TWM455317U - DC to DC constant current driving circuit - Google Patents

Description

DC to DC constant current drive circuit

The present invention relates to a novel DC-to-DC constant current driving circuit, which can be widely applied to a situation requiring a constant current control function, and a specific example can be applied to a constant current control of a Light Emitting Diode (LED), an output current amplitude and Pulse width modulation, and failure protection for abnormal conditions.

In the field of DC-to-DC switching power supply and lighting, the application of constant current output is very wide. For example, the current general-purpose LED driving scheme uses DC-DC constant-current driving mode, and it is applied in the display backlight field whether the display screen is a multi-string LED or Single string LED backlight, single string LED can directly achieve constant current and current regulation through the sampling circuit, multi-string LED applications can first pass adaptive discrete current sharing line.

However, since there is usually only a single signal input, the pulse width and amplitude of the current are difficult to accurately control, and an abnormality such as an open circuit short circuit occurs, and therefore, a driving circuit capable of reducing an abnormality is required.

The present invention aims to provide a DC-to-DC constant current driving circuit including: a DC-to-DC switching circuit, an output over-voltage protection circuit, a constant current sampling control circuit, an output current amplitude adjustment circuit, and an output. Current pulse width modulation circuit.

The DC-to-DC switch circuit includes: a current mode pulse width modulation (PWM) control chip, a boost inductor, a boost diode, and a first metal oxide half field effect transistor (Metal Oxide Semiconductor Field Effect Transistor, MOSFET). ), output voltage filter capacitor and first sampling resistor. One end of the boosting inductor is connected to an input voltage source, and the other end is connected to a drain of the first MOSFET and a positive pole of the boosting diode, a positive pole of the boosting diode and the output One end of the voltage filter capacitor is connected, and one end of the output voltage filter capacitor is connected to the first sampling resistor, and the first sampling resistor is connected to a source of the first MOSFET.

The output overvoltage protection line is connected to the DC to DC switch line and the LED string, the output overvoltage protection line includes a first voltage dividing resistor and a second voltage dividing resistor, A first voltage dividing resistor and the second voltage dividing resistor are coupled to the current mode pulse width modulation control wafer.

The constant current sampling control circuit is connected to the DC-to-DC switching circuit and the LED light string, and the constant current sampling control circuit includes a brightness control resistor, a brightness control capacitor, a second MOSFET, and a current output resistor, the LED a light string is coupled to the drain of the second MOSFET, a source of the second MOSFET is coupled to the current output resistor, and is coupled to the current mode pulse width modulation control chip, the gate of the second MOSFET The pole is coupled to the luminance control resistor and the luminance control capacitor, and the luminance control resistor is coupled to the current mode pulse width modulation control wafer.

The output current amplitude adjustment circuit includes a current amplitude adjustment resistor, and the external high frequency PWM signal is input to the current mode pulse width modulation control chip via the current amplitude adjustment resistor; the output current pulse width modulation circuit includes a signal An input resistor, the external low frequency PWM signal is coupled to the current mode pulse width modulation control chip via a signal input resistor.

The DC-to-DC constant current driving circuit of the present invention can control the pulse width and amplitude of the output current separately by the two PWM input signals, and can realize accurate current control. In addition, this circuit can effectively protect against abnormalities such as open circuit short circuit common in LED driving applications.

Features and exemplary embodiments of various aspects of the present work are described in detail below. The following description covers many specific details to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely provided to provide a clearer understanding of the present invention by the example of the present invention. The present invention is in no way limited to any specific configuration as set forth below, but without departing from the spirit of the present invention, any modification, substitution, or modification of the related elements or components.

The DC-to-DC constant current driving circuit of the present invention can be widely applied to various switching power supply occasions. For the convenience of description, the following specific circuit contents are carried out by using a light-emitting diode constant current driving circuit as an example, but the creation is not limited to LEDs. Constant current drive applications.

