JP2000224847A - Switching power device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress power consumed in a power factor improving circuit, when power saving operation is performed, and besides to suppress power consumed in an apparatus, by short-circuiting a power factor improving circuit by a change-over circuit when the power saving operation is performed. SOLUTION: If a power saving control signal P1 is received from a host system 6, for example, the voltage of a secondary output V1 is lowered to the voltage of an output V2 through a secondary control circuit 5, and operation is transferred to power saving operation. The output voltage of a power supplying winding N1 lowers to a level lower than a voltage set by a voltage regulation diode ZD2, a change-over device Tr2 operates via a resistor R2 and a voltage regulation diode ZD1, and power is supplied from a driving auxiliary winding N2 to a primary control circuit 3. Accordingly, a detecting device Tr1 does not operate by the function of a diode D2 and the voltage regulation diode ZD2. A relay RL1 stops its operation, the contact of the relay RL1 is short-circuited, and a power factor improving circuit 1 is short-circuited. When power saving operation is performed, power consumption in a capacitor C3, the diode D2, a resistor R1 and a detecting circuit 9 can be suppressed.

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, and more particularly to a switching power supply in which a power factor improving circuit for preventing harmonics is inserted.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional switching power supply device includes a power factor improving circuit 1 connected to a rectifying means D1 and a smoothing means C1, a switching element 2 connected to a smoothing means C1, and 1 for controlling the switching element 2
A secondary control circuit 3, a primary power supply winding N1 for supplying power to the primary control circuit 3 during normal operation, and a primary control circuit in response to a decrease in output voltage of the normal power supply winding N1 during power saving operation. 3 power supply winding N for power supply to power supply 3
And a transformer T1 for performing power conversion using the input from the smoothing means C1 as a primary-side input voltage and using the primary-side input voltage as a single or a plurality of secondary-side output voltages; A drive circuit 7 that rectifies and smoothes the line output voltage and the power saving control winding output voltage to supply a stabilized voltage to the primary control circuit 3, stabilizes the secondary output voltage, and saves power from the host system 6. A secondary control circuit 5 receives power control signal P1, performs power saving, and feeds back the output voltage from secondary side rectification and smoothing circuit 4 to primary control circuit 3 through photocoupler PC1.

[0003] The operation of this conventional switching power supply device is a power factor correction circuit 1 irrespective of a normal operation and a power saving operation.
By operating the device, the conduction angle of the input current is increased to reduce the harmonic components.

[0004]

In the conventional switching power supply device, the power factor correction circuit 1 is operated regardless of the normal operation and the power saving operation. There is a problem that power consumption occurs in the rate improvement circuit 1.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a switching power supply in which the power consumption of a power factor improving circuit during power saving operation is suppressed.

[0006]

In order to solve the above-mentioned problems, a switching power supply according to the present invention comprises a rectifier and a smoother for rectifying and smoothing an AC power supply, and a connection between the rectifier and the smoother. A power factor improving circuit, a switching element connected to the smoothing means, a primary control circuit for controlling the switching element, a power supply winding for supplying power to the primary control circuit during steady operation, and A driving auxiliary winding for supplying power to the primary control circuit in accordance with a voltage drop of the power supply winding during power saving operation,
A transformer for inputting an output from the smoothing means to a primary side and transmitting one or a plurality of output voltages to a secondary side;
Rectifies and smoothes the output voltage on the secondary side of this transformer.
A secondary rectification and smoothing circuit, and a secondary control circuit that stabilizes the output of the secondary rectification and smoothing circuit and transmits a power saving control signal from a host system to the primary control circuit to perform the power saving operation. A drive circuit for rectifying and smoothing the output voltage of the power supply winding and the driving auxiliary winding to supply a stabilized voltage to a primary control circuit, and a steady-state operation and a power-saving operation connected to the drive circuit. A switching element for switching power supply, a detecting element connected to the power supply winding for detecting a drop in output voltage of the power supply winding, and a short-circuit means for short-circuiting the power factor improving circuit by operation of the detecting element And characterized in that:

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a switching power supply according to an embodiment of the present invention will be described with reference to the drawings.

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

As shown in FIG. 1, a switching power supply according to an embodiment of the present invention includes a rectifier D1 and a smoother C1 for rectifying and smoothing an AC power supply, and a rectifier D1 and a smoother C1. Connected power factor improvement circuit 1
A switching element 2 connected to the smoothing means C1,
A primary control circuit 3 for controlling the switching element 2;
A power supply winding N1 for supplying power to the primary control circuit 3 during a steady operation, and a drive assist for supplying power to the primary control circuit 3 with a voltage drop of the power supply winding N1 during a power saving operation. The output from the smoothing means C1 is 1
Input to the secondary side and output one or more output voltages V to the secondary side
1, a transformer T1 for transmitting V2, and a transformer T1
Rectifying and smoothing circuit 4 for rectifying and smoothing the output voltage on the secondary side, and stabilizing the output of the secondary rectifying and smoothing circuit 4 and controlling the power saving control signal P1 from the host system 6.
Control circuit 5 that transmits power to the primary control circuit 3 by the photocoupler PC1 to perform a power saving operation, and a voltage obtained by rectifying and smoothing the output voltage of the power supply winding N1 and the driving auxiliary winding N2 and stabilizing the output voltage. Circuit 7 for supplying power to primary control circuit 3
A switching element Tr2 connected to the drive circuit 7 for switching power supply between normal operation and power saving operation; and a detection element connected to the power supply winding N1 for detecting a drop in the output voltage of the power supply winding N1. It comprises an element Tr1 and switching means 8 for short-circuiting the power factor correction circuit 1 by the operation of the detection element Tr1.

