PSR control chip output voltage control circuit

Abstract

The utility model discloses a PSR control chip output voltage control circuit which is at least provided with a first feedback resistor RFB1, a second feedback resistor RFB2 and a shunting module, one end of the first feedback resistor RFB1 is connected with the output end of a primary winding of a transformer, the other end of the first feedback resistor RFB1 is connected with one end of the second feedback resistor RFB2 and the input end of the shunting module, and the other end of the first feedback resistor RFB1 is connected with the output end of the primary winding of the transformer. The other end of the second feedback resistor RFB2 is connected with the FB end of the PSR control chip, and the output end of the shunt module is connected with the Vin end of the PSR control chip; a first voltage output by a primary winding of the transformer is divided by the first feedback resistor RFB1 and the second feedback resistor RFB2 to generate a second voltage; and the shunting module is used for starting shunting to reduce the current IFB flowing through the second feedback resistor RFB2 when the second voltage is greater than or equal to the first preset voltage. By adopting the technical scheme provided by the utility model, the output voltage range is expanded, and the circuit can be applied to a switching power supply with a large output voltage range or compatible with battery packs with different string numbers and different types.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, in particular to an output voltage control circuit of a PSR control chip. Background Art

[0002] Since the single cell voltage and capacity of storage devices such as batteries and supercapacitors (for the sake of convenience, batteries and battery packs are used instead below) are relatively low, it is difficult to use them directly in large systems. In practical applications, multiple batteries are often required to be connected in series to increase the voltage, and multiple batteries are often required to be connected in parallel to increase the capacity.

[0003] Since it is difficult to achieve complete consistency in production environment, process parameters, and raw materials, each single cell produced is different. And due to differences in the use environment, the differences between single cells will become larger and larger over time. After N single cells are connected in series, the capacity of the entire battery pack is less than N times the capacity of the worst battery, making it difficult to exert the performance of the battery pack. In order to maximize the available performance of the battery pack, a balancing circuit must be added to the battery pack. Since large-capacity batteries are used in application scenarios such as electric vehicles and energy storage power stations, traditional passive balancing methods are difficult to cope with. Active balancing applications are the trend of the industry, and active balancing uses DC / DC circuits to complete the function. The active balancing circuit requires constant current and voltage limiting at the battery end. When the voltage is lower than the set voltage, there will be no overcurrent or overload protection.

[0004] PSR mode offline control chips have been widely used in small and high power supply circuits due to their perfect protection functions, high maturity, and low cost. Figure 1 As shown, V b For a single battery to be discharged, the output is a battery pack of n strings. The control chip extracts the output voltage information by detecting the voltage Vsw-Vin across the primary winding L1 of the transformer at the end of demagnetization (the closed-loop compensation circuit inside the control chip U1 controls VFB=Vin). The actual control is performed by R FB The current, I FB =(Vsw-Vin) / R FB , adjust R FB The output voltage setting can be adjusted by changing the resistance value, Vo=(Ns / Np)*I FB *R FB .

[0005] When the output is overloaded or short-circuited to the ground, the output voltage is relatively low, and the transformer may not have time to demagnetize, causing the transformer current to become larger and larger and then saturated and out of control. Therefore, the control chip usually has output voltage undervoltage protection (that is, overload / short-circuit protection). When the output voltage Vo is lower than k times the set voltage (k*Vor*Ns / Np, where k is the output undervoltage protection proportional coefficient set by the chip, such as 0.6, and Vor is the flyback voltage of the set output voltage at the primary winding), the control chip turns off the drive output (Drv), waits for a while for the transformer to be fully demagnetized, and then restarts.

[0006] Since the battery is an energy storage system, the battery voltage remains basically constant for the converter and changes slowly within a certain range. In order to ensure normal operation within the range, the set output voltage of the converter is usually greater than or equal to the maximum voltage of the battery. Therefore, when the battery voltage is not the maximum value, the output load (the battery is approximately a constant voltage source load) is overloaded for the converter. When the battery voltage is lower than k*Vor*Ns / Np, the control chip is overloaded and cannot work normally.

