A DC converter and its power supply

Abstract

The present application provides a DC converter and its power supply. The power supply includes: a low-voltage power supply; the input end of the low-voltage power supply receives the output voltage of the DC converter; the output end of the low-voltage power supply serves as the low-voltage output end of the power supply; the low-voltage power supply includes: a first clamping diode, a current source, and a second switching tube; when the output voltage is greater than the first preset output voltage, the first clamping diode breaks down reversely so that the power supply voltage of the low-voltage power supply is the difference between the output voltage and the first preset voltage; wherein, the first preset voltage is the difference between the breakdown voltage of the first clamping diode and the threshold voltage of the first switching tube; the power supply of the DC converter uses fewer components, and the control of the power supply voltage to be the first preset voltage can be achieved by the reverse breakdown of the clamping diode, and the design difficulty is relatively small.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic circuits, and more specifically, particularly relates to a DC converter and its power supply. Background Art

[0002] In a process where the maximum withstand voltage of the VGS of a MOS (Metal-Oxide-Semiconductor Field-Effect Transistor) device is 5V, when the DC-DC converter outputs a voltage higher than 5V, the driving part of the PMOS transistor needs a voltage lower than the output voltage, that is, a voltage not exceeding 5V, otherwise it will exceed the withstand voltage of the MOS transistor and damage the device.

[0003] In the synchronous BOOST architecture of the DC-DC converter, the power PMOS transistor usually uses a voltage value equal to the output voltage to turn off the PMOS transistor during the switching process, and a 0V voltage value to turn on the PMOS transistor. However, under a specific process, the maximum VGS voltage value of the NMOS and PMOS transistors can only reach 5V. When the output voltage of the BOOST needs to reach more than 5V, when the PMOS transistor is turned on, if it is still turned on with a 0V voltage, the VGS voltage of the PMOS transistor will exceed 5V and damage the device. Therefore, in the case of high-voltage output, it is usually necessary to perform some processing on the voltage value of the PMOS transistor turn-on voltage to ensure that the VGS of the PMOS transistor does not exceed 5V. If no processing is done, a process with higher withstand voltage needs to be replaced, increasing the cost.

[0004] The prior art uses an LDO (low dropout regulator) circuit to generate the supply voltage, and thus inevitably involves the design of the LDO circuit; and the LDO circuit itself is relatively complex and involves problems such as compensation, with a relatively large design difficulty. Summary of the Invention

[0005] In view of this, an object of the present invention is to provide a DC converter and its power supply, which can achieve controlling the supply voltage to a first preset voltage by clamping through the reverse breakdown of a diode, with relatively small design difficulty.

[0006] The present invention discloses a power supply for a DC converter in a first aspect, including: a low-voltage power supply;

[0007] The input end of the low-voltage power supply receives the output voltage of the DC converter;

[0008] The output end of the low-voltage power supply serves as the low-voltage output end of the power supply;

[0009] The low-voltage power supply includes: a first clamping diode, a current source, a second switching transistor;

[0010] When the output voltage is greater than the first preset output voltage, the first clamping diode breaks down reversely, so that the power supply voltage of the low-voltage power supply is the difference between the output voltage and the first preset voltage; wherein, the first preset voltage is the difference between the breakdown voltage of the first clamping diode and the threshold voltage of the first switching transistor.

[0011] Optionally, when the output voltage is less than the first preset output voltage, the first clamping diode is turned off, so that the power supply voltage of the low-voltage power supply is the second preset voltage; wherein, the second preset voltage is less than the first preset voltage.

[0012] Optionally, the cathode of the first clamping diode is connected to the output end of the DC converter to receive the output voltage of the DC converter;

[0013] The anode of the first clamping diode is respectively connected to one end of the current source and the control end of the first switching transistor;

[0014] The other end of the current source and the first end of the first switching transistor are grounded;

[0015] The second end of the first switching transistor serves as the output end of the low-voltage power supply.

