Circuit for reducing standby power consumption

Abstract

The utility model discloses a circuit for reducing standby power consumption, which is used for reducing the standby power consumption of a charger and comprises a voltage sampling circuit, a voltage feedback circuit and a pulse width control circuit, and the voltage sampling circuit is connected between the voltage feedback circuit and the pulse width control circuit. The pulse width control circuit is provided with a pulse width signal receiving end used for being connected with a PWM signal output pin of an MCU of the charger; and the voltage sampling circuit is connected to a reference potential of a controller in the voltage feedback circuit through central nodes of an upper bias resistor and a lower bias resistor of the voltage sampling circuit.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic circuit technical field especially is related to a circuit that reduces standby power consumption. BACKGROUND

[0002] With the increasing demand for mobile wireless electric tools in people's life and production process, in addition to emphasizing simple and practical, higher requirements are put forward for standby time and endurance. Lithium batteries and other energy storage units are used more and more in mobile wireless electric tools, driving the rapid development of chargers and the expectation of high efficiency and energy saving, especially the expectation of as low standby power loss as possible.

[0003] The existing charger still has a high output voltage in standby mode. At this time, the primary side PWM control chip power supply winding and the secondary side MCU power supply winding according to the turn ratio relationship with the output winding, the voltage output by the auxiliary power supply winding is also a high voltage. At this time, the power loss of each power supply winding to the low dropout regulator (LDO) is P loss =(Vin-Vo)*Io, where Vin is the LDO power supply voltage, Vo and Io are the LDO output voltage and output current respectively. SUMMARY

[0004] In view of this, the utility model provides a circuit for reducing standby power consumption, which reduces the standby power consumption of the charger at a very low cost by changing the feedback loop control mode.

[0005] A circuit for reducing standby power consumption is used to reduce the standby power consumption of a charger, comprising a voltage sampling circuit, a voltage feedback circuit and a pulse width control circuit. The voltage sampling circuit is connected between the voltage feedback circuit and the pulse width control circuit. The pulse width control circuit has a pulse width signal receiving end for connecting the PWM signal output pin of the MCU of the charger. The voltage sampling circuit is connected to the reference potential of the controller in the voltage feedback circuit through the center node of the upper bias resistor and the lower bias resistor.

[0006] Further, the voltage sampling circuit comprises the upper bias resistor and the lower bias resistor, wherein the first end of the upper bias resistor is connected to the voltage output end of the charger, the second end of the upper bias resistor is connected to the first end of the lower bias resistor, and the second end of the lower bias resistor is grounded. The reference potential of the controller in the voltage feedback circuit is connected to the second end of the upper bias resistor and the first end of the lower bias resistor.

[0007] Further, the pulse width control circuit comprises a diode and a filter circuit, wherein the positive pole of the diode is connected to the second end of the upper bias resistor and the first end of the lower bias resistor, the negative pole of the diode is connected to the first end of the filter circuit, and the second end of the filter circuit is used for connecting the PWM signal output pin of the MCU.

[0008] Further, the filter circuit is an RC filter circuit.

[0009] Further, the RC filter circuit comprises two series-connected resistors and a capacitor, the two series-connected resistors are connected between the negative pole of the diode and the PWM signal output pin of the MCU, and one end of the capacitor is connected between the two resistors and the other end is grounded.

[0010] Further, the controller of the voltage feedback circuit is an adjustable precision voltage regulator, and the voltage feedback circuit realizes the charger output voltage negative feedback regulation function through the adjustable precision voltage regulator and a photoelectric coupler.

[0011] Further, the voltage feedback circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, the photoelectric coupler, a first diode, a first capacitor, and the adjustable precision voltage regulator; wherein the first end of the first resistor is connected to a first reference potential, the second end is connected to the second resistor, the first end of the first capacitor is connected to the fourth resistor, and the second end is connected to the second end of the upper bias resistor and the first end of the lower bias resistor; the first resistor, the second resistor, the third resistor, the first diode, the fourth resistor, and the first capacitor are connected in series; the photoelectric coupler is connected in parallel with the second resistor; the positive pole of the adjustable precision voltage regulator is grounded, and the negative pole is connected to the negative pole of the first diode; and the positive pole of the first diode is connected to the third resistor.

