JP3300173B2 - Overload detector and incandescent lamp controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload detecting device for detecting an overcurrent flowing when an overload occurs, and more particularly to an overload detecting device for a device having an incandescent lamp load.

[0002]

2. Description of the Related Art A general device for detecting an overcurrent converts a load current into a voltage using a current transformer or a resistor, and detects that an overcurrent has occurred when the value is equal to or greater than a predetermined value. This output was monitored to detect overcurrent.

[0003]

However, in these devices, since the overcurrent is detected irrespective of whether the increase in the load current is caused by the overload or the fluctuation of the input power supply voltage, the latter is used. Even if the change is caused by the fluctuation of the input power supply voltage, an overcurrent is detected to activate the protection circuit or limit the current. Further, in the case where the effective value detection circuit is provided, there is a problem that the circuit configuration becomes complicated and the device becomes expensive.

An object of the present invention is to provide an overload detection device and an incandescent lamp control device that can detect a change in input power supply voltage and detect an overcurrent by detecting an overcurrent in a DC manner. is there.

[0005]

FIG. 1 is a block diagram of an incandescent lamp control device according to the present invention.

[0006] The commercial AC power supply 1 is connected to an instantaneous value detection circuit 2 for detecting an instantaneous value of the AC input power supply voltage, and the detected instantaneous value is led to an overcurrent detection unit 3.

The AC input power supply voltage 1 is connected to an incandescent lamp 4, a triac 5, and a current transformer 6 for converting a load current i into a voltage v. The phase of the triac 5 is controlled by the phase control circuit 7, and the overcurrent detection unit 3 monitors the voltage v and detects the presence or absence of an overcurrent based on the instantaneous value signal from the instantaneous value detection circuit 2. Then, when an overcurrent is detected, a signal is output to the phase control circuit 7 so that the phase control in the triac 5 becomes half-wave lighting control.

[0008]

FIGS. 2A and 2B show the input power supply voltage waveform of the commercial AC power supply 1 and the load current i, that is, the waveform of the converted voltage v thereof. In the figure, a power supply voltage of 90 V and 110 V is input as an input power supply voltage, and a current waveform (converted voltage waveform) in the case of a normal current and an overcurrent at the input power supply voltage of 90 V, and an input power supply voltage. The load current waveform when the voltage is 110 V and the current is a normal current and an overcurrent is shown. That is, even if the input power supply voltage is low, an overcurrent may flow, while a normal current may flow even if the input power supply voltage is 110 V. Therefore, in the example shown in FIG. Assuming that an overcurrent i1 flows at an input power supply voltage of 90 V and a normal current i2 flows at an input power supply voltage of 110 V, respectively. As shown in the figure,
The overcurrent i1 is the conduction angle θ1, and the conduction angle of the normal current i2 is θ2.

In the case shown in FIG. 2 above, regardless of the magnitude of the input power supply voltage, the magnitude of the load current when the instantaneous value of each input power supply voltage reaches 110 V (predetermined voltage value) regardless of the magnitude of the input power supply voltage. , To see if it is greater than or equal to the threshold th.
If the current is equal to or larger than the threshold th, it is detected as an overcurrent. In the case where the phase control is performed as shown in the figure, normally, in order to set the conduction angle from 0 degrees as shown in the figure, θ1 and θ2, it is necessary to detect the overcurrent at which the input power supply voltage value becomes 110V. The timing is the timing of the latter half of the half cycle of the input power supply voltage (when the positive half cycle shown in the figure is used, the timing of the fall of the input power supply voltage).

