Constant current driving circuit and switching power supply

Abstract

The invention provides a constant-current driving circuit and a switching power supply. The constant-current driving circuit comprises a constant-current driving module and a protection module, one end of the constant current driving module is connected with a power supply module of the switching power supply, and the other end of the constant current driving module is connected with a load module; the protection module is connected with the constant current driving module, and a controlled end and a detection end of the protection module are connected with a control module of the switching power supply. The constant current driving circuit not only can provide constant current for the load module, but also is low in cost, and can protect the constant current driving module.

Description

Technical Field

[0001] This invention relates to the field of constant current drive technology, specifically to a constant current drive circuit and a switching power supply. Background Technology

[0002] With the popularization of new energy vehicles, various application products on these vehicles have also developed. Currently, most new energy vehicles have a wide voltage output of 9-16V, while many loads require constant current output, necessitating the construction of additional constant current circuits. The current method for building constant current circuits mainly involves using constant current chips to achieve constant current drive; however, constant current chips are typically expensive, increasing circuit costs. Summary of the Invention

[0003] This invention provides a constant current driving circuit, which aims to solve the problem of high cost of current constant current circuits.

[0004] In a first aspect, the present invention provides a constant current driving circuit, which includes a constant current driving module and a protection module; one end of the constant current driving module is connected to the power supply module of the switching power supply, and the other end of the constant current driving module is connected to the load module; the protection module is connected to the constant current driving module, and both the controlled end and the detection end of the protection module are connected to the control module of the switching power supply.

[0005] Furthermore, the constant current drive module includes a first switching transistor and a second switching transistor; the controlled terminal and the first terminal of the first switching transistor are both connected to the power supply module, and the second terminal of the first switching transistor is connected to the protection module; the controlled terminal of the second switching transistor is connected to the protection module, the first terminal of the second switching transistor is connected to the power supply module, and the second terminal of the second switching transistor is connected to the load module.

[0006] Furthermore, the constant current drive module also includes a first resistor; one end of the first resistor is connected to the power supply module, and the other end of the first resistor is connected to the first terminal of the second switching transistor.

[0007] Furthermore, the constant current drive module also includes a second resistor; one end of the second resistor is connected to the second terminal of the second switching transistor, and the other end of the second resistor is connected to the protection module and the load module respectively.

[0008] Furthermore, both the first and second switching transistors are bipolar transistors; the base and emitter of the first switching transistor are connected to the power supply module, the collector of the first switching transistor and the base of the second switching transistor are connected to the protection module, the emitter of the second switching transistor is connected to the power supply module, and the collector of the second switching transistor is connected to the load module.

[0009] Furthermore, the protection module includes a third switching transistor and a voltage divider circuit; the controlled terminal of the third switching transistor is connected to the control module, the first terminal of the third switching transistor is grounded, and the second terminal of the third switching transistor is connected to the second terminal of the first switching transistor and the controlled terminal of the second switching transistor respectively; one end of the voltage divider circuit is connected to the control module, and the other end of the voltage divider circuit is connected to the second terminal of the second switching transistor.

[0010] Furthermore, the voltage divider circuit includes a third resistor and a fourth resistor; one end of the third resistor is connected to the second terminal of the second switching transistor, the other end of the third resistor is connected to one end of the fourth resistor and the control module, and the other end of the fourth resistor is grounded.

[0011] Furthermore, the voltage divider circuit also includes a first capacitor, a first diode, and a second diode; one end of the first capacitor, the negative terminal of the first diode, and the positive terminal of the second diode are all connected to the third resistor, the other end of the first capacitor and the positive terminal of the second diode are both grounded, and the negative terminal of the second diode is connected to the power supply terminal.

[0012] Furthermore, the protection module also includes a fifth resistor, a sixth resistor, and a seventh resistor; one end of the fifth resistor is connected to the load of the load module, and the other end of the fifth resistor is connected to the power supply interface of the load module; one end of the sixth resistor is connected to the control module, and the other end of the sixth resistor is connected to the controlled electrode of the third switching transistor and one end of the seventh resistor, respectively, and the other end of the seventh resistor is grounded.

