CN102611207B - Power Management Module for RF-Powered Portable Devices - Google Patents

Abstract

The invention discloses a power management module for radio-frequency portable energy supply equipment, which comprises a multiband radio-frequency electric energy receiving circuit and a mode selector. The multiband radio-frequency electric energy receiving circuit is used for providing electric energy wide frequency range for a load circuit, and comprises a high-frequency receiving circuit, an ultrahigh-frequency receiving circuit and a microwave receiving circuit. Three input ends of the mode selector are connected with an output end of the high-frequency receiving circuit, an output end of the ultrahigh-frequency receiving circuit and an output end of the microwave receiving circuit. An output end of the mode selector is connected with the load circuit to transmit one of high-frequency wireless signal electric energy, ultrahigh-frequency wireless signal electric energy or microwave wireless signal electric energy to the load circuit. The portable electronic equipment can have the multiband radio-frequency electric energy receiving capacity within the wide frequency range by the aid of the power management module, the power management module can independently select out an optimal electric energy receiving mode to power the load, and accordingly voltage loss on a selection passage is reduced, and optimized power supply efficiency is realized.

Description

Power Management Module for RF-Powered Portable Devices

technical field

The invention relates to a power management module of a portable device powered by radio frequency, in particular to a power management module of a portable electronic device which uses radio frequency power transmission to provide power.

Background technique

Recently, the development of wireless power transmission technology provides a new source of power for portable devices, which is more cost-effective, convenient and environmentally friendly than the solution powered by ordinary batteries. Portable electronic devices: consumer products such as radio frequency identification cards (RFID tags), wireless mice, medical products such as wireless ECG monitors (wireless ECG monitors), and cochlear implants have all achieved low-power designs, and these low-power portable devices Electronic devices provide a broad space for more RF-powered applications.

RF power transmission for portable electronic devices can be divided into high-frequency mode, ultra-high frequency mode, and microwave mode.

The high-frequency mode is a technology based on high-frequency wireless signal power transmission (such as a signal frequency of 13.56MHz), that is, a pair of coupled inductive coils (coils) are used to transmit energy through inductive coupling, and the working distance is usually 5CM-10CM.

The UHF mode is a technology based on UHF wireless signal power transmission (such as 869MHz signal frequency), that is, using an antenna (such as a dipole antenna) to transmit energy through an electromagnetic radiation field.

Microwave mode is a technology based on microwave wireless signal power transmission (such as 2.45GHz signal frequency), and also uses the electromagnetic radiation field of the antenna to transmit energy. UHF and microwave modes can achieve a working distance of several meters.

For the wireless power supply of portable electronic devices, combining high-frequency mode, ultra-high frequency mode, and microwave mode to realize multi-band radio frequency power transmission in a wide frequency range can achieve the most flexible distance scheme and the optimal radio frequency power supply. able way. Therefore, a development trend of RF-powered portable electronic devices is to integrate high-frequency receiving modes, ultra-high frequency receiving modes, and microwave receiving modes. To realize the multi-band radio frequency power receiving capability with a wide frequency range, the technical difficulty is that the power management module of the portable device must be able to judge the best power receiving mode among the above three modes in real time to achieve the optimal power supply efficiency. For example, when the portable device is very close to the corresponding power transmitter, the power management module will automatically judge and select the high-frequency power receiving mode. When there is a certain distance between the portable electronic device and the power transmitter, the power management module will automatically judge and select the UHF or microwave power receiving mode. This requires the design of an intelligent mode selector inside the power management module. Its function is to detect in real time which of the above three receiving modes can generate the largest current to drive the load, and select this mode for the portable device. The load circuit supplies power.

The traditional voltage selector designed with diodes is not suitable for the work of the above-mentioned mode selector, because each diode has a PN junction forward voltage (0.7V), and it is noted that the ultra-high frequency receiving mode and microwave In the receiving mode, the electric energy received at the antenna end is usually relatively small, even if the output voltage is still in a relatively small range after the post-stage voltage doubler and rectification, if a PN junction conduction is subtracted from the current path through the mode selector If the on-voltage is low, the power management module may not be able to provide the normal working voltage required by the portable device, and it will also introduce waste of additional power consumption.

Contents of the invention

The present invention provides a power management module of a radio frequency powered portable device. A mode selector is designed inside the power management module. Its function is to detect in real time which of the above three receiving modes can generate the largest current to drive load, and select this mode to power the load circuit of the portable device.

