TWI422114B - A self powered feed forward charging circuit and design methodology for the protection of electrical energy storage devices - Google Patents

Description

Self-powered feedforward charging circuit and design method for protecting electronic energy storage device

The invention provides a charging design method for a super capacitor. In particular, the present invention provides a feedforward charging method for improving the charging technology of an energy storage element such as a super capacitor, which has low cost and simple structure.

As is well known, capacitors have many uses in electronic motor systems.

In terms of energy storage

When the capacitor is separated from its charging line, the capacitor stores energy, so it can be used as a battery to provide short-term power. Capacitors are commonly used in electronic devices used in conjunction with batteries to provide power when replacing batteries, to prevent stored data from disappearing due to lack of power. Capacitors are also commonly used in power supplies to mitigate the output of full-bridge or half-bridge rectifiers. Capacitors can also be used in a capacitive pump circuit to store energy to produce a higher voltage than the input voltage.

A supercapacitor (sometimes called an Electrochemical Double Layer Capacitor (EDLC) or an electric double layer capacitor) is an electrochemical capacitor with a high energy density, which is higher than a typical electrolytic capacitor. Thousand times. The derivative consumer product is applied as a charging power source for a snapshot function device, a portable media device or a solar device in a digital camera.

At present, there are three methods for charging supercapacitors commonly used in the industry: Among them: method (a): charging with a constant current to an operating voltage, and then charging with a constant voltage. Method (b): charging with a constant current to the vicinity of the operating voltage, converting to constant power charging, and then charging with a constant voltage. Method: (c) Voltage charging.

The foregoing two methods (a) and (b) require voltage detection and current detection, and have a complicated structure and high cost, and are suitable for use in equipment with high unit price and high power. Although the method (c) is simple in structure, when the super capacitor voltage exceeds the input voltage, the charging cannot be performed, so the efficiency is not good, and the requirement of the instantaneous maximum current or the maximum allowable operating temperature cannot be met, which may affect the service life of the super capacitor.

Therefore, it would be highly desirable to provide a charging method for a storage element such as a supercapacitor and its charging design circuit.

During the charging process of the super capacitor, the voltage and current of the charger must be kept below the maximum allowable voltage and maximum current or the maximum allowable operating temperature of the capacitor. Therefore, the industry usually uses constant current charging, followed by constant voltage charging, or The current is charged, followed by constant power and constant voltage charging, or only a simple voltage charging. Accordingly, the present invention is directed to a self-powered feedforward charging circuit and design method for an electronic energy storage device such as a supercapacitor. The difference between the conventional technology and the prior art is that a feedforward charging method and circuit are proposed to achieve the same design goal as the foregoing charging methods, and a simple, low-cost supercapacitor charging technology is completed. A theoretical charging design method is proposed for the existing supercapacitor to calculate the circuit parameters of the feedforward charger. In addition, the present technology also proposes two self-powered circuits, so that the charging system can be charged without an external power supply.

The self-powered feedforward charging circuit and design method proposed in the present case will not affect the service life of the capacitor for charging the general capacitor.

According to an aspect of the present invention, a charging method for an energy storage circuit is provided. The energy storage circuit includes a plurality of preset values, including:

(a) by using a self-charging circuit to receive a portion of the energy of the first electrical energy to supply a startup power required by a feedforward boost charging circuit; and (b) after the feedforward boost charging circuit is activated, The feedforward boost charging circuit charges the energy storage circuit in a feedforward manner, and the charged voltage and current do not exceed the preset values of the energy storage circuit, and energy transfer and transmission of the self-charging circuit The self-charging circuit provides a second electrical energy to the feedforward boost charging circuit.

According to still another object of the present invention, a self-powered feedforward charging circuit includes: a self-charging circuit for storing a portion of energy of a first electrical energy; and a feedforward boosting charging circuit for receiving from the self-charging circuit The energy of the first electric energy is activated; and a storage circuit includes a super capacitor and a protection circuit, and the feedforward boost charging circuit charges the energy storage circuit in a feedforward manner, and the feed forward The voltage charging circuit activates the protection circuit, and the protection circuit limits one of the supercapacitors to a maximum instantaneous current or a maximum operating temperature and a maximum voltage within a predetermined value.

