A method and circuit for real-time detecting an output voltage

Abstract

The present invention discloses a method for detecting output voltage in real time. CC Induction V out After the change of the chip voltage V CC Discharge, so that V CC The voltage decreases and eventually falls below V out , so that the demagnetization time of the next cycle begins when V out >V CC , V out V CC Power supply to achieve V CC V out The induction of the change, according to the chip voltage V CC The peak voltage value is obtained to obtain the output voltage V out , so that in each cycle, V CC The voltage is lower than V due to the discharge of the previous cycle out , V CC Can sense V out The present invention also provides a circuit for real-time output voltage detection, including a discharge circuit. By applying the above-described method to configure the discharge circuit, the circuit controls the controller voltage and detects changes in the output voltage in real time. The present invention has significant effects and is suitable for widespread promotion.

Description

Technical Field

[0001] The present invention relates to the technical field of switch circuits, and in particular to a method and circuit for real-time detection of output voltage. Background Art

[0002] With the rapid development of intelligent lighting, AC-DC non-isolated constant voltage buck structure is favored by users due to its simple structure and less peripheral circuits. Figure 1 As shown), V out The change will be reflected in V CC , that is, by sampling V CC The voltage can know the output voltage V out Using this V out The voltage detection method can save V in the peripheral circuit out Feedback resistor.

[0003] At present, there is a problem in the application of this solution. Since the entire circuit is a voltage-stabilizing circuit, a stable voltage is formed at both ends of the load, so V out remains constant, while V CC Will fluctuate with the mains electricity, so V CC Sometimes it is greater than V out , output voltage V out Less than V CC , then the diode D1 will be in the reverse bias state, so that V CC Cannot sense V out Changes, or not following V out changes, resulting in V out Not controlled by feedback.

[0004] In view of the above problems, there is an urgent need for a V CC The output voltage V out Less than V CC , thus V CC Cannot sense V out The change of V out Method and circuit for performing real-time detection of problems. Summary of the Invention

[0005] In view of the above defects, the technical problem solved by the present invention is to provide a method and circuit for real-time detection of output voltage to solve the V CC The output voltage V out Less than V CC , thus V CC Cannot sense V out The change of Vout The problem of real-time detection.

[0006] The present invention provides a method for real-time detection of output voltage, which specifically comprises the following steps:

[0007] Get the chip voltage V during the demagnetization phase of each cycle CC , when the chip voltage V CC When the chip voltage V CC Discharge to ensure the chip voltage V CC Peak value and output voltage V out Related;

[0008] Get the chip voltage V during the demagnetization phase of each cycle CC Peak voltage value;

[0009] According to the chip voltage V CC The peak voltage value is obtained to obtain the output voltage V out .

[0010] Preferably, the chip voltage V is obtained during the demagnetization phase of each cycle. CC The steps include:

[0011] Obtain the chip voltage V through the voltage divider circuit CC , where the divided voltage V FB =βV CC .

[0012] Preferably, the reference voltage is a preset value, or the reference voltage V ref is the chip operating voltage V at the beginning of each demagnetization stage CC The initial value of .

[0013] Preferably, the chip voltage V is obtained during the demagnetization phase of each cycle. CC The step of measuring the peak voltage value includes: sampling multiple chip voltages V in a preset time period during the demagnetization stage CC , take the highest value.

[0014] Preferably, when the chip voltage V CC When the voltage peaks in the demagnetization phase are equal, the system is considered to have entered a steady state. At this time, the chip voltage V CC The peak voltage value and output voltage V out equal.

[0015] The present invention further provides a circuit for real-time detection of output voltage, comprising a discharge circuit, wherein the discharge circuit controls the voltage of the controller according to the method described above.

[0016] Preferably, the discharge circuit includes a comparator, and the comparator input terminals are connected to the reference voltage and VCC The sampling voltage is obtained, and the output end of the comparator is connected to the switch unit, and the signal output by the comparator controls the operation of the switch unit.

