JPH05226982A - Pulse voltage generator - Google Patents

Abstract

PURPOSE:To provide the pulse voltage generator in which an isolation power supply is formed without use of an expensive and easily deteriorated component such as a photocoupler and which is used for a long time stably with less operation defect such as a fault. CONSTITUTION:Capacitors 14, 18, plural resistors 13, 50 connected in parallel with the capacitors 14, 18 and transistors(TRs) 20, 21 in Darlington connection to one of the resistors 13, 50 are provided between a primary side 17a and a secondary side 17b of an isolation power supply, and the resistance of the resistors 13, 50 connecting to the TRs 20, 21 specifying the operating period of the TRs 20, 21 and the capacitance of the capacitors 14, 18 in cooperation with the resistors 13, 50 are selected so as to repeat ON/OFF operation of the TRs 20, 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse voltage generator, and more particularly to a pulse voltage generator for generating a reference pulse voltage for a timer.

[0002]

2. Description of the Related Art Generally, electronic devices such as a dedicated television CCTV and a video tape recorder (VTR) are
Some devices have a built-in timer circuit as a function of time setting and the like. The reference pulse voltage of this timer circuit is taken out in synchronism with a commercial AC power supply frequency of 50 Hz or 60 Hz which is usually used as an input drive power supply, and has been used for time display of the electronic equipment. By the way, in the conventional reference pulse voltage generator for the timer circuit, there has been one in which the waveform is shaped and taken out from the AC output voltage on the secondary side through the insulating transformer formed of the silicon steel plate. In this type of device, it is necessary to enhance the insulating property in order to reduce various electrical noises. For example, there is a device in which electrical noises are removed by a circuit configuration using a photocoupler.

FIG. 4 is a circuit diagram showing an example of a pulse voltage generator using such a photocoupler. In this figure, the bridge rectifier circuit 50 is connected between a node A and a node C to a 50/60 Hz AC power source. The node D of the bridge rectifier circuit 50 is connected to the orthogonal ferrite transformer 5 via the switching transistor 53.
6. The primary side of the standby transformer 70 is connected, and the photocoupler 74 is connected to the primary side of the standby transformer 70.
Of the bridge rectifier circuit 50 and the switching transistor 69 are connected to form a primary side circuit of the standby transformer 70. In the primary side circuit of the standby transformer 70, the transistor 69 is operated, and when the transformer 70 is excited and a voltage is applied to the light emitting diode 74a, the phototransistor 74b, which is a light receiving element of the photocoupler 74, operates. Isolate electrical noise.

The circuit configuration of the primary side circuit of the transformer 70 will be described. The capacitor 51 is connected between the node E and the ground, and the resistor 52 is connected between the node F and the node G. Since the collector of the transistor 53 is connected to the node F, the node G is connected to the base, and the emitter is connected to the node H, the transistor 53 operates as a switching transistor. The orthogonal ferrite transformer 56 includes coils 56a to 56c and an iron core 5.
6d, and the coil 56a has a node H and a node K.
And the one end of the coil 56b is connected to the node J, and the other end of the coil 56b is connected to the resistor 57 and the capacitor 5.
5 is connected to the node G via a transistor 53.
When a base voltage of a predetermined magnitude is applied to the base of the transistor and the voltage becomes a predetermined voltage, the transistor 53 performs a switching operation.

One end of the coil 56c is grounded, and the other end is connected to the base of a transistor 61 via a resistor 58, a capacitor 59, a node L and a node N, and a base voltage is applied to the transistor 61. The resistor 60 is connected between the nodes LM, the node M and the collector of the transistor 61 are connected, and when the base voltage is applied to the transistor 61, the transistor 61 performs a switching operation and a current flows to the ground to remove noise. Is done. The diode 64 is connected between the node N and the ground in the opposite direction, and a desired voltage is applied to the base of the transistor 61.

The node C of the bridge rectifier circuit 50 is connected to the base of the transistor 69 via the resistor 66, the node Q and the node y, and the base voltage is applied to the transistor 69. A capacitor 67 is connected between the node Q and the ground to set the base voltage of the transistor 69 to a desired voltage. The emitter of the transistor 69 is grounded, the collector is connected to the photocoupler 74 as described above, and the switching operation of the transistor 69 causes a current corresponding to noise to flow to the ground to remove noise and remove noise to the secondary side. It As described above, in the primary side circuit of the transformer 70, the transistors 61, 69
By the operation of, noise such as external noise is removed from the secondary side.

