JPS62239832A - Constant power controller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a constant power control circuit that maintains power consumption in a load at a constant value.

[Prior Art] FIGS. 3 and 4 are diagrams showing a load circuit having a control circuit for maintaining power consumption in a load at a constant value.

FIG. 3 shows a circuit using a resistive load. In the figure, 1 is an AC power supply, 2 is a lamp which is a resistive load, 3 is a triac as a power control element, 4.5
．． 6 is a resistor and a diode that control the triac.
Bridge and phototransistor. Moshite LE
D6 is a light emitting diode that sends a signal to operate the phototransistor 6.

The light emitting diode LED 6 outputs pulsed light as a signal from an ignition (pulse) circuit, whose phase is synchronized with the AC power source 1, to the phototransistor 6, and generates a phototransistor.
The pulse signal converted into an electrical signal by the transistor 6 is applied to the input terminal of the trier 3 via the diode bridge 5.

As a result, the triac 3 operates according to the pulse signal, and a voltage synchronized with the pulse signal is supplied to the load, thereby performing power control. That is, when the load is a resistive load such as a lamp, the voltage waveform and current waveform are in the same phase as shown in FIG. By controlling , power control can be performed smoothly. For example, the brightness of the lamp is achieved by controlling the voltage applied to the load and the length of the non-energizing time TO. On the other hand, in order to keep the brightness of the lamp constant without being affected by fluctuations in the applied power supply voltage, it is necessary to adjust the brightness of the lamp during the non-energized state according to fluctuations in the power supply voltage.

It is only necessary to change the interval TO. In other words, this is achieved by lengthening To when the power supply voltage rises and shortening it when it falls.

However, as shown in Fig. 4, if the load on the triac 3 is an inductive load such as the transformer 8, the 6th
As shown in the figure, the phases of both the voltage and current waveforms are shifted from each other, and the current waveform causes a time delay t with respect to the voltage waveform. In the case of power control that keeps the brightness of the lamp constant without being affected by fluctuations in the power supply voltage, if the power supply voltage drops significantly, the non-energization time TO becomes
The time delay t may match the above-mentioned time delay t.

[Problem that the invention seeks to solve]

However, as a characteristic of the triac 3, when the current flowing through the triac 3 is 0, the triac turns off, so in the circuit with an inductive load shown in Figure 4, when the power supply voltage to the load drops significantly, the triac turns off. , when the time delay t coincides with the de-energization time To, self-turn-off of the triac and ignition control to the triac are performed simultaneously, causing an overcurrent in the transformer 8, which is the load. There was a problem that the flow caused the transformer to burn out.

The present invention has focused on the above-mentioned problems, and an object of the present invention is to provide a constant power control circuit whose purpose is to protect a load when the power supply voltage drops significantly.

(Means for Solving the Problems) This invention solves the problem in response to fluctuations in the power supply voltage to the inductive load.
This is a constant power control circuit that operates or stops the phase control means.

[Effect]

The constant power control circuit according to the present invention detects fluctuations in the power supply voltage supplied to the inductive load, and adjusts the power supply voltage value to the inductive load when controlling the phase of the power supply voltage according to this fluctuation. When becomes below a predetermined value, phase control is stopped to protect the inductive load.

(Example) An example of a constant power control circuit according to the present invention will be described based on FIGS. 1 and 2.

FIG. 1 is a block diagram of this embodiment, in which 1 is a power supply voltage detection circuit as a means for supplying fluctuations in the power supply voltage supplied to inductive loads such as motors and transformers, and 3 is the power supply voltage detection circuit. A power supply voltage inverting circuit 4 and 5 which inverts and outputs the height of the variation obtained in step 1 are an integrating circuit and a comparing circuit, respectively, constituting phase control means. 6 is a phase control signal from the comparator circuit 5 and a comparator circuit 1 to be described later.
Only when simultaneously receiving the phase control stop signal from
An AND circuit 7 outputs a phase control signal from the comparison circuit 5, and an AND circuit 7 outputs a phase control signal from the AND circuit.
This is an LED ignition circuit that emits light.

2 is a comparator circuit which outputs a phase control stop signal upon receiving from the power supply voltage detection circuit 1 that the power supply voltage supplied to the inductive load has significantly dropped, and outputs a phase control stop signal, and
The signal is sent to circuit 6 to stop phase control.

FIG. 2 is a diagram showing an example of a circuit in which each component included in the above-described block diagram is implemented in detail.

T1 is a transformer, D1-4 are diodes, and R.

, R1 is a resistor, and C3 is a capacitor, which constitute the power supply voltage detection circuit 1.

Note that 1 indicates a power source common to the inductive load.

When the power supply voltage 1 fluctuates, the fluctuation is also transmitted to the transformer T1, and is rectified by a diode bridge composed of diodes D, .about.4.

The rectified AC voltage is passed through resistor R1 to capacitor C.
1 and converted to DC voltage.

As a result, a DC voltage corresponding to the variation of the AC voltage can be obtained at the capacitor C1.

The power supply voltage inversion circuit 3 is composed of resistors R9, RIo, R++, and a transistor Q4, and the output voltage from the power supply voltage detection circuit 1 is applied to the resistors R9 and RI.

When the output voltage increases, the current flowing through the resistor R9 increases, and this current is input to the base of the transistor Q4. Therefore, the collector current of transistor Q4 increases and the collector voltage decreases. Conversely, when the output drops, the collector voltage increases. The power supply voltage inversion circuit 3 thus obtains an output that is inverted from the input.