[0017] Preferably, the switch unit is a MOS tube, the gate of the MOS tube is connected to the comparator, and the source is connected to the controller power supply V through a resistor R1. CC Connection, drain ground.

[0018] Preferably, the discharge circuit further includes V CC Voltage sampling circuit, the V CC The voltage sampling circuit includes a resistor R2 and a resistor R3 connected in series, one end of the resistor R2 is connected to the controller power supply V CC One end of the resistor R3 is connected to the resistor R2, and the other end is grounded.

[0019] Preferably, the reference voltage is sampled by a sampling and holding module, one end of which is connected to the V CC The voltage sampling circuit obtains the voltage at the beginning of the demagnetization period, and the other end is connected to the input end of the comparator. The sampling and holding module inputs a reference voltage to the comparator.

[0020] From the above scheme, it can be seen that the method for real-time detection of output voltage provided by the present invention is CC Induction V out After the change of the chip voltage V CC Discharge, so that V CC The voltage decreases and eventually falls below V out , so that the demagnetization time of the next cycle begins when V out >V CC , V out V CC Power supply to achieve V CC V out The induction of the change, according to the chip voltage V CC The peak voltage value is obtained to obtain the output voltage V out , so that in each cycle, V CC The voltage is lower than V due to the discharge of the previous cycle out , V CC Can sense V out The present invention also provides a circuit for real-time detection of output voltage, which controls the controller voltage by setting the discharge circuit using the above method, that is, each time V CC Induction V out After the change, open the discharge circuit, the chip voltage V CC Discharge, so that V CC Voltage lower than Vout , thereby detecting the change of the output voltage in real time. The present invention has significant effects and is suitable for wide promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 The circuit diagram of the existing AC-DC buck application circuit;

[0023] Figure 2 A process block diagram of a method for real-time output voltage detection provided by an embodiment of the present invention Figure 1 ;

[0024] Figure 3 A process block diagram of a method for real-time output voltage detection provided by an embodiment of the present invention Figure 2 ;

[0025] Figure 4 A circuit diagram of a circuit for real-time output voltage detection provided by an embodiment of the present invention;

[0026] Figure 5 for Figure 4 A detection timing diagram of a circuit for real-time detection of output voltage is shown;

[0027] Figure 6 A circuit diagram of another circuit for real-time output voltage detection provided by an embodiment of the present invention;

[0028] Figure 7 for Figure 6 The figure shows a detection timing diagram of a circuit for real-time detection of output voltage. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] like Figure 1 As shown, the switching circuit includes a rectifier bridge, a controller, a diode D1, a freewheeling diode D2, an inductor L, and an output load, where the controller power supply voltage is VCC , the load voltage is V out The working principle of the BUCK application that saves auxiliary winding and output feedback resistor is as follows: During the switch on period, the AC input voltage passes through the rectifier bridge to charge the inductor and supply power to the output. Since the chip is a floating structure, V CC >V out , D1 is cut off, and the controller is powered by C1; during the switch off period, which is the demagnetization stage, the inductor L and the output load, as well as the freewheeling diode D2, form a loop, and the output voltage V out , diode D1, and the controller form another loop, through which the inductor L provides energy to the controller.

[0031] During demagnetization: When V CC When it is the peak value during demagnetization, V CC +V D1 =V out +V D2 , V D1 and V D2 are the conduction voltage drops of diodes D1 and D2 respectively. D1 =V D2 , then V CC =V out . So V out The change of V CC , that is, by sampling V CC The voltage can know the output voltage V out In this way, the V out Feedback resistor.

[0032] In the above method, if there is an output voltage V out Less than V CC In the case of V CC +V D1 =V out +V D2 It is not true, so a discharge circuit needs to be designed to control V CC is in a reasonable range, so by sampling V CC The voltage response output voltage V out changes.

