted, and the excitation energy is transferred from the secondary winding 3b to the second winding.
Is discharged to the first output capacitor 5 through the diode 4b, and the secondary current Io1 decreases linearly. At this time, the second switching element 4a is also turned on. Even when the excitation energy to the first output capacitor 5 has been completely released, if the second switching element 4a is on, the secondary current Io1 flows in the reverse direction from the first output capacitor 5 to the secondary winding 3b.
Flows to reversely excite the transformer 3. The switching current detection circuit 12 detects the secondary current Io1, and the second control circuit 13 turns off the second switching element 4a when the secondary current Io1 reaches a predetermined value Io1th. The reversely excited winding voltages of the transformer 3 are inverted, and the reverse excitation energy is regenerated from the primary winding 3a to the input DC voltage source 1 via the first diode 2b. At this time, the first switching element 2a is also turned on by the first control circuit 11. Through the repetition of this operation, the ON period of the first switching unit 2 is Ton, and the OFF period of the first switching unit 2 (that is, the ON period of the second switching unit 4) is Tof.
f Assuming that the turns ratio between the primary winding 3a and the secondary winding 3b is N1, the relationship between the input and output DC voltages is represented by Vout1 = N1 · (Ton / Toff) · Vin, and the first control The first output DC voltage Vout1 can be stabilized by adjusting the on-period Ton of the first switching element 2a by the circuit 11. Further, the transmitted power is the product of the difference between the excitation energy and the reverse excitation energy of the transformer 3 and the switching frequency. Therefore, the fluctuation of the output power is the fluctuation of the difference between the excitation energy of the transformer 3 and the reverse excitation energy. . The feature of this switching power supply is that the switching current detection circuit 12
And the second control circuit 13 sets the secondary current Io1 for reversely exciting the transformer 3 to the predetermined value Io1th. Therefore, in a light load state, Ton and Toff are short, and the switching frequency is high. The change width is small, preventing a decrease in efficiency, and in an overload state, the switching frequency is reduced by increasing Toff, but the reverse excitation energy is secured and the zero cross turn-on can be maintained.

FIG. 11 shows a multi-output circuit configuration of the circuit configuration shown in FIG. 9. A plurality of secondary windings are provided in a transformer 3 and rectification and smoothing are performed to obtain a plurality of output DC voltages as in the conventional case. It becomes possible. In FIG. 11, the same components as those in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 11, reference numeral 3 denotes a transformer, which has a primary winding 3a, a first secondary winding 3b, and a second secondary winding 3c, 7 is a rectifier diode, 8 is a second output capacitor, Reference numeral 9-9 'denotes a second output terminal. The flyback voltage generated in the second secondary winding 3c of the transformer 3 is supplied through the rectifier diode 7 and the second output capacitor 8 to the second output DC. It is supplied to the load as voltage Vout2.

FIGS. 12A and 12B are operation waveform diagrams of this switching power supply device. FIG. 12A shows a case where both outputs are in a heavy load state, and FIG. 12B shows a case where both outputs are in a light load state. Thus, the voltage Vd across the first switching element 2a, the current Id flowing through the primary winding 3a, the current Io1 flowing through the first secondary winding 3b, and the current Io flowing through the second secondary winding 3c.
o2. The operation of the switching power supply configured as described above will be described with reference to FIGS. First, when the first switching means 2 is on, the input DC voltage Vin is input to the primary winding 3a, and the primary current Id excites the transformer 3 while increasing linearly. When the first switching means 2 is turned off, each winding voltage of the transformer 3 is inverted, and the excitation energy is
From the secondary winding 3b through the second diode 4b.
To the output capacitor 5, and at the same time, the second 2
The secondary winding 3c is discharged to the second output capacitor 8 via the rectifier diode 7, and the secondary currents Io1 and Io2 decrease linearly. At this time, the second switching element 4a is also turned on. Even when the excitation energy to the first output capacitor 5 is completely released, if the second switching element 4a is on, the first output capacitor 5
A secondary current Io1 flows in the reverse direction to the next winding 3b, and reversely excites the transformer 3. The switching current detection circuit 12 detects the secondary current Io1, and the second control circuit 13 outputs the secondary current Io1.
When o1 reaches a predetermined value Io1th, the second switching element 4a is turned off. The reversely excited winding voltages of the transformer 3 are inverted, and the reverse excitation energy is regenerated from the primary winding 3a to the input DC voltage source 1 via the first diode 2b. At this time, the first switching element 2a is also turned on by the first control circuit 11. Through the repetition of this operation, the first control circuit 11 adjusts the on-period Ton of the first switching element 2a, so that the first
Output DC voltage Vout1 can be stabilized. By providing a plurality of secondary windings and rectifying / smoothing means in the transformer 3 in this manner, it is possible to obtain an arbitrary plurality of output DC voltages, each of which is not stabilized (unstable). Since the output DC voltage substantially matches the output DC voltage to be stabilized and the voltage value proportional to the ratio of the number of windings, a multi-output power supply can be easily configured.

