JP2948425B2 - Switching power supply circuit - Google Patents

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 circuit used for consumer equipment such as a color television receiver and a video cassette recorder, and more particularly to reducing power consumption during standby operation of the consumer equipment. The present invention relates to a switching power supply circuit that can be used.

[0002]

2. Description of the Related Art In a conventional switching power supply circuit, for example, as described in JP-A-62-48264, power consumption of a main switching transistor during a steady operation is reduced to reduce power consumption. It is planned. However, since the operation of the main switching transistor during the standby operation is an unsaturated switching operation, the power loss is large, and no consideration has been given to reducing power consumption during the standby operation.

[0003]

FIG. 5 is a block diagram showing a conventional switching power supply circuit, and FIG. 6 is a waveform diagram showing operation waveforms of main parts in FIG. Now, an operation when the standby power is supplied to the load will be described.

The switching transistor 6 is shown in FIG.
When the voltage of the commercial power supply 5 as shown in FIG.
Regardless of the commercial power cycle, as shown in FIG.
A constant switching operation is performed continuously.

FIG. 7 shows a main part operation waveform in one cycle T of the switching operation of the transistor 6 at this time.

At the time of standby operation, power supply to the main load 4 is stopped under the control of the standby control circuit 3, so that the load is a light load of only the capacitors 28 and 29, the standby control circuit 3 and the output voltage detection circuit 12. Becomes Therefore, FIG.
As shown in (a), the operating frequency of the transistor 6 increases, the collector-emitter voltage v _CE increases, and the collector current i _C also becomes spike-like. As a result,
The operation of the transistor 6 is close to the class A operation, and FIG.
As shown in (b), the collector loss P of the transistor 6
_{Even C} alone results in a large power loss. Therefore, FIG.
Collector dissipation P _C of the transistor 6 shown in (b) in FIG. 6
As shown in (f), since power is generated in all sections of the commercial power supply cycle, a large power loss, that is, power consumption is generated. Also, since power loss depends on the voltage of the commercial power supply,
The higher the input voltage, the higher the power loss, that is, the more power consumption.

As described above, using a switching power supply circuit
When performing the standby operation, there is a limit in reducing the power consumption during the standby operation, and there is a problem that further reduction in power consumption cannot be achieved.

SUMMARY OF THE INVENTION It is an object of the present invention to realize low power consumption during standby operation when performing standby operation using a switching power supply circuit.

[0009]

In order to achieve the above-mentioned object, according to the present invention, the present invention is mounted on a device and used during a normal operation.
Supplies power to the load in the device, during standby operation
Is less than the power supplied to the load during the steady operation.
A switching power supply for supplying a small standby power to the load.
In source circuit, supplying power from a commercial power source to said load
Switching element and the commercial power during standby operation.
For each power supply cycle, the switching element
Power supply operation is performed in the first section of the
The power supply operation is stopped in the remaining second section of the power supply cycle.
Controlling the power supply operation of the switching element
Control means for applying the voltage of the commercial power supply,
The first section in the control means according to the voltage;
Variable means for changing the ratio with respect to the second section.

[0010]

According to the present invention, the power supply / reception operation of the device during the standby operation can be repeated at a maximum of a half cycle of the commercial power supply, and the power loss generated by the operation of the device can be reduced over the entire period. Compared with the operation, the power consumption is reduced to at least half or less, and low power consumption can be realized.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments, a circuit useful for understanding the embodiments will be described.
Will be described. FIG. 1 is a block diagram useful for understanding an embodiment of the present invention .
FIG. 2 is a circuit diagram showing a switching power supply circuit as a reference example , and FIG. 2 is a waveform diagram showing operation waveforms of main parts in FIG.

In FIG. 1, the switching power supply circuit comprises:
Commercial power supply 5, full-wave rectifier circuit 23, smoothing circuit 24, switching transformer 22, switching transistor 6, start-up and drive circuit 8, load and load-side rectifier circuit 25, photocouplers 26, 30, standby drive control circuit 2, It is composed of a constant circuit 1. Here, the load and the load side rectifier circuit 2
The standby control circuit 3 constituting the device 5 selects and instructs a standby state or a non-standby state of the device. Also, the photocoupler 26
Is a switch for transmitting information of the standby control circuit 3.
The time constant circuit 1 includes resistors 15 and 16, a zener diode 18, and a capacitor 19. The standby drive control circuit 2 includes a standby drive control transistor 20 and a resistor 21, and is set to control the transistor 6 based on information of the standby control circuit 3 only during standby operation of the device.

