Slope generation circuit

Abstract

The invention discloses a slope generation circuit, relates to the field of integrated circuit design, and aims to solve the problem of low charging rate of a charging capacitor caused by large leakage current of a slope generation circuit in a high-temperature environment in the prior art. The circuit comprises a slope generation main circuit, a temperature detection circuit and a compensation circuit, the slope generation main circuit is connected with the compensation circuit; the compensation circuit is connected with the temperature detection circuit; the temperature detection circuit is used for detecting the working environment temperature of MOS tubes in the slope generation main circuit and the compensation circuit; the compensation circuit is used for providing compensation current for a charging loop in the slope generation main circuit when the working environment temperature is greater than a preset temperature value; on the basis, the compensation current is provided for the charging loop when the working temperature reaches the preset temperature, so that the leakage current in the circuit is compensated, the charging rate of the charging capacitor is prevented from being reduced, and the influence of the leakage current of the transistor on the circuit is reduced.

Description

Technical Field

[0001] The invention relates to the field of integrated circuit design, in particular to a ramp generating circuit. Background Art

[0002] In a DCDC converter, it is usually necessary to add a soft start protection circuit to the circuit to achieve a slow start of the circuit and ensure the normal working state of the circuit. Figure 1 , Figure 1 The block diagram of the working principle of the soft start circuit in the DCDC converter in the prior art; wherein the soft start circuit is used to prevent overshoot voltage and surge current from being generated during the startup process. During the startup process, the output voltage gradually increases. Since the reference voltage of the output feedback voltage comes from the bandgap reference, the error amplifier always outputs a high level during the startup phase; based on this, the solution adopted in the prior art is to design a ramp generating circuit in which the ramp voltage replaces the reference voltage and compares with the output feedback during the startup process, so that the output voltage rises steadily and the surge current and overshoot voltage are suppressed. However, the ramp generating circuit is sensitive to temperature and is prone to leakage current. Especially when the operating temperature is greater than 100 degrees Celsius, the existing ramp generating circuit will generate a larger leakage current, resulting in a reduced charging rate of the capacitor, affecting the setup time of the entire circuit and failing to meet the startup requirements.

[0003] In view of this, it is urgent to propose a more advanced ramp generating circuit to solve the problem that the ramp generating circuit in the prior art has a large leakage current in a high temperature environment, resulting in a low capacitor charging rate. Summary of the invention

[0004] The purpose of the present invention is to provide a ramp generating circuit, which utilizes its own temperature detection circuit and compensation circuit. When the operating temperature is greater than a preset temperature value, the path connecting the compensation circuit and the ramp generating main circuit is opened to provide a compensation current for the charging circuit in the ramp generating main circuit, thereby avoiding the problem of a reduced capacitor charging rate; and solves the problem in the prior art that the ramp generating circuit has a large leakage current in a high temperature environment, resulting in a low charging rate of the charging capacitor.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a ramp generating circuit, which may include:

[0007] A ramp generating main circuit, a temperature detecting circuit and a compensation circuit;

[0008] The ramp generating main circuit is connected to a compensation circuit, and the compensation circuit is connected to the temperature detection circuit;

[0009] The temperature detection circuit is used to detect the working environment temperature of the MOS tubes in the ramp generation main circuit and the compensation circuit;

[0010] The compensation circuit is used to provide a compensation current for the charging circuit in the ramp generation main circuit when the working environment temperature is greater than a preset temperature value.

[0011] Preferably, the ramp generating main circuit comprises a first PMOS transistor, a second PMOS transistor, a current source, a charging capacitor, a first NMOS transistor, a first reference voltage source and a first comparator;

[0012] The first end of the current source is grounded, and the second end of the current source is connected to the drain of the first PMOS tube; the source of the first PMOS tube is connected to the power supply terminal, the gate of the first PMOS tube is connected to the gate of the second PMOS tube, and the gate of the first PMOS tube is connected to the drain of the first PMOS tube; the source of the second PMOS tube is connected to the power supply terminal, and the drain of the second PMOS tube is connected to the target terminal; the first end of the charging capacitor is connected to the target terminal, and the second end of the charging capacitor is grounded;

[0013] The positive phase input terminal of the first comparator is connected to the target terminal, the negative phase input terminal of the first comparator is connected to the first end of the first reference voltage source, and the output end of the first comparator is connected to the gate of the first NMOS tube; the second end of the first reference voltage source is grounded; the drain of the first NMOS tube is connected to the target terminal, and the source of the first NMOS tube is grounded.