The secondary side circuit of the transformer 70 is a coil 70.
One end of b is connected to the diode 97 in the forward direction via the node v, and the cathode of the diode 97 is connected to the node b via the node b.
The current that is connected to the V power supply node e and is excited by the coil 70b from the primary coil 70a through the iron core 70c is 5V.
Supplied to power. A diode 98 is reversely connected between the node v and the ground, a capacitor 99 is connected between the node b and the node d, a capacitor 102 is connected between the node d and the ground, and the coil 70b is connected to the coil 70b. A constant exciting current comes to flow in the 5V power supply.

The node a of the 5V power source is connected to the node w and the collector of the phototransistor 74b of the photocoupler 74 via the nodes T, V and X, and the line drawn from the node w has a rating of 5V / 0.1A. Is supplied to an external electronic device (not shown). The emitter of the phototransistor 74b has a resistor 76 connected between the node S and ground, and the base of the transistor 75 is connected to the node S so that a desired base voltage of the transistor 75 is applied to the base of the transistor 75. There is. Since the emitter of the transistor 75 is grounded, noise such as external noise is removed. A resistor 77 is connected between the node T and the node U, a capacitor 78 is connected between the node V and the node W, and 50/60 Hz switching is performed by an electronic device (not shown) by a line drawn from the node W. Do it by the side. The other end of the coil 70b passes through the node c and becomes 5
The capacitor 102 is connected to the V power supply node Z and the node d, and is connected between the node d and the ground, and a constant current flows through the node e of the 5V power supply.

The PRT transformer 80 includes coils 80a-8a.
0c and an iron core 80d, one end of the coil 80a is connected to one end of the coil 56a of the orthogonal ferrite transformer 56 via the capacitor 78 and the node K.
The other end of 0a is connected to the interlocking switch 100. When the interlock switch 100 is turned on, the relay circuit 91 operates and is connected to the node g of the 5V power supply via the node h. The relay circuit 91 is connected to the collector of the transistor 93 via the node i, and the base of the transistor 93 is connected with the resistor 94 between the node u and the ground.
An ON / OFF switch (not shown) of the electronic device is connected via the node u and the resistor 95, the ON / OFF switch (not shown) is turned on, and the transistor 93 is operated to operate 5
It is designed to start the V power supply. A diode 8 is provided in the forward direction at one end of the coil 80b of the PRT transformer 80.
1 is connected to the cathode of the diode 81 from the nodes 1 to
n are sequentially connected, and 135V power is supplied to an electronic device (not shown). A node t is connected to the node n via a resistor 86, and a resistor 90 is connected between the node t and the ground.

A diode 82 is connected in the forward direction to the node j of the coil 80b, and the cathode of the diode 82 is connected to the node o. A diode 83 is connected in the forward direction to the other end of the coil 80b, the cathode of the diode 83 is connected to the node l, and a capacitor 96 is connected between the node m and the ground to keep the exciting current flowing in a fixed direction. The node o is connected to one end of the coil 80c, the resistor 101 is connected between the node o and the node q, and the Zener diode 87 is connected between the node q and the ground to clamp a signal including a noise component. The base voltage of the transistor 84 is set to a desired voltage, and the transistor 8
4 is operated to flow a current including a noise component excited by the coil 80c to the ground to remove the noise. A capacitor 85 is connected between the node p and the ground, and a 15V power source line of an external electronic device (not shown) is drawn out.

