JPS6127249Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention includes a first power supply circuit that generates a first DC voltage, and a power supply circuit that generates the first DC voltage by receiving operating power from the first power supply circuit. In electronic equipment that is equipped with a second power supply circuit that generates a second DC voltage with a high voltage value and supplies the functional circuit of the electronic equipment as operating power, By providing a power supply circuit that operates to protect electronic equipment from abnormal heat generation and secondary destruction of components due to overcurrent and overvoltage, there is no risk of fire accidents or electric shock accidents due to failure, and reliability is improved. This was done with the aim of making it easier to obtain highly safe electronic equipment.

As described above, the first
A second DC voltage having a voltage value higher than the first DC voltage is generated by receiving operating power from the power supply circuit and the first power supply circuit, and operates the functional circuit of the electronic device. The second
An example of an electronic device equipped with a power supply circuit is a television receiver (hereinafter referred to as television).
(described as TV). below,
Problems with conventional devices will be explained using a case where the electronic device is a TV receiver as an example.

FIG. 1 is a block diagram of some components of a TV receiver, and in the figure, 1 is a first power supply circuit, and this first power supply circuit 1 is a block diagram of a part of the configuration of a TV receiver. It is for supplying operating power to the part, and it is, for example, a first DC voltage Vb (hereinafter simply referred to as DC voltage Vb or output voltage Vb) with a voltage value of about 100V to 120V. ) occurs. 2 is a second power supply circuit;
In this second power supply circuit 2, the pulses generated by the pulse generation circuit 3 are transmitted to the second power supply circuit 2 of the flyback transformer 4.
The sum of the DC voltage obtained by rectifying and smoothing the voltage boosted by the next winding 5 in a circuit including a diode D ₁ , a resistor R ₁ , and a capacitor C, and the output DC voltage Vb of the first power supply circuit 1 described above. A voltage of is applied to terminal 2a, but
The output voltage of this second power supply circuit 2 is the same as that of the first
DC voltage output to terminal 1a of power supply circuit 1 of
A second voltage value higher than Vb, e.g. 180V to 200V.
DC voltage Vh (hereinafter simply referred to as DC voltage Vh or output voltage Vh).

6 is a high voltage rectifier circuit, and this high voltage rectifier circuit 6
applies a required high-voltage DC voltage to the anode electrode 10 of the picture tube 8. 7 is a video output circuit which is a functional circuit in this embodiment, and the collector of the output transistor Q of this video output circuit 7 is connected to the picture tube 8.
The cathode 9 of the picture tube is connected to the cathode 9 of the picture tube, and a video signal of negative polarity as illustrated in FIG. 2 is supplied to the cathode 9 of the picture tube. When the video signal applied to the cathode 9 of the picture tube 8 is as shown in the second figure, the picture tube 8 is electrically powered in order to obtain the necessary DC bias voltage in the picture tube 8. Considering the physical characteristics, the DC voltage Vh of the second power supply circuit 2 to be applied to the collector of the output transistor Q of the video output circuit 7 via the resistor _R2 is 180 to 200V as described above.

Now, in the TV receiver having the above configuration, the second power supply circuit 2 may be damaged due to some reason, such as a break in the second winding 5 of the flyback transformer 4, a break in the resistor _R1 , or a break in the diode _D1 . If the output voltage from the second power supply circuit 2 fails due to
When Vh is no longer generated, the supply of operating power to the video output circuit 7 is stopped, and the output of the video output circuit 7 is eliminated. However, even in this state, the pulse generator 3 continues to operate. A high voltage DC voltage of, for example, 20 KV or more is continuously applied from the high voltage rectifier circuit 6 to the anode electrode 10 of the picture tube 8.

Therefore, in this state, since the bias voltage of the cathode of the picture tube 8 is OV, the beam current iB of the picture tube 8 is equal to the maximum beam current value in the picture tube 8 during normal operation. This overcurrent increases to two to three times as much as the current, and this overcurrent causes the high voltage rectifier circuit 6, pulse generating circuit 3, first power supply circuit 1, etc. to become overloaded.

By the way, as a means to prevent accidents caused by overcurrent in electronic equipment, it has been widely used for a long time to use fuses, and in the TV receiver shown in Figure 1, the first power source is A fuse 11 is connected to the output terminal 1a of the circuit 1, and the fuse 11 is designed to blow out when an excessive current flows, thereby protecting the circuit.