Technical scheme of the present invention is:

A power management module of a radio-frequency powered portable device, including a multi-band radio-frequency power receiving circuit of a wide frequency range that provides power to a load circuit, and the receiving circuit includes:

A high-frequency receiving circuit for receiving high-frequency wireless signal power;

UHF receiving circuit for receiving UHF wireless signal power;

Microwave receiving circuit, used to receive microwave wireless signal power;

The power management module also includes a mode selector, the three input terminals of the mode selector are respectively connected to the output terminals of the high-frequency receiving circuit, the ultra-high frequency receiving circuit, and the microwave receiving circuit. The output end of the selector is connected with the load circuit, and is used to select one of the high-frequency wireless signal power, the ultra-high frequency wireless signal power or the microwave wireless signal power to transmit to the load circuit.

The so-called choosing one usually means that the mode selector selects the highest voltage through the voltage comparator among the three received DC voltages, and only selects the receiving mode with the highest voltage to drive the load circuit to achieve the best power supply efficiency.

Preferably, the high-frequency receiving circuit includes:

Coil inductance, a rectifier connected to the coil inductance, the positive terminal of the rectifier is used as the output terminal;

Described ultra-high frequency receiving circuit comprises:

a first antenna, a first voltage doubler rectifier connected to the first antenna, the positive end of the first voltage doubler rectifier is used as an output end;

Described microwave receiving circuit comprises:

A second antenna, a second voltage doubler rectifier connected to the second antenna, the positive end of the second voltage doubler rectifier as an output end.

The mode selectors include:

A first controllable circuit, the input end of which is connected to the output end of the rectifier;

The second controllable circuit, the input end of which is connected to the output end of the first voltage doubler rectifier;

A third controllable circuit, the input end of which is connected to the output end of the second voltage doubler rectifier;

A first sensing resistor, one end of which is connected to the output end of the first controllable circuit, and the other end of which is connected to the load circuit;

A second sensing resistor, one end of which is connected to the output end of the second controllable circuit, and the other end of which is connected to the load circuit;

A third sensor group, one end of which is connected to the output end of the third controllable circuit, and the other end of which is connected to the load circuit;

The control unit, its three input terminals are respectively connected to the output terminals of the first controllable circuit, the second controllable circuit, and the third controllable circuit, and its three output terminals are respectively connected to the first controllable circuit, The control terminals of the second controllable circuit and the third controllable circuit.

Further, the first controllable circuit, the second controllable circuit, and the third controllable circuit are all composed of a first PMOS transistor, a second PMOS transistor, and a first NMOS transistor, and the first PMOS transistor of the The source is used as the input terminal of the controllable circuit, the gate is connected to the drain of the second PMOS transistor and the drain of the first NMOS transistor, and the drain is connected to the source of the second PMOS transistor, and is used as the output terminal of the controllable circuit The gate of the first NMOS transistor is connected to the gate of the second PMOS transistor and serves as the control terminal of the controllable circuit, and the source of the first NMOS transistor is grounded.

The above-mentioned technical solution can be realized by CMOS process design, and the feature of this technical solution is that the first PMOS is switched according to the level of the control terminal of the first controllable circuit, the second controllable circuit or the third controllable circuit. Whether the transistor is turned on as a MOS diode or as a MOS switch, another feature of this circuit is that neither the second PMOS transistor nor the first NMOS transistor as an auxiliary MOS switch is in the controllable circuit from input to output. Therefore, the on-resistance in the linear region does not need to be very small, so both the second PMOS transistor and the first NMOS transistor can be designed with a relatively small transistor size ratio, which can save the corresponding integrated circuit layout area.

Preferably, the rectifier is a bridge full-wave rectifier.

Further, the bridge full-wave rectifier includes:

Cross-coupled PMOS transistors P41, PMOS transistors P42, PMOS transistors P43, PMOS transistors P44 connected in the form of MOS diodes.

The positive and negative parts of the input waveform of the input RF AC signal can be converted to the same polarity, and a DC voltage is generated on the output filter capacitor. The rectifier can work well at high frequency wireless signal frequencies.

