A switching power supply circuit with uA-level no-load loss for BMU power supply

Abstract

The present invention discloses a switching power supply circuit with uA-level no-load loss for BMU power supply, which includes a main switching power supply circuit. The main switching power supply circuit includes a switching tube, a freewheeling diode, a filter inductor and a filter capacitor. The main switching power supply circuit is connected to a battery pack obtained by connecting multiple batteries in series to supply power to the whole. According to the characteristic of small BMU load current, the control method of the present invention is to generate a fixed and extremely small duty cycle oscillation signal as the PWM signal of the switching tube, so that the switching tube must work in the current discontinuous state, and at the same time, the output voltage is used to control the generation of the oscillation signal, so as to achieve the purpose of controlling the voltage. Such a design makes the circuit simple, with small driving loss, automatically limits the output current when the output is short-circuited, and has high reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and specifically to a switching power supply circuit with uA-level no-load loss for BMU power supply. Background Art

[0002] In the application scenarios of electrochemical energy storage and electric vehicles, it is often necessary to supply power in series with hundreds of batteries. These batteries are often first assembled into battery packs and then the battery packs are connected in series. There is a BMU in each battery pack for battery state estimation and protection. In the conventional technology, the power supply of the BMU often adopts the form of external centralized power supply. Such a power supply method requires power supply connections for each battery module, which increases the cost of the system and reduces the reliability of the system. In fact, we can draw power from the battery pack to generate the power supply required by the BMU, but this requires solving two problems:

[0003] 1. When the battery is not charging or discharging, the power supply of the BMU must be maintained, but only uA-level current can be drawn from the battery to avoid errors in the state of charge estimation of the battery or over-discharge of the battery caused by long-term small-current discharge and damage;

[0004] 2. When the battery is charging or discharging, it is necessary to ensure the efficiency of the BMU power supply to avoid excessive loss and cause thermal reliability problems of components.

[0005] Obviously, a switching power supply is used to step down the voltage of the battery pack to solve problem 2, but a general switching power supply chip often consumes several mA of current when it is no-load, which cannot solve problem 1. To solve problem 1, a switching power supply with low loss under no-load conditions needs to be found.

[0006] Therefore, a switching power supply circuit with uA-level no-load loss for BMU power supply is proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a switching power supply circuit with uA-level no-load loss for BMU power supply to solve the problems raised in the above background art.

[0008] To achieve the above purpose, the present invention provides the following technical solution: A switching power supply circuit with uA-level no-load loss for BMU power supply, including a main switching power supply circuit;

[0009] The main switching power supply circuit includes a switching tube, a freewheeling diode, a filter inductor and a filter capacitor;

[0010] The main switching power supply circuit is connected to a battery pack obtained by connecting multiple batteries in series for overall power supply;

[0011] The battery pack is connected to a starting circuit UB1 that provides a starting voltage and a low-power consumption control circuit UB4 that detects voltage;

[0012] The low-power consumption control circuit UB4 is connected to a fixed small-duty cycle square wave generator UB2;

[0013] The fixed small-duty cycle square wave generator UB2 is connected to a low-power consumption drive circuit UB3 that reduces drive static loss. The outputs DRV+ and DRV- of the low-power consumption drive circuit UB3 are respectively connected to the positive and negative electrodes of the switch tube input.

[0014] Preferably: The starting circuit UB1 includes a voltage source U01 and a voltage follower U02;

[0015] The voltage source U01 includes a resistor R38 and a diode D31;

[0016] One end of the resistor R38 is connected to VDD, the other end is connected to the diode D31 and serves as the output of the voltage source U01, and the other end of the diode D31 is connected to the negative electrode B- of the battery pack.

[0017] Preferably: The voltage follower U02 includes a triode Q31, a resistor R31, a resistor R37, and a MOS tube Q36;

[0018] The E pole of the triode Q31 is connected to the output of the voltage source U01, the C pole of the triode Q31 is connected to one end of the resistor R31 and the G pole of the MOS tube Q36, the other end of the resistor R31 is connected to the positive electrode B+ of the battery pack, the B pole of the triode Q31 is connected to VDD after being connected in series with the resistor R37, the D pole of the MOS tube Q36 is connected to B+, and the S pole is connected to VDD.