[0007]

In such a conventional configuration, the reverse excitation energy of the transformer is set to a fixed amount of regeneration under all operating load conditions, so that the load power greatly changes or increases. Improves the unstable output DC voltage drop (influence of cross-regulation) under light load conditions (especially when the load current of the output DC voltage to be stabilized and controlled is too small) when used for switching electronic equipment If you set a sufficient amount of regeneration to
Due to the operation loss, power consumption increases more than necessary at heavy load, and if the regenerative amount is set to keep the increase of power consumption under heavy load small, unstable output DC voltage drop at light load In addition, there is a problem that it is difficult to make an optimum setting under all operating load conditions, and furthermore, even when the load current of the unstable output DC voltage greatly changes or switches greatly, the stability of the output DC voltage is Not good (effect of load regulation),
In particular, there is a problem that the voltage rises sharply when the load becomes light, and there is a demand for the improvement of the cross regulation and the load regulation according to the operating load state of the electronic device.

[0008]

SUMMARY OF THE INVENTION In order to solve this problem, a switching power supply according to the present invention comprises an input DC voltage source connected to a primary winding of a transformer having at least a primary winding and a plurality of secondary windings. And first switching means for repeating on and off operations are connected in series, and a second secondary winding of the transformer is turned on and off complementarily to the first switching means.
Switching means and a first output capacitor are connected in series, a rectifier diode and a second output capacitor are connected in series to a second secondary winding of the transformer, and an input is provided when the first switching means is on. Applying a DC voltage to the primary winding of the transformer to store energy in the transformer;
When the first switching means is off, the energy is released from the plurality of secondary windings of the transformer, and the rectifying and smoothing means connected to the secondary winding of the transformer outputs a first output capacitor and a second output capacitor. The first capacitor
And a second switching means for turning on and off the first switching means in a complementary manner after the energy stored in the transformer is discharged from the secondary winding of the transformer. A first output DC voltage is applied to a first secondary winding of the transformer through the first secondary winding of the transformer and stores energy in the transformer. When the second switching means is off, the energy is transferred from the primary winding of the transformer to the first secondary winding. The input DC voltage source is regenerated, and the stabilization control of the first output DC voltage is performed by changing the ON period of the first switching means. 2 is characterized in that the ON period of the second switching means is controlled so as to improve the stability of the output DC voltage.

According to the present invention, when the load power of the electronic equipment used changes greatly or switches greatly, and when the load current of the unstable output DC voltage changes greatly or switches greatly, In addition, the on-period of the second switching means is controlled in accordance with the changing operating load state, and the amount of regeneration of the reverse excitation energy of the transformer is controlled, thereby improving the stability of the unstable output DC voltage. A power supply can be provided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, an input DC voltage source and an on / off operation are repeatedly performed on a primary winding of a transformer having at least a primary winding and a plurality of secondary windings. One switching means is connected in series, and a second switching means and a first output capacitor which are turned on / off complementarily to the first switching means are connected in series to a first secondary winding of the transformer, A rectifier diode and a second output capacitor are connected in series to a second secondary winding of the transformer, and an input DC voltage is applied to the primary winding of the transformer when the first switching means is on. Energy is stored in a transformer, and when the first switching means is off, the energy is released from a plurality of secondary windings of the transformer, and a first output is provided by rectifying and smoothing means connected to the secondary winding of the transformer. A first output DC voltage and a second output DC voltage are obtained at a capacitor and a second output capacitor, respectively, and the energy stored in the transformer is discharged from a secondary winding of the transformer, and then the first switching means is provided. A first output DC voltage is applied to a first secondary winding of the transformer through second switching means that is turned on and off complementarily with the first switching means, and energy is stored in the transformer, and when the second switching means is off, The energy is regenerated from the primary winding of the transformer to the input DC voltage source, and the stabilization control of the first output DC voltage is performed by changing the on-period of the first switching means. The on-period of the second switching means is controlled so as to improve the stability of the second output DC voltage which is unstable even in accordance with the operation load state. A switching power supply, the load power of the electronic equipment used is greatly changed, or when switching large, and further,
Even when the load current of the unstable second output DC voltage greatly changes or switches greatly, the on-period of the second switching means is controlled in accordance with the changing operating load state, and the reverse excitation of the transformer is performed. Controlling the amount of energy regeneration has the effect of improving the stability of the unstable second output DC voltage.