Preferably, the first voltage doubler rectifier or the second voltage doubler rectifier includes:

At least two full-wave rectifiers, at least one full-wave rectifier whose input is connected to the corresponding first antenna or second antenna, at least one full-wave rectifier input with two voltage doubler capacitors Connected to the corresponding first antenna or the second antenna, at least the output terminals of the two full-wave rectifiers are connected in series as the output terminals of the current stage circuit.

Further, the full-wave rectifier includes:

The cross-coupled PMOS transistor P51 and PMOS transistor P52, and the cross-coupled NMOS transistor N51 and NMOS transistor N52 form a differentially driven full-wave rectifier.

The circuit constitutes a differentially driven one-stage full-wave rectifier. By cascading several stages of the full-wave rectifier and adding a voltage doubler capacitor, the voltage doubler function similar to that of a charge pump can be realized. The input RF AC signal is converted from AC to DC and The voltage doubler can generate a DC voltage at the positive stage of its output filter capacitor, and this voltage doubler rectifier usually works at ultra-high frequency or microwave wireless signal frequency.

As another preferred solution, a first switch circuit and a second switch circuit are connected in series between the output terminal of the rectifier and the input terminal of the mode selector, and the connection terminals of the first switch circuit and the second switch circuit are connected via The rechargeable battery is grounded, and the control terminals of the first switch circuit and the second switch circuit are respectively connected to the two output terminals of the mode selector.

Through this solution, the control unit in the mode selector determines the operating states of the first switch circuit and the second switch circuit according to the real-time environment. If the first switch circuit is opened and the second switch circuit is closed, only the rechargeable battery is charged. If the first switch circuit and the second switch circuit are turned on at the same time, the rectifier of the high-frequency receiving circuit can charge the rechargeable battery and also supply power to the load circuit, which depends on the demand of the load circuit and the energy of the received electric energy, if The energy of the received electric energy is relatively weak, and the power of the rechargeable battery is relatively sufficient, then the first switch circuit can be closed, and the second switch circuit can be opened. The wireless signal power and the microwave wireless signal power received by the microwave receiving circuit are used to determine the best way to supply power to the load circuit in real time. This can greatly extend the standby time of the portable device on the rechargeable battery, thereby extending the overall operating time of the device.

The invention relates to a power management module of a portable device powered by radio frequency, which has the ability to receive multi-band radio frequency power in a wide frequency range for the portable electronic device, and achieves the most flexible distance scheme for radio frequency power supply. Its power management module can optimize the best power receiving mode by itself to supply power to the loaded load, so as to achieve the beneficial effect of optimal power supply efficiency. More importantly, the mode selector in the power management module avoids the voltage loss on the selection path, so that the ultra-high frequency power receiving or microwave power receiving mode can work normally at low voltage, and also avoids the waste of power consumption. At the same time, for portable electronic devices with built-in rechargeable batteries, the application of the invention can also improve their standby time, thereby greatly prolonging the overall working time of the electronic devices.

Description of drawings

FIG. 1 is an electrical block diagram of a power management module of a radio frequency powered portable device according to the present invention.

Fig. 2 is an electrical principle block diagram including a specific receiving circuit of the present invention.

Fig. 3 is an electrical block diagram of the mode selector of the present invention.

FIG. 4 is an electrical schematic diagram of the bridge full-wave rectifier of the present invention.

Fig. 5 is an electrical schematic diagram of the voltage doubler rectifier of the present invention.

Fig. 6 is a block diagram of the electrical principle of the present invention containing a rechargeable battery.

Detailed ways

Now in conjunction with accompanying drawing, the present invention will be further described:

As shown in Figure 1, the power management module of the radio frequency energy supply portable device of the present invention comprises a high-frequency receiving circuit 11, an ultra-high frequency receiving circuit 12, a microwave receiving circuit 13, a mode selector 2, a load circuit 3, and a high-frequency receiving circuit 11 , the output ends of the ultra-high frequency receiving circuit 12, and the microwave receiving circuit 13 are respectively connected to the input ends of the mode selector 2, and the output ends of the mode selector 2 are connected to the load circuit 3, and the mode selector 2 has a selective high-frequency receiving circuit Any circuit in the circuit 11, the ultra-high frequency receiving circuit 12 or the microwave receiving circuit 13.

