JPH0792205A - Source voltage detector - Google Patents

Abstract

PURPOSE:To detect a source voltage easily and to make it possible to transmit it to an electronic equipment by converting voltage detection output into current signal and by converting the signal into voltage signal again over a switch means provided between a power source and the electric equipment. CONSTITUTION:SW (switch means) is connected to both poles of a DC power source and a negative pole of electronic equipment. VD(voltage detecting means) divides a source voltage E and inputs a detected voltage Ve to CMP (comparator). Besides, a voltage of a capacitor C3 is made to be a constant voltage by REG (constant voltage regulator), divided and then inputted as a reference voltage Vk to the CMP. When the voltage Vk>voltage V1, the CMP turns an output on and makes a constant current I1 flow through a transistor TrQ3 and a resistor R7 of VC(voltage-current conversion circuit). TrQ3.Q4 is a current mirror circuit, and a current I2 being proportional to the current I1 flows through the TrQ4, turning on TrQ5 of CV(current-voltage conversion means) and making CTS (output signal) be at a Low level to start an operation of an inverter. Accordingly, even when the SW is interposed on the negative side, the voltage can be detected excellently and the CTS can be transmitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply voltage detecting device, and is used, for example, as a power supply detecting means of an inverter lighting device which operates on battery power.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing an example of a conventional power supply voltage detecting device. In the figure, E is a DC power source, 1 is a voltage detecting means, 2 is an electrolytic capacitor, 3 is an electronic device, 4 is a load,
Reference numeral 5 is a rectifying element. The voltage detection means 1 detects whether or not the voltage value of the DC power source E is a predetermined value, and outputs the output signal CTS.
And is composed of, for example, a resistance circuit that divides the voltage of the DC power supply E and a comparator that compares the divided voltage with a reference voltage. The electrolytic capacitor 2 is a capacitor having an appropriate capacity for stabilizing the power supply voltage of the electronic device 3. The electronic device 3 is, for example, an inverter type discharge lamp lighting device as shown in FIG. 6, and its operation is controlled by the output signal CTS of the voltage detection means 1. The rectifying element 5 is used to protect the electronic device 3 when the DC power source E is erroneously connected to the opposite polarity.

FIG. 6 shows an example of a circuit of an inverter type discharge lamp lighting device used as the electronic device 3. In this circuit, two MOSFETs are placed at both ends of the electrolytic capacitor 2.
8 and 9 are connected in series, and a series resonance circuit of an inductor L and a capacitor C is connected to both ends of one MOSFET 9 via a DC cut capacitor C ₁ .
A discharge lamp is connected in parallel as a load 4 to both ends of the capacitor C. Output signal CT of the voltage detection means 1 described above
When S is at high level, the output of the inverting circuit N ₁ is Lo
Since it is at the w level, the outputs of the AND circuits A ₁ and A ₂ are both at the low level. As a result, the MOSFET 8,
Both 9 are also turned off and the inverter device is stopped.
On the other hand, when the output signal CTS of the voltage detection means 1 is at low level, the output of the inverting circuit N ₁ becomes high level, so the high frequency signal output from the pulse oscillator OSC is output from the AND circuit A ₁ and the pulse oscillator OSC. The AND circuit A ₂ outputs a signal obtained by inverting the high frequency signal output by the inverter circuit N ₂ . This allows the MOS
The FETs 8 and 9 are alternately turned ON / OFF at a high frequency through the driving circuits 10 and 11, and generate a resonance voltage in the resonance circuit formed by the capacitor C and the inductor L to supply electric power to the discharge lamp 4.

In the circuit of FIG. 5, a diode is used as the rectifying element 5, but if the DC power source E is a battery of about 12 V, the forward voltage drop of the rectifying element 5 is large (a PN junction diode is 0.6 .About.1.0 V, about 0.5 V with a Schottky barrier diode), and when the power consumption of the inverter type discharge lamp lighting device and the discharge lamp 4 is large, for example, in the case of a 35 W load HID lighting device, the power supply current is It becomes several amperes (3 to 4 A), and the power loss of the rectifying element 5 becomes large (1.5 to 4 W).