The operation during the standby operation will be described with reference to FIG. As shown in FIG. 2A, the voltage waveform of the commercial power supply 5 is a sine wave with zero as a reference, the commercial power supply cycle is 1C, and A is applied to the start-up and drive circuit 8. The point voltage _VA is, as shown in FIG.
Is a positive voltage that is synchronized with the first half cycle (T1 = (1/2) C) of the first voltage. On the other hand, the point B voltage V _B applied to the time constant circuit 1 via the resistor 11 is, as shown in FIG. 2C, the next half cycle of the voltage of the commercial power supply 5 (T2 = (電源)).
This is a positive voltage synchronized with C).

Therefore, when the voltage of the commercial power supply 5 is applied, the positive voltage _VA in the T1 section synchronized with the first half cycle causes the base of the transistor 6 to have a voltage T1 as shown in FIG. Only during the interval, the base current i via the resistor 9
Flows. Thus, the transistor 6 begins to boot, drive winding 10, by the activation and the driving circuit 8 receives supply of a stable base current i _b, as shown in FIG. 2 (g), T4 (= T1) section , A collector current _ic flows to perform a switching operation, that is, an operation of supplying energy to a load.

However, as described above, during the standby operation,
Since the power supply to the main load 4 is stopped under the control of the standby control circuit 3, the load is a light load of only the capacitors 28 and 29, the standby control circuit 3, and the output voltage detection circuit 12. Therefore, as shown in FIG. 7A, the operating frequency of the transistor 6 is increased, the collector-emitter voltage v _CE is increased, and the collector current i _C is spiked. As a result, operation of the transistor 6 is close to class A operation, as shown in FIG. 7 (b), it continues to generate a large power loss alone collector loss P _C of the transistor 6.

Next, in synchronization with the first half cycle, the positive voltage V
When interval T1 to generate the _A ends in synchronization with the next half cycle, the positive T2 interval generates a voltage V _B, is initiated as shown in Figure 2 (c). This point B voltage V _B is applied to the time constant circuit 1 via the resistor 11 as shown in FIG. The time constant circuit 1, FIG. 2 B point voltage V _B shown in (c) and the waveform shaping, to obtain a C point voltage V _C shown in Figure 2 (d). Standby drive control circuit 2 is driven by the point C voltage V _C. Ie, T to C point voltage V _C is generated
During the two sections, the standby drive control transistor 20 incorporated in the standby drive control circuit 2 is in a conductive state.

As a result, simultaneously with the generation of the point B voltage V _B ,
As shown in FIG. 2 (f), and conducts standby driving control transistor 20 shown in FIG. 1, via a standby drive control circuit 2, pulling out the base current i and the base current i _b flowing in the transistor 6 . For this reason, as shown in FIGS. 2E and 2G, the base current of the transistor 6 becomes zero during the section T3 (= T2), and the collector current _ic
Also stops flowing. Further, from this, in the T3 (= T2) section corresponding to the half cycle after the commercial power supply cycle, FIG.
As shown in (h), power loss of the transistor 6 does not occur. The power supply to the load in the section T3 is performed by the discharge energy of the capacitor 28 shown in FIG.

When the next new cycle starts and the voltage _VA shown in FIG. 2B is generated in the first half cycle,
While generating power loss as shown in (h), subjected to power supply to the load, entering further half cycle after, if generated voltage V _B shown in FIG. 2 (c), the transistor 6 is cut off, the power The power is supplied to the load by the discharge energy of the capacitor 28 without any loss. The above operation is repeated every half cycle of the commercial power supply, and the power consumption during the standby operation is reduced.

The power loss in the case of the present embodiment, that is, Occurring period collector loss P _C is 2
As shown in (h), there is only the T1 section synchronized with the first half cycle of the commercial power supply cycle. In the case of the conventional method, FIG.
As shown in (f), the power loss of the transistor 6 is reduced by about 50%, that is, the power consumption is reduced as compared with the case where the power loss occurs in the entire section of the commercial power supply cycle.