[0011]

In the above pulse voltage generator, the DC output voltage is obtained by the rectifier diode 71 and the electrolytic capacitor 73 in the primary side circuit of the small ferrite standby transformer 70 that operates at high frequency, and the photo coupler 7 is used.
The switching transistor 75 is synchronized with the commercial frequency via the light emitting diode 74a of No. 4 and the switching operation is repeated. Therefore, in such a pulse voltage generator, the optical output is insulated via the photocoupler 74,
Since the switching frequency is transmitted to the secondary side circuit of the ferrite standby transformer 70, the transistor 75 is switched, and the waveform is shaped by the capacitor 78 to obtain the reference pulse voltage, the photocoupler 7 is used over time.
There was a problem that the photo coupler 74 could not be used stably for a long period of time due to the malfunction of the photo coupler 74 along with the deterioration of No. 4. This is because, in general, in a photocoupler, when the current transmissibility (CTR) of the optical output reaches 50% of the initial value, the photocoupler deteriorates and the operation becomes unstable, and stable operation for a long time cannot be expected. Further, in this pulse voltage generator, since the photocoupler 74 and the like are used in the primary side circuit of the standby transformer 70, there are problems in that the circuit configuration becomes complicated and the cost of parts increases.

Therefore, the present invention provides a pulse voltage generator capable of forming an insulated power supply without using expensive components such as a photocoupler which easily deteriorates and which can be used stably for a long time with less malfunction due to a failure or the like. The purpose is that.

[0013]

As a means for solving the above problems, the present invention provides a capacitor, a plurality of resistors connected in parallel to the capacitor, and a transistor in Darlington connection to one of the resistors. Is provided between the primary side and the secondary side of the isolated power supply, and cooperates with the capacitor,
The value of the resistor that defines the operating cycle of the transistor and the value of the capacitor that cooperates with the resistor are set so that the on / off operation of the transistor is repeated. Further, the Darlington-connected transistor is switched in synchronization with the power supply input frequency, and the waveform of the output voltage from the power supply generator is shaped based on the output of the transistor. Further, the values of a plurality of resistors connected in parallel to the capacitor are set so that the leakage current due to the resistor between the primary side and the secondary side of the isolated power supply is set to a certain value or less. is there.

[0014]

[Function] A plurality of resistors are connected in parallel to the capacitor, and a transistor is connected to one of the resistors in a Darlington connection, and the output voltage is regulated by the operation period,
These transistors are provided between the primary side and the secondary side of the isolated power supply, and the value of the resistor is set so as to cooperate with the capacitor to define the operation cycle of the transistor and repeat the on / off operation of the transistor. Set it to show the noise filter effect. Further, the transistor is switched in synchronization with the commercial frequency, and the output voltage waveform is shaped based on the output of the transistor. Furthermore, the value of multiple resistors connected in parallel with the capacitor is set so that the leakage current due to the discharge resistance between the primary side and the secondary side of the isolated power supply is set to a certain value or less, and long-term use is performed. To endure even.

[0015]

Embodiments of the pulse voltage generator of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an entire power supply circuit of an embodiment of the pulse voltage generator of the present invention.
The difference between the pulse voltage generator of the present invention and the conventional pulse voltage generator is that the circuit configuration of the primary side circuit of the standby transformer 70 is simplified. In FIG. 1, the bridge rectifier circuit 1 is connected between a node A and a node C to an AC power supply of 50 Hz or 60 Hz. The D-node of the bridge rectifier circuit 1 is connected to the primary side of the orthogonal ferrite transformer 7 and the standby transformer 17 via the transistor 4 for switching.

The bridge rectifier circuit 1 includes a capacitor 1
4, 18 and these capacitors 14, 18 cooperate with each other to form a time constant circuit.
3, 50 are connected, the base voltage is defined based on the time constants of the resistors 13, 50 and the capacitors 14, 18, and the transistor 20 whose operating frequency is determined is connected to the transistor 21 in Darlington connection. The capacitors 14, 18, the resistors 13, 50, and the transistors 20, 21 are provided between the primary side and the secondary side of the insulated power supply including the standby transformer, and the values of the discharging resistors 13, 50 are set. Is set so that the on / off operation of the transistors 20 and 21 is repeated. Then, the transistors 20 and 21 are connected to a commercial frequency of 50 Hz or 60 H.
Switching is performed in synchronization with z so that the output voltage waveform is shaped based on the output of the transistor 21. As described above, the circuit of FIG. 1 can obtain the reference pulse voltage without interposing a photocoupler unlike the conventional pulse voltage generator of this type.