The integrating circuit 4, which is composed of an operational amplifier Q5, a resistor R32, and a capacitor C2, functions to obtain To in FIG. That is, the output of the power supply voltage inversion circuit 3 is charged to the capacitor C2 via the resistor R1□.

The length of the charging time is proportional to the rise and fall of the output. In other words, when the power supply voltage 1 rises, the output of the power supply voltage detection circuit 1 also rises, and as a result, the output of the power supply voltage inverting circuit 3 falls, and the charging time for the capacitor C2 becomes longer (slower). ). Conversely, when the power supply voltage drops, the charging time becomes shorter (faster). In this way, the time To in FIG. 7 changes according to the rise and fall of the power supply voltage.

Operational amplifier Q6 and resistors RI3, RI4, R15, R0
6 and 5 constitute a comparator circuit which compares the output obtained from the integrating circuit 4 with a reference voltage and generates a firing signal as a differential output.

First, the reference voltage is a voltage for setting the brightness obtained during phase control, and is set by R24 and R15. The reference voltage is then applied to the non-inverting input terminal of the oven amplifier Q6. Further, the charge stored in the capacitor C2 of the integrating circuit 4 is applied to the inverting input terminal of the operational amplifier QB via the resistor R13. and op amp Q
In step 6, compare the power of two people and obtain the output. That is, while the reference voltage is constant, the output from the integrating circuit 4 has a positive firing voltage waveform, so the output of the operational amplifier Q6 obtains a negative firing voltage waveform.

The AND circuit of transistors Q7. Qa and resistance Rs
, RI7, RI8 and a diode D5. The AND circuit 6 produces an output when the two input levels are at the same high level, and does not produce an output when one or both of the input levels are at a low level. Transistor Q8 is normally OFF. The other transistor Q is the resistor R1
Since the base current is flowing through , it is in the ON state. Therefore, the potential of resistor R18 is at a low level.

Therefore, when the comparator circuit 5 outputs an output (negative pulse), the diode DS is turned on and the transistor Q7 is turned off, so that the potential of the resistor RI8 becomes high and is output as a positive pulse.

However, when transistor Q8 is turned on, current from resistor R18 flows through transistor Q8. Therefore, the potential of the resistor R18 becomes a low level, and even if the transistor Q7 is repeatedly turned on and off, the potential of the resistor R18 does not change, so no output is produced.

Transistor Q2. Q3, LED6, resistor Rs,
R7, Ra, and RI9 constitute an LED ignition circuit 7. Upon receiving the output from the AND circuit 6, the transistor Q3 turns on, current flows through the resistors R6 and R7, and the transistor Q2 turns on. At that time, resistors R8 and L
A current flows through the ED6 and the LED 6 emits light. This is sent as a phase control signal to the phototransistor 6 shown in FIG. 2, which turns on the triac 3 and performs phase control.

Comparison circuit 2 includes operational amplifier Q+, resistors R2, R3, and R4.
It consists of Resistors R2 and R3 are set by a power supply voltage value that stops phase control, and a reference voltage is obtained by the voltage division ratio and applied to the non-inverting input terminal of operational amplifier Q1.

The output from the power supply voltage detection circuit 1 is applied to one inverting input terminal, and the operational amplifier Q1 compares the two human input signals and generates a difference output. When the power supply voltage drops significantly, the output from the power supply voltage detection circuit 1 decreases, the difference from the reference voltage increases, and the output of the operational amplifier Q1 increases. Therefore, the transistor Q8 of the AND circuit 6 is turned on, and as described above, the transistor Q7 is turned on.
Even if the phase control signal is turned ON and OFF repeatedly, the phase control signal remains
Since it is not sent to the ED ignition circuit 7, phase control is stopped.

As explained above, the power supply voltage detection circuit 1, the power supply voltage detection circuit 3, the integration circuit 4, the comparison circuit 5, the AND circuit 6, and the LED ignition circuit 7 perform related operations to perform phase control, and Comparison circuit 2 of power supply voltage detection circuit 1.2, and
The AND circuits 6 perform related operations to stop sending out the phase control signal.

(Effects) As described above using the embodiments, according to the present invention, the overcurrent from the triac flows to the load when the power supply voltage drops significantly, and the load is protected from being burnt out. There is.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a circuit diagram of the same as above, Fig. 3 is a power control circuit diagram using a lamp as a resistive load, and Fig. 4 is a transformer as an inductive load. Figures 5 and 6 are diagrams showing the power control circuit used, and Figures 5 and 6 are diagrams showing waveforms of voltage and current flowing through resistive and inductive loads, respectively.
FIG. 7 is a diagram showing waveforms of current and voltage flowing through a load under power control. In FIG. 1, reference numeral 1 denotes a power supply voltage detection circuit 4 that detects fluctuations in power supply voltage, which controls the phase according to fluctuations in the power supply voltage. Integrator circuit 2 designates a comparison circuit that generates a signal to stop phase control.

Claims (1)

[Scope of Claims] Means for detecting fluctuations in the power supply voltage supplied to the inductive load; means for controlling the phase of the power supply voltage according to the fluctuation; means for controlling the power supply voltage to the inductive load to a predetermined value. When it becomes below,
A constant power control circuit comprising means for stopping the operation of the phase control means to protect the inductive load.