[0007] Usually, converter designs must be compatible with different numbers of strings and different types of battery packs, that is, they must be compatible with a relatively large output voltage range, while the control chip can only work normally within the range of (k*Vor~Vor). Since the proportional coefficient k set by the control chip cannot be modified by the external circuit, different resistance values ​​of feedback resistors R need to be adapted for applications with different numbers of battery strings. FB , or adapt to different transformer primary and secondary turns ratios.

[0008] From the above analysis, it can be seen that the existing solutions have at least the following disadvantages:

[0009] 1. The output voltage has a narrow application range and is limited in applications where the load voltage varies over a wide range;

[0010] 2. The circuit cannot be universal for applications with different numbers of batteries in series or different battery types. The feedback resistance value or the primary-secondary turns ratio of the transformer needs to be modified, which increases the difficulty of stocking.

[0011] Therefore, in view of the defects of the prior art, it is necessary to propose a technical solution to solve the technical problems existing in the prior art. Utility Model Content

[0012] In view of this, it is necessary to provide a PSR control chip output voltage control circuit, by setting the first feedback resistor R FB1 and the second feedback resistor R FB2 , and a shunt module is set to shunt from the middle point, thereby expanding the output voltage range.

[0013] In order to solve the technical problems existing in the prior art, the technical solution of the utility model is as follows:

[0014] A PSR control chip output voltage control circuit, at least a first feedback resistor R is set FB1 , the second feedback resistor R FB2 and shunt module, where the first feedback resistor R FB1 One end of the first feedback resistor R is connected to the output end of the primary winding of the transformer. FB1 The other end of the second feedback resistor R FB2 and the input end of the shunt module, the second feedback resistor R FB2 The other end is connected to the FB end of the PSR control chip, and the output end of the shunt module is connected to the Vin end of the PSR control chip; the first voltage output by the primary winding of the transformer is fed through the first feedback resistor R FB1 and the second feedback resistor R FB2 The shunt module is used to start the shunt when the second voltage is greater than or equal to the first preset voltage to reduce the current flowing through the second feedback resistor R FB2 The current I FB , otherwise it is in the cut-off state.

[0015] As a further improvement, when the first voltage is less than the second preset voltage, the Drv terminal of the PSR control chip turns off the driving output.

[0016] As a further improvement scheme, the shunt module includes at least a voltage threshold circuit and a current regulation circuit, wherein the voltage threshold circuit is used to turn on when the second voltage is greater than or equal to the first preset voltage, otherwise it is turned off; the current regulation circuit is used to regulate the loop current when the voltage threshold circuit is turned on.

[0017] As a further improvement, the shunt module further includes a reverse suppression circuit, which is used to prevent the shunt module from generating a reverse current.

[0018] As a further improvement, the voltage threshold circuit uses a voltage regulator Z1, the current regulation circuit uses a resistor R1, and the reverse suppression circuit uses a diode D1, wherein the negative end of the voltage regulator Z1 is connected to the first feedback resistor R FB1 and the second feedback resistor R FB2 The positive end of the voltage regulator Z1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the positive end of the diode D1, and the negative end of the diode D1 is connected to the Vin end of the PSR control chip.

[0019] As a further improvement, the resistor R1 is an adjustable resistor.

[0020] As a further improvement, the first preset voltage is the turn-on voltage V of the voltage regulator diode Z1 Z1 .

[0021] As a further improvement, the second preset voltage is:

[0022] Wherein,

[0023]

[0024] Vomin is the designed minimum output voltage, k is the voltage proportionality coefficient for the overload protection of the control chip, and 0 < k < 1; Vomin / k is the rated output voltage; is the turns ratio of the primary and secondary windings of the transformer; Vor is the voltage of the rated output voltage Vo reflected on the primary winding L1.