According to a second aspect of the present invention, there is provided a transformer which receives an input DC voltage, has at least a primary winding and a plurality of secondary windings, and is connected to the primary winding of the transformer. A first switching means for converting the input DC voltage into a high-frequency AC voltage by repeating on / off and inputting the high-frequency AC voltage to the primary winding, and a first secondary winding of the transformer; A second switching means for rectifying a flyback voltage generated in the secondary winding of the second step, and a second switching means for smoothing the flyback voltage rectified by the second switching means and supplying a first output DC voltage to a load. 1, a rectifier diode connected to a second secondary winding of the transformer, for rectifying a flyback voltage generated in the second secondary winding, and a rectifier diode rectified by the rectifier diode. A second output capacitor for smoothing the flyback voltage and supplying a second output DC voltage to a load, a first voltage detection circuit for detecting the first output DC voltage, and the second switching means. Turns off the first switching means, receives information from the first voltage detection circuit, and determines an on-period of the first switching means so as to stabilize the output DC voltage. A first control circuit, a switching current detection circuit for detecting a switching current flowing in the first secondary winding or the second switching means, and a second switching circuit for detecting the switching current after the first switching means is turned off. The switching means is turned on to receive information from the switching current detection circuit, and the switching current is changed by a signal from the control signal input terminal according to the operation load state. 2. The switching power supply device according to claim 1, further comprising a second control circuit configured to turn off said second switching means when the threshold current value reaches the threshold current value. When the load current of the unstable second output DC voltage greatly changes or largely changes, or when the load current of the unstable second output DC voltage greatly changes, the operation from the control signal input terminal changes. The stability of the unstable second output DC voltage is improved by controlling the ON period of the second switching means with a signal corresponding to the load state and controlling the amount of regenerative energy of the reverse excitation energy of the transformer. It has the effect that it can be done.

According to a third aspect of the present invention, there is provided a first DC current detecting circuit for detecting a first output DC current which is a load current of the first output DC voltage, When the switching current flowing through the secondary winding or the second switching means reaches a threshold current value that is changed by information from the first DC current detection circuit, the second switching means is turned off. 3. The switching power supply device according to claim 2, wherein the first output DC current of the electronic device to be used greatly changes or changes greatly even when the first output DC current changes greatly. By controlling the on-period of the second switching means in accordance with the output DC current of (i) and controlling the amount of reverse excitation energy regeneration of the transformer, An effect that it is possible to improve the stability of the second output DC voltage.

According to a fourth aspect of the present invention, there is provided a second DC current detecting circuit for detecting a second output DC current which is a load current of the second output DC voltage, When the switching current flowing through the secondary winding or the second switching means reaches a threshold current value that is changed according to information from the second DC current detection circuit, the second switching means is turned off. 3. The switching power supply device according to claim 2, wherein the second output DC current of the electronic device to be used changes greatly even when the second output DC current greatly changes or switches greatly. By controlling the on-period of the second switching means in accordance with the output DC current of (i) and controlling the amount of reverse excitation energy regeneration of the transformer, An effect that it is possible to improve the stability of the second output DC voltage.

According to a fifth aspect of the present invention, there is provided a first direct current detecting circuit for detecting the first output direct current, and a second direct current detecting circuit for detecting the second output direct current. And a circuit, wherein the first secondary winding or the second
The switching current flowing through the switching means is changed by a signal corresponding to an operation load state from the control signal input terminal, information from the first DC current detection circuit, and information from the second DC current detection circuit. 3. The method according to claim 2, wherein when said threshold current value is reached, said second switching means is turned off.
The switching power supply device according to claim 1, wherein the first output DC current and the second output DC current of the electronic device to be used largely change or largely change even when the control signal input terminal changes. The on-period of the second switching means is controlled by a signal corresponding to an operating load state to be performed, information from the first DC current detection circuit, and information from the second DC current detection circuit, Controlling the amount of regeneration of the excitation energy has the effect of improving the stability of the unstable second output DC voltage.

According to a sixth aspect of the present invention, a second voltage detecting circuit for detecting the second output DC voltage and the second switching means after the first switching means is turned off. And receives the information from the switching current detection circuit and the information from the second voltage detection circuit, and stabilizes the output DC voltage so as to stabilize the output DC voltage.
3. The switching power supply device according to claim 2, further comprising a third control circuit for determining an ON period of the switching means, wherein a load power of an electronic device used greatly changes.
Alternatively, when the switching is largely switched, and even when the load current of the unstable second output DC voltage is largely changed or largely switched, the information from the switching current detection circuit and the second voltage detection circuit , The on-period of the second switching means is controlled so as to stabilize the output DC voltage, and the amount of reverse excitation energy regenerated by the transformer is controlled. This has the effect that the voltage can be stabilized.

According to a seventh aspect of the present invention, a signal according to an operation load state from the control signal input terminal, information from the switching current detection circuit, and information from the second voltage detection circuit are transmitted. 7. The switching power supply according to claim 6, wherein an on-period of said second switching means is determined so as to stabilize said output DC voltage. When the power largely changes or switches greatly, and also when the load current of the unstable second output DC voltage greatly changes or largely switches, the change from the control signal input terminal also changes. Receiving a signal corresponding to an operation load state, information from the switching current detection circuit, and information from the second voltage detection circuit; By controlling the ON period of the second switching means so as to stabilize and controlling the amount of reverse excitation energy regeneration of the transformer, the second output DC voltage can be stabilized. Have.