[0019] Preferably: The fixed small-duty cycle square wave generator UB2 includes a resistor R32, a resistor R33, an oscillating capacitor C31, a triode Q32, and a logic NAND gate U31;

[0020] The input A of the logic NAND gate U31 is connected to one end of the oscillating capacitor C31, the other end of the capacitor C31 is grounded, the output of the logic NAND gate U31 is connected to the resistor R33 and the B pole of the triode Q32, and the E pole of the triode Q32 is connected to the resistor R32.

[0021] Preferably: The low-power consumption drive circuit UB3 includes a power amplifier U|1, an anti-saturation circuit U12, and an isolation transformer;

[0022] The power amplifier U11 includes a MOS tube Q33 and a MOS tube Q34;

[0023] The anti-saturation circuit U12 is a resistor R34;

[0024] The MOS transistors Q33 and Q34 are connected to the output of the logic NAND gate U31. The D electrodes of the MOS transistors Q33 and Q34 are connected to one end of the resistor R34, and the other end of the resistor R34 is connected to the isolation transformer TX31.

[0025] Preferably, the main circuit of the switching power supply includes a switching transistor Q35, a freewheeling diode D32, a filter inductor L31, and a filter capacitor C32.

[0026] The filter inductor L31 and the switching transistor Q35 are connected to the isolation transformer TX31. The two ends of the filter inductor L31 are also respectively connected to the freewheeling diode D32 and the filter capacitor C32.

[0027] Preferably, the low-power control circuit UB4 includes a resistor R35, a resistor R36, and a comparator U33.

[0028] U33 is a comparator with a reference voltage output. The reference voltage output is connected to the non-inverting input terminal of the comparator U33. The resistors R35 and R36 are connected in series and connected across the two ends of the capacitor C32 to form a voltage sampling circuit, and the intermediate connection point is connected to the inverting input terminal of U33.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: The switching power supply of the present invention uses simple logic devices as the control core of the switching power supply, thereby realizing the micro-power consumption of the switching power supply control circuit. According to the characteristic that the load current of the BMU is small, the control method of the present invention is to generate a fixed and extremely small duty cycle oscillation signal as the PWM signal of the switching transistor, so that the switching transistor must work in the current discontinuous state, and at the same time, the output voltage is used to control the generation of the oscillation signal, so as to achieve the purpose of controlling the voltage. Such a design makes the circuit simple, the driving loss small, automatically limits the output current when the output is short-circuited, and has high reliability. Description of the Drawings

[0030] Figure 1 is the circuit block diagram of the present invention;

[0031] Figure 2 is the block diagram of the starting circuit of the present invention;

[0032] Figure 3 is the block diagram of the low-power drive circuit of the present invention;

[0033] Figure 4 is the circuit diagram of the present invention. Detailed Embodiment

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Embodiment

[0035] Please refer toFigures 1-4 , the present invention provides a technical solution: a switching power supply circuit with uA-level no-load loss for BMU power supply, including a main switching power supply circuit;

[0036] The main switching power supply circuit includes a switching tube, a freewheeling diode, a filter inductor, and a filter capacitor;

[0037] The main switching power supply circuit is connected to a battery pack formed by connecting batteries B01 to B16 in series to supply power to the whole;

[0038] The battery pack is connected to a starting circuit UB1 that provides a starting voltage and a low-power consumption control circuit UB4 that detects voltage;

[0039] The low-power consumption control circuit UB4 is connected to a fixed small-duty-cycle square wave generator UB2;

[0040] The fixed small-duty-cycle square wave generator UB2 is connected to a low-power consumption drive circuit UB3 that reduces the drive static loss. The outputs DRV+ and DRV- of the low-power consumption drive circuit UB3 are respectively connected to the positive and negative poles of the input of the switching tube. When the switching tube is a MOSFET, they are connected to its G and S poles.