Referring to Fig. 1, there is shown a block diagram of a first embodiment of a DC-to-DC constant current driving circuit according to the present embodiment. As shown in Fig. 1, the DC-DC constant current driving circuit of the present invention comprises a DC-to-DC switching circuit 1, an output over-voltage protection circuit 2, a constant-current sampling control circuit 3, and a transmission. The current amplitude adjustment circuit 4 and the output current pulse width modulation circuit 5 are provided.

The DC-to-DC switch circuit 1 includes a current mode Pulse Width Modulation (PWM) control chip U1, a boost inductor L1, a boost diode D1, and a first metal oxide half field effect transistor (Metal Oxide Semiconductor Field Effect). Transistor, MOSFET) Q1, output voltage filter capacitor C2, first sampling resistor R _CS1 and second sampling resistor R _CS2 . One end of the boost inductor L1 is connected to the input voltage source VIN, and the other end is connected to the drain of the first MOSFET Q1 and the anode of the boost diode D1. The cathode of the boost diode D1 is connected to one end of the output voltage filter capacitor C2, and the other end of the output voltage filter capacitor C2 is connected to the first sampling resistor R _CS1 , and the first sampling resistor R _{CS1 is} connected to the source of the first MOSFET Q1 . pole.

The current mode pulse width modulation control chip U1 includes 10 function pins, as follows:

(1) VIN pin, input voltage source VIN through fuse F1, filtered by input filter capacitor C1 and filter capacitor C _VIN and connected to VIN pin for power supply of chip internal circuit; (2) GATE pin, connected to a gate of MOSFET Q1 and a constant current sampling control circuit 3 for controlling the switch of the first MOSFET Q1 and for adjusting the output current pulse width; (3) GND pin, wafer reference ground; (4) CS pin, via The second sampling resistor R _{CS2 is} connected to the source of the first MOSFET Q1 as the first MOSFET Q1 peak current sampling input pin; (5) the ISET pin is connected to the output current amplitude adjusting circuit 4, and the input external high frequency PWM signal For adjusting the output current amplitude; (6) REF pin, connecting filter capacitor C _REF ; (7) FB pin, output current setting, connected with constant current sampling control circuit 3, forming output current setting function; (8) COMP pin, system loop compensation, connection compensation capacitor C _CMP and compensation resistor R _CMP ; (9) OVP pin, output voltage overvoltage protection input pin, connection output overvoltage protection circuit 2 forms overvoltage protection function; 10) DIM pin, which is the PWM signal input pin Connected to the enable signal source ENA and the output current pulse width modulation circuit 5, the enable signal source ENA passes through the second diode D2, and is combined with the external low frequency PWM signal adjusted by the output current pulse width modulation circuit 5. Input to the DIM pin to control the output current pulse width.

The output overvoltage protection circuit 2 is connected to the DC to DC switch line 1 and the LED string, and includes a first voltage dividing resistor R _OVP1 and a second voltage dividing resistor R _OVP2 , a first voltage dividing resistor R _OVP1 and a second voltage dividing resistor R _{The OVP2 is} connected to the OVP pin of the current mode pulse width modulation control chip U1, thereby providing a sampling signal for diode connection detection and output overvoltage protection.

The constant current sampling control circuit 3 is connected to the DC-to-DC switch line 1 and the LED string, and includes a luminance control resistor R _DIM , a luminance control capacitor C _DIM , a second MOSFET Q2 , and a current output resistor RFB, the LED string and the second MOSFET. Q2's drain connection, the source of the second MOSFET Q2 is connected to the current output resistor RFB, and is connected to the FB pin of the current mode pulse width modulation control chip U1, and the gate and luminance control resistor R _{DIM of the} second MOSFET Q2 And the luminance control capacitor C _{DIM is} connected, and the luminance control resistor R _{DIM is} connected to the GATE pin of the current mode pulse width modulation control chip U1, and the sampling current mode pulse width modulation control gate signal of the GATE pin of the wafer U1 is passed. The luminance control resistor R _DIM and the luminance control capacitor C _{DIM are} filtered to form a control signal of the second MOSFET Q2, and the control signal of the second MOSFET Q2 is synchronized with the PMW signal originally provided by the external PMW signal to finally achieve a good current linearity function; The FB pin of the current mode pulse width modulation control chip U1 sets the output current by connecting the current output resistor RFB.