According to an eighth aspect of the present invention, there is provided a high-power video display circuit in which an output from the first output DC voltage is connected via an open / close switch, and an output from the second output DC voltage. And a television receiver control circuit that controls the open / close switch, the high-power video display circuit, the signal processing circuit, and the control signal input terminal. The control signal input terminal is controlled according to an operation state of a power video display circuit and an operation state of the signal processing circuit, or the first output DC current is detected, and the second output DC current is detected. , By detecting the second output DC voltage, the switching current flowing through the first secondary winding or the second switching means, that is, the switching current Characterized by being adapted to control the on period of the second switching means, according to claim 2 to 7
A television receiver using the switching power supply device according to (1), wherein the first output DC current of the high-power video display circuit changes significantly during an on-period of the on-off switch, and during an off-period of the on-off switch. A television receiver in which the first output DC current is cut off and the second output DC current of the signal processing circuit changes to a load state according to an operation mode such as an answering machine state or various standby states. Therefore, the control signal input terminal is controlled in accordance with the state of the open / close switch, the operation state of the high-power video display circuit, and the operation state of the signal processing circuit, or the first output DC current is detected. Detecting the second output DC current; detecting the second output DC voltage, thereby detecting the second output DC current in response to the changing operating load state. Controls the on period of the switching means, by controlling the amount of regeneration inverse excitation energy of the transformer, it is possible to improve the stability of the free of the second output DC voltage, thus reducing power consumption,
This has the effect of reducing costs.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a circuit configuration diagram of a switching power supply device according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an input DC voltage source, which is an input DC voltage Vi.
n. Reference numeral 2 denotes first switching means, which includes a first switching element 2a and a first diode 2b. Reference numeral 3 denotes a transformer having a primary winding 3a, a first secondary winding 3b, and a second secondary winding 3c.
n is input to the primary winding 3a of the transformer 3 as a high-frequency AC voltage by the first switching means 2. 4 is a second switching means, which is a second switching element 4a.
And the second diode 4b. 5 is a first output capacitor, 6-6 'is a first output terminal, and the flyback voltage generated in the first secondary winding 3b of the transformer 3 is equal to the second switching means 4 and the first output. It is supplied to the load via the capacitor 5 as a first output DC voltage Vout1. 7 is a rectifier diode, 8 is a second output capacitor, 9-9 'is a second output terminal, and the flyback voltage generated in the second secondary winding 3c of the transformer 3 is the rectifier diode 7 and the second Through the output capacitor 8 of
It is supplied to the load as a second output DC voltage Vout2. Reference numeral 10 denotes a first voltage detection circuit which detects a first output DC voltage. Reference numeral 11 denotes a first control circuit, which turns on the first switching element 2a after the second switching means 4 is turned off, receives information from the first voltage detection circuit 10, and outputs a first output DC voltage Vout1. Is determined so as to stabilize the ON period of the first switching element 2a. Reference numeral 12 denotes a switching current detection circuit,
The switching current flowing through the next winding 3b is detected. 13
Is a second control circuit, and 14 is a control signal input terminal. After the first switching means 2 is turned off, the second switching element 4a is turned on and the switching current detection circuit 12 is turned on.
When the switching current Io1 reaches a threshold current value Io1th which is changed by a signal from the control signal input terminal 14 according to the operation load state, the second switching element 4a is turned off. Having.

FIG. 2 is an operation waveform diagram of the switching power supply device. FIG. 2A shows a case where both outputs are in a heavy load state, and FIG. 2B shows a case where both outputs are in a light load state. Thus, the voltage Vd across the first switching element 2a, the current Id flowing through the primary winding 3a, the current Io1 flowing through the first secondary winding 3b, and the current Io flowing through the second secondary winding 3c.
o2. The operation of the switching power supply configured as described above will be described with reference to FIGS. First, when the first switching means 2 is on, the input DC voltage Vin is input to the primary winding 3a and
The secondary current Id excites the transformer 3 while increasing linearly. When the first switching means 2 is turned off, the transformer 3
Are excited, the excitation energy is released from the first secondary winding 3b to the first output capacitor 5 via the second diode 4b, and at the same time, the second secondary winding 3c Are discharged to the second output capacitor 8 through the rectifier diode 7 and the secondary currents Io1 and Io2
Decreases linearly. At this time, the second switching element 4
a is also turned on. Even when the excitation energy to the first output capacitor 5 is completely released, if the second switching element 4a is on, the first output capacitor 5 outputs the first 2
A secondary current Io1 flows in the reverse direction to the next winding 3b, and reversely excites the transformer 3. The switching current detection circuit 12 detects the secondary current Io1, and the second control circuit 13 outputs the secondary current Io1.
When o1 reaches a threshold current value Io1th that is changed by a signal from the control signal input terminal 14 according to the operation load state, the second switching element 4a is turned off. The reversely excited winding voltages of the transformer 3 are inverted, and the reverse excitation energy is regenerated from the primary winding 3a to the input DC voltage source 1 via the first diode 2b. At this time, the first switching element 2a is also connected to the first control circuit 11
Is turned on. Through the repetition of this operation, the on-period of the first switching means 2 is Ton, and the off-period of the first switching means 2 (that is, the on-period of the second switching means 4) is Toff. Assuming that the ratio of the number of turns of the secondary winding 3b to N1 is N1, the relationship between the input DC voltage and the first output DC voltage is represented by Vout1 = N1 · (Ton / Toff) · Vin. The first output DC voltage Vout1 can be stabilized by adjusting the ON period Ton of the first switching element 2a by the control circuit 11. The second output DC voltage Vout2 is, for example, when the load current of the stabilized first output DC voltage is large, the second output DC voltage Vout2 has a relatively high degree of stability. A signal from the terminal 14 reduces the threshold current value Io1th to reduce the amount of regeneration, or reduces the power consumption by preventing regeneration, or a load of the first output DC voltage that is stabilized and controlled. When the current is excessively small, the threshold current value Io is further increased by a signal from the control signal input terminal 14 in accordance with the magnitude of the load current of the second output DC voltage Vout2 which is unstable.
It is possible to improve the stability of the second output DC voltage Vout2 by appropriately setting 1th and setting the regeneration amount.

