TWI622261B - Half bridge resonant bidirectional DC to DC converter circuit - Google Patents

Abstract

The invention provides a half-bridge resonant bidirectional DC-to-DC converter circuit, comprising a half bridge buck-boost converter and a resonant DC-to-DC converter, the half bridge buck-boost converter coupled to one of the external DC a power supply for obtaining a wide input voltage range, the resonant DC-to-DC converter coupled to the half bridge buck-boost converter as a rear stage circuit of the half bridge buck-boost converter, the resonant DC The DC-to-DC converter is configured to control the direction of the bidirectional power flow and, in the fixed frequency mode, responsive to the half-bridge buck-boost converter to convert the input of the half-bridge buck-boost converter into an induced current output.

Description

Half bridge resonant bidirectional DC to DC converter circuit

The present invention discloses a DC-DC converter circuit, and more particularly to a half-bridge resonant bidirectional DC-to-DC converter circuit.

In the case of high voltage conversion ratio or where isolation requirements are required, a bidirectional DC-DC converter circuit with isolation must be used. The conventional circuit architecture includes a dual active full bridge converter, an LLC-SRC converter, and a two-stage series connection. Type converter and full bridge phase shift converter using push-pull current source.

For the dual active full-bridge converter, please refer to Figure 1. The principle of the dual active full-bridge converter is to control the power flow direction by the phase shift of the primary side and secondary side switches. The LLC-SRC converter is shown in Figure 2. The circuit structure of the LLC-SRC converter is composed of an LLC resonant circuit and an SRC (series) resonant circuit. The bidirectional power flow is controlled by the frequency conversion method. The disadvantage of the circuit is that the frequency variation range will become larger as the operating voltage becomes larger, and it is more difficult to control at low power.

Please refer to FIG. 3 and FIG. 4 . FIG. 3 and FIG. 4 respectively connect the circuit of the subsequent stage of FIG. 1 and FIG. 2 in series with a step-up and step-down converter to adapt to a larger working voltage range, wherein FIG. 3 can be called Two-stage dual active full bridge series lifting pressure Figure 4, can be called two-stage LLC-SRC series buck-boost converter, Figure 3 and Figure 4 are two-stage series converter, this two-stage circuit will reduce its overall efficiency And the cost increases.

Referring to FIG. 5A and FIG. 5B, adding a push-pull current source to the primary side of the converter and combining the full-bridge phase shift on the secondary side can make it a full-bridge phase shift conversion using a push-pull current source. Figure 5A shows an aspect using snubber as a switching clamp, and Figure 5B shows another aspect using active clamping. Since the circuit of FIG. 5A and FIG. 5B is only applicable to the application of the lower side voltage on the primary side, for the application of the primary side high voltage, since the voltage across the power switch is subjected to a high voltage, the circuit design is greatly limited and difficult. Practical application.

That is, in response to the power variation of the bidirectional DC-DC power converter, it is necessary to have a high voltage ratio change rate at the input or output terminal. If a resonant converter is used, a large range of frequency variation must be provided, so the design of the resonant circuit is adopted. It is difficult and inefficient. If a buck-boost converter circuit is added, a wide input voltage range can be obtained, but the frequency conversion method is used to obtain a fast response and a seamless bidirectional power adjustment mode switching is performed, and the currently known circuit cannot be completed.

In order to solve the shortcomings of the prior art, the present invention proposes a resonant circuit in a fixed frequency control mode, and in combination with a buck-boost conversion circuit, various problems of the prior art described above can be solved.

An object of the present invention is to provide a half-bridge resonant bidirectional DC-to-DC converter circuit, which is a resonant circuit with a fixed frequency control mode, and has a wide input voltage range and the advantage of controlling the bidirectional power flow direction. .

Another object of the present invention is to provide a half-bridge resonant bidirectional DC-to-DC converter circuit, which has a seamless bidirectional power adjustment mode switching, so that it can be operated immediately without power failure, because no additional control is required. The circuit has the advantage of simplifying the circuit design.

To achieve the above and other objects, the present invention provides a half-bridge resonant bidirectional DC-to-DC converter circuit, the half-bridge resonant bi-directional DC-to-DC converter circuit comprising a half bridge buck-boost converter, the half bridge type The buck-boost converter is coupled to an external DC power supply, the DC power supply provides a stable DC voltage, and the half-bridge buck-boost converter comprises: a first transistor, the 汲 is extremely coupled to the positive output of the DC power supply a second transistor having a source terminal coupled to the negative output terminal of the DC power source, a source terminal of the first transistor coupled to the 汲 terminal of the second transistor, and an inductor coupled to the input end thereof a first node between the source terminal of the first transistor and the second terminal of the second transistor; a first capacitor having an input coupled to the output of the inductor and an output coupled to the output a second node between the source terminal of the second transistor and the negative output of the DC power source; and a resonant DC-to-DC converter coupled to the half bridge buck-boost converter as the half bridge Lift Post-stage circuit of the converter, the resonant DC to DC converter is adapted in the fixed frequency mode The input of the half bridge buck-boost converter is converted to an induced current output in response to the half bridge buck-boost converter.