[0013] In a second aspect, the present invention also provides a switching power supply, the switching power supply including a power supply module, a control module, and the constant current drive circuit described in any of the above.

[0014] The present invention discloses a switching power supply including a power supply module, a control module, and a constant current drive circuit. The constant current drive circuit includes a constant current drive module and a protection module. The constant current drive module can provide a constant current to the load module, and the protection module can protect the constant current drive module when the circuit fails. Thus, while providing a constant current to the load module through the hardware circuit, the constant current drive module can also be protected, which not only reduces costs but also improves safety. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a block diagram of a constant current driving circuit provided in an embodiment of the present invention;

[0017] Figure 2 This is a circuit diagram of a constant current driving circuit provided in an embodiment of the present invention;

[0018] Figure 3 This is a partial circuit of a constant current drive module provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be understood that, when used in this specification and the appended claims, the terms “comprising” and “including” indicate the presence of the described features, integrals, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, operations, elements, components and / or collections thereof.

[0021] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0022] Furthermore, the directional terms used in this invention, such as "up," "down," "front," "back," "left," "right," "inner," "outer," and "side," are merely for reference to the accompanying drawings and the product's usage state. Therefore, the directional terms used are for illustrating and understanding this invention, and not for limiting it. Additionally, in the accompanying drawings, structures that are similar or identical are indicated by the same reference numerals.

[0023] See Figures 1 to 3 , Figure 1 This is a block diagram of a constant current driving circuit 100 provided in an embodiment of the present invention; Figure 2 This is a circuit diagram of a constant current drive circuit 100 provided in an embodiment of the present invention; Figure 3This is a partial circuit of the constant current drive module 10 provided in an embodiment of the present invention. For example... Figures 1 to 3 As shown, the constant current drive circuit 100 includes a constant current drive module 10 and a protection module 20; one end of the constant current drive module 10 is connected to the power supply module 200 of the switching power supply, and the other end of the constant current drive module 10 is connected to the load module 400; the protection module 20 is connected to the constant current drive module 10, and both the controlled end and the detection end of the protection module 20 are connected to the control module 300 of the switching power supply.

[0024] Specifically, the switching power supply may include a control module 300, a power supply module 200, and a constant current drive circuit 100. The constant current drive circuit 100 may include a constant current drive module 10 and a protection module 20. The constant current drive module 10 is connected to the power supply module 200 and the load module 400, respectively, and the protection module 20 is connected to the constant current drive module 10 and the control module 300, respectively.

[0025] The control module 300 may include an MCU for controlling the start and stop of the protection module 20 to protect the constant current drive module 10. For example, when a short circuit occurs in the circuit, the control module 300 controls the short-circuit module to conduct, so as to avoid damage to the constant current drive module 10.

[0026] The power supply module 200 provides the power supply voltage to the constant current drive module 10, such as 9-15V. The constant current drive module 10 is used to achieve constant current output, providing a constant current to the load module 400. The protection module 20 is mainly used for short-circuit protection and open-circuit detection. That is, when a short-circuit fault occurs in the circuit, it can prevent damage to the constant current drive module 10, and it can also detect whether there is an open-circuit fault in the circuit, so that the control module 300 can confirm the fault type.

[0027] In actual use, if the circuit is normal, the power supply module 200 supplies power to the load module 400 through the constant current drive module 10, which provides a constant current. If a circuit fault occurs, the protection module 20 can detect whether the fault is a short circuit or an open circuit and feeds the result back to the control module 300. When the fault is a short circuit, the protection module 20 is activated, thereby preventing damage to the constant current drive module 10.