The output current amplitude adjusting circuit 4 is configured to adjust the output current amplitude, and includes a current amplitude adjusting resistor R _ISET , and the external high frequency PWM signal is input to the ISET pin of the current mode pulse width modulation control chip U1 through the current amplitude adjusting resistor R _ISET , The inside of the wafer adjusts the output current amplitude according to the duty ratio of the PWM signal.

The output current pulse width modulation circuit 5 includes a signal input resistance R _DIM , and the external low frequency PWM signal is connected to the DIM pin of the current mode pulse width modulation control chip U1 through the signal input resistance R _DIM for adjusting the output current pulse width. The duty ratio of the input PWM pulse width signal is equivalent to the pulse width of the output current to achieve the purpose of adjusting the output current.

Referring to Fig. 2, there is shown a block diagram of a second embodiment of a DC-to-DC constant current driving circuit according to the present embodiment. As shown in FIG. 2, the second embodiment of the present DC-DC constant current driving circuit is mainly different from the first embodiment in the constant current sampling control circuit 3. The constant current sampling control circuit 3 of the second embodiment includes Second MOSFET Q2, first transistor Q3, second transistor Q4, first luminance control resistor R _DIM1 , second luminance control resistor R _DIM2 , third luminance control resistor R _DIM3 , fourth luminance control resistor R _DIM4 , An input resistor R _VIN1 , a second input resistor R _VIN2 , a first gate resistor R _{GATE1 ,} and a second gate resistor R _GATE2 .

The input voltage source VIN is connected to the collector of the first transistor Q3 via the first input resistor R _VIN1 , the enable signal source ENA of the second second body D2 and the externally regulated by the output current pulse width modulation circuit 5 The PWM input signal is connected to the base of the first transistor Q3 via the first luminance control resistor R _DIM1 , and is regulated by the enable signal source ENA of the second second polar body D2 and the output current pulse width modulation circuit 4 . The external PWM input signal is coupled to the emitter of the first transistor Q3 via a first luminance control resistor R _DIM1 and a second luminance control resistor R _DIM2 . The input voltage source VIN is connected to the collector of the second transistor Q4 via the second input resistor R _VIN2 , and the input voltage source VIN is connected to the base of the second transistor Q4 via the first input resistor R _VIN1 and the third luminance control resistor R _DIM3 . The input voltage source VIN is coupled to the emitter of the second transistor Q4 via a first input resistor R _VIN1 , a third luminance control resistor R _{DIM3 ,} and a fourth luminance control resistor R _DIM4 . The collector of the second transistor Q4 is further connected to the gate of the second MOSFET Q2 via the first gate resistor R _GATE1 , and the collector of the second transistor Q4 is connected via the first gate resistor R _GATE1 and the first gate resistor R _GATE2 To the source of the second MOSFET Q2, the drain of the second MOSFET Q2 is connected to an external LED string, and the current output resistor RFB is connected to the FB pin of the current mode pulse width modulation control chip U1.