[0033] Example 1

[0034] See also Figure 2 Now, a specific embodiment of a method for real-time detection of output voltage provided by the present invention is described. The specific steps of the method for real-time detection of output voltage include: obtaining the chip voltage V in the demagnetization stage of each cycle CC , when the chip voltage VCC When the chip voltage V CC Discharge to ensure the chip voltage V CC Peak value and output voltage V out Related; In this step, the chip operating voltage V CC , controlled within a reasonable range to prevent the chip from working V CC The voltage is higher than the output voltage V out , leading to the equation V CC +V D1 =V out +V D2 Not true.

[0035] like Figure 3 As shown, the chip voltage V in the demagnetization stage of each cycle is obtained. CC In this step, the voltage value of multiple chips V is sampled during the preset time period of the demagnetization stage. CC , the highest value is the chip voltage V CC In this step, the chip voltage V is obtained through the voltage divider circuit. CC , where the divided voltage V FB =βV CC .

[0036] When the chip voltage V CC When the voltage peaks in the demagnetization phase are equal, the system is considered to have entered a steady state. At this time, the chip voltage V CC The peak voltage value and output voltage V out equal.

[0037] When the system enters steady state, according to the chip voltage V CC The peak voltage value is obtained to obtain the output voltage V out In this step, the chip voltage peak value V CC Derived output voltage V out When the system enters the steady state, the chip voltage V CC The voltage peaks are equal to each other, and the equation V CC +V D1 =V out +V D2 The output voltage V can be calculated. out , thus saving the output voltage V out Sampling resistor.

[0038] The reference voltage is a preset value, or the reference voltage V ref is the chip operating voltage V at the beginning of each demagnetization stage CC The initial value of .

[0039] Example 2

[0040] Please also refer to Figure 4 and Figure 6 Based on the above embodiment, this application obtains the chip voltage V during the demagnetization phase of each cycle CC The sampling method is to use a voltage divider circuit, which includes two series resistors R2 and R3. The sampling voltage is recorded as βV CC , where β=R3 / R2+R3. The chip voltage can be obtained by the voltage divider resistor and the sampling voltage can be adjusted according to the actual situation. CC .

[0041] In the above embodiment, when the chip voltage V CC When the voltage is higher than the reference voltage, the reference voltage can be a preset fixed value, or the chip working voltage can be sampled at the beginning of each demagnetization stage as a reference voltage. In actual circuits, due to fluctuations in the mains power supply, it is not guaranteed to be stable in each cycle. Therefore, the method of sampling in each demagnetization stage is more practical, ensuring that after each cycle discharge, the chip voltage Vcc is consistent with the output voltage V out The difference is fixed.

[0042] When the reference voltage is a fixed value V ref When, such as Figure 5 Timing Figure 1 As shown:

[0043] The PWM timing curve indicates that when it is at a high level, the MOS tube is in the on stage, and the inductor in the system is in the charging stage; when it is at a low level, the MOS tube is in the off stage, and the inductor in the system is in the discharging stage, releasing the energy stored in the charging stage, that is, the demagnetization stage.

[0044] In the ab phase, the chip voltage V CC Can reflect the output voltage V out , because the previous cycle has a voltage on the chip V CC Discharge, resulting in chip voltage V CC At the beginning of demagnetization, the voltage is lower than the output voltage V out ,so Figure 1 The diode D1 in the middle is forward conducting, and the output voltage V out Supply voltage V to the chip CC Charge.

[0045] bc moment: At b moment, the chip voltage V CC Reaching the maximum value. At ac moment βV CC >V ref When the chip voltage V CC Start discharging, through the chip voltage VCC Comparison with the reference voltage will chip voltage V CC Pull down to make the chip voltage V CC Lower than the output voltage V out So that in the next demagnetization cycle, the chip voltage V CC Capable of sensing the output voltage V out When discharged to c, βVcc=V ref , stop V CC discharge.