[0012] Further, the voltage sampling circuit provides the minimum output voltage of the charger in standby mode based on the reference potential of the upper bias resistor, the lower bias resistor, and the controller.

[0013] Further, the pulse width control circuit is controlled by the MCU, and in the standby mode of the charger, the pulse width control circuit does not work, and in the working mode of the charger, the pulse width control circuit adjusts the charger output voltage to the required value according to the PWM signal output by the MCU.

[0014] The beneficial effects of the technical scheme of the utility model lie in: when the charger is not loaded, that is, in the standby mode, the circuit of the utility model can make the output voltage of the charger be the lowest no-load voltage as possible, so as to reduce the input voltage of the LDO circuit in the charger as possible, and then reduce the voltage difference between the input voltage and the output voltage of the LDO, so as to reduce the power loss of the LDO circuit and reduce the standby power consumption. Further, the MCU (Microcontroller Unit) of the charger does not need to work to output the Duty-PWM (Duty-Pulse Width Modulation) signal in the standby mode, the MCU enters the sleep mode, the power loss of the MCU is reduced, and thus the overall power consumption of the charger is further reduced; meanwhile, the circuit can meet the requirement of lifting the voltage when the load is connected, and a complex circuit does not need to be added. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is the circuit principle diagram of the utility model embodiment for reducing the standby power consumption of the charger.

[0016] Figure 2 is the circuit block diagram of the charger product in the utility model embodiment.

[0017] Figure 3 is the output voltage of the charger in the utility model embodiment in the standby mode and the working mode.

[0018] Figure 4 is the standby power consumption comparison diagram of the circuit of the utility model and the existing circuit in the actual application example. DETAILED DESCRIPTION

[0019] The utility model will be further described below in combination with the drawings, specific implementation manners and embodiments. It should be noted that the purpose of providing the embodiments is only for illustration, and not for any limitation.

[0020] The utility model embodiment provides a kind of circuit for reducing the standby power consumption of charger (hereinafter referred to as "the circuit"), Figure 1 As shown in the figure, it is a kind of exemplary circuit structure of the circuit, Figure 2 As shown in the figure, it is the exemplary circuit structure of the charger using the circuit. As Figure 1 And Figure 2 As shown in the figure, the circuit includes voltage sampling circuit, voltage feedback circuit and pulse width control circuit, voltage sampling circuit is connected between voltage feedback circuit and pulse width control circuit, pulse width control circuit is connected between voltage sampling circuit and charger MCU. Specifically, as Figure 1The center nodes of the upper and lower bias resistors of the voltage sampling circuit are connected to the reference potential of controller U1 in the voltage feedback circuit at point A, which is used to provide the sampled voltage signal to U1 to adjust the charger output voltage Vout; the pulse width control circuit is also connected to the voltage sampling circuit and the voltage feedback circuit at point A, which is used to adjust the output voltage Vout to a controllable voltage according to the Duty-PWM (Duty Cycle-Pulse Width Modulation) signal output by the MCU.

[0021] In some specific implementations, the voltage sampling circuit includes an upper bias resistor and a lower bias resistor. The first terminal of the upper bias resistor is connected to the charger's voltage output terminal Vout, and the second terminal is connected to the first terminal of the lower bias resistor. The second terminal of the lower bias resistor is grounded (GND). In the voltage feedback circuit, the controller's reference potential is connected to the second terminal of the upper bias resistor and the first terminal of the lower bias resistor. Figure 1 In the illustrated embodiment, the upper bias resistor includes two series resistors R5 and R6, and the lower bias resistor includes resistor R7. The reference potential of controller U1 in the voltage feedback circuit is connected between resistors R6 and R7, and the connection point is denoted as point A. The pulse width control circuit includes a diode D2 and an RC filter circuit. The RC filter circuit includes two series resistors R8 and R9 and a capacitor C2. One end of capacitor C2 is connected between resistors R8 and R9, and the other end is grounded to GND. The anode of diode D2 is connected to the second end of the upper bias resistor and the first end of the lower bias resistor, that is, the anode of diode D2 is also connected to point A along with the center node of the upper and lower bias resistors and the reference potential of controller U1. The cathode of diode D2 is connected to resistor R8, and resistor R9 is connected to the PWM signal output pin PWM_CV of the MCU, receiving the Duty-PWM signal from the MCU in the charger operating mode. The controller U1 of the voltage feedback circuit uses an adjustable precision voltage regulator. The voltage feedback circuit realizes the negative feedback regulation function of the charger output voltage through the adjustable precision voltage regulator and optocoupler PC1A.