In one embodiment of the present invention, the resonant DC-to-DC converter includes a first secondary side switching unit, a voltage conversion unit, and a second secondary side switching unit. The first secondary side switching unit is coupled to the half. The bridge-type buck-boost converter is coupled to the first side switch unit, and the second-stage switch unit is coupled to the voltage conversion unit.

In an embodiment of the present invention, the first side switch unit includes a first switch, a second switch, a third switch, and a fourth switch, and the input end of the first switch is coupled to the first capacitor a third node between the anode and the output of the inductor, the input of the second switch is coupled to a fourth node between the cathode of the first capacitor and the second node, the first switch The output end is coupled to the output end of the second switch, the input end of the third switch is coupled to the third node, the input end of the fourth switch is coupled to the fourth node, and the output end of the third switch The output is coupled to the output of the fourth switch.

In one embodiment of the present invention, the voltage conversion unit includes a first coil and a second coil, and the second coil induces a current flowing into the first coil to generate an induced voltage, and the number of turns of the first coil It is different from the number of turns of the second coil.

In one embodiment of the present invention, the first end of the first coil is coupled to a fifth node between the output end of the first switch and the output end of the second switch, and the second end of the first coil An output coupled to the third switch and the A sixth node between the outputs of the fourth switch.

In an embodiment of the present invention, the second side switch unit includes a fifth switch, a sixth switch, a second capacitor, and a third capacitor, and the input end of the fifth switch is coupled to the second coil The first end of the sixth switch is coupled to the first end of the second coil, the second capacitor is coupled to the second end of the second coil, and the third capacitor is coupled to the second end The second end of the coil, the fifth switch, the sixth switch, the second capacitor, and the third capacitor adjust and output the induced voltage.

In an embodiment of the present invention, the second side switch unit further includes a voltage control current source coupled to the output end of the fifth switch, the output end of the sixth switch, the second capacitor, and the third The capacitor outputs the induced current according to the adjusted induced voltage.

In one embodiment of the present invention, the first end of the second coil is coupled to a seventh node between the input end of the fifth switch and the input end of the sixth switch, and the second end of the second coil An eighth node coupled between the second capacitor and the third capacitor.

In one embodiment of the invention, the inductor acts as an input current source for the resonant DC to DC converter.

In an embodiment of the invention, the switching duty cycle of the half bridge buck-boost converter is 50%.

Thereby, the half-bridge resonant bidirectional DC-to-DC converter circuit of the present invention achieves a wide input voltage by the half bridge buck-boost converter The efficiency of the range; in addition, the resonant DC-to-DC converter can achieve the effect of controlling the direction of the bidirectional power flow; further, by the half-bridge buck-boost converter and the resonant DC-to-DC converter, It simplifies circuit design by enabling immediate operation without powering down.

The above summary, the following detailed description and the accompanying drawings are intended to further illustrate the manner, the Other objects and advantages of the present invention will be described in the following description and drawings.

100‧‧‧Half-bridge resonant bidirectional DC-to-DC converter circuit

110‧‧‧Half-bridge buck-boost converter

120‧‧‧Resonant DC to DC Converter

121‧‧‧First side switch unit

122‧‧‧Voltage conversion unit

123‧‧‧Second side switch unit

1000‧‧‧DC power supply

Cr‧‧‧first capacitor

Cd1‧‧‧second capacitor

Cd2‧‧‧ third capacitor

N1~N2‧‧‧first to second coil

Node1~Node8‧‧‧first to eighth nodes

T1~T2‧‧‧first to second transistors

S1~S6‧‧‧first to sixth switches

Vbat‧‧‧Stable DC voltage

Vd‧‧‧ induced voltage

Id‧‧‧Induction current

IL‧‧‧ current

Ir‧‧‧ Current

VCCS‧‧‧Voltage Control Current Source

Figure 1 is a detailed circuit diagram of a conventional dual active full bridge converter.

2 is a detailed circuit diagram of a conventional LLC-SRC converter.