The PWM signal provided by the enable signal source ENA is connected to the first luminance control resistor R _DIM1 and the second luminance control resistor R _DIM2 to control the first transistor Q3 switch, and the output signal of the first transistor Q3 is inverted from the PWM signal. And driving the second transistor Q4 by connecting the third luminance control resistor R _DIM3 and the fourth luminance control resistor R _DIM4 so that the output signal of the first transistor Q3 is inverted again, that is, the output signal of the second transistor Q4 is the same as the input. The PWM signal is in phase (step). In addition, due to the limited driving capability of the PWMM signal, the first transistor Q3 and the second transistor Q4 are respectively connected to the input voltage VIN through the first input resistor R _VIN1 and the second input resistor R _VIN2 to form two stages. Amplifying the line, ensuring normal driving of the second MOSFET Q2 through the connected first gate resistor R _GATE1 and the second gate resistor R _GATE2 ; in addition, the FB pin of the current mode pulse width modulation control chip U1 is set and output by connecting the current output resistor RFB Current.

Referring to Fig. 3, there is shown a block diagram of a third embodiment of a DC-to-DC constant current driving circuit according to the present embodiment. As shown in FIG. 3, the third embodiment of the DC-to-DC constant current driving circuit of the present invention mainly includes a load abnormal protection circuit 6 for realizing a protection function when the positive and negative terminals of the load are short-circuited. The load abnormality protection circuit 6 is connected to the FB pin of the current mode pulse width modulation control chip U1 and the OVP pin of the current mode pulse width modulation control chip U1, and includes a third diode D3, a short circuit protection resistor RSCP, and a short circuit protection. Capacitor C _SCP and third MOSFET Q5, the drain of the third MOSFET Q5 is connected to the OVP pin of the current mode pulse width modulation control chip U1, and the gate of the third MOSFET Q5 is short-circuit protected capacitor C _SCP , short-circuit protection resistor R _{The SCP} and the third diode D3 are connected to the FB pin of the current mode pulse width modulation control chip U1. When the positive and negative terminals of the load are short-circuited, the voltage on the current output resistor RFB rises rapidly, and the signal of the voltage is sampled and short-circuited. The protection resistor R _SCP and the short-circuit protection capacitor C _SCP filter the obtained signal and drive the third MOSFET Q5. When the third MOSFET Q5 operates, thereby lowering the OVP level, the current mode pulse width modulation control chip U1 immediately turns off the GATE connection. foot. The entire system ceases to work, thus achieving the purpose of protection.

Referring to Figures 4a and 4b, the LED strings used for driving can be individually LED strings (as shown in Figure 4a) or single strings (as shown in Figure 4b). The single-string LED can directly achieve constant current and current regulation through the sampling circuit. Multi-string LED applications can first pass the adaptive discrete current sharing line, and the total current can be used to achieve current constant and current regulation through the sampling line of the scheme.

The DC-to-DC constant current driving circuit of the present invention, the two PWM signal inputs can respectively control the pulse width and amplitude of the output current, and can realize accurate current control. In addition, this circuit can effectively protect against abnormalities such as open circuit short circuit common in LED driving applications.

The present invention has been described above with reference to the specific embodiments of the present invention, but it will be understood by those skilled in the art that various modifications, combinations and changes may be made to the specific embodiments without departing from the scope of the appended claims. The spirit and scope of this creation. In addition, any signal arrows in the drawings should be considered as merely illustrative and not restrictive, unless otherwise specifically indicated. Combinations of elements or steps are also considered to have been described when the term is foreseen to be unclear.

