WO2021075474A1

WO2021075474A1 - Vehicle lamp and control circuit

Info

Publication number: WO2021075474A1
Application number: PCT/JP2020/038833
Authority: WO
Inventors: 知幸市川
Original assignee: 株式会社小糸製作所
Priority date: 2019-10-17
Filing date: 2020-10-14
Publication date: 2021-04-22
Also published as: JPWO2021075474A1

Abstract

An inverting switching regulator (120) has a switching transistor (M1), an inductor (L1), and a rectification element (D1). A light source (110) is connected between an output terminal (OUT) of the inverting switching regulator (120) and ground. A protection switch (SW1) is disposed between the output terminal (OUT) of the inverting switching regulator (120) and ground. A protection circuit (146) turns on the protection switch (SW1) and fixes the switching transistor (M1) to an off state when the voltage (VBAT) of an input terminal (IN) of the inverting switching regulator (120) has exceeded a threshold value (VTH).

Description

Vehicle lighting and control circuits

This disclosure relates to vehicle lamps.

Automobiles and motorcycles (hereinafter referred to as vehicles) are equipped with various lighting equipment such as high beam, low beam, clearance lamp (position lamp), DRL (Daytime Running Lamp), and brake lamp. In recent years, the use of LEDs (light emitting diodes) as light sources used in these lamps has been promoted.

1 (a) to 1 (c) are diagrams showing conventional LED lighting circuits 800A to 800D. The light source 802 is an LED string including a plurality of N (N ≧ 2) LEDs connected in series. The lighting circuit 800A of FIG. 1A includes a boost converter that boosts _{the battery voltage V BAT} _{and generates a drive voltage V LED} between both ends of the light source 802. This type is adopted when the number N of LEDs in the LED string is large and the drive voltage V _LED = N × Vf _{to be applied between both ends of the light source 802 is higher than the battery voltage V BAT} (for example, 12 V). Vf is a forward voltage per LED.

When the number of LEDs in the LED string is small and the drive voltage V _LED (= N × Vf) _{to be applied between both ends of the light source 802 is lower than the battery voltage V BAT} , the configurations of FIGS. 1 (b) and 1 (c) are configured. Can be adopted. The lighting circuit 800B of FIG. 1B generates an optimum drive voltage V _LED _{by stepping down the battery voltage V BAT by a buck converter.} In this type, there is a problem that the light source 802 is turned off when the battery voltage V _{BAT falls below N × Vf.}

The lighting circuit 800C of FIG. 1 (c) boosts or lowers the _{battery voltage V BAT} by a buck-boost converter so that an _{optimum drive voltage V LED can be obtained.} In this type, the optimum drive voltage V _LED can be obtained regardless of the fluctuation of the battery voltage V _BAT , but since the operation differs between step-up and step-down, the circuit scale increases in the circuit form combining them. It leads to cost increase.

Japanese Unexamined Patent Publication No. 2013-0083615

As a result of examining a lighting circuit provided with an inverting regulator (polarity inverting converter), the present inventor has come to recognize the following problems.

FIG. 2 is a circuit diagram of a lighting circuit 800D including an inverting regulator. The inverting regulator is placed between both ends of the light source 802.
_{_{| V OUT | = (t ON}} / t OFF) × (V BAT -V sat -V F) ... (1)
Drive voltage can be applied. V _F is the voltage drop of the rectifying element _{806, V sat} is the saturation voltage of the switching transistor 804. The _{t on} the ON time of the switching transistor _{804, t off} is the off-time of the switching transistor 804. If approximated as _V _sat = V F = 0V, the output voltage _{V OUT} can be expressed by equation (2).
｜ V _OUT ｜＝ (t _ON / t _OFF ) × V _BAT … (2)
It is expressed as. In equation (2), (t _ON / t _OFF ) can be changed in the range from 0 to infinity _{, so that the drive voltage V LED} required by the light source 802 is irrespective of the magnitude of the _{battery voltage V BAT.} Can occur.