The application direction of the supercapacitor will greatly expand as the storage capacity per unit volume increases. Current charging methods include technologies suitable for high-end product applications (such as automotive, solar, power, etc.) or for low-end applications (such as toys, emergency lighting, etc.). These designs are not complex in structure, high in cost (in terms of high-end), and are inefficient, and cannot meet the requirements of instantaneous maximum current (or maximum allowable operating temperature), which will affect the service life of supercapacitors (referring to the low end). ).

Therefore, as shown in FIG. 1, the figure proposes a self-powered feedforward charging circuit 1 which is derived from the conventional supercapacitor charging. The self-powered feedforward charging circuit 1 includes three circuits, which are a self-charging circuit 11, a feedforward boost charging circuit 12, and a tank circuit 13. As shown in FIG. 2, the more detailed electronic component connection relationship in each of the circuits 11, 12, and 13 is that the self-charging circuit 11 includes a first diode D1 and a second diode D2. The first capacitor C1, the second capacitor C2, the fourth resistor R4, and the Zener diode Z1 having a stable voltage function in parallel with the second capacitor C2.

The feedforward boost charging circuit 12 includes a first resistor R1, a second resistor R2, a third resistor R3, an inductor L, a first switch S1, a third diode D3, and a comparator CM. 1. The energy storage circuit 13 includes a super capacitor SC1 and a protection circuit 131 including a second switching switch S2 and a fifth resistor R5 connected in series.

The first switch S1 of the present invention is an N-type metal oxide semiconductor field effect transistor, abbreviated as NMOSFET for the implementation example, and a detailed description of the connection of the NMOSFET as the end point of the first switch S1 is as follows: A source terminal S of the first switch S1 is coupled to a ground, and a Drain terminal of the first switch S1 is coupled to the inductor L and the third A contact Vy between the poles D3 and a gate terminal G of the first switch S1 are coupled to one of the outputs of the comparator CM1.

Wherein, the second switch S2 is N Channel Depletion MOS, one of the second switch S2 is coupled to the drain D of the end of the fifth resistor R5, the second one of the switch S2 is coupled to a source S One end of the super capacitor SC1 and one gate G of the second switch S2 are coupled to the other end of the fifth resistor R5.

Notably, in the initial state of charging, the super capacitor SC1 connected in parallel with the protection circuit 131 in the tank circuit 13 is preset with a maximum allowable instantaneous current value I _MAX (or a maximum allowable operating temperature) and a The maximum allowable voltage is preset to V _MAX . And the self-powered feedforward charging circuit 11 is configured with the first diode D1 and the second diode D2 having a "Rectifying" function on each charging path and the storage circuit 13 The third diode D is disposed to prevent the current stored in the first capacitor C1, the second capacitor C2, and the super capacitor SC1 from being reversed.

Description of the charging period for the super capacitor SC1

This type of external energy (also referred to as one of the first electric energy A), including chemical energy (battery) and light energy (photovoltaic cell, solar cell, etc.), is released, and the first electric energy A is passed through the self-charging circuit 11 The fourth resistor R4 causes the second capacitor C2 to store the first power A. The state of charge is also that the first power A is charged through the fourth resistor R4 before the feedforward boost charging circuit 12 is activated (the energy stored in the second capacitor C2 is called For a second power).

After a charging time t, the voltage value of a node voltage Vp reaches a threshold value, and the comparator in the feedforward boost charging circuit 12 is respectively activated through a first charging path path 1 and a second charging path 2 CM 1 and the first switch S1, and the comparator CM1 is an open collector output. The node voltage Vp generates a driving current through the third resistor R3 to turn on the internal transistor of the comparator CM1.