[0028] In a further embodiment, the constant current drive module 10 includes a first switching transistor Q1 and a second switching transistor Q2; the controlled terminal and the first terminal of the first switching transistor Q1 are both connected to the power supply module 200, and the second terminal of the first switching transistor Q1 is connected to the protection module 20; the controlled terminal of the second switching transistor Q2 is connected to the protection module 20, the first terminal of the second switching transistor Q2 is connected to the power supply module 200, and the second terminal of the second switching transistor Q2 is connected to the load module 400. Further, the constant current drive module 10 also includes a first resistor R1; one end of the first resistor R1 is connected to the power supply module 200, and the other end of the first resistor R1 is connected to the first terminal of the second switching transistor Q2. Further, the constant current drive module 10 also includes a second resistor R2; one end of the second resistor R2 is connected to the second terminal of the second switching transistor Q2, and the other end of the second resistor R2 is connected to both the protection module 20 and the load module 400. Furthermore, both the first switch Q1 and the second switch Q2 are transistors; the base and emitter of the first switch Q1 are connected to the power supply module 200, the collector of the first switch Q1 and the base of the second switch Q2 are connected to the protection module 20, the emitter of the second switch Q2 is connected to the power supply module 200, and the collector of the second switch Q2 is connected to the load module 400.

[0029] In this configuration, both the first switching transistor Q1 and the second switching transistor Q2 can be transistors. The base and emitter of the first switching transistor Q1 are connected to the power supply module 200, the collector of the first switching transistor Q1 and the base of the second switching transistor Q2 are connected to the protection module 20, the emitter of the second switching transistor Q2 is connected to the power supply module 200, and the collector of the second switching transistor Q2 is connected to the load module 400.

[0030] The first switching transistor Q1 is a constant current transistor switch. Utilizing its Vbe = 0.7V characteristic, it provides a control signal to the second switching transistor Q2, achieving constant current regulation. The second switching transistor Q2 is a constant current power switching transistor, acting as the main power switch, maintaining a stable load current under the control of the first switching transistor Q1. The first resistor R1 is the constant current setting resistor; the magnitude of the constant current can be adjusted by changing the resistance value of R1. The second resistor R2 is a short-circuit protection power distribution resistor, which shares some of the heat generated during a short circuit, preventing other components from being damaged by overheating.

[0031] When the circuit is powered on (power supply VCC is 9-16VDC): the emitter of the first switching transistor Q1 is stabilized at 0.7V due to the presence of the first resistor R1. At this time, the current flowing through the first resistor R1 is fixed at 70mA (determined by the resistance value of the first resistor R1). This current, through the control of the first switching transistor Q1, keeps the collector-emitter of the second switching transistor Q2 in a stable conducting state, ensuring that the current output to the load is always equal to the current flowing through the first resistor R1 (70mA). Even if the power supply voltage fluctuates within the range of 9-16V, or the voltage drop of the load changes slightly, the first switching transistor Q1 and the second switching transistor Q2 will adjust their conduction level to maintain the current flowing through the load at a constant 70mA, thereby achieving constant current drive.

[0032] As a further embodiment, the protection module 20 includes a third switch Q3 and a voltage divider circuit 21; the controlled terminal of the third switch Q3 is connected to the control module 300, the first terminal of the third switch Q3 is grounded, and the second terminal of the third switch Q3 is connected to the second terminal of the first switch Q1 and the controlled terminal of the second switch Q2 respectively; one end of the voltage divider circuit 21 is connected to the control module 300, and the other end of the voltage divider circuit 21 is connected to the second terminal of the second switch Q2.

[0033] In this configuration, the third switch Q3 can be a transistor. In this case, the base of the third switch Q3 is connected to the control module 300, the collector of the third switch Q3 is connected to the collector of the first switch Q1 and the base of the second switch Q2, and the emitter of the third switch Q3 is grounded. If the third switch Q3 is a load switching transistor, such as... Figure 2 As shown, the third switch Q3 is controlled by the LAMP1 signal output by the control module 300. When a short circuit occurs, it receives the LAMP1 signal and disconnects the load to achieve circuit protection.