1‧‧‧DC to DC switch circuit

2‧‧‧Output overvoltage protection circuit

3‧‧‧Constant current sampling control circuit

4‧‧‧Output current amplitude adjustment circuit

5‧‧‧Output current pulse width modulation circuit

6‧‧‧Load abnormal protection circuit

C1‧‧‧ input filter capacitor

C2‧‧‧Output voltage filter capacitor

C _CMP ‧‧‧compensating capacitor

C _DIM ‧‧‧luminance control capacitor

C _REF ‧‧‧Filter Capacitor

C _SCP ‧‧‧Short-circuit protection capacitor

C _VIN ‧‧‧Filter Capacitor

D1‧‧‧Boost diode

D2‧‧‧ second second polar body

D3‧‧‧ third diode

ENA‧‧‧Enable Signal Source

F1‧‧‧Fuse

L1‧‧‧Boost Inductance

Q1‧‧‧First Golden Oxygen Half Field Effect Crystal

Q2‧‧‧Second gold oxygen half field effect transistor

Q3‧‧‧First transistor

Q4‧‧‧Second transistor

Q5‧‧‧ Third Golden Oxygen Half Field Effect Crystal

R _CMP ‧‧‧compensation resistor

R _CS1 ‧‧‧first sampling resistor

R _CS2 ‧‧‧second sampling resistor

R _DIM ‧‧‧luminance control resistor

R _{DIM1 ‧‧‧First} brightness control resistor

R _{DIM2 ‧‧‧second} brightness control resistor

R _{DIM3 ‧‧‧3rd} brightness control resistor

R _{DIM4 ‧‧‧4th} brightness control resistor

RFB‧‧‧current output resistor

R _GATE1 ‧‧‧first gate resistor

R _GATE2 ‧‧‧second gate resistor

R _ISET ‧‧‧current amplitude adjustment resistor

R _{OVP1 ‧‧‧First} voltage divider resistor

R _{OVP2 ‧‧‧Second} voltage divider resistor

R _SCP ‧‧‧Short-circuit protection resistor

R _VIN1 ‧‧‧first input resistance

R _VIN2 ‧‧‧second input resistance

U1‧‧‧current mode pulse width modulation control chip

VIN‧‧‧ input voltage source

The present invention can be better understood from the following description of the specific embodiments of the present invention with reference to the accompanying drawings, wherein: FIG. 1 is a block diagram showing a first embodiment of a DC-to-DC constant current driving circuit according to the present embodiment. 2 is a block diagram showing a second embodiment of a DC-to-DC constant current driving circuit according to the present embodiment; FIG. 3 is a third embodiment of a DC-DC constant current driving circuit according to the present embodiment. A block diagram of an example; and Figures 4a and 4b show a multi-string or single-string LED load, respectively.

1‧‧‧DC to DC switch circuit

2‧‧‧Output overvoltage protection circuit

3‧‧‧Constant current sampling control circuit

4‧‧‧Output current amplitude adjustment circuit

5‧‧‧Output current pulse width modulation circuit

C1‧‧‧ input filter capacitor

C2‧‧‧Output voltage filter capacitor

C _CMP ‧‧‧compensating capacitor

C _DIM ‧‧‧luminance control capacitor

C _REF ‧‧‧Filter Capacitor

C _VIN ‧‧‧Filter Capacitor

D1‧‧‧Boost diode

D2‧‧‧ second second polar body

ENA‧‧‧Enable Signal Source

F1‧‧‧Fuse

L1‧‧‧Boost Inductance

Q1‧‧‧First Golden Oxygen Half Field Effect Crystal

Q2‧‧‧Second gold oxygen half field effect transistor

R _CMP ‧‧‧compensation resistor

R _CS1 ‧‧‧first sampling resistor

R _CS2 ‧‧‧second sampling resistor

R _DIM ‧‧‧luminance control resistor

RFB‧‧‧current output resistor

R _ISET ‧‧‧current amplitude adjustment resistor

R _{OVP1 ‧‧‧First} voltage divider resistor

R _OVP2 second voltage divider resistor

U1‧‧‧current mode pulse width modulation control chip

VIN‧‧‧ input voltage source

Claims (7)