As shown in Figure 2, the high-frequency receiving circuit 11 includes: a coil inductance 111, a rectifier connected to the coil inductance 111, the positive end of the rectifier is used as an output terminal, and the negative end is grounded; the ultra-high frequency receiving circuit 12 includes: a first antenna 121, The first voltage doubler rectifier connected with the first antenna 121, the positive end of the first voltage doubler rectifier is used as the output terminal, and the negative end is grounded; the microwave receiving circuit 13 includes: the second antenna 131, the second doubler connected with the second antenna 131 Voltage rectifier, the positive terminal of the second voltage doubler rectifier is used as the output terminal, the negative terminal is grounded, and the others are the same as in Figure 1.

As shown in Figure 3, the mode selector 2 includes: a first controllable circuit 21, whose input terminal IN21 is connected to the output terminal of the rectifier; a second controllable circuit 22, whose input terminal IN22 is connected to the output terminal of the first voltage doubler rectifier; The third controllable circuit 23, its input terminal IN23 is connected to the output terminal of the second voltage doubler rectifier; the first sensing resistor R21, one end of which is connected to the output terminal of the first controllable circuit 21, and the other end is connected to the load circuit 3; Two sensing resistors R22, one end of which is connected to the output end of the second controllable circuit 22, the other end of which is connected to the load circuit 3; the third sensing resistor R23, one end of which is connected to the output end of the third controllable circuit 23, and the other end of which is connected to the output end of the third controllable circuit 23 One end is connected to the load circuit 3; the control unit, its three input ends are respectively connected to the output ends of the first controllable circuit 21, the second controllable circuit 22, and the third controllable circuit 23, and its three output ends are respectively connected to the described The control terminal S1 , the control terminal S2 and the control terminal S3 of the first controllable circuit 21 , the second controllable circuit 22 , and the third controllable circuit 23 . The first controllable circuit 21, the second controllable circuit 22, and the third controllable circuit 23 have the same circuit principle, now take the first controllable circuit 21 as an example, the first PMOS transistor P1, the second PMOS transistor P2, the first NMOS transistor N1 is composed. The source of the first PMOS transistor P1 is used as the input terminal IN21 of the controllable circuit, the gate is connected to the drain of the second PMOS transistor P2 and the drain of the first NMOS transistor N1, and the drain is connected to the source of the second PMOS transistor P2 , and as the output terminal of the controllable circuit, the gate of the first NMOS transistor N1 is connected to the gate of the second PMOS transistor P2 and serves as the control terminal of the controllable circuit, and the source of the first NMOS transistor N1 is grounded.

In the second controllable circuit 22, the first PMOS transistor P21 is used instead of the first PMOS transistor P1, the second PMOS transistor P22 is used instead of the second PMOS transistor P2, and the first NMOS transistor N21 is used instead of the first NMOS transistor N1. Other circuit principles same.

In the third controllable circuit 23, the first PMOS transistor P31 is used to replace the first PMOS transistor P1, the second PMOS transistor P32 is used to replace the second PMOS transistor P2, and the first NMOS transistor N31 is used to replace the first NMOS transistor N1. Other circuit principles same.

In the initial state, the control unit outputs S1, S2, and S3 are all "0", so the second PMOS transistors P2, P22 in the first controllable circuit 21, the second controllable circuit 22, and the third controllable circuit 23, Both P32 are turned on, and the first NMOS transistors N1, N21, and N31 are all turned off. At this time, the first PMOS transistors P1, P21, and P31 are all working in the MOS diode state. At this time, it is equivalent to three inputs connected in parallel, and the outputs are all connected. second tube. The largest one of the three controllable circuit input DC voltages will quickly conduct the controllable circuit in the forward conduction mode of the MOS diode, and the current driving the load circuit is the largest, and the conduction of the controllable circuit will turn the mode selector The output clamped at the maximum input DC voltage minus a MOS diode forward conduction voltage drop (about the threshold voltage of the first PMOS transistor) amplitude, so the remaining two controllable circuits do not have enough The forward bias voltage makes the MOS diode conduct forward, and the current driving the load circuit is relatively small. In the initial state, the mode selector selects the input DC voltage with the strongest load capacity to drive the load circuit, that is, selects the power receiving circuit that generates the DC voltage.