And well known, the comparator CM 1 in the feed forward boost charging circuit 12 has two different input voltage values respectively at the two ends (the positive end (+) and the negative end (-)). The output of the comparator CM 1 outputs a voltage value of the node voltage Vp or a value close to zero volts. For example, if the positive terminal of the comparator CM 1 receives 5V and the negative terminal of the comparator CM 1 receives 4V, the output terminal of the comparator CM 1 outputs the voltage value of the node voltage Vp, if the comparison The positive terminal of the CM 1 receives 4V and the negative terminal of the comparator CM 1 receives 5V, and the output of the comparator CM 1 outputs a value close to zero volts.

In the present case, as shown in FIG. 3, a positive frequency (Saw Tooth Wave) of a fixed frequency is received at the positive end of the comparator CM 1 (need to understand that the sawtooth wave is a non-sinusoidal wave) Waveform (Non-Sinusoidal Waveform, in which the sawtooth wave input to the positive end of the comparator CM 1 climbs upwards with a gentle slope (Ramp) and rapidly falls with a steep slope. Forming a receiving voltage Vd between the first resistor R1 and the second resistor R2 at the negative terminal of the comparator CM1, wherein the input voltage Vd is via a voltage dividing circuit... The resulting voltage

Vd=V(1)*(R1/(R1+R2)) Equation 1, wherein the frequency of the sawtooth wave is 10 times or more the frequency of the input voltage Vd.

As shown in FIG. 3, the figure is a waveform diagram of the comparator CM 1 receiving two different electrical voltage values and outputting a large voltage value at an output terminal, wherein the vertical axis represents the voltage value and the horizontal axis represents the time.

During the period T1, when the positive terminal receives a voltage value Vs of the sawtooth wave that is greater than the input voltage Vd received by the negative terminal of the comparator CM1, the output of the comparator CM1 The node voltage Vp is output, wherein the node voltage Vp is greater than a specific threshold voltage V _th (Threshold Voltage), and then, when V _GS >V _th , the source S and the drain D of the NMOSFET S1 start to conduct. At this time, the NMOSFET S1 as a switch is in a Turn On state. The first power A charges the inductor L in the feedforward boost charging circuit 12 while the NMOSFET S1 as the switch is in an open state, and the first power A passes through the first diode D1. The first capacitor C1 is charged. At this time, the node voltage Vy is zero volts, so that the third diode D3 is in a non-conducting state, and the stored energy of the inductor L cannot charge the super capacitor SC1. When the feedforward boost charging circuit 12 is in a steady state, the current flowing through the inductor L is in a discontinuous current mode.

On the other hand, during the period T2, when the voltage value Vs of the sawtooth wave received by the positive terminal of the comparator CM1 is less than the input voltage Vd received by the negative terminal of the comparator CM1, the comparator CM1 The output outputs a voltage value close to zero volts, wherein the output voltage value is less than the threshold voltage _Vth , and then V _GS <V _th , and the source S and the drain D of the NMOSFET S1 are in an off state. At this time, the NMOSFET S1 as a switch is in a Turn Off state.

At this time, the NMOSFET S1 as a switch is in a closed state, and the node voltage Vy is boosted to turn on the third diode D3. The energy stored in the inductor L is subjected to the super capacitor SC1 via the third diode D3. Charging, the energy stored in the inductor L is transferred to the super capacitor SC1, and a part of the current I _{L of} the inductor L flows through the third diode D3 to include the second switch S2 and the fifth resistor R5. The protection circuit 131 is inside. The energy stored in the first capacitor C1 is transferred to the second capacitor C2 via the second diode D2. When the feedforward boost charging circuit 12 is in a steady state, the current flowing through the inductor L is in a discontinuous current mode.

However, for the length of the Turn-On time of the NMOSFET during T1 in Figure 3, this paper proposes...Feed Forward mode...

Ton/T=D, then Vs(1-D)=V(1)*(R1/(R1+R2))... Equation 2

Where D is Duty Cycle, Ton=T1, Vs is the maximum amplitude of the sawtooth wave, T=the reciprocal of the frequency f of the sawtooth wave (T=T1+T2, T2 is the NMOSFET turn-off time), Ton time The longer the length, the longer the charging time of the inductor L is, and the charging time of the first capacitor C1 is longer by the first power A. vice versa.