[0025] As a further improvement, the turn-on voltage V of the voltage regulator diode Z1 is set Z1 as: V z1 <I FB *R FB2 ;

[0026] Wherein, I FB is the feedback current.

[0027] As a further improvement,

[0028] The current flowing through the shunt module is:

[0029]

[0030] The maximum output voltage V omax can reach:

[0031]

[0032] Compared with the prior art, the present utility model expands the output voltage range by setting the first feedback resistor R FB1 and the second feedback resistor R FB2 , and setting the shunt module to shunt from the midpoint, so that it can be applied to a switching power supply with a large output voltage range, or be compatible with battery packs of different numbers of strings and different types; at the same time, in the actual production process, adopting the technical solution of the present utility model can be applicable to most application scenarios, without adjusting the circuit parameters according to each actual application, greatly reducing the difficulty of stocking in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 FIG. is the circuit schematic diagram of a small-power power supply constructed by a PSR control chip in the prior art.

[0034] Figure 2 The utility model provides a circuit schematic diagram of a PSR control chip output voltage control circuit.

[0035] Figure 3 The present invention provides a circuit diagram of a preferred implementation.

[0036] Figure 4 A circuit diagram of another preferred embodiment of the present invention is provided.

[0037] Figure 5 A circuit diagram of another preferred embodiment of the utility model is provided.

[0038] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0039] The technical solution provided by the utility model will be further described below in conjunction with the accompanying drawings.

[0040] See also Figure 2 , shown is a circuit schematic diagram of a PSR control chip output voltage control circuit provided by the utility model, at least a first feedback resistor R is set FB1 , the second feedback resistor R FB2 and shunt module, where the first feedback resistor R FB1 One end of the first feedback resistor R is connected to the output end of the primary winding of the transformer. FB1 The other end of the second feedback resistor R FB2 and the input end of the shunt module, the second feedback resistor R FB2 The other end is connected to the FB end of the PSR control chip, and the output end of the shunt module is connected to the Vin end of the PSR control chip; the output first voltage of the primary winding of the transformer is connected to the FB end of the PSR control chip through the first feedback resistor R FB1 and the second feedback resistor R FB2 The shunt module is used to start the shunt when the second voltage is greater than or equal to the first preset voltage to reduce the current flowing through the second feedback resistor R FB2 The current I FB , otherwise it is in the cut-off state.

[0041] In a preferred implementation, when the first voltage is less than the second preset voltage, the Drv terminal of the PSR control chip turns off the driving output.

[0042] In the above technical solution, the feedback resistor R FB Divide into two, namely R FB1 and R FB2, a shunt module is added between the connection points of the two resistors and the Vin terminal of the PSR control chip. The circuit parameters of the shunt module are designed. When the output voltage is in the low-voltage range, the shunt module does not work (is disconnected), and the circuit works normally as in the prior art Figure 1 When it is lower than the lower threshold (i.e., the second preset voltage), under-voltage (overload) protection is output; while when the output voltage is greater than the voltage set in the original manner, the shunt module works (conducts), and the feedback current I z shunts a part (I f ), and the feedback current I FB flowing into the control chip is less than the total feedback current I z , that is, the control chip believes that the output voltage has not reached the set value, so the actual effect is to increase the upper limit of the output voltage. As Figure 2 shown, the shunt module is designed not to work at low output voltages, the output overload protection function works normally, and the shunt module works at high output voltages, shunting a part of the feedback current and reducing the feedback current detected by the control chip. Among them, I z = I FB + I f , Vo = (Ns / Np) * (I FB * R FB2 + I z * R FB1 ) > (Ns / Np) * I FB (R FB2 + R FB1 ) = (Ns / Np) * I FB * R FB , thereby increasing the output voltage range.