[0014] Preferably, the compensation circuit includes a second NMOS tube and a third NMOS tube;

[0015] The gate of the second NMOS tube is grounded, the source of the second NMOS tube is grounded, and the drain of the second NMOS tube is connected to the source of the third NMOS tube; the gate of the third NMOS tube is connected to the temperature detection circuit, and the drain of the third NMOS tube is connected to the drain of the first PMOS tube.

[0016] Preferably, the transistor parameters of the first NMOS tube are the same as the transistor parameters of the second NMOS tube.

[0017] Preferably, the third NMOS tube is used to ensure the continuity between the compensation circuit and the ramp generating main circuit.

[0018] Preferably, the temperature detection circuit comprises: a PN junction, a second comparator and a second reference voltage source;

[0019] The negative phase input terminal of the second comparator is connected to the first end of the PN junction, the positive phase input terminal of the second comparator is connected to the first end of the second reference voltage source, and the output terminal of the second comparator is connected to the gate of the third NMOS tube;

[0020] The second end of the second reference voltage source is grounded; the second end of the PN junction is grounded.

[0021] Preferably, the PN junction is a PN junction with a negative temperature coefficient.

[0022] Preferably, when the voltage of the target terminal is less than the output voltage of the first reference voltage source, the output voltage of the first comparator is at a low level; when the voltage of the target terminal is equal to the output voltage of the first reference voltage source, the output voltage of the first comparator is at a high level, and the first NMOS tube is turned on; the first NMOS tube is used to ensure that the voltage of the target terminal is the output voltage of the first reference voltage source.

[0023] Preferably, when the working environment temperature is greater than a preset temperature value, the third NMOS tube is turned on, and the leakage current generated by the second NMOS tube is compensated to the charging circuit after being mirrored by a current mirror.

[0024] Preferably, when the working environment temperature rises, the voltage across the PN junction decreases as the temperature rises. When the temperature is higher than the preset temperature value, the temperature across the PN junction drops to below the output voltage of the second reference voltage source, and the output voltage of the second comparator changes from a low level to a high level, causing the third NMOS tube to start conducting and enter the linear region.

[0025] Compared with the prior art, the present invention provides a ramp generating circuit, which is provided by setting a ramp generating main circuit, a temperature detecting circuit and a compensation circuit; connecting the ramp generating main circuit with the compensation circuit, and connecting the compensation circuit with the temperature detecting circuit; using the temperature detecting circuit to detect the working environment temperature of the MOS tubes in the ramp generating main circuit and the compensation circuit; using the compensation circuit to provide a compensation current for the charging circuit in the ramp generating main circuit when the working environment temperature of the circuit is greater than a preset temperature value; based on this, using the NMOS tube of the same type as that in the ramp generating main circuit set in the compensation circuit, when the working environment temperature of the circuit is greater than a preset temperature value, the compensation circuit can compensate the corresponding current to the ramp generating main circuit according to the amount of current leaked in the ramp generating main circuit; the present invention provides The simulation results of the slope generating circuit provided by the present invention are compared with the simulation results of the prior art. It is shown that: within the normal temperature range, the simulation results of the two are very similar and relatively stable; however, with the increase of temperature, the solution in the prior art has the problem of current leakage leading to a decrease in charging voltage and a decrease in charging rate; while for the circuit provided by the present invention, the simulation results in a high temperature environment are not much different from those in a normal temperature range, and the problem of a decrease in charging voltage and a decrease in charging rate due to an increase in temperature does not occur. This proves that the slope generating circuit provided by the present invention has achieved a very low sensitivity of the circuit to temperature changes, and is almost unaffected by temperature changes. Compared with the prior art, it avoids the decrease in the charging rate of the charging capacitor in the ramp generating main circuit, and reduces the influence of the leakage current of the transistor on the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 It is a block diagram of the working principle of the soft start circuit in the DCDC converter in the prior art;