A DC-to-DC constant current driving circuit comprises: a DC-DC switching circuit comprising a current mode pulse width modulation control chip, a boosting inductor, a boosting diode, a first gold oxide half field effect transistor, An output voltage filter capacitor and a first sampling resistor, one end of the boost inductor is connected to an input voltage source, and the other end is opposite to the drain of the first gold-oxygen half-effect transistor and the boost diode a positive pole is connected, a cathode of the boosting diode is connected to one end of the output voltage filter capacitor, and the other end of the output voltage filter capacitor is connected to the first sampling resistor, and the first sampling resistor is connected to the first gold oxide a source of the half field effect transistor; an output overvoltage protection line connected to the DC to DC switch line and a light emitting diode string, the output overvoltage protection line comprising a first voltage dividing resistor and a second point a voltage resistor, the first voltage dividing resistor and the second voltage dividing resistor are connected to the current mode pulse width modulation control chip; a constant current sampling control circuit, and the DC to DC switching circuit and the The light diode sampling control circuit comprises a brightness control resistor, a brightness control capacitor, a second gold oxide half field effect transistor and a current output resistor, the light emitting diode string and the second a drain connection of the MOSFET, the source of the second MOSFET is connected to the current output resistor, and is coupled to the current mode pulse width modulation control chip, the second MOSFET a gate of the transistor is connected to the brightness control resistor and the brightness control capacitor, and the brightness control resistor is connected to the current mode pulse width modulation control chip; an output current amplitude adjustment circuit includes a current amplitude adjustment resistor, an external The high frequency pulse width modulation signal is input to the current mode pulse width modulation control chip through the current amplitude adjustment resistor; and an output current pulse width modulation circuit includes a signal input resistance and an external low frequency pulse width modulation signal The current mode pulse width modulation control chip is connected through a signal input resistor. The DC-to-DC constant current driving circuit according to the first aspect of the invention, wherein the current mode pulse width modulation control chip comprises: a VIN pin, which is filtered by an input filter capacitor and a filter capacitor. The VIN pin is used to control the internal circuit of the current mode pulse width modulation control chip; a GATE pin is connected to the gate of the first metal oxide half field effect transistor and the constant current is taken a control circuit for controlling the switch of the first metal oxide half field effect transistor and for adjusting the output current pulse width; a GND pin, the current mode pulse width modulation controlling the reference ground of the chip; a CS pin, via a second sampling resistor is connected to the source of the first gold-oxygen field-effect transistor as the first gold-oxygen half-field transistor peak current sampling input pin; an ISET pin is connected to the output current amplitude adjusting circuit Inputting the high frequency pulse width modulation signal; a REF pin connected to a filter capacitor; an FB pin connected to the constant current sampling control circuit; a COMP pin connected to a compensation capacitor and a compensation resistor; An OVP pin, the first voltage dividing resistor connected to the output overvoltage protection line and the second voltage dividing resistor; and a DIM pin connected to the consistent energy source and the output current pulse width modulation circuit, The enable signal source is input to the DIM pin via a second diode and combined with the external low frequency pulse width modulation signal adjusted by the output current pulse width modulation circuit. The DC-to-DC constant current driving circuit according to claim 2, further comprising a load abnormal protection circuit connected to the FB pin of the current mode pulse width modulation control chip and the OVP a pin includes a third diode, a short circuit protection resistor, a short circuit protection capacitor, and a third gold oxide half field effect transistor, wherein the drain of the third gold oxide half field effect transistor is connected to the OVP pin The gate of the third gold-oxygen half-effect transistor is connected to the FB pin via the short-circuit protection capacitor, the short-circuit protection resistor, and the third diode. When the positive and negative terminals of the load are short-circuited, the current output resistor The voltage rises rapidly, and after sampling the signal of the voltage, the obtained signal is filtered and driven by the short-circuit protection resistor and the short-circuit protection capacitor, and the third gold-oxygen half-effect transistor operates. Thus, the OVP level is pulled low, and the current mode pulse width modulation control chip immediately turns off the GATE pin. The direct current to direct current constant current driving circuit of claim 1, wherein the light emitting diode string is a plurality of strings of LED loads or a single string of LED loads. A DC to DC constant