[0034] One end of the voltage divider circuit 21 is connected to the collector of the second switching transistor Q2, and the other end of the voltage divider circuit 21 is connected to the control module 300, such as... Figure 2 As shown, the voltage divider circuit 21 is connected to the AD port of the control module 300 to output a detection signal to the AD port, so that the control module 300 can confirm the circuit status. For example, when the load terminal voltage is detected to be 0, the voltage detected by the AD port is also 0, and the control module 300 can confirm that there is a short circuit in the circuit and output the LAMP1 signal to control the third switch Q3 to turn on. When no voltage drop is detected at the load terminal, the voltage detected by the AD port is the voltage of the power supply module 200, and the control module 300 can confirm that there is an open circuit in the circuit.

[0035] As a further embodiment, the voltage divider circuit 21 includes a third resistor R3 and a fourth resistor R4; one end of the third resistor R3 is connected to the second terminal of the second switch Q2, the other end of the third resistor R3 is connected to one end of the fourth resistor R4 and to the control module 300, and the other end of the fourth resistor R4 is grounded.

[0036] One end of the third resistor R3 is connected to the collector of the second diode D2, and the other end of the third resistor R3 is connected to the fourth resistor R4 and the control module 300 respectively. The other end of the fourth resistor R4 is grounded. The third resistor R3 and the fourth resistor R4 are short-circuit / open-circuit voltage detection voltage divider resistors. The load status is determined by detecting the voltage value (AD=0V when short-circuited, AD=VCC when open-circuited).

[0037] In actual operation, the third resistor R3 and the fourth resistor R4 form a voltage divider circuit 21, which is connected to the AD detection port. When the load is short-circuited, the voltage at the load terminal is 0V, and the voltage detected by the AD is also 0V, thus determining the short-circuit state. When the AD detects 0V (short-circuit signal), it sends the LAMP1 signal, turns off the third switch Q3, cuts off the load circuit, terminates power consumption under the short-circuit state, and completely protects the circuit.

[0038] As a further embodiment, the voltage divider circuit 21 further includes a first capacitor C1, a first diode D1, and a second diode D2; one end of the first capacitor C1, the cathode of the first diode D1, and the anode of the second diode D2 are all connected to the third resistor R3, the other end of the first capacitor C1 and the anode of the second diode D2 are both grounded, and the cathode of the second diode D2 is connected to the power supply terminal.

[0039] In this configuration, the first diode D1 and the second diode D2 are connected in reverse series to achieve bidirectional clamping protection. When the AD detection voltage exceeds 5V (e.g., due to power surges or transient voltage spikes in the circuit), the second diode D2 conducts in the forward direction, clamping the AD voltage within 5V + diode voltage drop to prevent damage to the ADC interface of the control module 300 due to overvoltage. When the AD detection voltage is below 0V (e.g., due to transient reverse voltage from the load), the first diode D1 conducts in the forward direction, clamping the AD voltage above 0V - diode voltage drop to prevent damage to the ADC interface of the control module 300 due to reverse voltage.

[0040] The first capacitor C1 and the voltage divider circuit 21 form a low-pass filter circuit to filter out high-frequency noise. Power supply ripple (9-16V fluctuation of VCC), electromagnetic interference (EMI), and transient changes in the circuit can cause high-frequency fluctuations in the AD detection voltage. The first capacitor C1 presents a low impedance to high-frequency signals, bypassing the high-frequency noise of the AD to ground and allowing only the slowly changing DC voltage (the steady-state voltage used for open / short circuit judgment) to pass through, making the ADC sampling more stable and avoiding misjudgment of the load state due to noise (such as false open / short circuit reports).

[0041] As a further embodiment, there are a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; one end of the fifth resistor R5 is connected to the load of the load module 400, and the other end of the fifth resistor R5 is connected to the power supply interface of the load module 400; one end of the sixth resistor R6 is connected to the control module 300, and the other end of the sixth resistor R6 is connected to the controlled electrode of the third switch Q3 and one end of the seventh resistor R7, and the other end of the seventh resistor R7 is grounded.