[0028] Figure 2 It is a structural schematic diagram of a ramp voltage generating circuit in the prior art;

[0029] Figure 3 It is a schematic diagram of the structure of a soft start circuit with built-in automatic temperature compensation in the prior art;

[0030] Figure 4 A schematic diagram of the main structure of a ramp generating circuit provided by the present invention;

[0031] Figure 5 It is a schematic diagram of simulation verification results of a ramp generating circuit provided by the prior art 1 and the present invention under the same high temperature process.

[0032] Figure numerals: 400 - slope generating circuit, 410 - slope generating main circuit, 420 - compensation circuit, 430 - temperature detection circuit, A - target terminal, C - charging capacitor, Vref1 - first reference voltage source, Vref2 - second reference voltage source, I - current source, COMP1 - first comparator, COMP2 - second comparator. DETAILED DESCRIPTION

[0033] In order to facilitate the clear description of the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, the words "first", "second" and the like are used to distinguish the same items or similar items with substantially the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and do not limit their order of precedence. Those skilled in the art can understand that the words "first", "second" and the like do not limit the quantity and execution order, and the words "first", "second" and the like do not necessarily limit them to be different.

[0034] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0035] In the present invention, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects in the previous time are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

[0036] See also Figures 2 to 3 , Figure 2 It is a structural schematic diagram of a ramp voltage generating circuit in the prior art; Figure 3 The figure is a schematic diagram of the structure of a soft start circuit with built-in automatic temperature compensation in the prior art.

[0037] Figure 2The figure shows a traditional ramp generation circuit. The current mirror provides the current required by the circuit. MP1 and MP2 form a current mirror to mirror the current to the charging circuit. At the initial moment, the voltage at point A is 0, the voltage of Vref1 is higher than the voltage of node A, the output voltage of COMP1 is low level "0", MN1 is in the off state, and the current is all used to charge capacitor C. The voltage at point A rises slowly as the capacitor is charged. When the voltage at node A rises to a voltage higher than Vref1, the output voltage of comparator COMP1 flips from low level "0" to high level "1", MN1 starts to conduct, and the current starts to flow to MN1. The voltage at point A is clamped, and the voltage at point A no longer rises and remains unchanged. However, the MOS tube in the ramp circuit is sensitive to temperature changes. When the temperature rises, there will be a conductive path between the source and drain of MN1, forming a leakage current. Part of the current is discharged through the leakage path, causing the current through C to decrease, the charging rate of the charging capacitor to decrease, and the voltage rise rate at point A to decrease, affecting the settling time of the entire circuit.

[0038] Figure 3 The figure shows a ramp generating circuit with built-in temperature compensation, wherein MP1 and MP2, MP3 and MP4, MP5 and MP6 form three pairs of current mirrors. In the initial stage, the current mirror formed by MP1 and MP2 mirrors the current in the current source to the emitter of the transistor Q1, charges the capacitor C through Q1, and generates a ramp voltage to start the lower circuit. When the temperature reaches a high temperature, the two pairs of current mirrors formed by MP3 and MP4, MP5 and MP6 can also perform high temperature leakage current compensation to prevent the next stage circuit from being shut down by mistake, thereby realizing operation under high temperature conditions. However, since the leakage currents of MN1 and Q1 are not the same, they cannot be well compensated. At the same time, at high temperatures, the MN2 and MP3 transistors will also cause leakage current, resulting in a decrease in the charging rate of the charging capacitor, which affects the circuit.