[0046] cd stage: At the beginning of this stage, the discharge circuit does not work because the chip voltage V CC Less than the output voltage V out , output voltage V out Will give the chip voltage V CC Charging, so the chip voltage V CC Once the chip voltage V CC The partial pressure βV CC Greater than V ref , the discharge circuit starts working again, the chip voltage V CC If βV CC Less than V ref , the discharge circuit stops working again. This repeated action continues, and the chip voltage V CC Basically maintains fluctuation within a small range, it can be considered that the output voltage V out Maintain at a fixed value until the next cycle when PWM is at a high level and MOS is turned on.

[0047] Phase de: In this phase, the next cycle begins and the MOS tube is turned on. Since the controller is a floating structure, the chip voltage V CC Greater than the output voltage V out The diode D1 is cut off and the output voltage does not provide energy to the chip. However, the control chip is still working at this time, so the charge of the capacitor will be consumed and the chip voltage V CC Lower slowly.

[0048] ef: Enter the demagnetization phase of the next cycle. At this time, due to the chip voltage V CC The discharge circuit works to reduce the chip voltage V CC On the other hand, the power consumption of the chip during this cycle Ton will also lower the chip voltage V CC So the chip voltage V CC Output voltage V out Repeat the process of ae in this way to achieve the output voltage V out of sampling.

[0049] like Figure 5As shown, in each cycle when βV CC When it is at its peak value, after proportional calculation, the chip voltage V CC That is the output voltage V out , and this peak value is sampled in multiple cycles to feed back the output voltage.

[0050] When the reference voltage is the sample value in the demagnetization stage, such as Figure 7 Timing Figure 2 As shown:

[0051] ab: Entering the demagnetization stage, the chip voltage V CC Because of the discharge operation of the previous cycle, it is lower than the output voltage V out At this time, diode D1 is forward conducting and the output voltage V out Supply voltage V to the chip CC Power supply, chip voltage V CC When V CC =V out When V CC When the maximum value is reached, VCC is sampled and held at that value.

[0052] bc: Sample and hold circuit for V CC After sampling, the sampling voltage βV is obtained CC _SH, keep the sampling result. CC With βV CC _SH for comparison, start to give V CC Discharge, reduce V CC Voltage. At time c, V CC When the discharge detection threshold is reached, the switch tube M0 is turned off and no longer discharges.

[0053] cd stage: At the beginning of this stage, the discharge circuit does not work because V CC Less than V out , V out Will give V CC Charging, V CC Once V CC The partial pressure βV CC Greater than βV CC _SH, the discharge circuit starts working, V CC Decrease; if βV CC Less than βV CC _SH, the discharge circuit stops working. This repeated action continues, V CC Basically maintains fluctuations within a small range, it can be approximately considered that V CC is a fixed value until the next cycle Ton. CC The change of numerical value is a dynamic process, a sin wave state that is sometimes high and sometimes low. The value shown in the figure is an average value.

[0054] De stage: In this stage, it enters the Ton stage. Since the controller is a floating structure, V CC Greater than V out . Diode D1 is cut off, the output voltage V out No V CC Provide energy. At this time, the control chip is still working, so the charge of the capacitor will be consumed, V CC Lower slowly.

[0055] ef: Enter the demagnetization phase of the next cycle. At this time, due to the demagnetization phase V CC The discharge circuit works to reduce V CC voltage, on the other hand, the power consumption of the chip during this cycle Ton will also lower V CC So V CC <V out Repeat the process of ae in this way to achieve the output voltage V out of sampling.

[0056] Select a period of time during the demagnetization phase and calculate the chip voltage V CC Sampling is performed, and the highest value is selected after comparison as the peak value of this demagnetization stage. The premise of the equation mentioned in this application is that the system enters the steady state. Since all parameters are in a fluctuating state in the initial stage of the system, the equation must be established after the system runs smoothly and enters the steady state. The premise of judging the steady state is that the voltage peaks of multiple adjacent chips are equal. This method makes V CC Each cycle can sense the output voltage V out changes and make adjustments to them.