[0016] Optionally, the first switching transistor is a PMOS transistor;

[0017] The first end of the first switching transistor is the drain of the PMOS transistor;

[0018] The second end of the first switching transistor is the source of the PMOS transistor;

[0019] The control end of the first switching transistor is the gate of the PMOS transistor.

[0020] Optionally, further comprising: a high-voltage power supply;

[0021] The input end of the high-voltage power supply receives the output voltage of the DC converter;

[0022] The output end of the high-voltage power supply serves as the high-voltage output end of the power supply.

[0023] Optionally, the high-voltage power supply includes: a current-limiting resistor, a second clamping diode, and a second switching transistor;

[0024] When the output voltage is higher than the second preset output voltage, the second clamping diode breaks down reversely, so that the power supply voltage of the high-voltage power supply is the third preset voltage; wherein, the third preset voltage is the difference between the breakdown voltage of the second clamping diode and the threshold voltage of the second switching transistor.

[0025] Optionally, when the output voltage is lower than a second preset output voltage, the second clamping diode is turned off, so that the supply voltage of the high-voltage power supply is a fourth preset voltage.

[0026] Optionally, one end of the current-limiting resistor is connected to the first end of the second switching tube, and the connection point is connected to the output end of the DC converter to receive the output voltage of the DC converter;

[0027] The other end of the current-limiting resistor is respectively connected to the cathode of the second clamping diode and the control end of the second switching tube;

[0028] The anode of the second clamping diode is grounded;

[0029] The second end of the second switching tube serves as the output end of the high-voltage power supply.

[0030] Optionally, the second switching tube is an NMOS tube;

[0031] The first end of the second switching tube is the drain of the NMOS tube;

[0032] The second end of the second switching tube is the source of the NMOS tube;

[0033] The control end of the second switching tube is the gate of the NMOS tube.

[0034] A second aspect of the present invention discloses a DC converter, including: a DC conversion unit and a power supply as described in any one of the first aspects of the present invention;

[0035] The power supply is used to provide a supply voltage for the corresponding switching tube in the DC conversion unit.

[0036] As can be seen from the above technical solutions, a power supply for a DC converter provided by the present invention includes: a low-voltage power supply; the input end of the low-voltage power supply receives the output voltage of the DC converter; the output end of the low-voltage power supply serves as the low-voltage output end of the power supply and is connected to the PMOS tube; the low-voltage power supply includes: a first clamping diode, a current source, a second switching tube; when the output voltage is greater than a first preset output voltage, the first clamping diode is reversely broken down, so that the supply voltage of the low-voltage power supply is the difference between the output voltage and the first preset voltage; wherein, the first preset voltage is the difference between the breakdown voltage of the first clamping diode and the threshold voltage of the first switching tube; that is to say, the first preset voltage has nothing to do with the input voltage of the DC converter, avoiding the problem of overvoltage damage of the switching tube in the DC converter when the input voltage of the DC converter is too high; at the same time, the power supply of the DC converter uses fewer devices, and the supply voltage can be controlled to be the first preset voltage by reverse breakdown of the diode, and the design difficulty is small. Description of the Drawings

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on the provided drawings.

[0038] Figure 1 is a schematic diagram of a power supply for a DC converter provided by an embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of another power supply for a DC converter provided by an embodiment of the present invention;

[0040] Figure 3 is a schematic diagram of another power supply for a DC converter provided by an embodiment of the present invention;

[0041] Figure 4 is a schematic diagram of a DC converter and its power supply provided by an embodiment of the present invention. Detailed implementation manners

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0043] In this application, the term "comprising", "including", or any other variant thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0044] The embodiment of the present invention provides a power supply for a DC converter, which is used to solve the problem that in the prior art, an LDO circuit is used to generate the power supply voltage, and thus the design of the LDO circuit is inevitably involved; while the LDO circuit itself is relatively complex and involves compensation, and the design difficulty is relatively large.