[0042] Among them, such as Figure 3 As shown, Figure 3 One end of the fifth resistor R5 is connected to the load module 400, and the other end is connected to the power supply interface. The fifth resistor R5 is a power distribution resistor, which shares power during a short circuit to prevent damage to components. When a short circuit occurs in the load, the circuit still maintains a constant current of 70mA. At this time, the excess power generated by the short circuit is shared by the second resistor R2, the fifth resistor R5, and the third switch Q3, thus preventing damage to a single component due to overheating. The sixth resistor R6 is connected in series between the control module 300 and the base of the third switch Q3 to protect the third switch Q3, and the seventh resistor R7 is used to stabilize the current of the third switch Q3.

[0043] When the circuit is in normal constant current operation, assuming VCC is 13.5V and the target constant current is 70mA, the resistance of the first resistor R1 is 10Ω. The first switching transistor Q1, utilizing the characteristic of Vbe = 0.7V, stabilizes the base voltage of the second switching transistor Q2, enabling Q2 to continuously output a 70mA current to the load module 400. The third resistor R3 and the fourth resistor R4 transmit the voltage across the load module 400 to the AD detection port, and the control module 300 confirms that the circuit is working normally.

[0044] If a short circuit occurs in the load module 400, the first resistor R1, the first switch Q1, and the second switch Q2 will still maintain a 70mA current output. During a short circuit, the voltage drop of the load module 400 is approximately 0V, and the excess power is shared by the fifth resistor R5, the second resistor R2, and the third switch Q3 to prevent damage to a single component. The AD detection port detects a voltage of approximately 0V through the third resistor R3 and the fourth resistor R4; the control module 300 outputs the LAMP1 signal to the third switch Q3, controlling the third switch Q3 to disconnect, cutting off the power supply circuit of the load module 400, terminating the short circuit state, and achieving protection.

[0045] If an open circuit fault occurs, there will be no current in the circuit, and there will be no voltage drop across the fifth resistor R5 and the second resistor R2. The voltage across the parent and child modules will be approximately VCC. The third resistor R3 and the fourth resistor R4 will transmit this voltage to the AD detection port. If the detected voltage is VCC, the control module 300 will determine that the load is open. It can trigger a prompt (such as an indicator light alarm) or keep the third switch Q3 in the open state to avoid invalid power supply.

[0046] The present invention also provides a switching power supply, the switching power supply including a power supply module 200, a control module 300, and a constant current drive circuit 100 as described in any of the above embodiments. The constant current drive circuit 100 includes a constant current drive module 10 and a protection module 20; one end of the constant current drive module 10 is connected to the power supply module 200 of the switching power supply, and the other end of the constant current drive module 10 is connected to a load module 400; the protection module 20 is connected to the constant current drive module 10, and both the controlled end and the detection end of the protection module 20 are connected to the control module 300 of the switching power supply.

[0047] Specifically, the switching power supply may include a control module 300, a power supply module 200, and a constant current drive circuit 100. The constant current drive circuit 100 may include a constant current drive module 10 and a protection module 20. The constant current drive module 10 is connected to the power supply module 200 and the load module 400, respectively, and the protection module 20 is connected to the constant current drive module 10 and the control module 300, respectively.

[0048] The control module 300 may include an MCU for controlling the start and stop of the protection module 20 to protect the constant current drive module 10. For example, when a short circuit occurs in the circuit, the control module 300 controls the short-circuit module to conduct, so as to avoid damage to the constant current drive module 10.

[0049] The power supply module 200 provides the power supply voltage to the constant current drive module 10, such as 9-15V. The constant current drive module 10 is used to achieve constant current output, providing a constant current to the load module 400. The protection module 20 is mainly used for short-circuit protection and open-circuit detection. That is, when a short-circuit fault occurs in the circuit, it can prevent damage to the constant current drive module 10, and it can also detect whether there is an open-circuit fault in the circuit, so that the control module 300 can confirm the fault type.