[0039] In view of this, the present invention provides a ramp generating circuit and proposes a leakage current compensation method which is turned on when a set temperature is reached, thereby reducing the current consumed by the circuit and being almost unaffected by temperature changes. Compared with the prior art, the present invention avoids the decrease in the charging rate of the charging capacitor in the ramp generating main circuit and reduces the influence of the leakage current of the transistor on the circuit.

[0040] Next, the technical solution of the present invention is described in detail with reference to the accompanying drawings:

[0041] See also Figure 4 , Figure 4 A schematic diagram of the main structure of a ramp generating circuit provided by the present invention.

[0042] exist Figure 4In the embodiment, the ramp generating circuit 400 may include: a ramp generating main circuit 410, a temperature detecting circuit 430 and a compensation circuit 420; the ramp generating main circuit 410 is connected to the compensation circuit 420, and the compensation circuit 420 is connected to the temperature detecting circuit 430; wherein the temperature detecting circuit 430 is used to detect the working environment temperature of the MOS tubes in the ramp generating main circuit 410 and the compensation circuit 420; the compensation circuit 420 is used to provide a compensation current for the charging circuit in the ramp generating main circuit 410 when the working environment temperature is greater than a preset temperature value.

[0043] Based on this, a ramp generating circuit provided by the present invention is constructed, and a temperature detecting circuit 430 is used to detect the working environment temperature of the circuit. When the working environment temperature is lower than a preset temperature value, the compensation circuit 420 is disconnected from the ramp generating main circuit 410; when the working environment temperature is greater than or equal to the preset temperature value, the compensation circuit 420 is connected to the ramp generating main circuit 410 to provide a compensation current for the charging circuit in the ramp generating main circuit 410; because the compensation circuit 420 is provided with an NMOS tube of the same type as that in the ramp generating main circuit, when the working environment temperature of the circuit is greater than the preset temperature value, the compensation circuit can compensate the corresponding current to the ramp generating main circuit according to the amount of current leaked in the ramp generating main circuit; so that the charging circuit in the ramp generating main circuit will not cause the charging rate of the charging capacitor to decrease due to the leakage problem of the transistor, and will not affect the establishment of the circuit.

[0044] Preferably, the ramp generating main circuit 410 may include a first PMOS transistor, a second PMOS transistor, a current source I, a charging capacitor C, a first NMOS transistor, a first reference voltage source Vref1 and a first comparator COMP1.

[0045] Specifically, the first end of the current source I can be grounded, and the second end of the current source I can be connected to the drain of the first PMOS tube; the source of the first PMOS tube is connected to the power supply terminal, the gate of the first PMOS tube is connected to the gate of the second PMOS tube, and the gate of the first PMOS tube is connected to the drain of the first PMOS tube; the source of the second PMOS tube is connected to the power supply terminal, and the drain of the second PMOS tube is connected to the target terminal; the first end of the charging capacitor C is connected to the target terminal, and the second end of the charging capacitor C is grounded.

[0046] Further, the positive input terminal of the first comparator COMP1 can be connected to the target terminal, the negative input terminal of the first comparator COMP1 can be connected to the first end of the first reference voltage source Vref1, and the output terminal of the first comparator COMP1 can be connected to the gate of the first NMOS tube; the second end of the first reference voltage source Vref1 is grounded; the drain of the first NMOS tube is connected to the target terminal, and the source of the first NMOS tube is grounded.

[0047] Based on this, a ramp generating main circuit in a ramp generating circuit provided by the present invention is obtained, and the first NMOS tube in the ramp generating main circuit is used to charge the charging capacitor C, thereby establishing the circuit to be established by the present invention. When the ramp generating main circuit works in a high temperature state, the first NMOS tube is in a closed state at the initial moment, and the drain and source of the first NMOS tube still form a leakage path, causing current leakage, reducing the charging current of the charging capacitor C, and causing the voltage rise rate at point A to decrease.

[0048] Preferably, the compensation circuit 420 may include a second NMOS transistor and a third NMOS transistor.