[0045] See Figures 1 - 4 , the power supply for the DC converter includes: a low-voltage power supply 10.

[0046] The input terminal of the low-voltage power supply 10 is connected to the output terminal of the DC converter to receive the output voltage VO of the DC converter.

[0047] The output terminal of the low-voltage power supply 10 is used as the low-voltage output terminal of the power supply and is connected to the control terminal of the PMOS transistor PM1 of the DC converter. That is to say, the PMOS transistor PM1 of the DC converter is driven by the low-voltage power supply 10 through a corresponding drive circuit.

[0048] Specifically, the low-voltage power supply 10 includes: a first clamping diode D1, a current source CS, and a second switching transistor Q2.

[0049] When the output voltage VO of the DC converter is greater than the first preset output voltage, the first clamping diode D1 breaks down reversely, so that the supply voltage GND_P of the low-voltage power supply 10 is the difference between the output voltage VO and the first preset voltage.

[0050] Wherein, the first preset voltage is the difference between the breakdown voltage of the first clamping diode D1 and the threshold voltage of the first switching transistor Q1.

[0051] It should be noted that the clamping diode is a diode that can limit voltage. The breakdown voltage of the clamping diode is generally 5.6V, and the threshold voltage of the switching transistor is generally 0.9V; that is, the first preset voltage is 5.6 - 0.9 = 4.7V; it is less than 5V, and thus the gate-source voltage VGS of the PMOS transistor PM1 of the DC converter will not exceed 5V.

[0052] In this embodiment, the first preset voltage is independent of the input voltage VIN of the DC converter, avoiding the problem of overvoltage damage of the switching transistor in the DC converter when the input voltage VIN of the DC converter is too high; at the same time, that is, the devices used in the power supply of the DC converter are less, and the supply voltage can be controlled to be the first preset voltage by the reverse breakdown of the clamping diode, with less design difficulty and a simple circuit.

[0053] In addition, when the output voltage VO of the DC converter is less than the first preset output voltage, the first clamping diode D1 is turned off, so that the supply voltage GND_P of the low-voltage power supply 10 is the second preset voltage.

[0054] Wherein, the second preset voltage is less than the first preset voltage.

[0055] That is to say, the supply voltage GND_P of the low-voltage power supply 10 will not exceed the first preset voltage, and the first preset voltage is not enough to cause overvoltage damage to the corresponding switching transistor; thus, the problem of overvoltage damage of the switching transistor in the DC converter when the input voltage VIN of the DC converter is too high is avoided, improving the stability of the DC converter.

[0056] In practical applications, refer to Figure 3 , the specific connection relationships of the components in the low-voltage power supply 10 are as follows:

[0057] The cathode of the first clamping diode D1 is connected to the output terminal of the DC converter to receive the output voltage VO of the DC converter; the anode of the first clamping diode D1 is respectively connected to one end of the current source CS and the control terminal of the first switching transistor Q1; the other end of the current source CS and the first end of the first switching transistor Q1 are grounded; the second end of the first switching transistor Q1 serves as the output terminal of the low-voltage power supply 10.

[0058] In practical applications, the first switching transistor Q1 can be a PMOS transistor.

[0059] Specifically, the first end of the first switching transistor Q1 is the drain of the PMOS transistor; the second end of the first switching transistor Q1 is the source of the PMOS transistor; the control terminal of the first switching transistor Q1 is the gate of the PMOS transistor.

[0060] That is to say, the output terminal of the DC converter is connected to the cathode of the first clamping diode D1, the anode of the first clamping diode D1 is respectively connected to one end of the current source CS and the gate of the PMOS transistor, the source of the PMOS transistor serves as the output terminal of the low-voltage power supply 10 to output the supply voltage GND_P; the other end of the current source CS and the drain of the PMOS transistor are grounded.