_{In the inverting regulator, a potential difference of V BAT} −V _OUT = V _BAT + | V _OUT | is generated between the input terminal IN and the output terminal OUT, and this potential difference is generated between both ends of the switching transistor 804 and the rectifying element 806. It is applied.

In-vehicle devices are required to operate stably without deteriorating reliability even if the battery voltage fluctuates suddenly. For this reason, the in-vehicle device needs to be designed to pass the load dump test. In the load dump test, the battery voltage V _BAT transiently rises to several tens of V (for example, 30 V). If the output voltage V _OUT is −10V, a voltage of as much as 40V will be applied between the input / output terminals.

Therefore, if the lighting circuit 800D of FIG. 2 is designed so as to be able to clear the load dump test, it is necessary to increase the withstand voltage of the switching transistor 804 and the rectifier element 806, or to add a surge protection circuit, which is a factor of cost increase. It becomes.

The present disclosure has been made in view of such a problem, and one of the exemplary purposes of the embodiment is to provide a lighting circuit having enhanced resistance to load dump.

One aspect of this disclosure relates to vehicle lamps. Vehicle lighting equipment has a light source, a switching transistor, an inductor, and a rectifying element, and is provided between an inverting switching regulator in which the light source is connected between the output terminal and the ground, and between the output terminal and the ground of the inverting switching regulator. When the voltage between the input terminal and the ground of the inverting switching regulator or the voltage between the input terminal and the output terminal exceeds the threshold value, the protection switch is turned on and the switching transistor is fixed off. It is equipped with a circuit.

The rectifying element is a synchronous rectifying transistor, and the protection circuit may fix the synchronous rectifying transistor on when the voltage between the input terminal and the ground or the voltage between the input terminal and the output terminal exceeds the threshold value.

Another aspect of the present disclosure relates to a control circuit of an inverting switching regulator that drives a light source. The control circuit consists of an input terminal, an output terminal, a ground terminal, an inductor connection terminal, a switching transistor provided between the input terminal and the inductor connection terminal, and a synchronous rectifying transistor provided between the inductor connection terminal and the output terminal. A pulse signal that instructs the switching transistor and synchronous rectifying transistor to be turned on and off so that the protection transistor provided between the output terminal and the ground terminal and the current flowing through the load connected to the output terminal approach a predetermined target value. When the voltage between the input terminal and the ground terminal or the voltage between the input terminal and the output terminal exceeds the threshold value, the pulse modulator that generates the , The protection circuit for fixing the protection transistor on, the switching transistor off, and the synchronous rectification transistor on is provided.

Yet another aspect of the present disclosure is a vehicle lamp. This vehicle lighting fixture has a light source, a switching transistor, an inductor, and a rectifying element, and an inverting switching regulator in which a light source is connected between an output terminal and ground, a protection switch provided in parallel with the inductor, and inverting. When the voltage between the input terminal and the ground of the type switching regulator or the voltage between the input terminal and the output terminal exceeds the threshold value, the protection switch is turned on and the switching transistor is fixed to the off.

The rectifying element is a synchronous rectifying transistor, and the protection circuit may fix the synchronous rectifying transistor on when the voltage of the input terminal exceeds the threshold value.

Yet another aspect of the present disclosure relates to a control circuit of an inverting switching regulator that drives a light source. The control circuit consists of an input terminal, an output terminal, a ground terminal, an inductor connection terminal, a switching transistor provided between the input terminal and the inductor connection terminal, and a synchronous rectifying transistor provided between the inductor connection terminal and the output terminal. A protection transistor provided between the inductor connection terminal and the ground terminal, and a pulse that instructs the switching transistor and synchronous rectification transistor to turn on and off so that the current flowing through the load connected to the output terminal approaches a predetermined target value. The pulse modulator that generates the signal, the driver that drives the switching transistor and the synchronous rectification transistor based on the pulse signal, and the voltage between the input terminal and the ground terminal, or the voltage between the input terminal and the output terminal exceeds the threshold value. And a protection circuit that turns on the protection transistor, turns off the switching transistor, and fixes the synchronous rectification transistor on.