(Embodiment 2) FIG. 3 is a circuit configuration diagram of a switching power supply device according to a second embodiment of the present invention. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. 3, reference numeral 15 denotes a first DC current detection circuit for detecting a first output DC current Iout1, which is a load current of the first output DC voltage Vout1, and a first switching circuit 15 After the means 2 is turned off, the second switching element 4a is turned on and receives information from the switching current detection circuit 12,
When the switching current Io1 reaches a threshold current value Io1th that is changed according to information from the first DC current detection circuit 15, the second switching element 4a is turned off.

The operation of the switching power supply configured as described above will be described with reference to FIG. 3. The operation in which the first output DC voltage Vout1 of the output terminal 6-6 'is controlled stably has already been performed. The operation is the same as that described with reference to FIGS. Second output DC voltage Vout2
For example, when the first output DC current Iout1, which is the load current of the first output DC voltage that is being stabilized, is large, the second output DC voltage Vout2 has a relatively high degree of stability. Based on information from the DC current detection circuit 15, the threshold current Io1th may be reduced to reduce the amount of regeneration, or power may be reduced by preventing regeneration, or the first stabilization control may be performed. A first output DC current Io which is a load current of the output DC voltage
If ut1 is small, the first DC current detection circuit 1
5, the threshold current value Io1th is appropriately set, the regenerative amount is set, and the second output DC voltage Vout2 is set.
Can be improved.

(Embodiment 3) FIG. 4 is a circuit configuration diagram of a switching power supply device according to a third embodiment of the present invention. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 4, reference numeral 16 denotes a second DC current detecting circuit for detecting a second output DC current Iout2 which is a load current of the second output DC voltage Vout2. After the means 2 is turned off, the second switching element 4a is turned on and receives information from the switching current detection circuit 12,
When the switching current Io1 reaches a threshold current value Io1th that is changed according to information from the second DC current detection circuit 16, the second switching element 4a is turned off.

The operation of the switching power supply configured as described above will be described with reference to FIG. 4. The operation in which the first output DC voltage Vout1 of the output terminal 6-6 'is stably controlled has already been performed. The operation is the same as that described with reference to FIGS. Second output DC voltage Vout2
For example, the threshold current Io1th is appropriately set based on information from the second DC current detection circuit 16 in accordance with the magnitude of the second output DC current Iout2 which is the load current of the unstable second output DC voltage Vout2. By setting the regenerative amount, it is possible to improve the stability of the second output DC voltage Vout2.

(Embodiment 4) FIG. 5 is a circuit diagram of a switching power supply unit according to a fourth embodiment of the present invention. 5, the same components as those in FIGS. 1, 3, and 4 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 5, after the first switching means 2 is turned off by the second control circuit 13, the second switching element 4a is turned on to receive information from the switching current detection circuit 12, and the switching current Io1 becomes A threshold current value Io1 that is changed by a signal corresponding to the operation load state from the control signal input terminal 14, information from the first DC current detection circuit 15, and information from the second DC current detection circuit 16.
When it reaches th, the second switching element 4a is turned off.