[0061] When the cathode potential of the first clamping diode D1 is greater than its anode potential and exceeds its reverse breakdown voltage, the first clamping diode D1 breaks down in the reverse direction, and the current flowing through the first clamping diode D1 is equal to the current of the current source CS. The voltage VZD1 of the first clamping diode is equal to VO - 5.6, and the threshold voltage VTHP of the PMOS transistor is about 0.9V, then the supply voltage GND_P is about VO - 5.6 + 0.9 = VO - 4.7V. Furthermore, the voltage difference between the output voltage VO and the supply voltage GND_P can be made less than 5V, that is, the gate-source voltage VGS of the PMOS transistor PM1 of the DC power supply is less than 5V.

[0062] When the cathode potential of the first clamping diode D1 is less than its anode potential or does not exceed its reverse breakdown low voltage, the first clamping diode D1 is cut off, and the gate of the PMOS transistor is equivalent to being directly grounded, and the generated supply voltage VDD_N is the threshold voltage VTHP of the PMOS transistor.

[0063] In practical applications, refer to Figure 1 , the power supply further includes: a high-voltage power supply 20.

[0064] The input terminal of the high-voltage power supply 20 is connected to the output terminal of the DC converter to receive the output voltage VO of the DC converter.

[0065] The output terminal of the high-voltage power supply 20 is connected to the control terminal of the switching tube of the NMOS tube in the DC converter as the high-voltage output terminal of the power supply.

[0066] Specifically, the high-voltage power supply 20 includes: a current-limiting resistor R, a second clamping diode D2, and a second switching tube Q2.

[0067] When the output voltage VO is higher than the second preset output voltage, the second clamping diode D2 breaks down reversely, so that the supply voltage VDD_N of the high-voltage power supply 20 is the third preset voltage; wherein, the third preset voltage is the difference between the breakdown voltage of the second clamping diode D2 and the threshold voltage of the second switching tube Q2.

[0068] It should be noted that the breakdown voltage of the clamping diode is generally 5.6V, and the threshold voltage of the switching tube is generally 0.9V; that is, the first preset voltage is 5.6 - 0.9 = 4.7V; it is less than 5V, and thus the supply voltage GND_P of the low-voltage power supply 10 will not exceed 5V.

[0069] When the output voltage VO is lower than the second preset output voltage, the second clamping diode D2 is turned off, so that the supply voltage VDD_N of the high-voltage power supply 20 is the fourth preset voltage.

[0070] In practical applications, referring to Figure 2 , the specific connection relationship of each device in the high-voltage power supply 20 is as follows:

[0071] One end of the current-limiting resistor R is connected to the first end of the second switching tube Q2, and the connection point is connected to the output terminal of the DC converter to receive the output voltage VO of the DC converter; the other end of the current-limiting resistor R is respectively connected to the cathode of the second clamping diode D2 and the control terminal of the second switching tube Q2; the anode of the second clamping diode D2 is grounded; the second end of the second switching tube Q2 is used as the output terminal of the high-voltage power supply 20 to output high voltage.

[0072] In practical applications, the second switching tube Q2 can be an NMOS tube.

[0073] Specifically, the first end of the second switching tube Q2 is the drain of the NMOS tube; the second end of the second switching tube Q2 is the source of the NMOS tube; the control terminal of the second switching tube Q2 is the gate of the NMOS tube.

[0074] That is to say, the output terminal of the DC converter is connected to the cathode of the second clamping diode D2 through the current-limiting resistor R, the cathode of the second clamping diode D2 is connected to the gate of the NMOS tube, the source of the NMOS tube is used as the output terminal of the high-voltage power supply 20 to output the supply voltage, and the drain of the NMOS tube is connected to the output terminal of the DC converter.

