JP3427510B2 - Power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for converting a voltage of a DC power supply by a switching device including a flyback transformer and supplying the voltage to a load.
It is used for a lighting device of a vehicle headlamp.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram of a conventional discharge lamp lighting device. The circuit configuration will be described below. The primary winding N1 of the transformer T1 is connected to the DC power supply V1 via the switching element Q. The negative electrode of the DC power supply V1 is grounded. A smoothing capacitor C1 is connected to the secondary winding N2 of the transformer T1 via a diode D1. The smoothing capacitor C1 includes a series circuit of switching elements Q1 and Q2 and switching elements Q3 and Q4.
Series circuits are connected in parallel. Switching element Q
A discharge lamp as a load 1 is connected between the connection point of 1, Q2 and the connection point of the switching elements Q3, Q4.
The control circuit 2 includes switching elements Q1, Q2, Q3, Q.
4 and the control signal of the switching element Q are created. The control signal of the switching element Q is directly supplied from the control circuit 2 to the switching element Q.

FIG. 6 is an operation waveform diagram of this lighting device. The switching element Q is turned on / off at a high frequency by the control circuit 2, and an alternating voltage is generated across the secondary winding N2. The diode D1 rectifies the AC voltage, and the capacitor C1 smooths it and converts it into a DC voltage. The switching elements Q1, Q2, Q3, Q4 form a full bridge circuit, and a first state in which the switching elements Q1, Q4 are turned on and the switching elements Q2, Q3 are turned off,
The rectangular wave voltage is applied to the load 1 by alternating the second state in which the switching elements Q1 and Q4 are off and the switching elements Q2 and Q3 are on at a low frequency. The above operation is performed by the control circuit 2. The operating power supply of the control circuit 2 is supplied from the capacitor C2 charged by the DC power supply V1.

FIG. 7 shows a state in which a resistor R1 for detecting a load current is inserted. In the figure, 21 is a PWM control means, 22 is a low frequency oscillation circuit, and 23 is an inverting circuit. For example, the DC power source V1 is switched to a number 10 by the switching element Q1.
By switching at a high frequency of kHz, power is supplied to the load 1 via the transformer T1 and the diode D1. The capacitor C1 is provided to smooth the electric power, and the smoothed electric power is supplied to the switching element Q1.
Is applied to the load 1 via the polarity switching means 8 composed of Q4. The polarity switching means 8 switches the polarity of the voltage applied to the load 1 at a low frequency of, for example, several 100 Hz, so that the load 1 is applied with a substantially rectangular wave voltage alternating at a low frequency. This operation is performed by driving the polarity switching means 8 by the low frequency oscillation circuit 22 and the inverting circuit 23.
Further, the PWM control means 21 performs switching so as to supply appropriate power to the load 1 based on the load current obtained by the resistor R1 for current detection and the load voltage information obtained from the potential of the smoothing capacitor C1. The element Q is PWM-controlled. For example, constant power control of the load 1 is performed by controlling the value obtained by multiplying the load current and the load voltage to be constant. With the above configuration, the discharge lamp load 1 is lit with a voltage of a substantially rectangular wave.

[0005]

[SUMMARY OF THE INVENTION However, in the circuit shown in the conventional example, when the connection point a between the load 1 and the inverter device is grounded as shown in FIG. 7, FIG. 8, a path shown by a broken line in FIG. 9 A large current flows from the capacitor C1 and the secondary winding N2 of the transformer T1. Here, the ground fault means that the line leading to the load 1 is grounded due to an accident or the like. If there is no ground fault, the path shown by the broken lines in FIGS. 8 and 9 does not exist, so no current flows in this path during normal operation of the circuit. Further, the current limiting element does not exist in the loop indicated by the broken line caused by the ground fault. For this reason,
The current that should originally flow through the resistor R1 for current detection stops flowing through this resistor R1, and an excessive current flows as compared with the normal time due to the reason that the control means acts in the direction of increasing the current. Therefore, normal control cannot be performed and the load 1 cannot be stably lit. In some cases, problems such as circuit damage may occur. The same applies when the point b is grounded. FIG. 10 shows the wiring of the vehicle headlamp lighting device. DC power supply V consisting of a battery
The negative side of 1 is connected to the chassis (ground G), and if the wiring (point a or point b) from the ballast 9 to the lamp load 1 is mistakenly connected to the chassis, a ground fault current will flow through the chassis. It will flow.

Therefore, the present invention detects a ground fault even if the connection portion with the load is tentatively ground, and stops the operation of the circuit, thereby preventing problems such as damage to the device. It is intended. Another object of the present invention is to prevent the ground fault current itself .