The collector of the transistor 4 is connected to the node D of the bridge rectifier circuit 1 through the nodes E and F, and the emitter of the transistor 4 is connected to the node K through the node H and the coil 7a of the orthogonal ferrite transformer 7. This node K is connected to one end of the coil 17a on the primary side of the standby transformer 17 via the capacitor 16 and the other end of the coil 17a on the primary side is grounded to form a primary side circuit of the standby transformer 17. ..

The circuit configuration of the primary side circuit of the transformer 17 will be described. The capacitor 2 is connected between the node E and the ground, and the resistor 3 is connected between the node F and the node G. Since the collector of the transistor 4 is connected to the node F, the base is connected to the node G, and the emitter is connected to the node H, the transistor 4 operates as a switching transistor. The orthogonal ferrite transformer 7 includes coils 7a to 7c and an iron core 7d, the coil 7a is connected between the node H and the node K, and one end of the coil 7b is connected to the node J.
The other end of b is connected to the node G via a resistor 8 and a capacitor 6.
When a base voltage is applied to the base of the transistor 4 to reach a desired voltage, the transistor 4 performs a switching operation.

One end of the coil 7c is grounded and the other end is connected to the base of the transistor 12 via the resistor 9, the capacitor 6, the node L and the node N, and the base voltage is applied to the transistor 12. .. The resistor 11 is connected between the node LM and the node M and the transistor 12
When the base voltage is applied to the transistor 12, the transistor 12 operates and a current including noise flows to the ground, so that noise is removed from the secondary side. The diode 15 is connected in the opposite direction between the node N and the ground, and regulates so that a desired voltage is applied to the base of the transistor 12. Therefore,
As described above, in the primary side circuit of the transformer 17, the operation of the transistor 12 removes the overcurrent, and the coil 17a of the standby transformer 17 is grounded to remove the overcurrent. As described above, by eliminating the circuit for connecting the photocoupler and the coil 17 on the primary side of the standby transformer 17 unlike the conventional pulse voltage generator of this type, the circuit configuration can be simplified.

The node C of the bridge type rectifier circuit 1 is connected to the base of the transistor 20 via the discharging resistor 50, the node Q and the node y, and the base voltage is the transistor 2.
Applied to zero. Further, a capacitor 18 is connected between the node Q and the ground, and a diode 19 is connected in the opposite direction between the node y · n and the ground to set the base voltage of the transistor 20 to a desired voltage. The emitter of the transistor 20 is connected to the base of the transistor 21, the collector of the transistor 20 is connected to the collector of the transistor 21 at the node U, the transistor 20 and the transistor 21 are Darlington-connected, and the gain of the transistor used in the output stage is increased. If a high one is used, drive power can be reduced and a power supply circuit with low power consumption can be provided. These transistors 20, 21
The switching operation causes a current containing a noise component to flow to the ground and removes a signal containing the noise component.

In the above power supply circuit, the external noise 2 from the AC power supply is converted into capacitors 14, 18 such as ceramic capacitors which are suitable safety standard approved products. A so-called Neufilter effect is obtained, which protects electronic devices from malfunctions caused by static noise. For example, it is desirable to select the electrostatic capacitance C ₀ of the ceramic capacitor as 2,200 PF to 4,700 PF and the resistance value R ₁ of the discharging resistor as 2.2 MΩ. In this power supply circuit, the time constant decreases in inverse proportion to the product of C ₀ and R ₁ , so that the filter effect can be remarkably exhibited. Although the filter effect is improved as the value of the capacitance of the ceramic capacitor is increased, the leakage current may increase due to the potential difference between the primary side and the secondary side of the standby transformer 17. The limit value of leakage current is specified. For example, in Japan, it is less than 1.0mA for household electronic devices. Incidentally, since it is regulated to be 0.5mA or less in North America and 0.75mA or less in Europe, it is possible to meet the standards of major countries in the world by defining the limit value of leakage current to 0.5mA or less. In Japan, C ₀ = 4,700PF, R ₁ = 2.
In the case of 2 MΩ, the leakage current is represented by Il = (jwC ₀ + 1 / R ₁ ) V ₀ ... (1). Therefore, when Il = 0.21 mA + 0.064 mA = 0.274 mA V ₀ = 100 V _rms , Il = 0.274mA, so Il <1mA can be satisfied.