FIG. 7 is a circuit diagram of another conventional example. A MOSFET 6 is used instead of the diode of the rectifying element 5. When the MOSFET is properly selected and turned on, the conduction resistance Ron is considerably small (for example, Fuji Electric 2S
K1823 has an advantage that Ron = 17 mΩ) and a smaller power loss (0.15 to 0.3 W) than the circuit of FIG. However, since the N-channel MOSFET does not conduct unless the potential of the gate G is sufficiently higher than the potential of the source S, it is necessary to insert it between the negative side of the DC power source E and the negative power source input terminal of the electronic device 3. , The gate voltage is applied as shown in FIG. P channel MOSFE
Although the same connection is made to the positive electrode side at T, an N-channel MOSFET is generally used because there are few effective P-channel MOSFETs in the semiconductor process. By the way, the voltage detection means 1 and the electronic device 3 transmit the output signal CTS of the voltage detection means 1 by making the reference potential the same. That is, the negative power source input terminal of the electronic device 3 is set to the reference potential, and the output signal CTS of the voltage detecting means 1 is transmitted as the voltage level High level / Low level.

In the circuit of FIG. 7, the voltage detecting means 1 is connected to both ends of the electrolytic capacitor 2 in order to detect the power supply voltage. Here, the electrolytic capacitor 2 has a capacity that can absorb even a slight fluctuation of the DC power source E,
The capacity is sufficient when the discharge lamp is operating at its rated value.
By the way, suppose now that the discharge lamp has gone out for some reason. At this time, there is a case where the operation is restarted unless the discharge lamp is detected to be extinguished and the inverter device is stopped and then the power supply is reset.
For example, in a lighting device for an HID lamp used for a vehicle headlight, a high voltage of 10's of KV is generated to start the lamp due to the necessity of instantaneous restart. If the connector between them is momentarily disconnected and the lamp goes out, for safety reasons, the high voltage pulse is not generated, and the power is reset to restart. in this case,
Although not shown, the power switch inserted in series with the DC power source E is once opened and then closed again to operate the discharge lamp again, but the electric charge consumption of the electrolytic capacitor 2 is reduced. Therefore, the voltage detection means 1 cannot detect that the power supply is turned off by detecting that the power supply voltage is sufficiently high. Therefore, the inverter device is not restarted and the discharge lamp cannot resume operation. Alternatively, it is necessary to open the power switch for a sufficiently long time and wait until the electric charge of the electrolytic capacitor 2 is consumed.

FIG. 8 is a circuit diagram of a third conventional example. If the N-channel MOSFET 6 is inserted on the positive electrode side and the voltage detecting means 1 and the electronic device 3 are connected in the relationship as shown in FIG.
Although the problem of the circuit of is solved, as described above,
Since the gate voltage needs to be higher than the source voltage in order to turn on T6, it is necessary to add a circuit for boosting with a transformer or a dedicated drive circuit 7 as shown in FIG. 9, for example. , The device becomes complicated. Figure 9
In the drive circuit of, when the DC power supply E is reset,
Applying the pulse voltage Vp to the transistor Q ₁ causes resistance R
₁₁ charges the capacitor C ₂ through the diode D ₁ and
The N-channel MOSFET 6 is turned on in the forward direction. As a result, the N-channel MOSFET 6 and the diode D
₂ , the electrolytic capacitor 2 is discharged through the resistor R ₁₂ , the transistor Q ₁ , and the electronic device 3 detects the decrease in the power supply voltage and restarts. When the DC power source E is connected in the reverse direction, the transistor Q ₂ turns on and the diode D ₂
Since the capacitor C ₂ is discharged via the N channel MOSFET 6, the N-channel MOSFET 6 does not turn on. However, in this circuit, the pulse voltage V to the power reset transistor Q ₁
It is necessary to apply p to turn on the N-channel MOSFET 6, which is difficult to realize.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to detect a power supply voltage by a switch means inserted between a power supply and an electronic device. In the case of controlling according to the result, it is possible to favorably transmit the detection signal of the power supply voltage to the electronic device even if the voltage detection means is connected in parallel with the DC power supply.

[0009]

FIG. 1 shows the basic configuration of the present invention. In the figure, VD is a voltage detection means of the DC power supply E, VC is a voltage-current conversion means for converting the detection signal of the voltage detection means VD from a voltage value into a current value, and CV is a current for converting this current value into a voltage value again. A voltage conversion means. The wiring on the negative electrode side between the DC power source E and the electronic device 3 has a switch means S corresponding to the N-channel MOSFET 6 of FIG.
W is inserted. Electrolytic capacitors 2 are connected in parallel to both ends of the electronic device 3.