[0007]

In order to solve the above-mentioned problems, in the power supply device of the present invention, as shown in FIG. 1, a DC power supply V1 composed of a battery whose negative electrode is grounded.
Is connected to a primary winding N1 of the transformer T1 via a switching element Q whose one end is grounded, and a secondary winding N2 of the transformer T1 is connected to a capacitor C1 via a diode D1.
And a load circuit is connected to the capacitor C1 to switch the switching element Q to store energy in the transformer T1 and release the energy from the secondary winding N2 of the transformer T1. In a power supply device that operates, the switching element
The connection point between the child Q and the ground terminal of the DC power source V1 and the transformer
The diode D1 of the secondary winding N2 of the switch T1 is connected
A control circuit 2 for connecting a resistor R2 capable of detecting a ground fault current to the other end and stopping the operation of the switching element Q when a voltage due to the ground fault current is detected across the resistor R2. It is characterized by being provided.

Further, as shown in FIG. 3, insert a diode D2 in the direction to prevent the ground fault current to a path that ground fault current flows, as shown in FIG. 4, the direction of potential ground-fault current flows A switching element QX that is turned off when detected may be inserted.

[0009]

According to the present invention, the primary winding N1 of the transformer T1 is connected to the DC power source V1 composed of a battery whose negative electrode is grounded through the switching element Q whose one end is grounded. , A diode D1 on the secondary winding N2 of the transformer T1.
Capacitor C1 is connected via
Connect a load circuit to the switching element Q and DC
The connection point of the source V1 to the ground terminal and the secondary of the transformer T1
With one end where the diode D1 of the winding N2 is not connected
A resistor R2 capable of detecting a ground fault current is connected therebetween, and when the voltage due to the ground fault current is detected across the resistor R2, the operation of the switching element Q on the primary side of the transformer T1 is stopped. Therefore, even if the wiring to the load is erroneously grounded and a ground fault current flows, the operation of the switching element Q on the primary side of the transformer T1 is stopped to prevent a malfunction such as a device damage. be able to.

If the diode D2 is inserted in the direction in which the ground fault current flows in the direction in which the ground fault current flows, the ground fault current will flow even if the connection point to the load 1 is ground faulted due to an accident or the like. Can be blocked. The more detailed structure and operation of the present invention will be described in detail in the description of the embodiments below.

[0011]

1 is a circuit diagram showing an embodiment of the present invention. In the present embodiment, a resistor R2, which is an impedance element, is provided between the connection point OP between the primary side circuit and the secondary side circuit of the transformer T1, and the comparator 3 compares the potential between O and P. , The current flowing when the connection point a to the load 1 has a ground fault is detected to determine the ground fault, and in that case, the output of the comparator 3 changes and the control circuit 2
It is possible to prevent the circuit from being damaged by stopping the operation of.
Normally, in the state where there is no ground fault, the current flowing between O and P is only a small signal current such as a voltage on the secondary side and a signal for detecting the current and driving the switching element. In the case of a ground fault, an excessively large current is passed between O and P as compared with this, so that it is detected by the resistor R2. Note that when the lamp starting circuit 4 having the pulse generator PG and the pulse transformer PT is interposed between the inverter device and the load 1 as in the circuit shown in FIG.
The same effect is obtained when the point or the point d is grounded.

FIG. 3 is a circuit diagram showing the configuration of the invention of claim 2 . When either one of the two wires leading to the load 1 is ground-faulted, for example, when the point b is ground-faulted, a large current may flow in the route of the loop Y shown by the broken line, and the circuit may be destroyed. . Therefore, in the circuit of FIG. 3 , the diode D2 is inserted between the primary winding N1 and the secondary winding N2 of the transformer T1. The diode D2 can prevent or limit the ground fault current and prevent the circuit from being broken.
In addition, the diode D2 is made conductive in a steady state.

FIG. 4 is a circuit diagram showing the configuration of the invention of claim 3 . When either one of the two wires leading to the load 1 is ground-faulted, for example, when the point b is ground-faulted, a large current flows through the route of the loop Y shown by the broken line, which may cause the circuit to be destroyed. is there. Therefore, in the circuit of FIG. 4, the output voltage V2 is detected by the resistors R3 and R4 so that the voltage V2 of the capacitor C1 does not rise excessively, and when the value becomes higher than a predetermined value, the control circuit 2 causes the switching element to switch. Stop the operation of Q. Further, the switching element QX is inserted between the primary winding N1 and the secondary winding N2 of the transformer T1. Normally, the potential at the point P is high and only a minute current flows from the point P to the point O. Therefore, the output of the error amplifier 5 is at the high level and the switching element QX is turned on. At the time of a ground fault,
Although the potential at the point O becomes high and a large current tries to flow between the points O and P, the output of the error amplifier 5 becomes the low level,
The switching element QX turns off. In this way, the switching element QX is normally turned on, and when a ground fault current is about to flow, it is turned off. As a result, the ground fault current can be prevented or limited, and the destruction of the circuit can be avoided. Further, when the switching element QX is turned on, the detection value of the output voltage V2 becomes high with reference to the point e, the operation of the switching element Q can be stopped, and the safety can be further improved.