[0022] Continue to refer to Figure 1In some specific embodiments, the voltage feedback circuit comprises resistors R1-R4, a photocoupler PC1A, a diode D1, a capacitor C1 and an adjustable precision voltage regulator U1. The first end of the resistor R1 is connected to a first reference potential (e.g. 12V), the second end of the resistor R1 is connected to the resistor R2, the first end of the capacitor C1 is connected to the resistor R4, and the second end of the capacitor C1 is connected to the second end of the upper bias resistor and the first end of the lower bias resistor (i.e. connected to point A); the resistor R1, the resistor R2, the resistor R3, the diode D1, the resistor R4 and the capacitor C1 are connected in series; the photocoupler PC1A is connected in parallel with the resistor R2 and optically coupled with the photocoupler PC1B on the primary side of the charger; the positive terminal of the adjustable precision voltage regulator U1 is connected to ground, and the negative terminal of the adjustable precision voltage regulator U1 is connected to the negative terminal of the diode D1; the positive terminal of the diode D1 is connected to the resistor R3. In the voltage feedback circuit, the functions of the resistors R1 and R3 are to limit and adjust the current of the photocoupler PC1A; the resistor R2 provides the lowest bias current for the photocoupler PC1A; the resistor R4 and the ceramic capacitor C1 form an RC circuit to adjust the response speed of the photocoupler PC1A. In the present embodiment, the adjustable precision voltage regulator U1 can be a TL431.

[0023] The working principle of the circuit for reducing the standby power consumption of the charger will be described in detail below with reference to Figure 1 and Figure 2 .

[0024] In the standby mode, the charger MCU does not work, and no Duty-PWM signal is output, so the pulse width control circuit does not participate in the circuit work. At this time, the output voltage Vout of the charger is controlled by the voltage sampling circuit. When the detection circuit of the charger detects that a load is connected, the MCU is awakened by the wake-up signal, and the charger enters the full-load working mode. At this time, the MCU generates a Duty-PWM signal with a duty cycle less than 50% to the pulse width control circuit to control the output voltage Vout (raised to the required voltage value). The maximum feature of the circuit is that in the standby mode, the lowest output voltage is controlled by the voltage sampling circuit to reduce the power loss of the whole machine, and when the full-load working mode is entered, the pulse width control circuit still participates in the work, and the output voltage controlled by the pulse width can be realized.

[0025] Specifically, in the standby mode, the circuit is essentially a feedback loop circuit of a TL431. At this time, the output voltage Vout of the charger is determined by the resistance values of R5, R6 and R7 and the reference potential of the TL431, i.e.

[0026]

[0027] Vref is the reference voltage of the adjustable precision voltage regulator TL431, which is usually 2.5V. Since R5, R6, R7 have been previously set to correspond to the proportion of the resistance value of the lower limit of the output voltage (the proportion of the sum of R5 and R6 to R7), the minimum output voltage can be obtained when the output voltage Vout is controlled by the voltage sampling circuit in standby mode.

[0028] As Figure 2 , according to the turn ratio relationship between the secondary MCU power supply winding and the output winding of the transformer, when the output winding obtains the minimum output voltage, the voltage at the diode D6 on the MCU power supply winding also reaches the minimum, that is, the input voltage of LDO2 is the lowest, while the output voltage of LDO2 is the reference voltage 12V unchanged, and at this time the difference between the input voltage and the output voltage of LDO2 is also minimized. At this time, the loss of LDO2 is:

[0029] P loss_LDO =(V in_min -V o )×I o (2)

[0030] Among them, V in_min is the input voltage of LDO2 in standby mode, V o is the output voltage of LDO2, and I o is the output current of LDO2.

