JPH0746038Y2 - Protector - Google Patents

Description

[Detailed Description of the Invention] Industrial field of application The present invention uses a microcomputer having a last power memory function, and the power is supplied only from the remote control power supply circuit to the microcomputer. The present invention relates to a protection device when a + B voltage is short-circuited in a device that controls a television receiver with a remote control device that has a standby mode in which power supply is prohibited.

2. Description of the Related Art Recently, in television receivers using a microcomputer for channel selection, those using a microcomputer using a last power memory have been increasing. A microcomputer with a last power memory function means that even if + V _{cc of the} microcomputer _drops to the reset level (70 to 80% of + V _cc ), it does not enter the standby mode and remembers the state before the reset. The microcomputer that goes into standby mode only when + _Vcc drops to about 20%.
By using this microcomputer, there is an advantage that the microcomputer can take measures against a momentary power failure and a malfunction (standby) of the television receiver due to static electricity such as lightning.

Hereinafter, in a television receiver using this last power memory microcomputer with reference to the drawings,
The conventional protective action when the + B voltage is short-circuited will be described with reference to FIG.

In FIG. 3, 1 is a standby circuit, 3 is a last power memory microcomputer, 4 is a remote control power supply circuit, and 5 is a regulator for stabilizing the + B voltage. The microcomputer 3 is supplied with + _Vcc from the regulator 5 or the remote control power supply circuit 4, and the operation of the remote control power supply circuit 4 is controlled by the ON / OFF output of the microcomputer 3.

Conventionally, as a protection device for a + B voltage short circuit of a TV set, there are a method of keeping the temperature rise within a standard value with respect to an increase of a load current at the time of short circuit, a method of disconnecting the + B line at the time of short circuit by using a fuse resistor, etc. However, in the circuit configuration as shown in FIG. 3, when the + B voltage is short-circuited, the + of the last power memory microcomputer 3
Supply of V _cc stops. When + _{Vcc of the} last power memory microcomputer 3 falls below the reset level, the ON / OFF terminal of the last power memory microcomputer 3 which was at the "HIGH" level until then becomes "LO" momentarily.
It falls to the W "level, the remote control power supply circuit 4 which has been in the non-operating state until then operates, and + V _cc is supplied from the remote control power supply circuit 4, and the + V of the microcomputer 3 is supplied.
_cc goes up.

Here, the conventional microcomputer went into the standby state when + V _cc falls below the reset level.
The microcomputer 3 in the figure has a last power memory function to prevent static electricity, so + V _cc
There therefore returns to the state (+ B voltage short circuit) before even if below the reset level not to the standby state again lowered the + V _cc of the microcomputer 3, the remote control power supply circuit 4 again becomes below the reset level is operated. This state is represented by the solid line in the flowchart of FIG.

Problems to be Solved by the Invention Thus, in the circuit of FIG. 3, when the + B voltage is short-circuited,
The + B voltage is intermittently supplied, the temperature rise exceeds the standard value, and the normal + B voltage load current is large, so an overcurrent that opens the fuse resistance at the time of short circuit cannot be obtained. Further, there is a problem that the resistance becomes large even in the direction of satisfying the temperature rise below the specified value, which is not consistent with the recent movements such as single printed circuit board and cost reduction.

In view of the above problems, the present invention provides a protection device for a television receiver with a remote control device using a microcomputer of last power memory, which can stop supplying + B voltage itself by using a standby mode. It is provided.

Means for Solving the Problems In order to solve the above problems, the protective device of the present invention is + B.
A detection circuit for detecting a voltage short-circuit state is provided between the microcomputer of the last power memory, the standby circuit, and the + B voltage line, and when the + B voltage is short-circuited, the detection output of the detection circuit forcibly stands by. It is provided with a configuration for putting it in a state.

The present invention has the above-mentioned configuration, and when the + B voltage is short-circuited, it puts the television receiver in the standby state, which can suppress an excessive temperature rise of the device, and greatly contributes to downsizing of the device. .