[0057] In another embodiment, the steady state may not be judged. Since the non-steady state time is very short and the system quickly enters the steady state after power-on, the peak points of several deviations in the early stage will be averaged by a large number of peak points after entering the steady state. Therefore, in long-term sampling, the difference is not large and can also be used as the basis for the output voltage.

[0058] Example 3

[0059] Please also refer to Figure 4 and Figure 6 Now, a specific embodiment of a circuit for real-time output voltage detection provided by the present invention is described. The circuit for real-time output voltage detection includes a discharge circuit, which is used to control the voltage of the controller. The discharge circuit includes a comparator, and the negative input terminal of the comparator is connected to the reference voltage V ref , its positive input terminal is connected to V CCThe sampling voltage, the output of the comparator is connected to the switch unit, and the signal output by the comparator controls the operation of the switch unit. The switch unit is a MOS tube, the gate of the MOS tube is connected to the comparator, and the source is connected to the controller power supply V through the resistor R1. CC The drain is grounded. The comparator uses an offset comparator. The discharge circuit also includes V CC Voltage sampling circuit, V CC The voltage sampling circuit includes resistors R2 and R3 connected in series. One end of resistor R2 is connected to the controller power supply V CC One end of the resistor R3 is connected to the resistor R2, and the other end is connected to the positive input terminal of the comparator. Here, as long as the relevant performance of the discharge circuit can be achieved, it is within the scope of protection of this application document.

[0060] The comparator is provided with a storage module, which is used to store the voltage value to be compared with the controller voltage divider. The storage module is provided with a reference voltage value V ref is a fixed value. In each demagnetization cycle, V out Through the diode to V CC Charging, V CC Increases, when the controller voltage V CC The partial pressure βV CC >V ref When the comparator output is high, the switch unit M O Turn on, V CC The voltage is gradually lowered.

[0061] The comparator also has a threshold module, which is used to store the voltage threshold parameters and maintain the voltage of the controller in a stable range. CC When the switching tube M is lower than a certain value, O Disconnect, maintain V CC voltage, avoid setting V CC Here, as long as the relevant performance functions of the threshold module and the stored-value module can be achieved, they are within the scope of protection of this application document.

[0062] The specific operation process is to first set the reference voltage value V in the storage module. ref , set the threshold parameters of voltage change in the threshold module; when the discharge circuit starts, compare V CC The partial pressure βV CC With V ref The size relationship, when βV CC >V ref When the comparator output is high, the switch unit M O Turn on, V CC The voltage is gradually lowered; when βV CC ≤V refWhen the comparator outputs a signal to control the switch unit M O In the non-conducting state, no V CC Discharge is performed. Switching unit M O In the on state, V CC The voltage is always within the threshold parameters set by the threshold module.

[0063] The discharge circuit also includes a sampling and holding module. The reference voltage is sampled by the sampling and holding module. One end of the sampling and holding module is connected to V CC The voltage sampling circuit captures the voltage at the start of the demagnetization cycle. The other end is connected to the negative input of the comparator. The sample-and-hold module inputs a reference voltage to the comparator. Any device that can achieve the aforementioned performance and function of the sample-and-hold module is within the scope of protection of this application.

[0064] The specific operation process is to first CC After sampling and holding βV CC _SH, then with βV CC Compare; due to βV CC _SH remains unchanged during a demagnetization cycle, while βV CC Will follow V CC decreases and decreases, when V CC When the value drops to a certain value, the switch unit M O Disconnect, V CC No longer lower.

[0065] The comparator voltage is the controller voltage V CC The sampling and holding voltage of the sample and hold module is βV CC _SH, βV CC _SH value and βV out Equal. V CC The discharge threshold is V CC β times, so V CC The discharge reference voltage is adjusted every cycle to ensure that after each cycle discharge, V CC The difference from the output voltage is fixed.