In the present embodiment , the ratio of the power supply section and the non-supply section in the cycle of the commercial power supply ((power supply section / commercial power supply cycle) = duty) is determined by the voltage of the applied commercial power supply 5. 50% constant regardless of size
(T1 = T2 = T3 = T4). Therefore, the power loss of the transistor 6 depends on the voltage of the commercial power supply 5 and tends to increase as the applied voltage of the commercial power supply 5 increases.

Therefore, next, a switching power supply circuit in which this is improved to further reduce the power consumption will be described.
This will be described as an example.

FIG. 3 is a circuit diagram showing a switching power supply circuit as one embodiment of the present invention, and FIG. 4 is a waveform diagram showing operation waveforms of main parts in FIG.

In this embodiment, the time constant circuit 1 shown in FIG.
, A time constant circuit 31 having a threshold value is provided,
The ratio (duty) between the power supply section and the non-supply section in the commercial power supply cycle is determined by the time constant circuit 3 having this threshold value.
By automatically varying the duty in accordance with the applied voltage of the commercial power supply, the duty is automatically controlled for each applied voltage of the commercial power supply, thereby reducing power consumption during standby operation.

In FIG. 3, the standby drive control circuit 2 comprises:
A standby drive control transistor 20 and a resistor 21 are provided. The time constant circuit 31 having a threshold value includes a resistor 14 for determining a threshold value, zener diodes 17 and 18 for setting a reference voltage, and resistors 15 and 16 for providing a time constant.
And the capacitor 19, and the conduction time of the standby drive control transistor 20 incorporated in the standby drive control circuit 2 is determined by the time constant.

The operation during the standby operation will be described with reference to FIG. It should be noted that the description will be made only for the points different from the operation of the reference example shown in FIG .

As shown in FIG. 4B, when the period T1 in which the point A voltage _VA is generated is synchronized with the first half cycle,
As shown in FIG. 4C, a point B voltage V _B is generated in synchronization with the next half cycle, and at the same time as the generation of the B point voltage V _B ,
The transistor 6 is turned off as described above. This rise and illustration of the waveform of the voltage at the point B V _B shown in FIG. 4 (c) 4
This is indicated by the fact that the start of turning off the transistor 6 shown in (g) is in phase.

At this time, the voltage V _B at the point _B is
As shown in (a) and (c), the magnitude changes according to the magnitude of the voltage applied to the commercial power supply 5. Therefore,
As shown in FIG. 3, such a point B voltage V _B
When applied to the time constant circuit 31 having a threshold value through the circuit, the circuit portion having the threshold value, that is, the resistor 14 and the zener diodes 17 and 18, and the time constant circuit portion, that is, the resistors 15 and 16, the capacitor As a result, as shown in FIG. 4 (d), the generated C-point voltage V _C varies in the section where it occurs like T3 or T3 ′ according to the magnitude of the voltage applied to the commercial power supply 5 as shown in FIG. .

When the C-point voltage V _C is generated, the standby drive control transistor 20 is turned on. Therefore, the section in which the C-point voltage V _C is generated determines the conduction period of the standby drive control transistor 20. ing. Therefore, this conduction period also depends on the magnitude of the voltage applied to the commercial power supply 5 as shown in FIG.
As shown in (f), it changes like T3 or T3 '.

At this time, the time constants of the resistors 15 and 16 and the capacitor 19 of the time constant circuit 31 shown in FIG.
As shown in FIG. 4, by setting the period longer than at least a half cycle of the commercial power supply (section T3), as shown in FIG. 4B, a positive voltage V _A synchronized with the commercial power supply 5 driving the transistor 6 is obtained. 4F, since the standby drive control transistor 20 continues to conduct as shown in FIG. 4F, the transistor 6 does not conduct simultaneously with the generation of the point A voltage _VA . This is a T5 interval A point voltage V _A shown in FIG. 4 (b), because the waiting time of driving the control transistor 20 is pulled out of the base current i and the base current i _b flows to the transistor 6. The supply of power to the load during the cut-off period T3 of the transistor 6 is performed by the discharge energy of the capacitor 28 shown in FIG.