current driving circuit includes: A DC-to-DC switching circuit includes a current mode pulse width modulation control chip, a boost inductor, a boost diode, a first gold oxide half field effect transistor, an output voltage filter capacitor, and a first sampling resistor One end of the boosting inductor is connected to an input voltage source, and the other end is connected to the drain of the first MOSFET and the anode of the boosting diode, and the cathode of the boosting diode is One end of the output voltage filter capacitor is connected, and the other end of the output voltage filter capacitor is connected to the first sampling resistor, the first sampling resistor is connected to the source of the first metal oxide half field effect transistor; an output overvoltage a protection circuit connected to the DC-to-DC switch circuit and a light-emitting diode lamp string, the output over-voltage protection circuit comprising a first voltage dividing resistor and a second voltage dividing resistor, the first voltage dividing resistor and the first a bipolar resistor is connected to the current mode pulse width modulation control chip; a constant current sampling control circuit is connected to the DC to DC switch line and the LED string, and the constant current sampling control circuit The invention comprises a second gold oxide half field effect transistor, a first transistor, a second transistor, a first brightness control resistor, a second brightness control resistor, a third brightness control resistor, and a fourth brightness control resistor. a first input resistor, a second input resistor, a first gate resistor, and a second gate resistor, the input voltage source being coupled to the collector of the first transistor via the first input resistor, an external low frequency pulse The wide modulation input signal is connected to the base of the first transistor via the first luminance control resistor via the signal input resistor, and the external low frequency pulse width modulation input signal is controlled by the first luminance after the signal is input to the resistor a resistor and the second luminance control resistor are coupled to the emitter of the first transistor, the input voltage source is coupled to the collector of the second transistor via the second input resistor, the input voltage source passing through the first input resistor And the third luminance control resistor is connected to the base of the second transistor, and the input voltage source is connected to the second power via the first input resistor, the third luminance control resistor and the fourth luminance control resistor The emitter of the body, the collector of the second transistor is connected to the gate of the second MOS field via the first gate resistor, and the collector of the second transistor is via the first thyristor and The second gate resistor is connected to the source of the second metal oxide half field effect transistor, and the drain of the second gold oxide half field effect transistor is connected to an external light emitting diode string, and the current output resistor is connected to The current mode pulse width modulation control chip; an output current amplitude adjustment circuit comprising a current amplitude adjustment resistor, an external high frequency pulse width modulation signal is input to the current mode pulse width modulation control chip via the current amplitude adjustment resistor And an output current pulse width modulation circuit including a signal input resistance, an external low frequency pulse width modulation The signal is coupled to the current mode pulse width modulation control chip via a signal input resistor. The DC-to-DC constant current driving circuit according to claim 5, wherein the current mode pulse width modulation control chip comprises: a VIN pin, which is filtered by an input filter capacitor and a filter capacitor. The VIN pin is used for power supply of the current mode pulse width modulation control chip; a GATE pin is connected to the gate of the first metal oxide half field effect transistor and the constant current sampling control circuit to control the first a gold oxide half field effect transistor switch for adjusting the output current pulse width; a GND pin, the current mode pulse width modulation control chip reference ground; a CS pin connected to the second sampling resistor a source of the first gold-oxygen half-field effect transistor, as the first gold-oxygen half-field effect transistor peak current sampling input pin; an ISET pin connected to the output current amplitude adjustment circuit, inputting the high-frequency pulse width modulation a signal; a REF pin, connected to a filter capacitor; a FB pin, connected to the constant current sampling control circuit; a COMP pin, connected to a compensation capacitor and a compensation resistor; an OVP pin, connected to the output The first voltage dividing resistor of the voltage protection circuit and the second voltage dividing resistor; and a DIM pin connected to the uniform energy signal source and the output current pulse width modulation circuit, the enabling signal source passing through a second The diode is coupled to the DIM pin by the external low frequency pulse width modulation signal adjusted by the output current pulse width modulation circuit. The DC-to-DC constant current driving circuit according to claim 5, wherein the LED strings are respectively a plurality of LED loads or a single string LED load.