The drive circuit 7 includes a power supply winding N
1 and diodes D3 and D4 for rectifying and smoothing the output voltage from the driving auxiliary winding N2, capacitors C2 and C4,
A switching element Tr2 that operates when the output voltage of the power supply winding N1 drops, and a resistor R that is an operating means of the switching element Tr2
2. Constant voltage diode ZD1 and constant voltage diode ZD
And 1.

Further, the detecting circuit 9 includes a detecting element T for detecting a drop in the output voltage of the power supply winding N1 of the transformer T1.
r1, a resistor R1, a constant voltage diode ZD2, and a diode D for supplying stabilized power to the switch element Tr1.
2, the switching circuit 8 includes a relay RL1 having a contact b for short-circuiting or operating the power factor correction circuit 1 by the operation of the switch element Tr1.

Next, the operation of the switching power supply according to one embodiment of the present invention will be described with reference to the drawings.

The operation of the switching power supply according to one embodiment of the present invention is such that, in a steady state, the secondary outputs V1 and V2 of the transformer T1 which receives the output of the smoothing means C1 and converts the voltage are 2
The power is stabilized by the secondary control circuit 5 and transmitted to the primary control circuit 3 through the photocoupler PC1. The power supply to the primary control circuit 3 is supplied from the power supply winding N1 of the transformer T1 and the switching element Tr2 Becomes OFF, the detecting element Tr1 for detecting the power saving operation operates the relay RL1 through the diode D4, the constant voltage diode ZD2, the capacitor C3, and the resistor R1, and when the detecting element Tr1 operates because the relay RL1 has the b contact, The contact of the relay RL1 is opened and the power factor correction circuit 1 operates.

When a power saving control signal P1 from the host system 6 is received, the voltage of the output V1 on the secondary side is reduced to the voltage of the output V2 via the secondary control circuit 5, and the operation shifts to a power saving operation. As a result, the output voltage of the power supply winding N1 decreases, falls below the voltage set by the constant voltage diode ZD2, passes through the resistor R2 and the constant voltage diode ZD1, and the switching element Tr2 operates to operate from the driving auxiliary winding N2. Power is supplied to the primary control circuit 3.

Therefore, the detection element Tr1 does not operate due to the diode D2 and the constant voltage diode ZD2, and the relay RL
1 stops operation, the contact of the relay RL1 is short-circuited, and the power factor correction circuit 1 is short-circuited. In the power saving operation, the capacitor C3, the diode D2, the resistor R1, the detection element Tr1,
Since no current flows through the constant voltage diode ZD2, no power is consumed in the detection circuit 9.

[0016]

As described above, according to the switching power supply of the present invention, the power factor improving circuit is short-circuited during the power saving operation by the switching circuit without consuming power in the detection circuit during the power saving operation. By suppressing power consumption in the power factor improving circuit during power saving operation, there is an effect of suppressing power consumption of the device during power saving operation.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram of a conventional switching power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power factor improvement circuit 2 Switching element 3 Primary control circuit 4 Secondary side rectification and smoothing circuit 5 Secondary control circuit 6 Host system 7 Drive circuit 8 Switching circuit 9 Detection circuit 10 Power supply device C1 Smoothing means C2, C3, C4 Capacitor D1 Rectifier D2, D3, D4 Diode N1 Power supply winding N2 Driving auxiliary winding P1 Power saving control signal PC1 Photocoupler R1, R2, R3, R4 Resistance RL1 Relay T1 Transformer Tr1 Detection element Tr2 Switching element ZD1, ZD2 Constant voltage diode

Claims (1)

[Claims] 1. A rectifier and a smoother for rectifying and smoothing an AC power supply, a power factor improving circuit connected between the rectifier and the smoother, a switching element connected to the smoother, and a switching device. A primary control circuit for controlling elements, a power supply winding for supplying power to the primary control circuit during a steady operation, and the primary control in response to a voltage drop of the power supply winding during a power saving operation A transformer having a driving auxiliary winding for supplying power to the circuit, and inputting an output from the smoothing means to a primary side and sending one or more output voltages to a secondary side; Rectifying and smoothing circuit for rectifying and smoothing the output voltage on the side, stabilizing the output of the secondary rectifying and smoothing circuit, and transmitting the power saving control signal from the host system to the primary control circuit to Power saving operation A secondary control circuit for performing operations, a drive circuit for rectifying and smoothing the output voltage of the power supply winding and the driving auxiliary winding and supplying a stabilized voltage to the primary control circuit, and a drive circuit connected to the drive circuit. A switching element for switching between power supply for steady operation and power saving operation, a detection element connected to the power supply winding for detecting a decrease in output voltage of the power supply winding, and And a short-circuit means for short-circuiting the rate improvement circuit.