As described above, the presence or absence of an overcurrent is detected based on whether or not the detected value of the load current when the instantaneous value becomes 110 V at the time of the fall of the input power supply voltage exceeds the threshold value th. Therefore, regardless of whether the input power supply voltage is 110 V or 90 V, the load current detection timing is always the instantaneous timing of 110 V, and the fluctuation of the input power supply voltage is canceled from the overcurrent detection. More specifically, if the input power supply voltage is increased to 110 V, the effective value of the load current also increases as long as the load does not change, so that the effective value may become an overcurrent. However, the load current is detected at the instant when the input power supply voltage indicates 110 V. Therefore, unless the load is overloaded, the load current at this instant timing is the same as when the input power supply voltage is 100 V. Instantaneous value 110
It should be the same as the load current at the timing at V. Similarly, when the input power supply voltage drops to 90 V, the instantaneous value 1
The load current at the timing of 10 V is such that the input power supply voltage is 1
It should be the same as the load current at the timing of the instantaneous value 110V at the time of 00V. On the other hand, when the overload state occurs, the load current when the input power supply voltage is 110 V, 100 V, 90 V, or the instantaneous value is 110 V becomes an overcurrent. That is, since it is determined whether or not the load current at the instantaneous value timing of 110 V is an overcurrent, the fluctuation of the input power supply voltage is canceled, and only the case where the overcurrent is caused by the overload can be detected.

FIG. 3 shows a method of controlling the phase of a load current when an overcurrent (due to an overload) is detected. As shown in the figure, when an overcurrent is detected, half-wave lighting control is performed (the area indicated by hatching in the figure is turned on). For this reason, the brightness of the incandescent lamp 4 is reduced by half in the overcurrent state.
At this time, as shown in FIG. 3, since the phase control is repeatedly turned on and off every half cycle, there is little noise generated as compared with the normal phase control in which the conduction angle is controlled within a half cycle. Extremely low. Therefore, there is an advantage that the influence on the surroundings is reduced. When noise countermeasures are taken, it is also possible to control the phase at an arbitrary brightness between the conduction angle of 0 and 90 degrees.

[0012]

FIG. 4 is a specific circuit diagram of an incandescent lamp control device according to an embodiment of the present invention.

In the figure, 10 is AC100V, 50
/ 60 Hz commercial AC power supply voltage, and four incandescent bulbs 11 are connected in parallel as incandescent bulbs of a load. The incandescent ball 11 has a current transformer T as a current-voltage conversion means.
1 and triacs Q1 and Q2 are connected. I
C3 is composed of a microcomputer, b, c, and d are input terminals, and a is an output terminal.
The phase control signal is output to the output terminal a. This signal is converted into a current by the transistor Q5, and drives the triac Q2 for phase control. Diode D1
And the resistor R1 detects a predetermined voltage of 110 V,
When 10 V is detected, the transistor Q4 guides a detection signal to the input terminal b of IC3. As described later, when the IC 3 detects the rising of the input terminal b,
As shown in (A), when the instantaneous value of 110 V is detected at the falling part of the latter half of the positive half cycle of the input power supply voltage, the overcurrent state at that time is detected based on the signal of the input terminal d.

The secondary output of the current transformer T1 is half-wave rectified by a diode D3,
IC2 which is appropriately divided by R3 to constitute a comparator
Input to the inverted input terminal. On the other hand, the input power supply voltage is half-wave rectified by the diode D2, divided by the resistors R4 to R6, and input to the non-inverting input terminal of the IC2. Therefore, in the IC2, when the input power supply voltage is in a positive half cycle, the voltage divided by the resistors R4 to R6 is used as a reference voltage, and this reference voltage and a voltage corresponding to the load current obtained by the current transformer T1 are used. In comparison, when the reference voltage is higher than the voltage detected by the transformer T1, it outputs "H" assuming that a normal current is flowing, and outputs "L" as it is determined that an overcurrent is flowing in the opposite case. Output. I
Since the output is input to the input terminal d of C3, IC3
In the end, the presence or absence of an overcurrent is detected by checking the level of the input terminal d at the timing when the instantaneous value 110 V is detected in the latter half of the input power supply voltage.

The transistor Q3 detects the zero cross timing of the input power supply voltage and guides it to the input terminal c of the IC3. The IC 3 detects the frequency of the input power supply voltage based on the zero cross timing (that is, knows the frequency by counting the time between the zero cross timings), and outputs the output to the output terminal a according to the fluctuation of the input power supply voltage. An operation for controlling the timing of the gate control signal is performed. The IC1 shown in the figure and its surrounding diode and capacitor circuits constitute a power supply circuit for supplying a DC operating voltage to the IC3.