3 is a detailed circuit diagram of a first aspect of a conventional two-stage series converter.

4 is a detailed circuit diagram of a second aspect of a conventional two-stage series converter.

Figure 5A is a detailed circuit diagram of a first aspect of a conventional full bridge phase shift converter using a push-pull current source.

Figure 5B is a detailed circuit diagram of a second aspect of a conventional full bridge phase shift converter using a push-pull current source.

6 is a schematic circuit diagram of an embodiment of a half-bridge resonant bidirectional DC-to-DC converter circuit according to the present invention.

7 is a detailed circuit diagram of another embodiment of the half-bridge resonant bidirectional DC-to-DC converter circuit of the present invention.

8A is a view showing a first equivalent circuit of another embodiment of the half-bridge resonant bidirectional DC-to-DC converter circuit of the present invention.

Figure 8B is a Bode diagram of the current control loop of Figure 8A.

9A is a view showing a second equivalent circuit of another embodiment of the half-bridge resonant bidirectional DC-to-DC converter circuit of the present invention.

Figure 9B is a Bode diagram of the current control loop of Figure 9A.

Fig. 10A is a view showing a third equivalent circuit of another embodiment of the half-bridge resonant bidirectional DC-to-DC converter circuit of the present invention.

Figure 10B is a Bode diagram of the current control loop of Figure 10A.

11 is a detailed circuit diagram of a half-bridge resonant bidirectional DC-to-DC converter circuit of the present invention connected in series with a single-phase three-wire converter.

12A to 12D are diagrams showing the relationship between the inductor current and the control current of the half bridge buck-boost converter of FIG.

The embodiments of the present invention are described below by way of specific examples, and those skilled in the art can readily appreciate other advantages and functions of the present invention from the disclosure herein.

Please refer to FIG. 6 , which is a circuit diagram of an embodiment of a half-bridge resonant bidirectional DC-to-DC converter circuit 100 of the present invention. As shown in FIG. 6, the half-bridge resonant bi-directional DC-to-DC converter circuit 100 includes a half-bridge buck-boost converter 110 and a resonant DC-to-DC converter 120. The half-bridge buck-boost converter 110 is coupled. An external DC power supply 1000, the DC power supply 1000 provides a stable DC voltage V _bat input, and the half bridge buck-boost converter 110 is used to obtain a wide input voltage range. The resonant DC to DC converter 120 is coupled. Connected to the half bridge buck-boost converter 110 as a later stage circuit of the half bridge buck-boost converter 110, the resonant DC to DC converter 120 is used to control the bidirectional power flow direction, The resonant DC-to-DC converter 120 is responsive to the half-bridge buck-boost converter 110 in a fixed frequency mode and converts the input of the half-bridge buck-boost converter 110 into an induced current _Id output. The half bridge buck-boost converter 110 includes a first transistor T1, a second transistor T2, an inductor L, and a first capacitor _Cr . The first transistor T1 is coupled to the positive output terminal of the DC power supply 1000, and the source terminal of the second transistor T2 is coupled to the negative output terminal of the DC power supply 1000. The source terminal of the first transistor T1 It is coupled to the 汲 terminal of the second transistor T2. Node1 a node between the source terminal of the inductance L of an input terminal coupled to the first transistor T1 and the drain terminal of the second transistor T2, the input terminal of the first capacitor C _r is coupled to the The output of the first capacitor C _r is coupled to a second node Node2 between the source terminal of the second transistor T2 and the negative output terminal of the DC power supply 1000. The resonant DC-to-DC converter 120 includes a first-order side switch unit 121, a voltage conversion unit 122, and a second-order side switch unit 123. The first-order side switch unit 121 is coupled to the half-bridge buck-boost converter 110. The voltage conversion unit 122 is coupled to the first side switch unit 121. The second-order side The switch unit 123 is coupled to the voltage conversion unit 122.

Please refer to FIG. 7, which is a detailed circuit diagram of another embodiment of the half-bridge resonant bidirectional DC-to-DC converter circuit 100 of the present invention. As shown in FIG. 7, the first side switch unit 121 can include a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4. A third node between the positive electrode Node3 drain terminal of the first switch S1 may be coupled to the first capacitor C _r and an output terminal of the inductor L, the second source terminal S2 of the switch may be coupled to the first Node4 a fourth node between the negative electrode and a capacitance C _r of the second node Node2, the source terminal of the first switch S1 may be coupled to the drain terminal of the second switch S2. The third terminal S3 can be coupled to the third node Node3, and the source of the fourth switch S4 can be coupled to the fourth node Node4. The source terminal of the third switch S3 can be coupled to the first The 汲 extreme of the four switch S4. According to this, by the combination of the first to fourth switches S1 to S4, the first-stage side switching unit 121 can adjust the input of the half-bridge step-up and step-down converter 110 on the first side and output a current I _{r .} .