The secondary side circuit of the standby transformer 17 is
One end of the coil 17b is connected to the diode 25 in the forward direction via the node v, the cathode of the diode 25 is connected to the 5V power supply node e via the node b, and the primary side coil 17a is excited to the coil 17b via the iron core 17c. The supplied current is supplied to the 5V power supply. A diode 26 is connected in the reverse direction between the node v and the ground, an electrolytic capacitor 27 is connected between the node bd, an electrolytic capacitor 28 is connected between the node d and the ground, and a constant excitation is generated from the coil 17b. The current will flow to the 5V power supply.

The node a of the 5V power source is connected to the node U via the node W, the node X, the node V, and the resistor 22, and at the time of the switching operation of the transistors 20 and 21, the external electronic device via the 5V / 0.1 A line. 5V / 0.1 A will be supplied to (not shown). Further, the collector of the transistor 21 passes through the node U and then the node w.
50 / 60Hz connected to the node and drawn from the node w
Switching of 50/60 Hz is performed on the electronic device (not shown) side by the line.

The PRT transformer 31 includes coils 31a to 3a.
1c and an iron core 31d, one end of a carp 31a is connected to one end of a coil 7a of the orthogonal ferrite transformer 7 via a capacitor 29 and a node K, and the other end of the coil 31a is connected to an interlock switch 30. When the interlock switch 30 is turned on, the relay circuit 45 operates and is connected to the node g of the 5V power supply via the node h. The relay circuit 45 is connected to the collector of the transistor 47 via the node i, the base of the transistor 47 is connected to the resistor 48 between the node u and the ground, and the relay circuit 45 is turned on / off via the node u and the resistor 49. An OFF switch (not shown) is connected. Therefore, an ON / OFF switch (not shown) is turned on to operate the transistor 47 to start the 5V power supply, and an ON / OFF switch (not shown) is turned off to make the transistor 47 non-conductive and set to 5V.
The power supply can be turned off.

A diode 32 is connected to one end of the coil 31b of the PRT transformer 31 in the forward direction, nodes 1 to n are connected in order to the cathode of the diode 32, and 135V is supplied by a 135V power source line drawn from the node n.
Power is supplied to an electronic device (not shown). A node t is connected to the node n via a load resistor 44, and a load resistor 43 is connected between the node t and the ground.

A diode 33 is connected in the forward direction to the node j of the coil 31b, and the cathode of the diode 33 is connected to the node o. A diode 34 is connected to the other end of the coil 31b in the forward direction, a cathode of the diode 34 is connected to the node l, a capacitor 35 is connected between the node m and the ground, and an exciting current flows in a fixed direction. .. The cathode of the diode 33 is a node o
, A resistor 37 is connected between the node o and the node q, a zener diode 41 is connected between the node q and the ground, and an overcurrent is clamped to set the base voltage of the transistor 84 to a desired voltage. 38 is operated to flow the current excited by the coil 31c to the ground for insulation. In addition, an electrolytic capacitor 3 is provided between the node p and the ground.
6 is connected and 15 is pulled out from the node p
Connect to external electronic equipment (not shown) by V power line
5V power is supplied.

FIG. 2 is a circuit diagram showing a main part of the power supply circuit of FIG. FIG. 3 is a diagram showing a timing chart of signal waveforms at main points in FIG. In FIG. 2, V ₀ is shows the voltage applied to the resistor 13 for discharge, the current flowing through the resistor 50 for I _B are discharged, V ₂ is 50 / 60Hz
It is a pulse voltage applied between the line and ground. For example,
The value of the discharging resistor 13 is set to R ₃ , and the discharging resistor 50
Letting R ₁ be the value of the discharge resistance when the value of is defined as R ₄ , the discharge resistance value R ₁ can be obtained by the following calculation of the resistance value. R ₁ = R ₃ R ₄ / (R ₃ + R ₄ ) ... (2) By selecting the resistance values R ₃ and R ₄ , the leakage current Il of the above formula (1) depending on the value R ₁ of the discharge resistance. Is calculated using the above equation (2), it is set to about 64 μA. That is, the resistance value R ₃ of the discharging resistor 13 is set so that the leakage current due to the discharging resistance is set to about 64 μA so that the Darlington-connected transistors 20 and 21 repeat the ON / OFF switching operation, and the discharging resistor 13 has the resistance value R ₃ . By selecting the resistance value R ₄ of the resistor 50, the noise filter effect can be remarkably exhibited.