It should be noted that any combination of the above components and those in which the components and expressions of the present disclosure are mutually replaced between methods, devices, systems, etc. are also effective as aspects of the present disclosure.

According to certain aspects of the present disclosure, resistance to load dumps can be increased.

1 (a) to 1 (c) are diagrams showing a conventional LED lighting circuit. It is a circuit diagram of a lighting circuit including an inverting regulator. It is a block diagram of the lamp system including the lamp module according to the embodiment. It is an operation waveform diagram of the lamp module of FIG. It is a circuit diagram of the control IC that can be used for the lamp module of FIG. It is a block diagram of the lamp system including the lamp module according to the second embodiment. It is a circuit diagram of the control IC that can be used for the lamp module of FIG.

Hereinafter, the present disclosure will be described based on a preferred embodiment with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings shall be designated by the same reference numerals, and redundant description will be omitted as appropriate. Further, the embodiment is an example without limiting the disclosure, and all the features and combinations thereof described in the embodiment are not necessarily essential to the invention.

In the present specification, the "state in which the member A is connected to the member B" means that the member A and the member B are physically directly connected, and that the member A and the member B are electrically connected to each other. It also includes the case of being indirectly connected via other members, which does not substantially affect the connection state, or does not impair the functions and effects performed by the combination thereof.

Similarly, "a state in which the member C is provided between the member A and the member B" means that the member A and the member C, or the member B and the member C are directly connected, and their electricity. It also includes the case of being indirectly connected via other members, which does not substantially affect the connection state, or does not impair the functions and effects produced by the combination thereof.

Further, in the present specification, the reference numerals attached to electric signals such as voltage signals and current signals, or circuit elements such as resistors and capacitors have their respective voltage values, current values, resistance values, and capacitance values as required. It shall be represented.

FIG. 3 is a block diagram of a lamp system 1 including the lamp module 100A according to the embodiment. The lamp system 1 includes a battery 2, a switch 4, and a lamp module 100A.

The lamp module 100A receives a power supply voltage (battery voltage V _BAT ) from the battery 2 via the switch 4. The lamp module 100A emits light when the battery voltage V _BAT is supplied. The lamp module 100A may receive a control signal for switching on / off of light emission from an ECU (Electronic Control Unit) (not shown).

The lamp module 100A includes a light source 110, an inverting switching regulator 120, a protection switch SW1 and a controller 140. The light source 110 includes a plurality of N (N = 3 in FIG. 3) light emitting elements 112 connected in series. The light emitting element 112 is, for example, an LED, an LD (laser diode), an organic EL (Electro Luminescence) element, or the like. In this example, the inverting switching regulator 120 is a diode rectifying type, but it may be a synchronous rectifying type in which the rectifying element D1 is replaced with a transistor.

The inverting switching regulator 120 includes a switching transistor M1, an inductor L1, a rectifying element D1, and an output capacitor C1. The light source 110 is connected between the output terminal OUT and the ground GND so that the anode is on the GND side and the cathode is on the OUT terminal side. The switching transistor M1 is an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

The protection switch SW1 is provided between the output terminal OUT of the inverting switching regulator 120 and the ground GND. The protection switch SW1 is off during normal operation of the inverting switching regulator 120.

The controller 140 controls on / off of the switching transistor M1 by feedback control so that the _{drive current I LED} flowing through the light source 110 approaches a predetermined target amount I _REF. The controller 140 monitors the battery voltage _{V BAT,} to control the protection switch SW1 based on the battery voltage _{V BAT.}

For example, the controller 140 includes a converter controller 142, a driver 144, and a protection circuit 146. Converter controller 142, so that the current detection signal _{V CS} corresponding to the drive current _{I LED} approaches the reference signal _{V REF,} the duty ratio, the pulse width (on-time), off-time, pulse signal Sp at least one frequency varies To generate. The driver 144 drives the switching transistor M1 based on the pulse signal Sp.