The operation of the switching power supply configured as described above will be described with reference to FIG. 5, but the operation in which the first output DC voltage Vout1 of the output terminal 6-6 'is controlled stably has already been performed. The operation is the same as that described with reference to FIGS. Second output DC voltage Vout2
For example, when the first output DC current Iout1, which is the load current of the first output DC voltage that is being stabilized, is large, the second output DC voltage Vout2 has a relatively high degree of stability. The threshold current Io1th is reduced by the signal according to the operation load state from the signal input terminal 14 and the information from the first DC current detection circuit 15 to reduce the amount of regeneration or reduce the power consumption by preventing regeneration. For example, when the first output DC current Iout1, which is the load current of the stabilized first output DC voltage, is too small, the load of the more unstable second output DC voltage Vout2 is reduced. The control signal input terminal 1 according to the magnitude of the second output DC current Iout2 which is the current
4 and the information from the first DC current detection circuit 15 and the second DC current detection circuit 1
6, the regenerative amount is set by appropriately setting the threshold current value Io1th, and the second output DC voltage Vout2 is set.
Can be improved.

(Embodiment 5) FIG. 6 is a circuit configuration diagram of a switching power supply device according to a fifth embodiment of the present invention. In FIG. 6, the same components as those in FIG. In FIG. 6, reference numeral 17 denotes a second voltage detection circuit, which detects a second output DC voltage. 18
Is a third control circuit. After the first switching means 2 is turned off, the second switching element 4a is turned on, and information from the switching current detection circuit 12 and information from the second voltage detection circuit 17 are transmitted. Receiving second output DC voltage V
It has a function of determining the ON period of the second switching element 4a so as to stabilize out2.

The operation of the switching power supply configured as described above will be described with reference to FIG. 6. The operation in which the first output DC voltage Vout1 of the output terminal 6-6 'is controlled stably has already been performed. The operation is the same as that described with reference to FIGS. Generally, the second output DC voltage V
out2 decreases when the load current increases, and increases when the load current decreases (influence of load regulation). In general, when there is no regeneration via the second switching means 4, when the load current of the first output DC voltage to be stabilized and controlled increases, the unstable second output DC voltage rises and becomes stable. When the load current of the first output DC voltage to be controlled to be reduced decreases, the unstable second output DC voltage decreases (effect of cross-regulation). According to the regeneration through the second switching means 4, Increasing the amount of regeneration to increase the unstable second output DC voltage,
By reducing the amount of regeneration, the unstable second output DC voltage can be reduced. From the above, the switching power supply device according to the fifth embodiment of the present invention
The third control circuit 18 stabilizes the second output DC voltage Vout2 based on the information from the switching current detection circuit 12 and the information from the second voltage detection circuit 17 for detecting the second output DC voltage. The on-period (regeneration amount) of the second switching element 4a is controlled, and is controlled by a change in the load current of the first output DC voltage and a change in the second output DC current which are controlled to be stabilized. It is possible to suppress the fluctuation of the second output DC voltage Vout2 to be caused. However, as compared with the stabilization of the first output DC voltage by controlling the first switching means 2, the response sensitivity is more stable in stabilizing the second output DC voltage by controlling the second switching means 4. (gain)
It is desirable that the stabilization control range be limited to the necessary range according to the actual operation load fluctuation range.

(Embodiment 6) FIG. 7 is a circuit diagram of a switching power supply according to a sixth embodiment of the present invention. 7, the same components as those in FIGS. 1 and 6 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 7, after the first switching means 2 is turned off by the third control circuit 18, the second switching element 4 a is turned on, and the signal and the switching current from the control signal input terminal 14 according to the operation load state are output. Upon receiving information from the detection circuit 12 and information from the second voltage detection circuit 17, the second output DC voltage Vo
ut2 so as to stabilize the second switching element 4
The ON period of “a” is determined.

The operation of the switching power supply configured as described above will be described with reference to FIG. 7, but the operation in which the first output DC voltage Vout1 of the output terminal 6-6 'is stably controlled has already been performed. The operation is the same as that described with reference to FIGS. The switching power supply device according to the sixth embodiment of the present invention detects a signal corresponding to an operation load state from a control signal input terminal 14, information from a switching current detection circuit 12, and a second output DC voltage. The on-period (regeneration amount) of the second switching element 4a is controlled by the third control circuit 18 based on the information from the voltage detection circuit 17 to stabilize the second output DC voltage Vout2. And it is possible to suppress the fluctuation of the second output DC voltage Vout2 which is caused by the change of the load current of the first output DC voltage and the change of the second output DC current which are controlled to be stabilized. Become. The control by the signal according to the operation load state from the control signal input terminal 14 is performed, for example, when the load current of the stabilized first output DC voltage is large, the second output DC voltage Vout2 is originally set. Since the stability is relatively high, the controllable control operation of the second output DC voltage is limited by the signal from the control signal input terminal 14 or the power consumption is reduced by not performing the stabilization control. This makes it possible to improve the stability of the second output DC voltage Vout2 in an operation load state to be subjected to stabilization control.

Needless to say, there are various methods in the switching current detection circuit, such as a method of detecting the actual current by converting it into a voltage and a method of detecting the time based on the switching waveform.