The voltage conversion unit 122 can include a first coil N1 and a second coil N2. The second coil N2 induces a current I _r flowing into the first coil N1 to generate an induced voltage V _d , and the number of turns of the first coil N1 is different from the number of turns of the second coil N2 . Accordingly, the voltage value of the DC voltage can be changed by the induction between the first coil N1 and the second coil N2, and the conversion ratio of the changed voltage value is equal to the first coil N1 and the second coil N2. Number ratio.

In addition, the first end of the first coil N1 can be coupled to a fifth node Node5 between the source terminal of the first switch S1 and the 汲 terminal of the second switch S2, and the second end of the first coil N1 The sixth node Node6 can be coupled between the source terminal of the third switch S3 and the drain terminal of the fourth switch S4. The second side switch unit 123 can include a fifth switch SR1, a sixth switch SR2, a second capacitor C _d1 , a third capacitor C _{d2 ,} and a voltage control current source VCCS. The source of the fifth switch SR1 is coupled to the first end of the second coil N2. The second switch SR2 is coupled to the first end of the second coil N2. The second capacitor C _{d1 is} coupled. The second capacitor C _{d2 is} coupled to the second end of the second coil N2 at the second end of the second coil N2. The fifth switch SR1, the sixth switch SR2, the second capacitor C _d1 and the third capacitor C _d2 adjust and output the induced voltage V _d . The voltage control current source VCCS is coupled to the 汲 terminal of the fifth switch SR1, the source terminal of the sixth switch SR2, the second capacitor C _d1 and the third capacitor C _d2 , and outputs the voltage according to the adjusted induced voltage. Induced current I _d . According to the combination of the fifth switch SR1, the sixth switch SR2, the second capacitor C _d1 and the third capacitor C _d2 , the second secondary side switching unit 123 can be adjusted on the second secondary side. The induced voltage V _{d is} output, and the induced current I _d is output according to the adjusted induced voltage by the voltage controlled current source VCCS.

In addition, the first end of the second coil N2 can be coupled to a seventh node Node7 between the source terminal of the fifth switch SR1 and the 汲 terminal of the sixth switch SR2, and the second end of the second coil N2 The eighth node Node8 can be coupled between the second capacitor C _d1 and the third capacitor C _d2 . The inductor L can be used as an input current source of the resonant DC-to-DC converter 120.

Compared with the frequency conversion control mode of the conventional LLC-SRC converter shown in FIG. 2, the half-bridge resonant bidirectional DC-to-DC converter circuit 100 of the present invention uses a fixed frequency control method, so there is no such LLC- The range in which the SRC converter frequency variation range will increase as the operating voltage becomes larger. Compared with the full bridge phase shift converter using the push-pull current source as shown in FIGS. 5A and 5B, the first-stage side switching unit 121 of the half-bridge resonant bidirectional DC-to-DC converter circuit 100 of the present invention can The use of power components with lower withstand voltage specifications can reduce the limitations on circuit design and reduce the difficulty of practical applications.

Hereinafter, the theoretical basis of the half-bridge resonant bidirectional DC-to-DC converter circuit 100 of the present invention as shown in FIG. 7 will be described by means of an equivalent circuit. Please refer to FIG. 8A, which is a view of an equivalent circuit of FIG. According to the first equivalent circuit of Figure 8A and using the state average rule: If you ignore the changes in V _bat and V _r , you can get (1): Considering the current sensing ratio K _s and the gain of the PWM, you can get: The design of the first-order system current error amplifier ( G _CA ) can be designed by using two types of error amplifiers. The current control loop Bode diagram is shown in Figure 8B. Since the PWM control voltage can only be sawtoothed in one cycle. The wave signal meets once, so the maximum bandwidth of the current loop ( ω _co ) is limited by the rising slope of V _{con which} is less than the rising slope of the PWM sawtooth wave ( V _t ), and the rising slope of V _con can be the slope of the sensed inductor current drop. It is determined by the gain G _CA amplification, so the above limitation can be obtained: ( V _r / L ) K _s G _{CA ,max} ( ω _co )= V _t f _s (4) After reorganizing (4), we can obtain: From equations (3) and (5), and using G _{CA , max} ( ω _co ) H _i ( ω _co ) = 1, you can get: After reorganizing (6), you can get:

It can be seen from equation (8) that if the design is controlled by the rising slope of the control voltage V _con , the theoretical maximum current loop bandwidth may be higher or closer to the switching frequency, so it cannot be set with this value. The general bandwidth ( ω The choice of _co ) can be set at 1/4~1/8 of the switching frequency. When the bandwidth ( ω _co ) is selected, the K-factor method can be used to make z= ω _co /K, p= ω _co /K of the second type error amplifier.