The converter controller 142 may be a ripple control controller, and can use hysteresis control (Bang-Bang control), bottom detection on-time fixed control, peak detection off-time fixed control, and the like. In the case of bottom detection on-time fixed control, the on-time may be feedback-controlled so that the switching frequency becomes constant. Further, in the case of the peak detection off time fixed control, the off time may be feedback controlled so that the switching frequency becomes constant.

Alternatively, the converter controller 142 _{includes an error amplifier that amplifies the error between the current detection signal VCS} and the reference signal V _REF , and at least one of the duty ratio, frequency, on-time, off-time, and frequency changes according to the output of the error amplifier. The pulse signal Sp may be generated.

_{The protection circuit 146 monitors the voltage VBAT} of the input terminal IN of the inverting switching regulator 120, asserts a protection signal when a predetermined determination condition (referred to as an overvoltage determination condition) is satisfied, turns on the protection switch SW1, and switches. The transistor M1 is fixed off. The protection circuit 146 may notify the converter controller 142 of the occurrence of an overvoltage, and the converter controller 142 may respond by fixing the pulse signal Sp to an off-level. Alternatively, the control signal from the protection circuit 146 may be supplied to the driver 144, and the driver 144 may fix the switching transistor M1 off in response to the control signal.

For example, the overvoltage determination condition may be that the voltage between the input terminal IN and the ground terminal (simply referred to as the input voltage V _BAT ) exceeds the threshold value V _TH. In this case, the protection circuit 146 is configured to compare the _{input voltage V BAT} with the threshold voltage V _TH relative to the ground voltage V _GND.

Alternatively, the overvoltage determination condition may be that the differential voltage V _DIFF (V _DIFF = V _BAT- V _OUT ) between the input terminal IN and the output terminal OUT exceeds the threshold value V _TH. In this case, the protection circuit 146 may be configured to compare the _{input voltage V BAT} with the threshold voltage V _TH '= V _TH + V _OUT with reference to the voltage V _{OUT of the output terminal OUT.}

The above is the configuration of the lamp module 100A. Next, the operation will be described. FIG. 4 is an operation waveform diagram of the lamp module 100A of FIG.

The advantage of the lamp module 100A becomes clear by comparison with the comparative technique. Therefore, the comparison technique will be described first. In the comparative technique, the protection switch SW1 does not exist, and when the battery voltage V _BAT exceeds the threshold value V _TH , the switching of the switching transistor M1 is stopped. FIG. 4 shows the operation of the comparative technique with a chain double-dashed line.

Before time t _0, _{the battery voltage V BAT} of the rated level V _TYPE (12 to 14 V) is supplied, and the drive voltage I _LED is stabilized to the target current amount I _REF. The output voltage V _{OUT at} this time is stabilized to −Vf × N. Vf is the forward voltage of the light emitting element 112.

At time _{t 0,} the battery voltage _{V BAT} jumps to over-voltage _{V OV.} When the battery voltage V _BAT exceeds the threshold value V _TH _{at time t 1} , the switching transistor M1 is fixed to off. As a result, the drive current I _LED decreases with time.