(Embodiment 7) FIG. 8 is a block diagram of a television receiver using a switching power supply according to a second embodiment of the present invention. 8, reference numeral 19 denotes a switching power supply according to the present invention, and reference numeral 20 denotes an on / off switch 2 for switching the output of the switching power supply 19 from the first output DC voltage.
A high-power video display circuit such as a deflection circuit or a high-voltage circuit for displaying video mainly during normal times,
Is a signal processing circuit to which the output from the second output DC voltage of the switching power supply 19 is connected, and which includes processes such as an answering machine and various standbys; 23, an on / off switch 22, a high power video display circuit 20, This is a television receiver control circuit that controls the processing circuit 21 and the control signal input terminal 14 of the switching power supply 19.

The operation of the television receiver configured as described above will be described with reference to FIG. Normally, the first output DC current of the high-power video display circuit 20 changes greatly during the ON period of the open / close switch 22, and the first output DC current is cut off during the OFF period of the open / close switch 22, and the signal processing circuit Since the second output DC current of the television receiver 21 changes to a load state according to an operation mode such as an answering machine state or various standby states, the state of the open / close switch 22 and the high power video display circuit 20
Controls the control signal input terminal 14 in accordance with the operation state of the signal processing circuit 21 or detects the first output DC current, detects the second output DC current, and outputs the second output DC current. By detecting the voltage, the on-period of the second switching means 4 of the switching power supply 19 is controlled in accordance with the changing operating load state,
By controlling the amount of reverse excitation energy regenerated by the transformer 3 of the switching power supply 19, it is possible to improve the stability of the unstable second output DC voltage, thereby reducing power consumption and cost. Becomes possible.

[0033]

As described above, according to the present invention, an input DC voltage source and first switching means for repeatedly turning on and off are connected in series to a primary winding of a transformer having at least a primary winding and a plurality of secondary windings. , And a second switching means and a first output capacitor, which are turned on and off complementarily to the first switching means, are connected in series to a first secondary winding of the transformer, and a second output of the transformer is connected to the second secondary winding of the transformer. A rectifier diode and a second output capacitor are connected in series to the secondary winding, and when the first switching means is on, an input DC voltage is applied to the primary winding of the transformer to store energy in the transformer; When the first switching means is off, the energy is released from the plurality of secondary windings of the transformer, and the first output capacitor and the rectifying and smoothing means are connected to the secondary winding of the transformer. Respectively to the second output capacitor to obtain a first output DC voltage and the second output DC voltage,
After discharging the energy stored in the transformer from the secondary winding of the transformer, the first output DC voltage is applied to the first switching means of the transformer via the second switching means which turns on and off complementarily with the first switching means. Energy is stored in the transformer when applied to the secondary winding, and when the second switching means is off, the energy is regenerated from the primary winding of the transformer to the input DC voltage source, and the first output DC voltage Is controlled by changing the on-period of the first switching means, and the second control is performed so as to improve the stability of the unstable second output DC voltage even in response to the changing operating load state. It is characterized in that the on-period of the switching means is controlled, and is used when the load power of the electronic device to be used greatly changes or switches greatly. Further, even when the load current of the unstable output DC voltage greatly changes or largely switches, the on-period of the second switching means is controlled in accordance with the changing operation load state, and the reverse of the transformer is performed. By controlling the amount of regeneration of the excitation energy, it is possible to provide a switching power supply that improves the stability of the unstable output DC voltage.

[Brief description of the drawings]

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

FIG. 2 is an operation waveform diagram of the switching power supply device according to one embodiment of the present invention;

FIG. 3 is a circuit configuration diagram of a switching power supply device according to a second embodiment of the present invention.

FIG. 4 is a circuit configuration diagram of a switching power supply device according to a third embodiment of the present invention.

FIG. 5 is a circuit configuration diagram of a switching power supply device according to a fourth embodiment of the present invention.

FIG. 6 is a circuit configuration diagram of a switching power supply device according to a fifth embodiment of the present invention.

FIG. 7 is a circuit configuration diagram of a switching power supply device according to a sixth embodiment of the present invention.

FIG. 8 is a block diagram of a television receiver according to an embodiment of the present invention.

FIG. 9 is a circuit configuration diagram of a conventional switching power supply device.

FIG. 10 is an operation waveform diagram of a conventional switching power supply device.

FIG. 11 is a circuit configuration diagram of a conventional switching power supply device.

FIG. 12 is an operation waveform diagram of a conventional switching power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input DC voltage source 2 1st switching means 3 Transformer 4 2nd switching means 5 1st output capacitor 6-6 '1st output terminal 7 Rectifier diode 8 2nd output capacitor 9-9' 2nd Output terminal 10 First voltage detection circuit 11 First control circuit 12 Switching current detection circuit 13 Second control circuit 14 Control signal input terminal 15 First DC current detection circuit 16 Second DC current detection circuit 17 Second Voltage detection circuit 18 Third control circuit 19 Switching power supply device of the present invention 20 High power video display circuit 21 Signal processing circuit 22 Open / close switch 23 Television receiver control circuit

Claims (8)