FIG. 5 is a flowchart showing an operation procedure performed by the IC 3 when an instantaneous value of 110 V is detected at the falling edge of the latter half of the input power supply voltage (at the time of rising of the signal b) as shown in FIG. is there.

That is, when the rising of the signal b is detected, the level of the signal d, which is the output level of the comparator IC2, is read, and it is determined whether the level is "L" or "H".
If it is "H", it is considered that a normal load current is flowing, and the flow returns as it is. If it is "L", it is considered that an overcurrent is flowing, and the incandescent bulb 11 is shown in FIG. The gate control signal a output to the output terminal a is controlled so that such half-wave lighting control is performed. That is, the gate control signal is turned on at θ0 (conduction angle 0) in FIG.
(Conduction angle 180 degrees), the gate control signal is turned off, and θB
At a conduction angle of 360 degrees, the gate control signal is turned on. By repeating this operation, half-wave lighting control can be performed.

Although the current transformer T1 is used as the current-voltage conversion circuit, any other current-voltage circuit or element can be used as a resistor or the like.

Although an overload detecting device is described in which an incandescent lamp whose impedance is almost a resistance is used as a load, when an impedance load includes an L component and a C component, a phase delay or advance of a current with respect to a voltage is detected. Providing means,
The load current is detected in consideration of the phase delay (advance).

[0020]

According to the present invention, there is an advantage that an overcurrent in an overload state can be easily detected without complicating the circuit configuration. Further, since the detection of the presence or absence of the overcurrent is performed in the latter half of the half cycle of the input power supply voltage, the overcurrent detection can be performed without any problem even in a device that performs the phase control. Furthermore, in the incandescent lamp control device, when an overcurrent is detected, the incandescent lamp is controlled to half-wave lighting, so that the brightness is reduced by half, so that it is easy for the surrounding people to know that the overload state is present. In addition to the above, there is an advantage that the generation of noise, which tends to increase due to an overcurrent, can be suppressed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an incandescent lamp control device using an overload detection device according to the present invention.

FIG. 2 is a diagram for explaining the operation of the overload detection device.

FIG. 3 is a diagram illustrating a phase control operation of an overcurrent detection value in the incandescent lamp control device.

FIG. 4 is a specific circuit diagram of the incandescent lamp control device according to the embodiment of the present invention.

FIG. 5 is a flowchart showing an operation of a main part of the incandescent lamp control device.

[Explanation of symbols]

 1—Commercial AC input power supply 2—Instantaneous value detection circuit 3—Overcurrent detection section 4—Incandescent lamp 5—Triac 6—Current transformer (current-voltage conversion means) 7—Phase control circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02H 9/02 G01R 19/165 G05F 1/10 G05F 1/455 H05B 39/04

Claims (3)

(57) [Claims] An instantaneous value detecting means for detecting an instantaneous value of the AC input power supply voltage; a current-voltage converting means for converting a load current into a voltage; and an instantaneous value of the AC input power supply voltage detected by the instantaneous value detecting means. An overload detection device comprising: an overload detection unit configured to perform overcurrent detection based on whether a voltage value of the current-voltage conversion unit at a predetermined voltage value is equal to or greater than a threshold value. 2. An apparatus according to claim 1, further comprising phase control means for controlling a phase of a load current, wherein said overload detection means detects an instantaneous value detected by said instantaneous value detection means in a latter half of a half cycle of an AC input power supply voltage. An overload detection device, wherein overcurrent detection is performed based on a voltage value of the current-voltage conversion means at a predetermined voltage value. 3. An incandescent lamp comprising: an overload detecting device according to claim 2; an incandescent lamp load; and means for controlling half-wave lighting of the incandescent lamp load when the overcurrent detecting means detects an overcurrent. Control device.