In the following second state, the voltage difference across the sensing resistor R21, the sensing resistor R22, and the sensing resistor R23 is transmitted to the control unit. The resistance values of the three sensing resistors can be small but must be the same, and the magnitude of the voltage difference can be easily identified by the control unit, such as through a simple comparison circuit. The largest voltage difference between the two ends of the sensing resistor comes from the above-mentioned controllable circuit using the forward conduction of the MOS diode, because its output current is the largest. In this way, the control unit can set the control terminal of the controllable circuit that generates the maximum voltage difference to "1", so that the second PMOS transistor in the controllable circuit is turned off, and the first NMOS transistor is turned on. At this time, the first PMOS transistor It works as the linear conduction state of the MOS switch, and the forward conduction voltage drop of the MOS diode generated in the initial state can be removed, and the current path from the input to the output of the controllable circuit realizes the path of micro-voltage drop loss, It also has the effect of driving a load circuit more efficiently. While the control terminals of the other two controllable circuits remain "0", they still maintain the working state of the MOS diode. In the second state, the mode selector removes the forward conduction voltage drop of the MOS diode from its input to the output current path, and enhances the driving capability of the selected power receiving circuit to the load circuit.

In summary, through the first controllable circuit 21, the second controllable circuit 22, the third controllable circuit 23 and the subsequent stage sensing resistor R21, sensing resistor R22, and sensing resistor R23, a simple control unit, the most efficient receiving mode can be automatically selected among the high-frequency power receiving mode, the ultra-high frequency power receiving mode and the microwave power receiving mode to supply power to the load circuit 3 . More importantly, when the power management module selects the receiving mode of the ultra-high frequency receiving circuit or the microwave receiving circuit as the effective receiving mode, the output DC voltage of the related first voltage doubler rectifier and the second voltage doubler rectifier is relatively small, the above can be The characteristics of micro-voltage drop loss in the current path from the input of the control circuit to its output can ensure the normal supply voltage drive of the load circuit under low voltage conditions.

In the same way, any one or both of the first controllable circuit 21, the second controllable circuit 22, the third controllable circuit 23 and its subsequent stage sensing resistor R21, sensing resistor R22, and sensing resistor R23 can be To work according to the above-mentioned working principle, it only needs to make small changes in the control unit.

As shown in Figure 4, the rectifier in the high-frequency receiving circuit 11 adopts a bridge-type full-wave rectifier, which includes: cross-coupled PMOS transistors P41, PMOS transistors P42, PMOS transistors P43 and PMOS transistors P44 connected in the form of MOS diodes, and output terminals The two ends of Out4+ and Out4- are connected to the filter capacitor C4, and the input ends are In4+ and In4-, which are connected to the inductance coil 111 .

As shown in Figure 5, the first voltage doubler rectifier and the second voltage doubler rectifier have the same electrical principle. Taking one of the voltage doubler rectifiers as an example, it is composed of a full-wave rectifier 1221 and a full-wave rectifier 1222 in series with basically the same circuit structure. The full-wave rectifier 1221 includes: cross-coupled PMOS transistors P51 and PMOS transistors P52, and cross-coupled NMOS transistors N51 and NMOS transistors N52 form a differentially driven full-wave rectifier. The full-wave rectifier 1222 includes cross-coupled PMOS transistors P511, PMOS transistors P521, cross-coupled NMOS transistors N511, NMOS transistors N521, and two capacitors C511 and C521 to form a differentially driven full-wave rectifier. The differential input terminals In5+ and In5- of the full-wave rectifier 1221 are connected to the first antenna 121, and the differential input terminals In5+ and In5- of the full-wave rectifier 1222 are connected to the first antenna 121 through the voltage doubler capacitor C511 and the voltage doubler capacitor C521, two The output terminals of the full-wave rectifier are connected in series as the output terminals Out5+ and Out5- of the circuit of this stage, and the two ends of the output terminals are connected to the filter capacitor C5.

As shown in Figure 6, the first switch circuit K61 and the second switch circuit K62 are connected in series between the output terminal of the rectifier and the input terminal of the mode selector, and the connection terminals of the first switch circuit K61 and the second switch circuit K62 are connected by a rechargeable battery E63 Grounded, the control terminals of the first switch circuit K61 and the second switch circuit K62 are connected to the two output terminals of the mode selector 3 respectively, and the others are the same as in FIG. 2 . This circuit can satisfy some portable devices (such as wireless mouse) that require rechargeable batteries to maintain a long standby time.