Here, since the impedance of the light emitting element 112 becomes high in the low current region, the electric charge of the output capacitor C1 remains in the comparative technique, and as shown by the one-point chain line in FIG. 4, the negative output voltage V _OUT = V _LED. 'Remains. Thus, in the comparative art, between the input terminal IN and the output terminal OUT of the inverting switching regulator _120, so that the voltage of the _V OV ₊ V _LED 'is applied. In the comparative technique, it may be necessary to take measures such as configuring the switching transistor M1 and the rectifying element D1 with a high withstand voltage, or adding a surge protection circuit for suppressing an overvoltage of the input terminal IN. When the switching transistor M1 or the rectifying element D1 is composed of a high withstand voltage element, its on-resistance becomes high, and when the switching transistor M1 is composed of a MOSFET, the heat generation loss increases due to an increase in gate drive charge and the like. There is a problem to do. Further, if the switching transistor M1 and the rectifying element D1 are configured with a high withstand voltage, it becomes difficult to integrate the elements in an IC (Integrated Circuit), and the external components such as the switching transistor M1 and the rectifying element D1 are mounted on the substrate together with the IC. There is also a problem that it becomes necessary to lay out the electronic components, the area for mounting the electronic components increases, and the size increases.

The operation of the lamp module 100A of FIG. 3 will be described. The operation of the lamp module 100A is shown by a solid line.

At time _{t 0,} the battery voltage _{V BAT} jumps to over-voltage _{V OV.} When the battery voltage V _BAT exceeds the threshold value V _TH _{at time t 1} , the protection switch SW1 is turned on and the switching transistor M1 is fixed to off.

When the switching transistor M1 is turned on, the voltage V _LED between both ends of the light source 110 quickly decreases to near zero, and the negative output voltage V _OUT (<0V) rapidly rises to near zero ground voltage. As a result, the input / output voltage V _IN- V _OUT of the inverting switching regulator 120 becomes an overvoltage _VOV.

Protection switch SW1 is in the ON state, the coil current _{I L,} protection switch SW1, the rectifying element D1, flows in the loop comprising the inductor L1, the coil current _{I L} is attenuated with time.

The above is the operation of the lamp module 100A. According to the lighting equipment module 100A, the voltage _{applied to the input terminal IN and the output terminal OUT after the battery voltage V BAT} becomes an overvoltage _VOV can be made smaller than that of the comparative technique, and the switching transistor M1 and the rectification can be performed. The voltage applied to the element D1 can be reduced. As a result, the withstand voltage required for the switching transistor M1 and the rectifying element D1 can be reduced, the surge protection circuit can be omitted, or the configuration of the surge protection circuit can be simplified.

(Modification example 1)
The threshold value V _TH may be set with reference to _{the output voltage V OUT} of the inverting switching regulator 120.
V _TH = V _OUT + ΔV

(Modification 2)
The switching transistor M1 may be a P channel transistor.

(Circuit configuration example)
FIG. 5 is a circuit diagram of a control IC 300 that can be used for the lamp module 100A of FIG. The lamp module 100B includes a light source 110, a control IC (Integrated Circuit) 300, an inductor L1 and an output capacitor C1. The control IC 300 is an IC in which the main parts of the inverting switching regulator 120 and the controller 140 of FIG. 3 are integrated.

The control IC 300 includes an input pin IN, an output pin OUT, a switching pin (inductor connection pin) LX, a ground pin GND, and a bootstrap pin BS. A battery voltage V _BAT is supplied to the input pin IN, and the cathode of the light source 110 and the output capacitor C1 are connected to the output pin OUT. The inductor L1 is connected to the LX pin, and the GND pin is grounded. _{A bootstrap capacitor CBS} is connected between the BS pin and the LX pin.

The switching regulator of FIG. 5 is a synchronous rectification type, and the control IC 300 includes a switching transistor M1 and a synchronous rectification transistor M2 (rectifying element D1 of FIG. 3). The protection switch SW1 is provided between the OUT terminal and the GND terminal. The switching transistor M1, the synchronous rectifying transistor M2, and the protection switch SW1 are N-channel MOSFETs. _{The converter controller 302 detects the current I LED} flowing through the light source 110, and generates a pulse signal Sp so that the detected current I _LED approaches the target current I _REF. The driver 304 drives the switching transistor M1 and the synchronous rectifier transistor M2 based on the pulse signal Sp.