[0043] See Figure 3 , the circuit schematic diagram of a preferred embodiment of the present invention is shown. Among them, the shunt module is composed of three parts: a voltage threshold circuit, a current regulation circuit, and a reverse current suppression circuit. Among them, the voltage threshold circuit is used to conduct when the second voltage is greater than or equal to the first preset voltage, otherwise it is turned off; the current regulation circuit is used to regulate the loop current when the voltage threshold circuit conducts. The reverse suppression circuit is used to prevent the shunt module from generating reverse current.

[0044] The voltage threshold circuit judges whether the voltage V FB2 across R RFB2 exceeds the set threshold Vth (i.e., the first preset voltage). If V RFB2 ≥Vth, it conducts and allows the I f current to pass. If V RFB2 <Vth, it is turned off and does not allow the I f current to pass; the current regulation circuit regulates the magnitude of I f , that is, the shunt magnitude, and further regulates the degree of expansion of the output voltage upper limit; the reverse suppression circuit blocks If When the current reverses, the voltage at the SW point is a pulse waveform, switching back and forth between 0V and V b +(Np / Ns)*Vo. When the SW point is 0V, the voltage across the shunt module reverses, and the current I f has a reverse tendency, interfering with normal operation and needs to be blocked.

[0045] See Figure 4 , which shows the circuit schematic diagram of another preferred embodiment of the present invention. Among them, the voltage threshold circuit uses the zener diode Z1, the current regulation circuit uses the resistor R1, and the reverse suppression circuit uses the diode D1. Among them, the negative terminal of the zener diode Z1 is connected to the first feedback resistor R FB1 and the second feedback resistor R FB2 are connected. The positive terminal of the zener diode Z1 is connected to one end of the resistor R1. The other end of the resistor R1 is connected to the positive terminal of the diode D1. The negative terminal of the diode D1 is connected to the Vin terminal of the PSR control chip.

[0046] In the above circuit, the zener diode Z1 forms a voltage threshold circuit, and the first preset voltage is the turn-on voltage V Z1 of the zener diode Z1. That is, when V RFB2 > V Z1 , Z1 conducts, and when V RFB2 < V Z1 it turns off; the resistor R1 adjusts the magnitude of the shunt current If; the diode D1 plays a role in suppressing the reverse current. It is designed that k*Vor is equal to the minimum output voltage Vomin. That is, when the output voltage is lower than k*Vor, output undervoltage protection (short-circuit protection) is performed, and the technical solution of the present invention can maintain this safety function. Specifically, it is shown in the following formula.

[0047]

[0048] The second preset voltage is:

[0049] Among them, Vomin is the designed minimum output voltage, k is the voltage proportionality coefficient of the overload protection of the control chip, 0 < k < 1; Vomin / k is the rated output voltage; is the turns ratio of the primary and secondary windings of the transformer; Vor is the voltage of the rated output voltage Vo reflected on the primary winding L1.

[0050] The feedback resistor is designed as follows:

[0051]

[0052] Set the turn-on voltage V Z1 of the zener diode Z1 to be: V z1 <I FB *RFB2 ; Among them, I FB is the feedback current. When the above circuit is working, the shunt module needs to be started before Vsw-Vin approaches Vor. z1 FB *R FB2 The Zener diode Z1 is turned on.

[0053] When the output voltage reaches the upper limit, the current flowing through the shunt module is:

[0054]

[0055] Using the technical solution of this utility model, the maximum output voltage V omax Accessible:

[0056] The output voltage range is greatly improved. The lower limit of the output voltage is determined by the resistance values ​​of RFB1 and RFB2. FB1 and R FB2 The voltage divider value of the resistance and the voltage of the voltage regulator tube VZ1 determine whether the shunt module is turned on, and the resistance value R1 can adjust the shunt current. In a preferred embodiment, the resistor R1 is an adjustable rheostat.