[0014]

According to the invention of claim 1, the transformer 1
Connect a DC power supply consisting of a battery whose negative electrode is grounded through a switching element whose one end is grounded to the next winding,
In a power supply device in which a capacitor is connected to a secondary winding of a transformer via a diode and a load circuit is connected to the capacitor, a connection between the switching element and a ground end of a DC power supply is provided.
The connecting point and the diode of the secondary winding of the transformer are connected.
A resistor that can detect a ground fault current is connected to one end that is not connected, and when the voltage due to the ground fault current is detected across this resistor, the operation of the switching element of the primary winding of the transformer is stopped. Therefore, even if the connection line to the load is grounded, there is an effect that damage to the device can be prevented.

According to the second and third aspects of the invention, a secondary power source of the transformer is connected to the primary winding of the transformer by connecting a DC power source comprising a battery whose negative electrode is grounded through a switching element whose one end is grounded. In a power supply device in which a capacitor is connected to the winding via a diode and a load circuit is connected to the capacitor, the switching element and the DC power supply are grounded.
The connection point to the end and the diode of the secondary winding of the transformer
Since a rectifying means such as a diode is inserted between the end that is not connected and the ground, even if the connection line to the load is grounded, a large current due to grounding can be prevented, and damage to the device, etc. There is an effect that can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the invention of claim 1;

FIG. 2 is a circuit diagram showing a main configuration of another embodiment of the invention of claim 1;

FIG. 3 is a circuit diagram showing the configuration of the invention of claim 2.

FIG. 4 is a circuit diagram showing a configuration of an invention of claim 3;

FIG. 5 is a circuit diagram of a conventional non-insulated power supply device.

FIG. 6 is an operation waveform diagram of a conventional non-insulated power supply device.

FIG. 7 is a circuit diagram of a conventional non-insulated power supply device when a ground fault occurs.

FIG. 8 is a circuit diagram showing a first current path during a ground fault in the conventional example.

FIG. 9 is a circuit diagram showing a second current path during a ground fault of the conventional example.

FIG. 10 is an explanatory diagram showing a wiring state of a conventional vehicle headlight lighting device.

[Explanation of symbols]

V1 DC power supply T1 transformer D1 diode C1 capacitor R2 Ground fault current detection resistor Q switching element 1 load 2 control circuit 3 Voltage detector

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihisa Hirata 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Toshiro Nakamura, 1048 Kadoma, Kadoma City, Osaka Matsushita Electric Works, Ltd. ( 72) Inventor, Hideki Hamada, 1048, Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works, Ltd. (56) Reference JP-A-1-99472 (JP, A) JP-A-51-33839 (JP, A) JP-A-hei 5-328740 (JP, A) JP-A-5-137326 (JP, A) Actual development Sho 59-104214 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02M 7/48 H05B 41/24

Claims (3)

(57) [Claims] 1. A primary winding of a transformer is connected to a DC power source composed of a battery whose negative electrode is grounded through a switching element whose one end is grounded, and a capacitor is connected to a secondary winding of the transformer through a diode. Is connected to the capacitor, a load circuit is connected to the capacitor, the switching element is switched, energy is accumulated in the transformer, and the energy is discharged from the secondary winding of the transformer to perform a flyback operation. in, the
The connection point between the switching element and the ground terminal of the DC power supply
The secondary winding diode of the transformer is not connected
A resistor that can detect a ground fault current is connected between the one end and a control unit that stops the operation of the switching element when a voltage due to the ground fault current is detected at both ends of the resistor. Power supply. 2. A primary winding of a transformer is connected to a DC power source composed of a battery whose negative electrode is grounded through a switching element whose one end is grounded, and a capacitor is connected to a secondary winding of the transformer through a diode. Is connected to the capacitor, a load circuit is connected to the capacitor, the switching element is switched, energy is accumulated in the transformer, and the energy is discharged from the secondary winding of the transformer to perform a flyback operation. in, the
The connection point between the switching element and the ground terminal of the DC power supply
The secondary winding diode of the transformer is not connected
A power supply device characterized in that a rectifying means is inserted between the one end and a direction to prevent a ground fault current. 3. The rectifying means includes a second switching element and a second switching element when the voltage applied across the second switching element is a voltage in a direction in which a ground fault current flows.
3. The power supply device according to claim 2, wherein the power supply device is configured by a voltage detecting unit that brings the switching element of 1 above into a non-conducting state.