JP3766624B2 - Switching power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a switching power supply that performs on / off control by a secondary-side photocoupler driving power supply circuit.
[0002]
[Prior art]
FIG. 5 shows a conventional switching power supply circuit, in which a primary battery 25 that cannot be charged is used as an auxiliary power supply for the photocoupler drive circuit 18, and the DC output voltage is turned on / off by the secondary side switch 17. Whenever the primary battery 25 of the photocoupler driving circuit 18 is consumed and a sufficient voltage cannot be obtained, it is necessary to replace the battery, which causes problems in terms of maintenance, management, and cost.
[0003]
[Problems to be solved by the invention]
As described above, in the conventional switching power supply, the battery needs to be replaced whenever the primary battery 25 is consumed and a voltage sufficient to turn on / off the output voltage cannot be obtained. There has been a demand for a circuit configuration of a switching power supply that can be made unnecessary and easy to maintain.
[0004]
[Means for Solving the Problems]
The present invention solves the above problems,
A rectification / smoothing circuit including a first diode 12 and a first smoothing capacitor 13 connected to the secondary side;
A switching control circuit 6 that drives the switching element 5 on the primary side, and a photocoupler drive circuit 18 that is connected to the secondary side switch 17,
In the switching power supply connected by the photocoupler 15,
The photocoupler drive circuit 18 includes:
A series circuit of a second diode 24, a first resistor 23, and a second smoothing capacitor 22 is provided between the cathode of the first diode 12 and the cathode of the photocoupler 15 in the rectifying / smoothing circuit. connection,
The negative electrode of the secondary battery 19 or electric double layer capacitor (hereinafter abbreviated as EDLC) 28 is connected to the cathode of the diode of the photocoupler 15, and the third diode 21 is connected to the positive electrode via the second resistor 20. The anode is connected to the cathode of the fourth diode 26 via the third resistor 27;
The cathode of the third diode 21 and the anode of the fourth diode 26 are connected to the connection point of the first resistor 23 and the second smoothing capacitor 22, and the connection point and one end of the secondary side switch 17 are connected. The other end of the switch 17 and the anode of the diode of the photocoupler 15 are connected by a fourth resistor 16 ;
The switching power supply is characterized in that the terminal voltage V1 of the second capacitor 22 is configured to be higher than the terminal voltage V2 of the secondary battery 19 or the EDLC 28 .
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The photocoupler drive circuit 18 of the switching power supply shown in FIG. 1 (or FIG. 3) has a second diode 24 and a first resistor 23 between the cathode of the first diode 12 and the cathode of the diode of the photocoupler 15. And a series circuit of the second smoothing capacitor 22,
The negative electrode of the secondary battery 19 (or EDLC 28) is connected to the cathode of the diode of the photocoupler 15, the anode of the third diode 21 is connected to the positive electrode via the second resistor 20, and the third resistor 27 is connected. The cathode of the fourth diode 26 is connected via
The cathode of the third diode 21 and the anode of the fourth diode 26 are connected to the connection point of the first resistor 23 and the second smoothing capacitor 22, and the connection point and one end of the secondary side switch 17 are connected. The other end of the switch 17 and the anode of the diode of the photocoupler 15 are connected by a fourth resistor 16.
Here, the photocoupler 15 connected to the switching control circuit 6 on the primary side has a function of outputting the DC voltage V ₀ when the phototransistor is turned on and stopping the output when the phototransistor is turned off.
Therefore, when the secondary side switch 17 is turned on, as shown in FIG. 2 (or FIG. 4) (a), the rechargeable secondary battery 19 (or EDLC 28) connected in parallel to both ends of the capacitor 22 and the capacitor 22 is provided. Current flows from the series circuit consisting of the second resistor 20 and the third diode 21 to the photodiode of the photocoupler 15 via the fourth resistor 16 and the phototransistor is turned on, so that the switching control circuit 6 operates. The DC voltage V ₀ is output. As shown in FIG. 2 (or FIG. 4) (b), the direct current voltage V ₀ causes the photodiode to pass through the second diode 24, the first resistor 23, the secondary switch 17, and the fourth resistor 16. Is supplied with current. At this time, by setting the terminal voltage V1 of the capacitor 22 to be higher than the terminal voltage V2 of the secondary battery 19, the current flowing out from the secondary battery 19 becomes 0A, the consumption can be reduced, and the DC voltage V _By charging the secondary battery 19 (or EDLC 28) from ₀ through the second diode 24, the first resistor 23, the fourth diode 26, and the third resistor 27, the charging current (arrow dotted line) flows and charges, The replacement cycle of the secondary battery becomes sufficiently long, the number of replacements decreases, and maintenance management becomes easy. Further, in the case of EDLC, the replacement cycle is further increased, and no replacement is possible until the product life of the power supply.