Claims (6)

1. the power management module of a radio frequency energy supply portable set, comprise the multiband RF electric energy receiving circuit that the wide frequency ranges of electric energy is provided to load circuit, it is characterized in that, described receiving circuit comprises:

High frequency receiving circuit, for receiving the high-frequency wireless signals electric energy, described high frequency receiving circuit comprises: coil inductance, with the rectifier that described coil inductance is connected, the anode of described rectifier is as output;

The hyperfrequency receiving circuit, for receiving ultra-high frequency wireless signal electric energy, described hyperfrequency receiving circuit comprises: the first antenna, with the first voltage-doubler rectifier that described the first antenna is connected, the anode of described the first voltage-doubler rectifier is as output;

The microwave receiving circuit, for receiving microwave wireless signal electric energy, described microwave receiving circuit comprises: the second antenna, with the second voltage-doubler rectifier that described the second antenna is connected, the anode of described the second voltage-doubler rectifier is as output;

Also comprise mode selector in described power management module, three inputs of described mode selector connect respectively the output of described high frequency receiving circuit, hyperfrequency receiving circuit, microwave receiving circuit, the output of described mode selector is connected with load circuit, for select one described high-frequency wireless signals electric energy, ultra-high frequency wireless signal electric energy or microwave wireless signal electric energy are sent to load circuit, described mode selector comprises:

The first controlable electric current, its input connects the output of described rectifier;

The second controlable electric current, its input connects the output of described the first voltage-doubler rectifier;

The 3rd controlable electric current, its input connects the output of described the second voltage-doubler rectifier;

The first sensing resistor, the one end connects the output of described the first controlable electric current, and its other end connects described load circuit;

The second sensing resistor, the one end connects the output of described the second controlable electric current, and its other end connects described load circuit;

The 3rd sensing electricity group, the one end connects the output of described the 3rd controlable electric current, and its other end connects described load circuit;

Control unit, its three inputs connect respectively the output of described the first controlable electric current, the second controlable electric current, the 3rd controlable electric current, and its three outputs connect respectively the control end of described the first controlable electric current, the second controlable electric current, the 3rd controlable electric current;

Wherein, described the first controlable electric current, the second controlable electric current, the 3rd controlable electric current is by a PMOS transistor, the 2nd PMOS transistor, the first nmos pass transistor forms, the transistorized source electrode of a described PMOS is as the input of this controlable electric current, grid connects the drain electrode of the transistorized drain electrode of the 2nd PMOS and the first nmos pass transistor, drain electrode connects the transistorized source electrode of the 2nd PMOS, and as the output of this controlable electric current, the grid of described the first nmos pass transistor connects the transistorized grid of the 2nd PMOS and as the control end of this controlable electric current, the source ground of described the first nmos pass transistor.

2. the power management module of radio frequency energy supply portable set as claimed in claim 1, is characterized in that, described rectifier is bridge full wave rectifier.

3. the power management module of radio frequency energy supply portable set as claimed in claim 2, is characterized in that, described bridge full wave rectifier comprises:

Cross-linked PMOS transistor P41, PMOS transistor P42, the PMOS transistor P43 connected in MOS diode mode, PMOS transistor P44.

4. the power management module of radio frequency energy supply portable set as described as claim 1 or 3, is characterized in that, described the first voltage-doubler rectifier or the second voltage-doubler rectifier comprise:

At least two full-wave rectifiers, at least described its input of full-wave rectifier is connected with corresponding the first antenna or the second antenna connects, the input of an at least described full-wave rectifier is connected with corresponding the first antenna with two multiplication of voltage electric capacity or the second antenna connects, after the output series connection of at least described two full-wave rectifiers as the output of circuit at the corresponding levels.

5. the power management module of radio frequency energy supply portable set as claimed in claim 4, is characterized in that, described full-wave rectifier comprises:

Cross-linked PMOS transistor P51, PMOS transistor P52, cross-linked nmos pass transistor N51, nmos pass transistor N52 have formed the full-wave rectifier of differential driving.

6. the power management module of radio frequency energy supply portable set as claimed in claim 1, it is characterized in that: between the output of described rectifier and the input of mode selector, connect the first switching circuit, second switch circuit, the link of described the first switching circuit and second switch circuit is through rechargeable battery ground connection, and the control end of described the first switching circuit, second switch circuit connects respectively two outputs of described mode selector.

Images