_{The protection circuit 306 compares the voltage V BAT} of the input pin IN with the threshold value V _TH, and when V _BAT > V _TH , asserts the protection signal OVP and turns on the protection switch SW1. Further, the driver 304 fixes the switching transistor M1 to off and the synchronous rectifier transistor M2 to on in response to the assertion of the protection signal OVP.

In FIG. 5, when the _{determination condition is that the differential voltage V DIFF} exceeds the threshold voltage V _TH , the protection circuit 306 _{monitors the input voltage V IN} and the output voltage V _OUT , and the differential voltage V _DIFF = V. _{When IN-} V _OUT exceeds the threshold voltage _VTH , the protection signal OVP is asserted, the protection switch SW1 is turned on, the switching transistor M1 is turned off, and the synchronous rectifying transistor M2 is turned on.

The control IC 300 may be configured so that its reference voltage (ground voltage) is not the external ground voltage V _GND but the voltage V _{OUT of the OUT pin.} In this case, the protection circuit 306 generates a threshold voltage V _TH '(V _TH '= V _OUT + V _TH _{) with reference to the voltage V OUT of the} OUT pin, and the threshold voltage V _{TH'and the} input pin. The IN voltage V _BAT may be compared. This is equivalent to comparing the differential voltage V _DIFF with the threshold V _TH.

_{A constant voltage VREG} is applied to the BS pin via the diode D2. Diode D2 constitute a bootstrap circuit with a capacitor C _BS external. A voltage higher than the voltage of the LX pin by _VREG is generated in the BS pin. Driver 304, by using the voltage _{V BS} of BS pin, to drive the switching transistor M1.

The above is the configuration of the lamp module 100B equipped with the control IC 300. In this control IC 300, when the OVP signal is asserted, a current flows through a loop including the protection switch SW1, the synchronous rectifier transistor M2, and the inductor L1. Other operations are the same as those in FIG.

The synchronous rectifier transistor M2 may be turned off when the protection signal OVP is asserted. In this case, when the protection signal OVP is asserted, a current flows through the loop including the body diode of the synchronous rectifier transistor M2.

(Embodiment 2)
FIG. 6 is a block diagram of a lamp system 1 including the lamp module 100C according to the second embodiment. The lamp system 1 includes a battery 2, a switch 4, and a lamp module 100C.

The lamp module 100C includes a protection switch SW2 instead of the protection switch SW1 shown in FIG. The protection switch SW2 is connected in parallel with the inductor L1. _{When the voltage V BAT} of the input terminal IN of the inverting switching regulator 120 exceeds the threshold value V _TH , the protection circuit 146 turns on the protection switch SW2 and fixes the switching transistor M1 to off. The protection switch SW2 may employ a bidirectional switch capable of bidirectional current cutoff so as not to interfere with the normal operation of the inverting switching regulator 120.

The above is the configuration of the lamp module 100C. Next, the operation will be described. In the normal state, the protection switch SW2 is off. When the overvoltage state is detected by the protection circuit 146, the protection switch SW2 is turned on. As a result, the electric charge of the output capacitor C1 is discharged via the rectifying element D1 and the protection switch SW2, and the voltage V _LED between both ends of the light source 110 quickly becomes 0V.

FIG. 7 is a circuit diagram showing a specific configuration example (100D) of the lamp module 100C of FIG. The control IC 300D is an IC in which the main parts of the inverting switching regulator 120 and the controller 140 of FIG. 6 are integrated.

The control IC 300D includes a protection switch SW2 provided between the LX pin and the GND pin. The protection switch SW2 includes two transistors M31 and M32 connected in anti-series. The protection circuit 306 generates the gate signals of the transistors M31 and M32 so that the protection switch SW2 is turned off in the normal state and the protection switch SW2 is turned on in the overvoltage state. Others are the same as the control IC 300 of FIG.

According to this control IC 300D, the same effect as that of the control IC 300 of FIG. 5 can be obtained.