[0031] It can be seen that in standby mode, the charger obtains the minimum output voltage through the setting of the voltage sampling circuit, thereby reducing the input-output voltage difference of the LDO circuit (including LDO-1 and LDO-2), reducing the power consumption of the LDO circuit in standby mode, and thereby reducing the power consumption of the charger circuit. At the same time, since the MCU does not work and enters sleep mode, the Duty-PWM signal does not need to be output, so the LDO output current I o will also be further reduced, and thereby the power consumption of the whole circuit is further reduced.

[0032] In the access load, full load working mode, MCU output Duty-PWM signal, pulse width control circuit D2, R8, R9, C2 participate in the whole working circuit, and only when Duty-PWM signal duty cycle <50% (because there is D2, only the pull-down current works, the pulse width control circuit works. At this time, according to Kirchhoff's law KCL, I1=I2+I3, the output voltage of the charger adjusted by the pulse width control circuit is:

[0033]

[0034] Among them, D is the duty cycle of Duty-PWM signal, D fThe forward voltage drop of diode D2. It can be seen that in the full load working mode, the circuit of the utility model controls the charger output voltage Vout at the required voltage value according to the Duty-PWM signal through the pulse width control circuit, and ensures the normal work of the charger.

[0035] In addition, through the above analysis, it can be seen that when the MCU enters the sleep mode in the standby mode, the TL431 negative feedback circuit can be used; when the standby mode is exited, the corresponding Duty-PWM signal output by the MCU can obtain the corresponding required voltage.

[0036] Specific application case:

[0037] A lithium battery charger product, the requirement specification requires to reduce the power loss in standby mode. Because the output voltage range of the charger is wide, and there are auxiliary power supply windings in the primary side and secondary side of the transformer, it is necessary to provide power supply for the primary side PWM control chip and the like, and low dropout linear regulator (LDO) is used, so it is important to reduce the loss of LDO. The input voltage range of the practical application circuit is 90-264V AC, and the output voltage range is 16.5V-45V. In the full load working mode, constant current and constant voltage output are realized through MCU control, and the power loss in standby mode is required to be <0.5W.

[0038] The device selection values of the practical application case are as shown in the following table 1:

[0039] Position Specification Unit U1 TL431 PC1 (PC1A, PC1B) PC817C (opto-coupler model) R1 620 Ω R2 2.2 KΩ R3 3.9 KΩ R4 180 KΩ R5.R6 100 KΩ R7 36 KΩ R8 5.6 KΩ R9 7.5 KΩ C1 0.1 μF C2 47 nF D1.D2 1N4148

[0040] The corresponding relationship between the output voltage in standby mode and the output voltage in full load working mode of the practical application case and the Duty-PWM signal Figure 3 As shown, in the standby mode, the MCU enters the sleep mode, and the output voltage is stabilized at 16.39V; in the full load working mode, the voltage feedback circuit, the pulse width control circuit and the voltage sampling circuit together constitute a feedback loop to adjust the output voltage according to the Duty-PWM signal of the MCU. The output voltage and the Duty-PWM signal are in inverse proportional linear relationship. When the duty ratio of the Duty-PWM signal is 0%, the output voltage is the highest, which is 45.4V. When the duty ratio of the Duty-PWM signal is >50%, the output voltage is the minimum value, which is 16.39V.