During the period T2, the energy stored in the inductor L is charged to the super capacitor SC1 via the third diode D3, and the voltage Vy to avoid charging is reduced by 0.7V (0.7V is the third diode D3). The forward bias voltage, wherein Vy-0.7=V _O1 ) exceeds the maximum allowable voltage preset value V _{MAX of} the super capacitor SC1, and the present invention proposes

K=2L/((R5+N Channel Depletion Mode internal resistance)*T)...Form 3

Notably, wherein the value of the node voltage Vy is the largest when D is approximately equal to 0.43. The design should select the appropriate first resistor R1, the second resistor R2 and the K value so that (the node voltage Vy is reduced by 0.7V), even if D is equal to 0.43, the maximum allowable voltage of the super capacitor SC1 is not exceeded. The preset value is V _MAX .

The energy stored in the inductor L during T2 is charged to the supercapacitor SC1 via the third diode D3, so that the current to avoid charging exceeds the maximum allowable instantaneous current value I _{MAX of} the super capacitor SC1 (or maximum allowable Operating temperature), by the following inductor peak current i _p ...

Under the assumption, i _p /2*T2/T (the average current of T stored in the inductor L during T2 via the third diode D3 to charge the supercapacitor SC1) is smaller than the super capacitor The maximum allowable instantaneous current value I _MAX (or the maximum allowable operating temperature) of SC1 and i _p /2*T2/T are much larger than (Vy-0.7)/(internal resistance of R5+N Channel Depletion Mode), where Vy-0.7 =V _O1 .

Description of the operation of the protection circuit in parallel with the supercapacitor SC1 during charging of the supercapacitor SC1

For the charging period of the super capacitor SC1, when V _GS >V _{th of the} N Channel Depletion MOS S2, the source S and the drain D of the N Channel depletion MOS S2 are in an on state. At this time, the N Channel Depletion MOS S2 as a switch is in a Turn On state. According to Equation 3 (the resistance value of the fifth resistor R5 + the internal resistance value of the N Channel Depletion Mode), V _O1 does not exceed the maximum allowable voltage preset value V _{MAX of} the super capacitor SC1.

When the super capacitor SC1 is charged, when the V _GS <V _{th of the} N Channel Depletion MOS S2, the source S and the drain D of the N channel depletion MOS S2 are in an off state. At this time, the N Channel Depletion MOS S2 as a switch is in a Turn Off state to prevent the charge stored in the super capacitor SC1 from flowing to the fifth resistor R5.

Therefore, in view of the conventional shortage of charging the supercapacitor SC1, the feedforward boost charging circuit 12 of the present invention has been well verified for charging the supercapacitor SC1 of this type of energy storage device in a feedforward manner.

Based on the connection circuit relationship between the self-charging circuit 11 , the feedforward boost charging circuit 12 and the internal electronic components of the storage circuit 13 , when the super capacitor SC1 is replaced with a general capacitor in parallel with the protection circuit 131 , The feedforward boost charging circuit charging the general capacitor in the aforementioned feedforward manner does not affect the service life of the capacitor.

1‧‧‧ self-powered feedforward charging circuit

11‧‧‧ self-charging circuit

D1‧‧‧First Diode

D2‧‧‧ second diode

C1‧‧‧first capacitor

C2‧‧‧second capacitor

R4‧‧‧fourth resistor

Z1‧‧‧Zina diode

12‧‧‧Feed-forward boost charging circuit

R1‧‧‧first resistance

R2‧‧‧second resistance

R3‧‧‧ third resistor

L‧‧‧Inductance

S1‧‧‧first switch

D3‧‧‧ third diode

CM 1‧‧‧ comparator

13‧‧‧ Energy storage circuit

131‧‧‧Protection circuit

SC1‧‧‧Super Capacitor

S2‧‧‧Second switch

R5‧‧‧ fifth resistor

Figure 1, which is a block diagram of a self-powered feedforward charging circuit.