[0049] Specifically, the gate of the second NMOS tube can be grounded, the source of the second NMOS tube can be grounded, and the drain of the second NMOS tube can be connected to the source of the third NMOS tube; the gate of the third NMOS tube can be connected to the temperature detection circuit, and the drain of the third NMOS tube can be connected to the drain of the first PMOS tube.

[0050] Preferably, the transistor parameters of the first NMOS tube are the same as those of the second NMOS tube, and the second NMOS tube is used to generate a compensation current; because the first NMOS tube and the second NMOS tube can work in the same environment, the second NMOS tube can generate as much compensation current as the leakage current generated by the first NMOS tube. In other words, the leakage current caused by MN1 and MN2 is the same at the same temperature. When in a high temperature state, the leakage current formed by the drain and source of MN2 will be provided to the charging circuit through the current mirror image to compensate for the leakage current of MN1, so that the current flowing through C remains stable at different temperatures, so that the voltage rise rate of node A is not affected by temperature.

[0051] Preferably, the third NMOS tube is used to ensure the continuity between the compensation circuit and the ramp generating main circuit; specifically, the third NMOS tube is used to turn off or open the path between the compensation circuit 420 and the ramp generating main circuit 410, so that when the working environment temperature is lower than the preset temperature value, the compensation circuit 420 is disconnected from the ramp generating main circuit 410, and when the working environment temperature is greater than or equal to the preset temperature value, the compensation circuit 420 is connected to the ramp generating main circuit 410 to provide a compensation current for the charging circuit in the ramp generating main circuit 410, and the compensation current is the compensation current generated by the second NMOS tube.

[0052] Preferably, the temperature detection circuit 430 may include: a PN junction, a second comparator COMP2 and a second reference voltage source Vref2.

[0053] Specifically, the negative phase input terminal of the second comparator COMP2 can be connected to the first end of the PN junction, the positive phase input terminal of the second comparator COMP2 can be connected to the first end of the second reference voltage source Vref2, and the output terminal of the second comparator COMP2 can be connected to the gate of the third NMOS tube; the second end of the second reference voltage source Vref2 is grounded; and the second end of the PN junction is connected to the ground.

[0054] Preferably, the PN junction is a PN junction with a negative temperature coefficient; when the temperature rises, the voltage across the PN junction decreases as the temperature rises. When the temperature is higher than a preset temperature, such as 120°C, the temperature across the PN junction drops below Vref2. At this time, the input voltage at the positive end of the second comparator COMP2 is higher than the negative end, and the output voltage of the second comparator COMP2 is reversed, and the output voltage changes from a low level "0" to a high level "1". It should be noted that the preset temperature can be set according to the actual application scenario, and different types of PN junctions can be used to realize the opening or closing of the temperature detection and compensation path.

[0055] Based on this, a temperature detection circuit 430 is constructed, and the PN junction therein is used to monitor the working environment temperature. When the temperature is greater than or equal to the preset temperature, the second comparator is used to output a high level, so that the third NMOS tube is turned on and enters the linear region. The compensation current generates a current mirror structure image in the main circuit through the ramp, compensating for the leakage current of the first NMOS tube caused by the high temperature.

[0056] Specifically, the working principle of a ramp generating circuit of the present invention is as follows: a current source provides the current required by the circuit, and MP1 and MP2 form a current mirror to mirror the current and provide it to the charging capacitor C for charging. At the initial moment, the voltage at point A is 0, the voltage of the first reference voltage source Vref1 is higher than the voltage at node A, and the output voltage of the first comparator COMP1 is a low level "0". After charging for a period of time, when the voltage at node A rises to a voltage higher than the voltage of the first reference voltage source Vref1, the output voltage of the first comparator COMP1 flips from a low level "0" to a high level "1", MN1 starts to conduct, and the current starts to flow to MN1, the voltage at point A is clamped, and the voltage at point A no longer rises and remains unchanged. When working in a high temperature state, MN1 is in a closed state at the initial moment, and the drain and source of MN1 will still form a leakage path, causing current leakage, reducing the charging current of the charging capacitor C, and causing the voltage rise rate at point A to decrease; at this time, the output voltage of the second comparator COMP2 in the temperature detection circuit is reversed, and the output voltage changes from a low level "0" to a high level "1", and the switch tube MN3 starts to turn on and enters the linear region, and the compensation current will begin to be mirrored through the current mirror structure to compensate for the leakage current of MN1 caused by the high temperature.