[0041] The same PCBA as the above practical application case is used, 16.39V (the no-load voltage in standby mode of the circuit in the embodiment) and 44.43V (the no-load voltage in standby mode of the traditional circuit) are obtained by changing D1, R5, R6 and R7, respectively. The charger whole machine power loss data in standby mode is tested, and the following table 2 is obtained:

[0042] Input voltage Conventional circuit standby power consumption Improved circuit standby power consumption 90V / 60Hz 799.72mW 313.82mW 110V / 60Hz 805.46mW 324.4mW 230V / 50Hz 853.24mW 373.0mW 264V / 50Hz 888.44mW 396.9mW

[0043] The measured power consumption data of Table 2 above is made into a line graph, as shown in Figure 4 It can be seen that the standby power consumption of the charger complete machine in the embodiment is reduced a lot, the circuit for reducing standby power consumption of the utility model plays a good role in reducing standby power consumption, the effect is very obvious, and the design expectation demand is reached. It is not only suitable for ordinary chargers, but also suitable for chargers with wide output voltage range; and the circuit structure is relatively simple, no complex and high-cost devices are used, and the circuit cost is extremely low.

[0044] The above is a further detailed description of the utility model in combination with specific preferred embodiments, and the specific implementation of the utility model cannot be limited to these descriptions. For those skilled in the art to which the utility model belongs, without departing from the concept of the utility model, a number of equivalent substitutions or obvious modifications can be made, and the performance or use is the same, which should be regarded as belonging to the protection scope of the utility model.

Claims

1. A circuit for reducing standby power consumption of a charger, for reducing standby power consumption, characterized by: The voltage sampling circuit is connected between the voltage feedback circuit and the pulse width control circuit, and the pulse width control circuit has a pulse width signal receiving end for connecting a PWM signal output pin of an MCU of the charger.

2. The circuit for reducing stand-by power consumption according to claim 1, wherein: The voltage sampling circuit includes the upper bias resistor and the lower bias resistor, wherein a first end of the upper bias resistor is connected to a voltage output end of the charger, a second end of the upper bias resistor is connected to a first end of the lower bias resistor, and a second end of the lower bias resistor is grounded.

3. The circuit for reducing stand-by power consumption as recited in claim 2, wherein: The pulse width control circuit includes a diode and a filter circuit, wherein a positive electrode of the diode is connected to the second end of the upper bias resistor and the first end of the lower bias resistor, a negative electrode of the diode is connected to a first end of the filter circuit, and a second end of the filter circuit is used for connecting the PWM signal output pin of the MCU.

4. The circuit for reducing stand-by power consumption according to claim 3, wherein: The filter circuit is an RC filter circuit.

5. The circuit for reducing stand-by power consumption according to claim 4, wherein: The RC filter circuit includes two series-connected resistors and a capacitor, one end of the capacitor is connected between the two resistors, and the other end of the capacitor is grounded.

6. The circuit for reducing stand-by power consumption according to claim 3, wherein: The controller of the voltage feedback circuit is an adjustable precision voltage source, and the voltage feedback circuit realizes the charger output voltage negative feedback adjustment function through the adjustable precision voltage source and a photoelectric coupler.

7. The circuit for reducing stand-by power consumption of claim 6, wherein: The voltage feedback circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, the photoelectric coupler, a first diode, a first capacitor, and the adjustable precision voltage source, wherein a first end of the first resistor is connected to a first reference potential, a second end of the first resistor is connected to the second resistor, a first end of the first capacitor is connected to the fourth resistor, and a second end of the first capacitor is connected to the second end of the upper bias resistor and the first end of the lower bias resistor; the first resistor, the second resistor, the third resistor, the first diode, the fourth resistor, and the first capacitor are connected in series; the photoelectric coupler is connected in parallel with the second resistor; a positive electrode of the adjustable precision voltage source is grounded, and a negative electrode of the adjustable precision voltage source is connected to a negative electrode of the first diode; and a positive electrode of the first diode is connected to the third resistor.

8. A circuit for reducing standby power consumption as claimed in any one of claims 1 to 7, characterized in that: The voltage sampling circuit provides the lowest output voltage of the charger in the standby mode based on the upper bias resistor, the lower bias resistor, and the reference potential of the controller.

9. The circuit for reducing stand-by power consumption of claim 8, wherein: The pulse width control circuit is controlled by the MCU, and does not work in the standby mode of the charger, and adjusts the charger output voltage to a required value according to the PWM signal output by the MCU in the working mode of the charger.

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