2 is a diagram of a more detailed electronic component inside a self-charging circuit, a feedforward boost charging circuit, and a tank circuit.

As shown in FIG. 3, the figure is a waveform diagram of the comparator CM 1 receiving two different electric voltage values and outputting a large voltage value at an output end, wherein the vertical axis voltage value and the horizontal axis represent time.

1. . . Self-powered feedforward charging circuit

11. . . Self-charging circuit

D1. . . First diode

D2. . . Second diode

C1. . . First capacitor

C2. . . Second capacitor

R4. . . Fourth resistor

Z1. . . Zener diode

12. . . Feedforward boost charging circuit

R1. . . First resistance

R2. . . Second resistance

R3. . . Third resistance

L. . . inductance

S1. . . First switch

D3. . . Third diode

CM1. . . Comparators

13. . . Energy storage circuit

131. . . protect the circuit

SC1. . . Super capacitor

S2. . . Second switch

R5. . . Fifth resistor

Claims (12)

A charging method for a storage circuit, the storage circuit comprising a plurality of preset values, comprising: receiving a part of energy of a first electric energy by using a self-charging circuit to supply a feedforward boost charging circuit And after the feedforward boost charging circuit is activated, the feedforward boost charging circuit charges the energy storage circuit in a feedforward manner, and the charged voltage and current do not exceed the preload of the energy storage circuit. a value, wherein the feedforward boost charging circuit uses a first equation having a feed forward mode to generate a duty cycle D, the preset value including a maximum allowable instantaneous current value, a maximum allowable operation The temperature, a maximum allowable voltage preset value, or any combination thereof, the first equation is as follows: Where Vs is the maximum amplitude value of an input sawtooth voltage, V(1) is an input voltage, R1 is a first resistance, R2 is a second resistance, and is substituted into a second equation to determine whether the maximum allowable voltage is satisfied. The default value, the second equation is as follows: Where V _{y is} the voltage of one of the energy storage elements of the energy storage circuit plus the voltage of the diode coupled to the energy storage element, K=2L/((R5+ internal resistance of the second switch)*T T is the switching period of one of the first switching switches, R5 is the fifth resistor, L is an inductance, and the duty cycle D is substituted into a third-party program to determine whether the maximum allowable instantaneous current value is satisfied. The three equations are as follows: Where i _p is an inductor peak current flowing through the energy storage element; and the feed forward boost charging circuit causes energy transfer inside the self-charging circuit and provides a second power to the feed forward through the self-charging circuit The charging circuit is pressurized, and the feedforward boost charging circuit transfers energy to the tank circuit. The charging method of claim 1, wherein the feedforward boost charging circuit comprises a first resistor, a second resistor, a third resistor, the inductor, a first switch, and a first a diode and a comparator, one end of the first resistor and one end of the second resistor are coupled to the negative input end of the comparator, and the other end of the second resistor is coupled to the ground, the positive input of the comparator The terminal receives a sawtooth wave and is coupled at its output end to the gate of the first switch and one end of the third resistor, the inductor being coupled to the drain of the first switch and the other of the first resistor Between one end, the self-charging circuit includes a second diode, a third diode, a first capacitor, a second capacitor, a fourth resistor, and a Zener diode. The first capacitor One end is coupled to the gate of the first switch, and the other end of the first capacitor is electrically connected to one end of the second diode and one end of the third diode, and the other end of the third diode The second capacitor is coupled to the other end of the third resistor, and the second capacitor is connected in parallel with the Zener diode. One end of the second capacitor is electrically connected to the other end of the third diode, the other end of the third resistor, and one end of the fourth resistor, and the other end of the second capacitor is grounded; and the energy storage circuit includes a a first capacitor is coupled between the drain of the first switch and one end of the super capacitor, and the second switch and the fifth resistor are coupled between the first switch and the fifth resistor. In series, the super capacitor is coupled between the source of the second switch and ground. The charging method of claim 1, wherein the feedforward boost charging circuit charges the super capacitor in a form of converting the first electric energy into a maximum allowable instantaneous current value that the super capacitor can tolerate, the maximum The allowable operating temperature, the maximum allowable voltage preset value, or any combination thereof. The