[0057] In summary, the ramp generating circuit provided by the present invention can achieve: when the voltage of the target terminal A is less than the output voltage of the first reference voltage source, the output voltage of the first comparator is a low level; when the voltage of the target terminal is equal to the output voltage of the first reference voltage source, the output voltage of the first comparator is a high level, and the first NMOS tube is turned on; the first NMOS tube is used to ensure that the voltage of the target terminal is the output voltage of the first reference voltage source.

[0058] When the working environment temperature is greater than a preset temperature value, the third NMOS tube is turned on, and the leakage current generated by the second NMOS tube is compensated to the charging circuit after being mirrored by the current mirror.

[0059] When the working environment temperature rises, the voltage across the PN junction decreases as the temperature rises. When the temperature is higher than the preset temperature value, the temperature across the PN junction drops to a level lower than the output voltage of the second reference voltage source, and the output voltage of the second comparator changes from a low level to a high level, causing the third NMOS tube to start conducting and enter the linear region; the compensation current will begin to be mirrored through the current mirror structure to compensate for the leakage current of MN1 caused by the high temperature, thereby reducing the current consumed by the circuit and reducing the impact of temperature changes on the circuit.

[0060] In order to further verify that the ramp generating circuit provided by the present invention can effectively solve the problem that the ramp generating circuit in the prior art has a large leakage current under a high temperature environment, resulting in a low charging rate of the charging capacitor, a plurality of test pieces are made using the ramp generating circuit provided by the present invention and the ramp generating circuit of the prior art, and simulation tests are carried out at different working temperatures; please refer to Figure 5 , Figure 5 It is a schematic diagram of simulation verification results of a ramp generating circuit provided by the prior art 1 and the present invention under the same high temperature process.

[0061] exist Figure 5 In the figure, both the prior art 1 and the present invention were tested at 4 different temperatures, as shown in the figure: 125°C, 175°C, 200°C and 225°C. The horizontal axis of the coordinate system corresponding to the curves of the prior art 1 and the present invention represents time in us, and the vertical axis represents voltage in mV.

[0062] pass Figure 5The curve graph shown can be obtained without doubt: in the scheme 1, the temperature detection circuit sets 125℃ as the threshold value. When the temperature is lower than 125℃, the leakage current can be ignored and the compensation circuit does not participate in the work; when the temperature is higher than 125℃, the compensation circuit starts to work. From the simulation results, it can be seen that when the temperature is 125℃, the circuit performance of the two schemes is almost the same. As the temperature increases (175℃, 200℃ and 225℃), the rising slope in the prior art 1 (circuit without compensation) changes with the increase of temperature, and the time to reach the saturation voltage is gradually extended, and the time required to reach the saturation voltage will be longer under the condition of higher temperature; while the rising slope in the present invention (circuit with compensation) does not change significantly with the increase of temperature; it can be seen that the scheme of the present invention is very low in sensitivity to temperature changes, and the difference between the simulation curve with a temperature greater than 125℃ and the simulation curve with a temperature lower than 125℃ is very small, and it is almost unaffected by temperature changes; the charging rate of the charging capacitor of the scheme provided by the present invention will not decrease due to the current leakage in the main circuit of the ramp generation, and will not affect the establishment of the ramp circuit.

[0063] Based on this, a ramp generating circuit provided by the present invention realizes controlling the conduction of the switch tube according to temperature changes, thereby controlling the compensation of the leakage current in the circuit, solving the problem of the ramp generating circuit in the prior art having a large leakage current in a high temperature environment resulting in a low charging rate of the charging capacitor, and avoiding the influence of the leakage current generated in the circuit above the set temperature on the circuit.