[0010]

As described above, according to the present invention, the voltage detecting means V
Since the voltage of the DC power source E is detected by D, the detected voltage value is converted into a current value, and the current value is converted back to the voltage value across the switching means SW and transmitted to the electronic device 3, N
Even if the channel MOSFET is inserted in the negative electrode and the voltage detecting means VD is parallel to the DC power source E, the voltage detecting means V
The output signal of D can be satisfactorily transmitted.

[0011]

FIG. 2 is a circuit diagram of the first embodiment of the present invention.
The circuit configuration will be described below together with the operation. First, the drain side of the N-channel MOSFET 6 of the switch means SW is connected to the negative electrode of the DC power source E, and the source side is connected to the negative electrode of the electronic device 3. The source is connected to the positive electrode of the DC power source E through the series circuit of resistors R _1, R _2, a connection point of the resistors R _1, R ₂ is, N-channel MOSFET6
Is connected to the gate. As a result, the switch means SW similar to the conventional example of FIG. 7 is configured. When viewed from the switch means SW, the voltage detection means VD is provided on the DC power source E side.
Is provided. The voltage across the DC power source E is divided by the resistors R ₅ and R ₆ with the positive electrode as the reference, and is input to the negative input terminal of the comparator CMP as the detection voltage Ve. Further, in order to apply the reference voltage Vk to the comparator CMP, a capacitor C ₃ is connected to the DC power source E via a diode D _3, and the voltage of the capacitor C ₃ is a constant voltage by a three-terminal type constant voltage regulator REG. Has been converted. The constant voltage regulator REG is for negative output, and for example, industry standard 7900 series is used. The output of the constant voltage regulator REG is a resistor R ₃ ,
The voltage is divided by R ₄ and is input to the positive input terminal of the comparator CMP as the reference voltage Vk. The comparator CMP is an open collector output type circuit (for example,
NEC's μPC277) is used, and the detection voltage Ve
Is compared with the reference voltage Vk, and when Vk> Ve, that is, when the voltage of the DC power source E becomes a voltage sufficient for the operation of the electronic device 3, the open collector output of the comparator CMP is turned ON. As a result, a constant current I ₁ flows through the transistor Q ₃ and the resistor R ₇ of the voltage-current conversion circuit VC. The transistors Q ₃ and Q _{4 form} a current mirror circuit, and a current I ₂ proportional to the current I ₁ flowing in the transistor Q ₃ flows in the transistor Q ₄ . This current I ₂ flows through the series circuit of the resistors R ₈ and R ₉ , the transistor Q ₅ is turned on, and the output signal CTS becomes Low level. The output signal CTS is input to, for example, an inverter device as shown in FIG.
When S becomes low level, the inverter device starts operating. Therefore, even if the N-channel MOSFET is inserted in the wiring on the negative electrode side, the voltage of the DC power source E can be well detected and the output signal CTS can be transmitted to the electronic device 3 side, so that the conventional drawback can be solved.

FIG. 3 is a circuit diagram of the second embodiment of the present invention. In the present embodiment, the voltage across the DC power source E is divided by the resistors R ₅ and R ₆ with the positive electrode as a reference, and is input to the negative input terminal of the comparator CMP as the detection voltage Ve. Further, in order to apply the reference voltage Vk to the comparator CMP, a capacitor C ₃ is connected to the DC power source E via a diode D _3, and the voltage of the capacitor C ₃ is a constant voltage by a three-terminal type constant voltage regulator REG. Has been converted. The constant voltage regulator REG is for positive output, and for example, industry standard 7800 series is used. The output of the constant voltage regulator REG is a resistor R ₃ ,
The voltage is divided by R ₄ and is input to the positive input terminal of the comparator CMP as the reference voltage Vk. The comparator CMP is an open collector output type circuit (for example,
NEC's μPC277) is used, and the detection voltage Ve
Is compared with the reference voltage Vk, and when Vk <Ve, that is, when the voltage of the DC power source E becomes a voltage sufficient for the operation of the electronic device 3, the open collector output of the comparator CMP is turned off. As a result, the current I ₁ flows from the output of the constant voltage regulator REG to the transistor Q ₃ via the resistor R ₇ . The transistor Q ₃ and the transistor Q _{4 form} a current mirror circuit, and the transistor Q ₄
And the transistor Q _5, the current I ₂ proportional to the current I ₁
Flows. Also, transistor Q ₅ and transistor Q ₆
Is a current mirror circuit, and transistor Q
₆ and transistor Q ₇ have a current I proportional to current I _2.
3 flows. Further, the transistor Q ₇ and the transistor Q ₈ constitute a current mirror circuit, current flows I ₄ which is proportional to the current I ₃ to the transistor Q _8. As a result, a voltage drop occurs in the resistor R ₁₀ and the output signal CT
S becomes Low level. When Ve <Vk, the open collector output of the comparator CMP is turned on.
Then, the currents I ₁ , I ₂ , I ₃ , I ₄ become zero, and the output signal CTS becomes High level. By doing so, it is possible to obtain the same effect as that of the embodiment of FIG. 2 without using the positive electrode as a reference.