charging method according to claim 1, wherein the feedforward boosting The charging circuit causes the internal energy transfer mode of the self-charging circuit to be in the switching state, the energy storage of the first capacitor is transferred to the second capacitor through the second diode, and the second The average stored energy of the capacitor is equal to the average power consumption of the feedforward boost charging circuit and the tank circuit. The charging method of claim 2, wherein: when the super capacitor is charged, the second switch makes the super capacitor and the fifth resistor in parallel; and when the super capacitor is discharged, the second switch A switch separates the super capacitor from the fifth resistor. The charging method of claim 1, wherein when the feedforward boost charging circuit is in a steady state, the current flowing through the inductor is in a discontinuous current mode. The charging method of claim 1, wherein the first electric energy charges the second capacitor through the fourth resistor before the feedforward boost charging circuit is activated. A self-powered feedforward charging circuit comprising: a self-charging circuit for storing a portion of energy of a first electrical energy; and a feedforward boosting charging circuit for receiving a portion of energy of the first electrical energy from the self-charging circuit to be activated; And a storage circuit including a super capacitor and a protection circuit, the feedforward boost charging circuit charges the storage circuit in a feedforward manner, and the feedforward boost charging circuit activates the protection circuit, and the protection The circuit limits one of the maximum allowable instantaneous current values of the supercapacitor, a maximum allowable operating temperature, a maximum allowable voltage preset value, or any combination thereof within a predetermined value. The self-powered feedforward charging circuit of claim 8, wherein the feedforward boosting charging circuit is activated, and the self-charging circuit averages a portion of the energy stored in the first electrical energy equal to the feedforward boosting The charging circuit and the energy storage circuit consume an average of electrical energy. A self-powered feedforward charging circuit as described in claim 8 of the patent application, The feed forward boost charging circuit includes a first resistor, a second resistor, a third resistor, an inductor, a first switch, a first diode, and a comparator, the first resistor One end of the second resistor is coupled to the negative input terminal of the comparator, and the other end of the second resistor is coupled to the ground. The positive input terminal of the comparator receives a sawtooth wave and is coupled at the output end thereof. The inductor is coupled between the drain of the first switch and the other end of the first resistor; the self-charging circuit is connected to the gate of the first switch a second diode, a third diode, a first capacitor, a second capacitor, a fourth resistor, and a Zener diode, and one end of the first capacitor and the gate of the first switch The other end of the first capacitor is electrically connected to one end of the second diode and one end of the third diode, and the other end of the third diode is coupled to the third resistor One end, the second capacitor is connected in parallel with the Zener diode, and one end of the second capacitor and the third diode The other end of the third resistor is electrically connected, one end of the fourth resistor is electrically connected, and the other end of the second capacitor is grounded; and the energy storage circuit includes a super capacitor, a second switch, and a first a fifth resistor, the first diode is coupled between the drain of the first switch and one end of the super capacitor, the second switch is connected in series with the fifth resistor, and the super capacitor is coupled to the second Switch the source of the switch to ground. The self-powered feedforward charging circuit of claim 8, wherein the feedforward boost charging circuit uses the feedforward mode to use a first equation having a feed forward mode to generate a responsibility Cycle D, the first equation is as follows: Where Vs is the maximum amplitude value of an input sawtooth voltage, V(1) is an input voltage, R1 is the first resistance, R2 is the second resistance, and is substituted into a second equation to determine whether the maximum allowable voltage is satisfied. The default value, the second equation is as follows: Where K=2L/((R5+ internal resistance of the second switch)*T), T is one switching cycle of the first switch, R5 is the fifth resistor, L is the inductor, and the responsibility is Cycle D is substituted into a third-party program to determine whether the maximum allowable instantaneous current value is met. The third-party program is as follows: . The self-powered feedforward charging circuit of claim 8, wherein when the second switch is turned on, the super capacitor is in a charging state, and when the second switch is turned off (Turn off) When the super capacitor is charged, it is saturated.