[0041] As Figure 2 and Figure 4 shown: The starting circuit UB1 includes a voltage source U01 and a voltage follower U02;

[0042] The voltage source U01 includes a resistor R38 and a diode D31;

[0043] One end of the resistor R38 is connected to VDD, the other end is connected to the diode D31 and serves as the output of the voltage source U01, and the other end of the diode D31 is connected to the negative pole B- of the battery pack.

[0044] As Figure 2 and Figure 4 shown: The voltage follower U02 includes a triode Q31, a resistor R31, a resistor R37, and a MOS tube Q36;

[0045] The E pole of the triode Q31 is connected to the output of the voltage source U01, the C pole of the triode Q31 is connected to one end of the resistor R31 and the G pole of the MOS tube Q36, the other end of the resistor R31 is connected to the positive pole B+ of the battery pack, the B pole of the triode Q31 is connected to VDD after being connected in series with the resistor R37, the D pole of the MOS tube Q36 is connected to B+, and the S pole is connected to VDD; Through the above settings, when power is applied, the starting circuit UB1 provides a starting voltage to VDD. After the start is completed, the VDD voltage is higher than the starting voltage, and the output of the starting circuit UB1 naturally turns off, and the starting circuit enters a low-power consumption state.

[0046] As Figure 4As shown: The fixed small-duty-cycle square-wave generator UB2 includes a resistor R32, a resistor R33, an oscillation capacitor C31, a triode Q32, and a logic NAND gate U31;

[0047] One input terminal A of the logic NAND gate U31 is connected to one end of the oscillation capacitor C31, and the other end of the capacitor C31 is grounded. The output of the logic NAND gate U31 is connected to the resistor R33 and the base of the triode Q32, and the emitter of the triode Q32 is connected to the resistor R32. Through the above settings, the fixed small-duty-cycle square-wave generator UB2 generates a square-wave signal with a fixed duty cycle to drive the switching tube of the switching power supply, and the duty cycle of this square-wave signal is very small, with a duty cycle of 0.25%, so as to ensure that the switching power supply always operates in the current discontinuous mode, which enables the switching power supply to naturally obtain the ability of output current limiting without the need for an additional current limiting circuit, thus also reducing the static power consumption of the circuit.

[0048] As Figure 3 and Figure 4 As shown: The low-power drive circuit UB3 includes a power amplifier U11, an anti-saturation circuit U12, and an isolation transformer;

[0049] The power amplifier U11 includes a MOS tube Q33 and a MOS tube Q34;

[0050] The anti-saturation circuit U12 is a resistor R34;

[0051] The MOS tubes Q33 and Q34 are connected to the output of the logic NAND gate U31. The drains of the MOS tubes Q33 and Q34 are connected to one end of the resistor R34, and the other end of the resistor R34 is connected to the isolation transformer TX31. Through the above settings, in the form of transformer isolation, the static loss of the drive is reduced.

[0052] As Figure 4 As shown: The main circuit of the switching power supply includes a switching tube Q35, a freewheeling diode D32, a filter inductor L31, and a filter capacitor C32;

[0053] The filter inductor L31 and the switching tube Q35 are connected to the isolation transformer TX31, and the two ends of the filter inductor L31 are also respectively connected to the freewheeling diode D32 and the filter capacitor C32.

[0054] As Figure 4 As shown: The low-power control circuit UB4 includes a resistor R35, a resistor R36, and a comparator U33;

[0055] U33 is a comparator with a reference voltage output. The reference voltage output is connected to the non-inverting input terminal of the comparator U33. Resistors R35 and R36 are connected in series and across both ends of capacitor C32 to form a voltage sampling circuit, and the connection point in the middle is connected to the inverting input terminal of U33. Through the above settings, the low-power control circuit UB4 detects VDD, and its output signal serves as the enable signal for the fixed small-duty-cycle square-wave generator UB2. When the low-power control circuit UB4 detects that VDD is higher than the set value, its output signal prohibits the fixed small-duty-cycle square-wave generator UB2 from generating square-wave pulses. When the low-power control circuit UB4 detects that VDD is lower than the set value, its output signal allows the fixed small-duty-cycle square-wave generator UB2 to generate square-wave pulses. This makes the control circuit simple and effective and reduces the static power consumption.