FIG. 4 is a circuit diagram of the third embodiment of the present invention.
It In this embodiment, the voltage detecting means VD is a resistor R₇Alone
It is configured. Resistance R₇The voltage across the
It is almost equal to the voltage, and the transition of the voltage-current conversion circuit VC
Star Q₃Is a current I corresponding to the voltage of the DC power source E.₁Flow
Be done. Transistor Q₃And transistor Q_FourIs current
Mirror circuit is composed of transistor Q_FourThe electric
Flow I₁Current I proportional to ₂Flows. This current is the current −
Resistance R of voltage conversion means CV₆Flow to the DC power source E
It is converted into a detection voltage Ve proportional to the pressure. Capacitor C
₃And the constant voltage regulator REG control the inverter device.
It can also be used as a power supply circuit for the control circuit, and its constant voltage
Output voltage to resistance R₃, R_FourDivided by the reference voltage V
It is input to the comparator CMP as k and the detected voltage Ve
Compared to. When Ve> Vk, that is, DC power
When the voltage of the source E becomes sufficient to operate the electronic device 3,
The open collector output of the comparator CMP is not turned on.
Therefore, the output signal CTS becomes Low level. By this
Then, the inverter device starts operating. Also, Ve <V
At k, the open collector output of comparator CMP
Force is OFF, resistance R_TenConstant voltage via
The output of the output signal REG is supplied and the output signal CTS becomes High.
It becomes the h level. As a result, the same operation as that of the embodiment of FIG.
However, in this embodiment, the capacitor
C₃And constant voltage regulator REG to control the inverter device.
Since it can also be used as the power supply circuit for the control circuit, the number of parts can be reduced.
The advantage is that

[0014]

According to the present invention, the detection output of the voltage detecting means connected between both ends of the power supply is converted into a current signal, and the current signal is again converted to the voltage by passing through the switch means between the power supply and the electronic device. Since the signal is converted and transmitted to the electronic device to control the operation of the electronic device, for example, an N-channel power MOSFET is inserted on the negative electrode side as a switch for reverse connection protection between the power supply and the electronic device, Even when the power loss is reduced as compared to the case where a rectifying element such as a diode is used, the power supply voltage can be easily detected and transmitted to the electronic device.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic configuration of the present invention.

FIG. 2 is a circuit diagram of the first embodiment of the present invention.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a first conventional example.

FIG. 6 is a circuit diagram of an inverter device used as an electronic device.

FIG. 7 is a circuit diagram of a second conventional example.

FIG. 8 is a circuit diagram of a third conventional example.

FIG. 9 is a circuit diagram showing a dedicated drive circuit used in a third conventional example.

[Explanation of symbols]

 E DC power supply 2 Electrolytic capacitor 3 Electronic device SW switch means VD voltage detection means VC voltage-current conversion means CV current-voltage conversion means

Claims (1)

[Claims] 1. A power supply, an electronic device supplied with power from the power supply, a switch means inserted into at least one line between the power supply and the electronic device, and at least conducting during operation of the electronic device, and a power supply. A device for controlling the operation of the electronic device by transmitting the detection result of the voltage detecting device to the electronic device, and converting the detection output of the voltage detecting device into a current signal. And a means for converting the converted current signal into a voltage signal again as a signal transmission means.