Embodiment A + B voltage short-circuit protection device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of a + B voltage short-circuit protection device according to an embodiment of the present invention. The same components as those of the conventional one are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 1, reference numeral 1 is a standby circuit, and 2 is a + B voltage short circuit detecting circuit, which is composed of a transistor 2a, a resistor 2b, a capacitor 2c and a diode 2d. 3 is a last power memory microcomputer, 4 is a remote power supply circuit, and 5 is a regulator. The detection circuit 2 has a resistor 2b and a capacitor 2c between the emitter and base of the transistor 2a.
The parallel circuit is connected, and the other end of the parallel circuit is connected to the + B voltage line via the diode 2d. The base is connected to the ON / OFF terminal of the microcomputer 3 and the collector is connected to the standby terminal 1a of the standby circuit 1.

The operation of the + B voltage short-circuit protection device configured as described above will be described below with reference to FIGS. 1 and 2. In addition, in FIG. 2, the flow of operation is shown by a broken line.

In FIG. 1, the + B voltage is normally supplied, that is, the ON / OFF terminal 3a of the microcomputer 3 is at the "HIGH" level in the so-called normal state, but the + B voltage is higher than the + V _{cc of the} microcomputer. The diode 2d in the voltage short detection circuit 2 is in the cutoff state,
The transistor 2a is "OFF". Here, when the + B voltage is short-circuited, the diode 2d becomes conductive, the transistor 2a turns “ON”, and the standby terminal 1a of the standby circuit 1 becomes “LO”.
Then, the standby circuit 1 is operated and the television receiver is set to the standby state. At this time, the remote control power supply circuit 4 is operated, and + V _cc of the microcomputer 3 is supplied from this remote control power supply circuit 4. Since the microcomputer 3 is the last power memory, it does not output the standby command and the ON / OFF terminal 3a
Remains at "HIGH" level, the transistor 2a continues to be "ON", and the device enters the standby state. In this way, the supply of the + B voltage itself is stopped. When the + B voltage is short-circuited, the transistor 2a is turned on, the standby circuit 1 activates the remote control power supply circuit 4, and the regulator 5 supplies + V to the microcomputer 3.
_Since + V _cc is supplied from the remote control power supply circuit 4 before the supply voltage of _cc reaches the reset level, the signal of the ON / OFF terminal 3 remains "HIGH".

As described above, according to the present embodiment, the ON / OFF terminal 3a of the microcomputer 3 having the last power memory function is +
By connecting the B voltage short circuit detection circuit 2, it is possible to surely perform short circuit protection.

As described above, according to the present invention, by providing the + B voltage short detection circuit between the control output terminal of the microcomputer of the last power memory and the standby circuit,
When the + B voltage is short-circuited, the detection output of the short-circuit detection circuit forces the device into the standby state, and as a result,
Each circuit and element can be protected when the + B voltage is short-circuited.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a protection device according to an embodiment of the present invention,
FIG. 2 is a flow chart for explaining the operation of the + B voltage short-circuit detection circuit of the present invention and the conventional short-circuit detection circuit at the time of + B voltage short circuit, and FIG. 3 is a circuit diagram of the conventional short-circuit detection circuit. 1 ... Standby circuit, 2 ... + B voltage short circuit detection circuit, 3 ... Microcomputer with last power memory function, 4 ... Remote control power supply circuit.

Claims (1)

[Scope of utility model registration request] 1. A microcomputer having a last power memory in which a + B voltage is stabilized and supplied as a power supply voltage, and an operation is controlled by a control output of the microcomputer to stop power supply to circuits other than the microcomputer. A standby circuit, a + B voltage short-circuit detection circuit which is inserted between the + B voltage line, the control output terminal of the microcomputer and the standby circuit, and which operates when the + B voltage is short-circuited to bring the standby circuit into an operating state; And a remote control power supply circuit that supplies the power supply voltage to the microcomputer instead of the + B voltage by operating the protection device of the + B voltage supply source.