[0056] Working principle:

[0057] Resistors R31, diode D31, triode Q31, resistor R37, resistor R38, and MOS transistor Q36 form the startup circuit UB1.

[0058] Resistors R38 and diode D31 form the voltage source U01. One end of resistor R38 is connected to VDD, the other end is connected to diode D31 and serves as the output of the voltage source, and the other end of diode D31 is connected to the negative terminal B- of the battery pack (i.e., the circuit ground).

[0059] The voltage follower U02 is implemented by triode Q31, resistors R31, R37, and MOS transistor Q36, and can also be replaced by other devices with amplification capabilities, such as triodes. The output of the voltage source is connected to the E pole of triode Q31. The C pole of triode Q31 is connected to one end of resistor R31 and the G pole of MOS transistor Q36. The other end of resistor R31 is connected to the positive terminal B+ of the battery pack. The B pole of Q31 is connected to VDD after series-connected with resistor R37. The D pole of MOS transistor Q36 is connected to B+, and the S pole of MOS transistor Q36 is connected to VDD, which is also the output of the startup circuit.

[0060] Resistors R32, R33, oscillating capacitor C31, triode Q32, and logic NAND gate U31 form the fixed small-duty-cycle square-wave generator UB2, and can also be replaced by other square-wave generators. For example, it can be composed of a comparator and resistive-capacitive elements. U31 is a logic NAND gate, and its input terminal A is connected to one end of the oscillating capacitor C31, and the other end of the oscillating capacitor C31 is grounded. When powered on, U31 outputs a high level and charges the oscillating capacitor C31 through resistor R33. When the voltage of the oscillating capacitor C31 is higher than the high-level threshold of U31, U31 outputs a low level and discharges the oscillating capacitor C31 rapidly through resistor R33, resistor R32, and triode Q32. The output of U31 is also the output of the fixed small-duty-cycle square-wave generator and serves as the input signal for the subsequent drive circuit.

[0061] MOS transistor Q33, MOS transistor Q34, resistor R34, and isolation transformer TX31 form a low-power drive circuit. Among them, MOS transistors Q33 and Q34 form a power amplifier. Resistor R34 is an anti-saturation circuit, and the anti-saturation circuit can also be implemented by a capacitor.

[0062] Q35, D32, L31, and C32 form the main circuit of a conventional BUCK switching power supply. Q35 is a switching transistor, which is a MOSFET here and can also be replaced by other switching devices. D32 is a freewheeling diode. L31 and C32 are the output filter inductor and output filter capacitor respectively.

[0063] Resistors R35, R36, and U33 form a low-power control circuit. Among them, U33 is a comparator with a reference voltage output. The reference voltage output is connected to the non-inverting input terminal of U33. Resistors R35 and R36 are connected in series and across both ends of capacitor C32 to form a voltage sampling circuit, and the intermediate connection point is connected to the inverting input terminal of U33. Resistors R35, R36, and the reference voltage output of U33 jointly determine the reference value VREF of the output voltage of the switching power supply. The output terminal of U33 is connected to the other input terminal B of U31. When the VDD voltage is higher than VREF, U33 outputs a low level, the square wave generator outputs a constant high level, and Q35 is turned off; when the VDD voltage is lower than VREF, U33 outputs a high level, the square wave generator outputs a square wave signal, and Q35 operates in a continuous switching state.

[0064] An extremely low no-load loss. For a lithium iron phosphate battery pack with 16 cells in series, when the supply voltage is 5V and no load is connected, the current drawn by the switching power supply of the present invention from the battery pack is less than 1uA.