FIG. 3A shows a voltage signal V ₀ applied between the discharging resistor 13 and the ground. It is assumed that the crest level is 282.8 V and the time T for one cycle is 20 mS. To do. FIG. 3 (b) shows a current I _B flowing through the transistor 20 node-based 2 in the current flowing through the resistor 50 for discharge, FIG. 3 (c), a pulse to be applied between the ground and the 50 / 60Hz line The voltage is V ₂ . In the above formula (1), if R ₃ = R ₄ = 4.7MΩ, current I _B flowing through the base of the transistor 20 in FIG. 2, for example, in 32Myuei, the reference pulse voltage of 50Hz in this case peak-to-peak Can obtain 5V.

In the above pulse voltage generator, since it is not necessary to connect the photocoupler 74 to the primary coil 17a of the standby transformer 17 as in the conventional case, there is a problem of life due to deterioration of the photocoupler 74 even when used for a long time. It will be possible to solve it. Further, since the windings of the primary coil 17a of the standby transformer 17, the rectifying diode, the electrolytic capacitor and the like can be reduced, the cost can be prevented from increasing due to the reduction in the number of components. In the above embodiments, the commercial frequency of about 50 Hz or 60 Hz is illustrated. However, the commercial frequency can be applied to the frequency normally used for the commercial power source, and even the commercial power source frequency used in Europe and the United States. The present invention can be applied.

Any type of resistor may be used as the discharging resistors 13 and 50. For example, by using a variable resistor as the resistor, the discharging resistor 13 may be used.
It becomes easier to arbitrarily select the resistance value R _{3 of} the discharge resistor 50 and the resistance value R ₄ of the discharging resistor 50. By changing the resistance value of the variable resistor, the leakage current due to the discharge resistor can be quickly increased. Will be able to be specified in. In the above example,
Ceramic capacitors are used as the capacitors 14 and 18, but the capacitors are not limited thereto. In the above embodiment, the case where the resistors 13 and 50 are changed has been described.
The present invention is not limited to this, and the capacitors 14 and 18 may be variable instead of the resistors 13 and 50.

[0031]

As described above, according to the present invention, since it is not necessary to connect a photocoupler or the like to the primary coil of the standby transformer, the problem of life due to deterioration of the photocoupler or the like is caused even when used for a long time. It can be resolved. Also, winding of the primary coil of the standby transformer,
Since the components such as the rectifier diode and the electrolytic capacitor can be reduced, it is possible to achieve an excellent effect that the cost can be prevented from increasing due to the reduction in the number of components.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a pulse voltage generator of the present invention.

FIG. 2 is a circuit diagram showing a main part of the power supply circuit of FIG.

FIG. 3 is a diagram showing a timing chart of signal waveforms at main points in FIG.

FIG. 4 is a circuit diagram showing an example of a conventional pulse voltage generator.

[Simple explanation of symbols]

 1 Diode Rectifier Circuit 4 Switching Transistor 7 Orthogonal Ferrite Transformer 12 Switching Transistor 13 Discharge Resistor 14 Capacitor 17 Standby Transformer 18 Capacitor 20 Switching Transistor 21 Switching Transistor 50 Discharge Resistor

Claims (3)

[Claims] 1. A capacitor, a plurality of resistors connected in parallel to the capacitor, and a transistor Darlington-connected to one of the plurality of resistors are provided between a primary side and a secondary side of an isolated power supply. And a resistor connected to the transistor that defines the operating cycle of the transistor and a value of the capacitor that cooperates with the resistor, are set so that the on / off operation of the transistor is repeated. Voltage generator. 2. The transistors connected in Darlington are switched in synchronization with a frequency for power supply drive input,
The pulse voltage generator according to claim 1, wherein the waveform of the output voltage from the power generator is shaped based on the output of the transistor. 3. The values of a plurality of resistors connected in parallel with the capacitor are set so that a leakage current by the resistors between the primary side and the secondary side of the isolated power supply is set to a certain value or less. The pulse voltage generator according to claim 1 or 2.