[Claims] 1. An input DC voltage source and first switching means which repeats on and off are connected in series to a primary winding of a transformer having at least a primary winding and a plurality of secondary windings,
A second switching means and a first output capacitor, which are turned on and off complementarily with the first switching means, are connected in series to a first secondary winding of the transformer, and a second secondary winding of the transformer is connected. A rectifier diode and a second output capacitor are connected in series, and when the first switching means is on, an input DC voltage is applied to the primary winding of the transformer to store energy in the transformer, When the means are off, the energy is transferred to a plurality of transformers.
The first output capacitor and the second output capacitor are discharged by the rectifying and smoothing means which is discharged from the secondary winding and connected to the secondary winding of the transformer.
The first output DC voltage and the second output DC voltage are respectively obtained in the output capacitor, and after the energy stored in the transformer is released from the secondary winding of the transformer, the first output DC voltage and the second output DC voltage are complementary to the first switching means. A first output DC voltage is applied to a first secondary winding of the transformer via second switching means for turning on and off, and stores energy in the transformer. When the second switching means is off, the energy is stored in the transformer. Regeneration from the primary winding of the transformer to the input DC voltage source, stabilization control of the first output DC voltage is performed by changing the on-period of the first switching means, and further, the operating load state is changed. A switch characterized in that the on-period of the second switching means is controlled so as to improve the stability of the second output DC voltage which is unstable even when the second switching means is stable. Ring power supply. And a transformer having at least a primary winding and a plurality of secondary windings, the transformer being connected to a primary winding of the transformer, and being repeatedly turned on and off. Switching means for converting the voltage into a high-frequency AC voltage and inputting the voltage to the primary winding; and a flyback connected to the first secondary winding of the transformer and generated in the first secondary winding. A second switching means for rectifying the voltage, a first output capacitor for smoothing the flyback voltage rectified by the second switching means, and supplying a first output DC voltage to a load; A rectifier diode connected to the second secondary winding and rectifying a flyback voltage generated in the second secondary winding; A second output capacitor that supplies a second output DC voltage to the load, a first voltage detection circuit that detects the first output DC voltage, and the first output capacitor after the second switching unit is turned off. A first control circuit for turning on the switching means, receiving information from the first voltage detection circuit, and determining an ON period of the first switching means so as to stabilize the output DC voltage; First
A switching current detection circuit for detecting a switching current flowing through the secondary winding or the second switching means, and after the first switching means is turned off, the second switching means is turned on to detect the switching current. Upon receiving information from the circuit, when the switching current reaches a threshold current value that is changed by a signal corresponding to an operation load state from a control signal input terminal, the second switching means is turned off. Second
The switching power supply device according to claim 1, comprising a control circuit. 3. A first DC current detection circuit for detecting a first output DC current that is a load current of the first output DC voltage, wherein the first DC current detection circuit is provided, and the first secondary winding or the second switching is provided. 2. The method according to claim 1, wherein the second switching means is turned off when a switching current flowing through the means reaches a threshold current value that is changed according to information from the first DC current detection circuit. 2
A switching power supply as described. 4. A second DC current detection circuit for detecting a second output DC current which is a load current of the second output DC voltage, wherein the first DC winding or the second switching is provided. 2. The method according to claim 1, wherein the second switching means is turned off when a switching current flowing through the means reaches a threshold current value that is changed according to information from the second DC current detection circuit. 2
A switching power supply as described. 5. A first detecting means for detecting the first output DC current.
And a second DC current detection circuit for detecting the second output DC current, wherein the switching current flowing through the first secondary winding or the second switching means is When reaching a threshold current value that is changed by a signal according to an operation load state from a control signal input terminal and information from the first DC current detection circuit and information from the second DC current detection circuit, 3. The switching power supply according to claim 2, wherein said second switching means is turned off. 6. A second detecting means for detecting the second output DC voltage.
And after the first switching means is turned off, the second switching means is turned on, and receives information from the switching current detection circuit and information from the second voltage detection circuit, 3. The switching power supply device according to claim 2, further comprising a third control circuit that determines an ON period of the second switching means so as to stabilize an output DC voltage. 7. A signal according to an operation load state from the control signal input terminal, information from the switching current detection circuit, and information from the second voltage detection circuit,
7. The switching power supply device according to claim 6, wherein an on-period of said second switching means is determined so as to stabilize said output DC voltage. 8. A high-power video display circuit to which an output from the first output DC voltage is connected via a switch, a signal processing circuit to which an output from the second output DC voltage is connected, A television receiver control circuit for controlling the switch, the high power video display circuit, the signal processing circuit, and the control signal input terminal, the state of the open / close switch, the operation state of the high power video display circuit, and the signal Controlling the control signal input terminal according to the operation state of the processing circuit, or detecting the first output DC current, detecting the second output DC current, detecting the second output DC voltage By doing
The switching current flowing through the first secondary winding or the second switching means, that is, an ON period of the second switching means, is controlled. A television receiver using a switching power supply.