However, the fuse 11 described above is generally
The electronic equipment is designed so that it will not blow out due to the inrush current when the power switch is turned on, and will be able to perform a reliable blowout operation against the excessive current that would flow if the load of the first power supply circuit 1 was completely short-circuited. A device that fuses at a current value that is about 60 to 40% larger than the maximum current value during normal operation is used, but as mentioned above, the cathode voltage of the picture tube 8
The increase in current generated in the first power supply circuit 1 in response to the increased beam current flowing in the picture tube 8 when OV occurs is about 1.5 to 2 times that in the normal operating state, so as mentioned above, It is extremely difficult to reliably blow out the fuse 11 during an abnormal operation that occurs when the output voltage of the second power supply circuit 2 becomes 0. If circuit 3, first power supply circuit 1, etc. continue to operate in an overloaded state, abnormal heat generation or destruction may occur in these parts, which in extreme cases may cause a fire or electric shock. I used to let them do things.

Therefore, in the past, the heat dissipation characteristics of components that generate abnormal heat in the event of a failure were set based on abnormal conditions, or the components that generate heat were installed away from combustible parts. However, the above-mentioned solution methods have caused problems such as high costs and poor productivity, and improvements have been desired. The present invention provides a power supply circuit for electronic equipment that can solve the above-mentioned conventional drawbacks.The specific details of the power supply circuit for electronic equipment according to the present invention are described below with reference to Fig. 3. An embodiment of the power supply circuit for an electronic device according to the present invention will be explained. In FIG. 3, the same drawing numerals as used in FIG. 1 are used for components corresponding to those of the TV receiver shown in FIG.

In FIG. 3, D ₂ is a diode, and the anode of this diode D ₂ is connected to the output terminal 1a side of the first power supply circuit 1, and the cathode is connected to the output terminal 2a side of the second power supply circuit 2. It is connected between the output terminals of the first and second power supply circuits 1 and 2 with a connection polarity such that they are connected.

The output voltage Vb of the first power supply circuit 1 and the output voltage Vh of the second power supply circuit 2 are designed to have a relationship of Vb<Vh when the TV receiver is operating in a normal operating state. Therefore, the first and second
The diode _D2 connected between the output terminals of the power supply circuits 1 and 2 is kept non-conducting while the TV receiver is operating under normal operating conditions. However, if the second power supply circuit 2 breaks down for some reason, the output voltage of the second power supply circuit 2 becomes lower than the output voltage Vh under normal operating conditions.
When the output voltage Vb of the first power supply circuit 1 is lower than that of the first power supply circuit 1, the diode _D2 becomes conductive, and the operating power of the video output circuit 7 is supplied from the first power supply circuit 1. Therefore, even if the second power supply circuit 2 fails and the output voltage of the second power supply circuit 2 becomes 0, the operating power is not supplied to the video output circuit 7 from the first power supply circuit 1. It is given,
Since an insufficient bias voltage is applied to the cathode 9 of the picture tube 8, the beam current flowing through the picture tube 8 is equal to the normal beam current.
The increase will be limited to around 1.5 times.

In this way, in the power supply circuit of the present invention, even if the second power supply circuit 2 fails, abnormal heat generation or 2 Therefore, according to the present invention, it is possible to easily provide a power supply circuit with a sufficiently good protection function for the component parts in the event of a failure. It is clear that it is possible to provide an electronic device that does not have the above-mentioned conventional problems.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional circuit, FIG. 2 is an explanatory waveform diagram, and FIG. 3 is a block diagram of a circuit according to the present invention. DESCRIPTION OF SYMBOLS 1...First power supply circuit, 2...Second power supply circuit, _D1 , _D2 ...Diode, 3...Pulse generator, 4...Flyback transformer, 7...Video output circuit, 8... ...Picture tube.

Claims (1)

[Scope of utility model registration request] a first power supply circuit that generates a first DC voltage;
Receiving operating power from the first power supply circuit, generating a second DC voltage having a higher voltage value than the first DC voltage, and supplying the second DC voltage as operating power to the functional circuit of the electronic device. In a power supply circuit of an electronic device in which the power supply circuit is biased to the second power supply circuit, the connection polarity is set in a forward direction from the output end side of the first power supply circuit to the output end side of the second power supply circuit. By connecting the diode, when the second power supply circuit is not generating the second DC voltage, the first DC voltage can be applied to the functional circuit via the diode. Power supply circuit for electronic equipment.