[0065] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A switching power supply circuit with uA-level no-load loss for BMU power supply, including a main switching power supply circuit, characterized in that: The main switching power supply circuit includes a switching transistor, a freewheeling diode, a filter inductor, and a filter capacitor; The main switching power supply circuit is connected to a battery pack obtained by connecting multiple batteries in series to supply power to the whole; The battery pack is connected to a starting circuit UB1 that provides a starting voltage and a low-power consumption control circuit UB4 that detects voltage; The low-power consumption control circuit UB4 is connected to a fixed small-duty-cycle square wave generator UB2; The fixed small-duty-cycle square wave generator UB2 is connected to a low-power consumption drive circuit UB3 that reduces the drive static loss, and the outputs DRV+ and DRV- of the low-power consumption drive circuit UB3 are respectively connected to the positive and negative poles of the input of the switching transistor; The fixed small-duty-cycle square wave generator UB2 includes a resistor R32, a resistor R33, an oscillating capacitor C31, a triode Q32, and a logic NAND gate U31; One end of the oscillating capacitor C31, the resistor R32, and the resistor R33 is connected to the input terminal A of the logic NAND gate U31, the output terminal of the low-power consumption control circuit UB4 is connected to the input terminal B of the logic NAND gate U31, the other end of the capacitor C31 is grounded, the output terminal of the logic NAND gate U31 is connected to the other end of the resistor R33 and the base of the triode Q32, and the emitter of the triode Q32 is connected to the other end of the resistor R32.

2. The switching power supply circuit with uA-level no-load loss for BMU power supply according to claim 1, characterized in that: The starting circuit UB1 includes a voltage source U01 and a voltage follower U02; The voltage source U01 includes a resistor R38 and a diode D31; One end of the resistor R38 is connected to VDD, the other end is connected to the diode D31 and serves as the output of the voltage source U01, and the other end of the diode D31 is connected to the negative pole B- of the battery pack.

3. The switching power supply circuit with uA-level no-load loss for BMU power supply according to claim 2, wherein: The voltage follower U02 includes a triode Q31, a resistor R31, a resistor R37, and a MOS transistor Q36; The emitter of the triode Q31 is connected to the output of the voltage source U01, the collector of the triode Q31 is connected to one end of the resistor R31 and the gate of the MOS transistor Q36, the other end of the resistor R31 is connected to the positive pole B+ of the battery pack, the base of the triode Q31 is connected to VDD after being connected in series with the resistor R37, the drain of the MOS transistor Q36 is connected to B+, and the source is connected to VDD.

4. A switching power supply circuit with uA-level no-load loss for BMU power supply according to claim 1, characterized in that: The low-power consumption drive circuit UB3 includes a power amplifier U11, an anti-saturation circuit U12, and an isolation transformer; The power amplifier U11 includes a MOS transistor Q33 and a MOS transistor Q34; The anti-saturation circuit U12 is a resistor R34; The MOS transistors Q33 and Q34 are connected to the output of the logic NAND gate U31, the drains of the MOS transistors Q33 and Q34 are connected to one end of the resistor R34, and the other end of the resistor R34 is connected to the isolation transformer TX31.

5. The switching power supply circuit with uA-level no-load loss for BMU power supply according to claim 1, characterized in that: The main switching power supply circuit includes a switching transistor Q35, a freewheeling diode D32, a filter inductor L31, and a filter capacitor C32; The filter inductor L31 and the switching transistor Q35 are connected to the isolation transformer TX31, and the two ends of the filter inductor L31 are also respectively connected to a freewheeling diode D32 and a filter capacitor C32.

6. The switching power supply circuit with uA-level no-load loss for BMU power supply according to claim 1, wherein: The low-power consumption control circuit UB4 includes a resistor R35, a resistor R36, and a comparator U33; U33 is a comparator with a reference voltage output. The reference voltage output is connected to the non-inverting input terminal of the comparator U33. The resistor R35 and the resistor R36 are connected in series and connected across both ends of the capacitor C32 to form a voltage sampling circuit, and the middle connection point is connected to the inverting input terminal of U33.

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