Further, as shown in FIG. 4D, the conduction of the next transistor 6 is controlled by the drive control transistor 2 during standby.
The base potential of 0, i.e., reduced the C point voltage V _C, is after the period T3 which waits drive control transistor 20 is cut off. As a result, as shown in FIG. 4G, the conduction of the transistor 6 is limited to the section T4, and can be shorter than a half cycle of the commercial power supply cycle. Transistor 6 has T
At the same time as supplying power to the load in the four sections, power loss during the operation period occurs only during the T4 section as shown in FIG. Note that the operation waveform and power loss of the transistor 6 in the section T4 are the same as those shown in FIGS. 7A and 7B. In this way, the above operation is repeated in the cycle of the commercial power supply.

According to the present embodiment, as shown in FIG. 4H, the power loss of the transistor 6 is as shown in FIG.
The power consumption can be reduced by 50% or more compared to the case shown in FIG. That is, the transistor 6 does not operate in the whole section of the commercial power supply cycle, but conducts only in a section T4 shorter than a half cycle of the commercial power supply cycle according to the applied voltage of the commercial power supply 5. In addition, the conduction interval T4 of the transistor 6 that causes power loss is shortened, and power consumption during standby operation is reduced.

In the above embodiment , the commercial power supply cycle of the live part is used. However, a timer function (such as pulse width control) by a microcomputer included in the standby control circuit 3 of the non-live part is used. The same effect can be obtained by controlling the main switching power supply circuit.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to this, and various modifications can be made. For example, in the above-described embodiment, the switching power supply circuit of the current drive type bipolar transistor system has been described. However, the present invention can be applied to a switching power supply circuit of a voltage drive type FET system.

[0034]

According to the present invention, the power consumption during the standby operation can be reduced to 50% or less of that of the conventional circuit with an easy and inexpensive circuit configuration, so that the efficiency and the economy can be improved.

When the commercial power supply voltage is rated at 100 V AC,
When the standby power consumption is 1 W and the AC 220 V is rated, there is an effect that a high performance of standby power consumption 2 W is obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a switching power supply circuit as a reference example of the present invention.

FIG. 2 is a waveform diagram showing an operation waveform of a main part in FIG.

FIG. 3 is a circuit diagram showing a switching power supply circuit as one embodiment of the present invention.

FIG. 4 is a waveform diagram showing operation waveforms of main parts in FIG.

FIG. 5 is a block diagram showing a conventional switching power supply circuit.

FIG. 6 is a waveform chart showing an operation waveform of a main part in FIG. 5;

FIG. 7 is a waveform diagram showing a main part operation waveform in one cycle T in FIG. 6;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 time constant circuit 2 standby drive control circuit 3 standby control circuit 4 main load 5 commercial power supply 6 switching transistor 8 startup and drive circuit 9 startup resistance
DESCRIPTION OF SYMBOLS 10 ... Drive winding, 11 ... Resistance, 12 ... Output voltage detection circuit, 14, 15, 16 ... Resistance, 17, 18 ... Zener diode, 19 ... Capacitor, 20 ... Stand-by drive control transistor, 21 ... Resistance, 22 ... Switching transformer,
23 ... full-wave rectifier circuit, 24 ... smoothing circuit, 25 ... load and load side rectifier circuit, 26 ... photocoupler, 27 ... drive control circuit, 28, 29 ... capacitor, 30 ... photocoupler,
31 A time constant circuit having a threshold value.

Claims (1)

(57) [Claims] 1. A mounted in the device, during normal operation, the supplied power to a load in the device, the standby operation, the constant
Standby less than the power supplied to the load during normal operation
In a switching power supply circuit for supplying power for use to the load, a switching element for supplying electric power from a commercial power supply to the load, and in a standby operation, for each commercial power supply cycle, the switching element is connected to the power supply for a certain period of the commercial power supply cycle. No.
In the section 1, the power supply operation is performed, and
In the remaining second section, control means for controlling the power supply operation of the switching element and the voltage of the commercial power supply are applied so as to stop the power supply operation, and the voltage corresponding to the applied voltage is applied.
The first section and the second section in the control means
A switching power supply circuit , comprising: a variable means for varying a ratio with the interval .