[0057] When the output voltage extension range accuracy is not required, the circuit can be simplified, and the voltage threshold / current regulation / reverse suppression can be achieved by a single diode. Figure 5 , which is a circuit schematic diagram of another preferred embodiment of the utility model, the diode D1 itself has a threshold voltage function, and the VI curve of the diode also has a current regulation function.

[0058] The technical solution of the utility model is not necessarily applicable to battery charging and discharging applications, but can also be applied to adjustable switching power supplies with a large variation range.

[0059] The above embodiments are only used to help understand the method and core idea of ​​the utility model. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made to the utility model without departing from the principle of the utility model, and these improvements and modifications also fall within the scope of protection of the claims of the utility model.

[0060] 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 may 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 will conform to the widest scope consistent with the principles and novel features disclosed herein.​

Claims

1. A PSR control chip output voltage control circuit, characterized in that: At least set the first feedback resistor R FB1 , the second feedback resistor R FB2 and shunt module, where the first feedback resistor R FB1 One end of the first feedback resistor R is connected to the output end of the primary winding of the transformer. FB1 The other end of the second feedback resistor R FB2 and the input end of the shunt module, the second feedback resistor R FB2 The other end is connected to the FB end of the PSR control chip, and the output end of the shunt module is connected to the Vin end of the PSR control chip; the first voltage output by the primary winding of the transformer is fed through the first feedback resistor R FB1 and the second feedback resistor R FB2 The shunt module is used to start the shunt when the second voltage is greater than or equal to the first preset voltage to reduce the current flowing through the second feedback resistor R FB2 The current I FB , otherwise it is in the cut-off state.

2. The PSR control chip output voltage control circuit according to claim 1, characterized in that: When the first voltage is less than the second preset voltage, the Drv terminal of the PSR control chip turns off the driving output.

3. The PSR control chip output voltage control circuit according to claim 1 or 2, characterized in that: The shunt module includes at least a voltage threshold circuit and a current regulating circuit, wherein the voltage threshold circuit is used to be turned on when the second voltage is greater than or equal to the first preset voltage, otherwise it is turned off; the current regulating circuit is used to regulate the loop current when the voltage threshold circuit is turned on.

4. The PSR control chip output voltage control circuit according to claim 3, characterized in that: The shunt module further includes a reverse suppression circuit, which is used to prevent the shunt module from generating a reverse current.

5. The PSR control chip output voltage control circuit according to claim 4, characterized in that: The voltage threshold circuit uses a voltage regulator tube Z1, the current regulation circuit uses a resistor R1, and the reverse suppression circuit uses a diode D1, wherein the negative end of the voltage regulator tube Z1 is connected to the first feedback resistor R FB1 and the second feedback resistor R FB2 The positive end of the voltage regulator Z1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the positive end of the diode D1, and the negative end of the diode D1 is connected to the Vin end of the PSR control chip.

6. The PSR control chip output voltage control circuit according to claim 5, characterized in that: The resistor R1 is an adjustable variable resistor.

7. The PSR control chip output voltage control circuit according to claim 5, characterized in that: The first preset voltage is the turn-on voltage V of the voltage regulator tube Z1. Z1 .

8. The PSR control chip output voltage control circuit according to claim 5, characterized in that: The second preset voltage is: in, Vomin is the minimum output voltage of the design, k is the voltage proportionality coefficient for the control chip's overload protection, where 0 < k < 1; Vomin / k is the rated output voltage; is the turns ratio of the primary and secondary windings of the transformer; Vor is the voltage of the rated output voltage Vo reflected on the primary winding L1.

9. The PSR control chip output voltage control circuit according to claim 7, characterized in that: Set the turn-on voltage V of the voltage regulator Z1 Z1 =V z1 FB *R FB2 ;​ Among them, I FB is the feedback current.

10. The PSR control chip output voltage control circuit according to claim 9, characterized in that: The current flowing through the shunt module is: Maximum output voltage V omax Accessible:

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