[0075] When the cathode potential of the second clamping diode D2 is greater than its anode potential and exceeds its reverse breakdown voltage, the second clamping diode D2 breaks down reversely. The voltage VZD2 across the two ends of the second clamping diode D2 remains unchanged, and the current flowing through the second clamping diode D2 is equal to (VO - VZD2) / R. By changing the magnitude of R, the current flowing through the diode can be changed to change the driving ability of the clamping diode. After the current passes through the NMOS transistor, its source voltage VDD_N remains unchanged. Using the reverse breakdown voltage of the second clamping diode D2 to be approximately 5.6V and the threshold voltage VTHN of the NMOS transistor to be approximately 0.9V, the generated supply voltage VDD_N is 5.6 - 0.9 = 4.7V. And this supply voltage does not change with the change of the input voltage VIN or the output voltage VO. When the input voltage VIN is less than 4.7V, the efficiency of the DC converter is relatively high.

[0076] When the cathode potential of the second clamping diode D2 is less than its anode potential or does not exceed its reverse breakdown low voltage, the second clamping diode D2 is cut off. The gate of the NMOS transistor is equivalent to being directly connected to the output terminal of the DC converter, that is, the output voltage VO of this DC conversion directly drives this NMOS transistor, and then the generated supply voltage VDD_N is VO - 0.9.

[0077] In practical applications, the relationship between the input voltage VIN and the output voltage VO of the DC converter is determined by the duty cycle D, where D = (VO - VIN) / VIN. The larger the gate-source voltage VGS of the NMOS transistor in the DC converter, the smaller its on-resistance RDSON and the higher the efficiency.

[0078] It should be noted that when the existing DC converter is a boost circuit, the power supply voltage of the driving circuit of the NMOS transistor can directly use the input voltage VIN of the DC power supply. If the input voltage VIN is directly used, the high potential of the NMOS transistor drive changes with the change of the input voltage VIN. When the input voltage VIN is low, such as when the input voltage VIN is less than 4.7V, the VGS voltage of the NMOS transistor is low, and the corresponding on-resistance of the NMOS transistor is large, which will reduce the efficiency of the DC converter.

[0079] In this embodiment, when the input voltage VIN is low, the supply voltage remains at 4.7V or the output voltage VO, and the output voltage VO is the voltage after boosting the input voltage VIN. Furthermore, the output voltage VO is larger, thereby improving the efficiency of the NMOS transistor in the DC converter.

[0080] Another embodiment of the present invention provides a DC converter, see Figure 4 including: a DC conversion unit (including such as Figure 4The L, NM1, and PM1 shown), the drive circuit, and the power supply provided in any of the above embodiments (including as shown in Figure 4 10 and 20 shown).

[0081] The power supply is used to provide a driving voltage for the corresponding switching tubes in the DC conversion unit through the drive circuit.

[0082] It should be noted that the power supply voltage provided by the power supply for the drive circuit is the same as the driving voltage provided by the drive circuit for the corresponding switching tubes. That is, by controlling the magnitude of the power supply voltage, the magnitude of the driving voltage is controlled, and the gate-source voltage of the switching tubes is within a preset range.

[0083] The DC conversion unit is a boost circuit. Of course, it is not excluded that the DC conversion unit is a buck circuit. When the DC conversion unit is a boost circuit, it includes: an inductor L, an NMOS transistor NM1, and a PMOS transistor PM1.

[0084] One end of the inductor L serves as the input end of the boost circuit to receive the input voltage.

[0085] The other end of the inductor L is respectively connected to the drain of the NMOS transistor NM1 and the drain of the PMOS transistor PM1; the source of the NMOS transistor NM1 is grounded; the source of the PMOS transistor PM1 serves as the output end of the boost circuit.

[0086] The gate of the NMOS transistor NM1 is connected to the output end of the high-voltage power supply 20 in the power supply, and the gate of the PMOS transistor PM1 is connected to the output end of the low-voltage power supply 10 in the power supply.

[0087] For the specific structure and principle of the power supply, please refer to the power supply provided in the above embodiments for details, and will not be elaborated here one by one, and all are within the protection scope of this application.