[0050] In actual use, if the circuit is normal, the power supply module 200 supplies power to the load module 400 through the constant current drive module 10, which provides a constant current. If a circuit fault occurs, the protection module 20 can detect whether the fault is a short circuit or an open circuit and feeds the result back to the control module 300. When the fault is a short circuit, the protection module 20 is activated, thereby preventing damage to the constant current drive module 10.

[0051] The constant current drive module disclosed in this invention can provide a constant current to the load module, and the protection module can protect the constant current drive module when the circuit fails. Thus, while providing a constant current to the load module through the hardware circuit, the constant current drive module can also be protected, which not only reduces costs but also improves safety.

[0052] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A constant current drive circuit, characterized in that, Applications in switching power supplies, including: A constant current drive module, one end of which is connected to the power supply module of the switching power supply, and the other end of which is connected to the load module; A protection module is provided, which is connected to the constant current drive module, and both the controlled end and the detection end of the protection module are connected to the control module of the switching power supply.

2. The constant current drive circuit as described in claim 1, characterized in that, The constant current drive module includes a first switching transistor and a second switching transistor; The controlled terminal and the first terminal of the first switching transistor are both connected to the power supply module, and the second terminal of the first switching transistor is connected to the protection module; The controlled terminal of the second switching transistor is connected to the protection module, the first terminal of the second switching transistor is connected to the power supply module, and the second terminal of the second switching module is connected to the load module.

3. The constant current drive circuit as described in claim 2, characterized in that, The constant current drive module also includes a first resistor; One end of the first resistor is connected to the power supply module, and the other end of the first resistor is connected to the first terminal of the second switching transistor.

4. The constant current drive circuit as described in claim 3, characterized in that, The constant current drive module also includes a second resistor; One end of the second resistor is connected to the second terminal of the second switching transistor, and the other end of the second resistor is connected to the protection module and the load module respectively.

5. The constant current drive circuit as described in claim 2, characterized in that, Both the first switching transistor and the second switching transistor are bipolar transistors; The base and emitter of the first switching transistor are both connected to the power supply module, the collector of the first switching transistor and the base of the second switching transistor are both connected to the protection module, the emitter of the second switching transistor is connected to the power supply module, and the collector of the second switching transistor is connected to the load module.

6. The constant current drive circuit as described in claim 2, characterized in that, The protection module includes a third switching transistor and a voltage divider circuit; The controlled terminal of the third switch is connected to the control module, the first terminal of the third switch is grounded, and the second terminal of the third switch is connected to the second terminal of the first switch and the controlled terminal of the second switch, respectively. One end of the voltage divider circuit is connected to the control module, and the other end of the voltage divider circuit is connected to the second terminal of the second switching transistor.

7. The constant current drive circuit as described in claim 6, characterized in that, The voltage divider circuit includes a third resistor and a fourth resistor; One end of the third resistor is connected to the second terminal of the second switching transistor, and the other end of the third resistor is connected to one end of the fourth resistor and the control module, respectively. The other end of the fourth resistor is grounded.

8. The constant current drive circuit as described in claim 7, characterized in that, The voltage divider circuit also includes a first capacitor, a first diode, and a second diode; One end of the first capacitor, the cathode of the first diode, and the anode of the second diode are all connected to the third resistor. The other end of the first capacitor and the anode of the second diode are both grounded, and the cathode of the second diode is connected to the power supply terminal.

9. The constant current drive circuit as described in claim 6, characterized in that, The protection module also includes a fifth resistor, a sixth resistor, and a seventh resistor; One end of the fifth resistor is connected to the load of the load module, and the other end of the fifth resistor is connected to the power supply interface of the load module. One end of the sixth resistor is connected to the control module, and the other end of the sixth resistor is connected to the controlled electrode of the third switch and one end of the seventh resistor, respectively. The other end of the seventh resistor is grounded.

10. A switching power supply, characterized in that, The switching power supply includes a power supply module, a control module, and a constant current drive circuit as described in any one of claims 1-9.

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