Although the present disclosure has been described using specific terms and phrases based on the embodiment, the embodiment merely indicates the principle and application of the present disclosure, and the embodiment is defined in the claims. Many modifications and arrangement changes are permitted without departing from the ideas of the present disclosure.

This disclosure can be used for vehicle lamps.

1 Lamp system 2 Battery 4 Switch 100 Lamp module 110 Light source 112 Light emitting element 120 Inverted switching regulator SW1 Protection switch 140 Controller 142 Converter controller 144 Driver 146 Protection circuit 300 Control IC
302 Converter controller 304 Driver 306 Protection circuit

Claims

Light source and
An inverting switching regulator that has a switching transistor, inductor, and rectifying element, and the light source is connected between the output terminal and ground.
A protection switch provided between the output terminal of the inverting switching regulator and ground,
When the voltage between the input terminal and the ground of the inverting switching regulator or the voltage between the input terminal and the output terminal exceeds the threshold value, the protection switch is turned on and the switching transistor is fixed to the off. ,
A vehicle lamp that is characterized by being equipped with.
The rectifying element is a synchronous rectifying transistor.
The protection circuit is characterized in that when the voltage between the input terminal and the ground or the voltage between the input terminal and the output terminal exceeds the threshold value, the synchronous rectifier transistor is fixed on. The vehicle lighting equipment according to 1.
A control circuit for an inverting switching regulator that drives a light source.
Input terminal and
Output terminal and
Ground terminal and
Inductor connection terminal and
A switching transistor provided between the input terminal and the inductor connection terminal,
A synchronous rectifier transistor provided between the inductor connection terminal and the output terminal,
A protection transistor provided between the output terminal and the ground terminal,
A pulse modulator that generates a pulse signal instructing on / off of the switching transistor and the synchronous rectifier transistor so that the current flowing through the load connected to the output terminal approaches a predetermined target value.
A driver that drives the switching transistor and the synchronous rectifier transistor based on the pulse signal,
When the voltage between the input terminal and the ground terminal or the voltage between the input terminal and the output terminal exceeds the threshold value, the protection transistor is turned on, the switching transistor is turned off, and the synchronous rectifying transistor is turned on. With a protection circuit fixed to
A control circuit characterized by comprising.
Light source and
An inverting switching regulator that has a switching transistor, inductor, and rectifying element, and the light source is connected between the output terminal and ground.
A protection switch provided in parallel with the inductor and
When the voltage between the input terminal and the ground of the inverting switching regulator or the voltage between the input terminal and the output terminal exceeds the threshold value, the protection switch is turned on and the switching transistor is fixed to off. Circuit and
A vehicle lamp that is characterized by being equipped with.
The rectifying element is a synchronous rectifying transistor.
The protection circuit is characterized in that when the voltage between the input terminal and the ground or the voltage between the input terminal and the output terminal exceeds the threshold value, the synchronous rectifier transistor is fixed on. The vehicle lighting equipment according to 4.
A control circuit for an inverting switching regulator that drives a light source.
Input terminal and
Output terminal and
Ground terminal and
Inductor connection terminal and
A switching transistor provided between the input terminal and the inductor connection terminal,
A synchronous rectifier transistor provided between the inductor connection terminal and the output terminal,
A protection transistor provided between the inductor connection terminal and the ground terminal,
A pulse modulator that generates a pulse signal instructing on / off of the switching transistor and the synchronous rectifier transistor so that the current flowing through the load connected to the output terminal approaches a predetermined target value.
A driver that drives the switching transistor and the synchronous rectifier transistor based on the pulse signal,
When the voltage between the input terminal and the ground terminal or the voltage between the input terminal and the output terminal exceeds the threshold value, the protection transistor is turned on, the switching transistor is turned off, and the synchronous rectifying transistor is turned on. A protection circuit that is fixed on and
A control circuit characterized by comprising.