[0064] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0065] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the claims of the present invention and their equivalents.

Claims

1. A ramp generating circuit, characterized in that: include: A ramp generating main circuit, a temperature detecting circuit and a compensation circuit; The ramp generating main circuit is connected to a compensation circuit, and the compensation circuit is connected to the temperature detection circuit; The temperature detection circuit is used to detect the working environment temperature of the MOS tubes in the ramp generation main circuit and the compensation circuit; The compensation circuit is used to provide a compensation current for the charging circuit in the ramp generation main circuit when the working environment temperature is greater than a preset temperature value.

2. The circuit according to claim 1, characterized in that The ramp generating main circuit includes a first PMOS transistor, a second PMOS transistor, a current source, a charging capacitor, a first NMOS transistor, a first reference voltage source and a first comparator; The first end of the current source is grounded, and the second end of the current source is connected to the drain of the first PMOS tube; the source of the first PMOS tube is connected to the power supply terminal, the gate of the first PMOS tube is connected to the gate of the second PMOS tube, and the gate of the first PMOS tube is connected to the drain of the first PMOS tube; the source of the second PMOS tube is connected to the power supply terminal, and the drain of the second PMOS tube is connected to the target terminal; the first end of the charging capacitor is connected to the target terminal, and the second end of the charging capacitor is grounded; The positive phase input terminal of the first comparator is connected to the target terminal, the negative phase input terminal of the first comparator is connected to the first end of the first reference voltage source, and the output end of the first comparator is connected to the gate of the first NMOS tube; the second end of the first reference voltage source is grounded; the drain of the first NMOS tube is connected to the target terminal, and the source of the first NMOS tube is grounded.

3. The circuit according to claim 2, characterized in that The compensation circuit includes a second NMOS tube and a third NMOS tube; The gate of the second NMOS tube is grounded, the source of the second NMOS tube is grounded, and the drain of the second NMOS tube is connected to the source of the third NMOS tube; the gate of the third NMOS tube is connected to the temperature detection circuit, and the drain of the third NMOS tube is connected to the drain of the first PMOS tube.

4. The circuit according to claim 3, characterized in that The transistor parameters of the first NMOS tube are the same as the transistor parameters of the second NMOS tube.

5. The circuit according to claim 3, characterized in that The third NMOS tube is used to ensure the continuity between the compensation circuit and the ramp generating main circuit.

6. The circuit according to claim 3, characterized in that The temperature detection circuit includes: a PN junction, a second comparator and a second reference voltage source; The negative phase input terminal of the second comparator is connected to the first end of the PN junction, the positive phase input terminal of the second comparator is connected to the first end of the second reference voltage source, and the output terminal of the second comparator is connected to the gate of the third NMOS tube; The second end of the second reference voltage source is grounded; the second end of the PN junction is grounded.

7. The circuit according to claim 6, characterized in that The PN junction is a PN junction with a negative temperature coefficient.

8. The circuit according to any one of claims 1 to 7, characterized in that: When the voltage of the target terminal is less than the output voltage of the first reference voltage source, the output voltage of the first comparator is at a low level; When the voltage of the target terminal is equal to the output voltage of the first reference voltage source, the output voltage of the first comparator is at a high level, and the first NMOS tube is turned on; The first NMOS tube is used to ensure that the voltage of the target terminal is the output voltage of the first reference voltage source.

9. The circuit according to any one of claims 1 to 7, characterized in that: When the working environment temperature is greater than a preset temperature value, the third NMOS tube is turned on, and the leakage current generated by the second NMOS tube is compensated to the charging circuit after being mirrored by the current mirror.

10. The circuit according to any one of claims 1 to 7, characterized in that: When the working environment temperature rises, the voltage across the PN junction decreases as the temperature rises. When the temperature is higher than the preset temperature value, the temperature across the PN junction drops to below the output voltage of the second reference voltage source, and the output voltage of the second comparator changes from a low level to a high level, causing the third NMOS tube to start conducting and enter the linear region.

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