[0066] Discharge circuit control chip voltage V CC In the demagnetization stage, the initial state is not higher than the output voltage V out , according to the chip voltage V CC The voltage value is used to obtain the output voltage V out , and reduce the voltage value V by discharging CC , at each V CC Induction V out After the change, open the discharge circuit to make V CC The voltage decreases and eventually falls below V outIn this way, when the demagnetization time of the next cycle begins, V out >V CC , V out V CC Power is supplied so that the output voltage value can be correctly sampled in the next cycle. This discharge circuit and its sampling method make V CC It can sense the output voltage change in each cycle or several cycles, thereby achieving V CC V out The output voltage V out Precise sampling.

[0067] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced. Contents not described in detail in the embodiments of the present invention belong to the prior art known to professional and technical personnel in this field.

[0068] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for real-time detection of output voltage, characterized in that: Applied to AC-DC buck switching circuit, the switching circuit includes rectifier bridge, controller, diode D1, freewheeling diode D2, inductor L and output load, where the controller power supply voltage is V CC , the load voltage is V out , the specific steps include: Get the chip voltage V during the demagnetization phase of each cycle CC , when the chip voltage V CC When the chip voltage V CC Discharge to ensure the chip voltage V CC Peak value and output voltage V out Related; In this step, the chip operating voltage V CC , controlled within a reasonable range to prevent the chip from working V CC The voltage is higher than the output voltage V out , leading to the equation V CC +V D1 =V out +V D2 does not hold true to save the output voltage V out Sampling resistor; where V D1 and V D2 are the forward voltage drops of diodes D1 and D2 respectively; The chip voltage V is obtained during the demagnetization phase of each cycle. CC The steps include: Obtain the chip voltage V through the voltage divider circuit CC , where the divided voltage V FB =βV CC ; Get the chip voltage V during the demagnetization phase of each cycle CC Peak voltage value; The chip voltage V is obtained during the demagnetization phase of each cycle. CC The step of measuring the peak voltage value includes: sampling multiple chip voltages V in a preset time period during the demagnetization stage CC , take the highest value; According to the chip voltage V CC The peak voltage value is calculated using the equation V CC +V D1 =V out +V D2 , get the output voltage V out ; When the chip voltage V CC When the voltage peaks in the demagnetization phase are equal, the system is considered to have entered a steady state. At this time, the chip voltage V CC The peak voltage value and output voltage V out equal.

2. The method for real-time output voltage detection according to claim 1, wherein: The reference voltage is a preset value, or the reference voltage V ref is the chip operating voltage V at the beginning of each demagnetization stage CC The initial value of .

3. A circuit for real-time detection of output voltage, characterized in that: A discharge circuit is included, and the discharge circuit controls the voltage of the controller according to the method according to any one of claims 1-2.

4. The circuit for real-time output voltage detection according to claim 3, characterized in that: The discharge circuit includes a comparator, the input terminals of which are connected to a reference voltage and V CC The sampling voltage is obtained, and the output end of the comparator is connected to the switch unit, and the signal output by the comparator controls the operation of the switch unit.

5. The circuit for real-time output voltage detection according to claim 4, characterized in that: The switch unit is a MOS tube, the gate of the MOS tube is connected to the comparator, and the source is connected to the controller power supply V through the resistor R1. CC Connection, drain ground.

6. The circuit for real-time output voltage detection according to claim 5, characterized in that: The discharge circuit also includes V CC Voltage sampling circuit, the V CC The voltage sampling circuit includes a resistor R2 and a resistor R3 connected in series, one end of the resistor R2 is connected to the controller power supply V CC One end of the resistor R3 is connected to the resistor R2, and the other end is grounded.

7. The circuit for real-time output voltage detection according to claim 6, characterized in that: The reference voltage is sampled by a sampling and holding module, one end of which is connected to the V CC The voltage sampling circuit obtains the voltage at the beginning of the demagnetization period, and the other end is connected to the input end of the comparator. The sampling and holding module inputs a reference voltage to the comparator.

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