[0088] The features described in each embodiment in this specification can be replaced or combined with each other. For the same or similar parts between the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple. For the relevant parts, reference can be made to the partial description of the method embodiments. The systems and system embodiments described above are only illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative work.

[0089] Those skilled in the art may further realize that the units and algorithm steps of each example described in connection with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods for each specific application to implement the described functions, but such implementation should not be considered to exceed the scope of the present invention.

[0090] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power supply for a DC converter, characterized in that, Comprising: A low-voltage power supply; The input end of the low-voltage power supply receives the output voltage of the DC converter and is connected to the source electrode of the first PMOS transistor in the DC converter; The output end of the low-voltage power supply serves as the low-voltage output end of the power supply and is connected to the gate electrode of the first PMOS transistor; The low-voltage power supply includes: a first clamping diode, a current source, and a first switching transistor; The cathode of the first clamping diode serves as the input end of the low-voltage power supply; The anode of the first clamping diode is respectively connected to one end of the current source and the control end of the first switching transistor; The other end of the current source and the first end of the first switching transistor are grounded; The second end of the first switching transistor serves as the output end of the low-voltage power supply; When the output voltage is greater than the first preset output voltage, the first clamping diode breaks down reversely, so that the supply voltage of the low-voltage power supply is the difference between the output voltage and the first preset voltage; wherein, the first preset voltage is the difference between the breakdown voltage of the first clamping diode and the threshold voltage of the first switching transistor.

2. The power supply for the DC converter according to claim 1, characterized in that When the output voltage is less than the first preset output voltage, the first clamping diode is cut off, so that the supply voltage of the low-voltage power supply is the second preset voltage; wherein, the second preset voltage is less than the first preset voltage.

3. The power supply for the DC converter according to claim 1, characterized in that, The first switching transistor is a PMOS transistor; The first end of the first switching transistor is the drain electrode of the PMOS transistor; The second end of the first switching transistor is the source electrode of the PMOS transistor; The control end of the first switching transistor is the gate electrode of the PMOS transistor.

4. The power supply for the DC converter according to claim 1, characterized in that, Further comprising: A high-voltage power supply; The input end of the high-voltage power supply receives the output voltage of the DC converter; The output end of the high-voltage power supply serves as the high-voltage output end of the power supply.

5. The power supply for the DC converter according to claim 4, characterized in that, The high-voltage power supply includes: a current-limiting resistor, a second clamping diode, and a second switching transistor; When the output voltage is higher than the second preset output voltage, the second clamping diode breaks down reversely, so that the supply voltage of the high-voltage power supply is the third preset voltage; wherein, the third preset voltage is the difference between the breakdown voltage of the second clamping diode and the threshold voltage of the second switching transistor.

6. The power supply for a DC converter according to claim 5, characterized in that, When the output voltage is lower than the second preset output voltage, the second clamping diode is cut off, so that the supply voltage of the high-voltage power supply is the fourth preset voltage.

7. The power supply for the DC converter according to claim 5, characterized in that, One end of the current-limiting resistor is connected to the first end of the second switching transistor, and the connection point is connected to the output end of the DC converter to receive the output voltage of the DC converter; The other end of the current-limiting resistor is respectively connected to the cathode of the second clamping diode and the control end of the second switching transistor; The anode of the second clamping diode is grounded; The second end of the second switching transistor serves as the output end of the high-voltage power supply.

8. The power supply for the DC converter according to claim 7, characterized in that, The second switching transistor is an NMOS transistor; The first end of the second switching transistor is the drain electrode of the NMOS transistor; The second end of the second switching transistor is the source electrode of the NMOS transistor; The control end of the second switching transistor is the gate electrode of the NMOS transistor.

9. A DC converter, characterized in that, Comprising: A DC conversion unit, a drive circuit, and the power supply according to any one of claims 1-8 The power supply is used to provide a driving voltage for the corresponding switching transistor in the DC conversion unit through the driving circuit.

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