[0006]
【Example】
FIG. 1 (or FIG. 3) is a circuit diagram of a switching power supply according to an embodiment of the present invention. FIG. 2 (or FIG. 4) (a) turns on the secondary side switch 17 in FIG. 1 (or FIG. 3). FIG. 2 (or FIG. 4) and FIG. 2 (b) show the current flow when the DC voltage V _{0 is} output in FIG. 1 (or FIG. 3) and the secondary battery 19. It is a figure which shows the flow (arrow dotted line) of the charging current. FIG. 5 is a circuit diagram of a conventional switching power supply. Here, the secondary battery 19 (or EDLC 28) of FIG. 1 (or FIG. 3) is charged via the second diode 24, the first resistor 23, the fourth diode 26, and the third resistor 27. As a result, the battery replacement cycle can be extended by a factor of five compared to the conventional example of FIG. 5 using the primary battery 25, the number of battery replacements is greatly reduced, and maintenance management is facilitated. In addition, it was possible to reduce the number of batteries used. (In addition, when the EDLC 28 was used, the number of times the EDLC was replaced was further reduced.)
[0007]
【The invention's effect】
As described above, in the switching power supply according to the present invention, a rechargeable battery (or EDLC) is used for the photocoupler driving circuit, and a charging current is supplied to the secondary battery (or EDLC) even during the operation of the switching power supply. Charging can significantly increase the battery (or EDLC) replacement cycle, greatly reduce the number of battery (or EDLC) replacements, facilitate maintenance, and maintain the battery (or EDLC). It is also possible to reduce the number of units used.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a switching power supply according to an embodiment of the present invention.
2A is a diagram showing a flow of current when the secondary side switch 17 is turned on in FIG. 1, and FIG. 2B is a diagram of current at the time of output of the DC voltage V _{0 in} FIG. It is a figure which shows a flow (arrow solid line) and the flow (arrow dotted line) of the charging current to the secondary battery 19. FIG.
FIG. 3 is a circuit diagram of a switching power supply according to another embodiment of the present invention.
4A is a diagram showing a flow of current when the secondary side switch 17 is turned on in FIG. 3, and FIG. 4B is a diagram of current at the time of output of the DC voltage V _{0 in} FIG. It is a figure which shows a flow (arrow solid line) and the flow (arrow dotted line) of the charging current to EDLC28.
FIG. 5 is a circuit diagram of a switching power supply according to a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AC power supply 2 Full wave rectifier circuit 3, 7 Smoothing capacitor 4 Primary winding 5 Switching element (NPN transistor)
6 switching control circuit 8 diode 9 auxiliary winding 10 secondary winding 11 converter transformer 12 first diode 13 first smoothing capacitor 14 load resistor 15 photocoupler 16 fourth resistor 17 secondary side switch 18 photocoupler drive circuit 19 Secondary battery 20 Second resistor 21 Third diode 22 Second smoothing capacitor 23 First resistor 24 Second diode 25 Primary battery 26 Fourth diode 27 Third resistor 28 Electric double layer capacitor (EDLC) )

Claims (1)

A rectifying / smoothing circuit including a first diode connected to the secondary side and a first smoothing capacitor; a switching control circuit for driving the switching element on the primary side; and a photocoupler driving circuit connected to the secondary side switch; The
In switching power supplies connected by photocouplers,
The photocoupler drive circuit is
A series circuit of a second diode, a first resistor, and a second smoothing capacitor is connected between the cathode of the first diode of the rectifying / smoothing circuit and the cathode of the diode of the photocoupler;
The negative electrode of the secondary battery or the electric double layer capacitor is connected to the cathode of the diode of the photocoupler, the anode of the third diode is connected to the positive electrode via the second resistor, and the fourth diode is connected via the third resistor. Connect the cathode of
The cathode of the third diode and the anode of the fourth diode are connected to the connection point of the first resistor and the second smoothing capacitor, the connection point and one end of the secondary side switch are connected, and the switch Is connected to the anode of the photocoupler diode with a fourth resistor ,
A switching power supply, wherein the terminal voltage of the second capacitor is configured to be higher than the terminal voltage of the secondary battery or the electric double layer capacitor .

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