When the output voltage of the half-bridge resonant bi-directional DC-DC converter is maintained by the buck-boost converter, the second equivalent circuit of FIG. 9A can be used for the resonant circuit analysis, wherein the buck-boost converter will be a current source. Representative, the average voltage ( V r) is the voltage that the high-voltage side voltage is reflected by the transformer to the low-voltage side: From the input side of the buck-boost converter: When considering the voltage sensing ratio Kv and using the formula (10), the small signal model of the voltage loop can be obtained as follows: For the design of the first-order system current error amplifier ( G _EA ), two types of error amplifiers can be used to design. The voltage control loop Bode diagram is shown in Figure 9B, because its bandwidth is limited by the second pass of the DC link. The wave can therefore be designed at 20 Hz to allow the current command I _{LC to} have a lower secondary chopping.

If the output voltage can be maintained by the buck-boost converter, the analysis of the half-bridge resonant circuit can be performed using the third equivalent circuit of FIG. 10A, and the output converter is represented by a current source, and the input current The source is represented by the output current I _{L of the} buck-boost converter. The average voltage of V _{r is} the voltage on the low voltage side of the high voltage side voltage reflected by the transformer: If the output power of the buck-boost converter is P _o , then I _L can be: The working waveform of the circuit is shown in Fig. 10B. The resonance of the circuit is formed by the leakage inductance L _{r of the} transformer and the resonant capacitor C _r . Resonant tank impedance: When the first switch S1, the fifth switch SR1, and the switch SR4 are turned on, the following equation of state can be obtained:

The rate of increase of the current of the self-inductive current I _{m for} half a week is: Using equations (17) and (18), we can obtain: V _r ( t ) = A sin ω _o t + B cos ω _o t + V _b (19) where A and B are parameters to be determined. (19) Substituting (17) is available: I _r ( t ) = I _L + ω _o C _r B sin ω _o t - ω _o C _r A cos ω _o ^t (20) if the switch is to achieve zero voltage switching and its To achieve zero current conduction, the bypass diode must make I _r (0) = 0, and Ir in the beginning of (20) must resonate to a negative value, that is, B < 0, therefore: I _r (0 ) = I _L - ω _o C _r A =0 (21) is obtained by (21): It is known that the charge and discharge of C _{r are} balanced, and the average value of V _r (t) half cycle in (22) is equal to V _b : Substituting (22) and (23) for: The condition that B<0 is obtained by (24) is: f _s < f _o (25), that is, the switching frequency of the switch needs to be lower than the resonance frequency.

Hereinafter, the result of the circuit and control method of the half-bridge resonant bidirectional DC-to-DC converter circuit 100 of the present invention is verified by an embodiment provided in FIG. As shown in FIG. 11, the half-bridge resonant bidirectional DC-to-DC converter circuit 100 of the present invention is connected in series with a single-phase three-wire converter 2000 at the rear stage and connected to the mains, so that the load of the single-phase three-wire output is not Balanced, the output of the 110Vac/110Vac/220Vac output is 100W/500W/0W. As shown in the simulation diagrams 12A to 12D, the mains parallel currents Isa and Isb are stable when the time is 0.15 seconds, and the DC side busbar voltages Vd1 and Vd2 are stable, and the load is unbalanced at the load end when the time is 0.15 seconds. After about 0.02 seconds, the parallel current Isa and Isb tend to be stable, and the load currents ILa and ILb are completely unaffected. The inductor current IL and the control current ILc of the half-bridge buck-boost converter are as shown in FIG. 12A to FIG. 12D. Therefore, the circuit proposed by the present invention can indeed perform bidirectional power flow control. It can also change the seamless working mode and compensate the current of the unbalanced load at the same time. The circuit and the control method of the half-bridge resonant bidirectional DC-to-DC converter circuit 100 of the present invention are relatively simple and high in efficiency, and can solve the high step-up ratio, the high output/input voltage change, and the seamless bidirectional power flow switching. problem.

In summary, the half-bridge resonant bidirectional DC-to-DC converter circuit of the present invention can achieve a wider input voltage range by the half-bridge buck-boost converter; in addition, the resonant DC transfer The DC converter can achieve the effect of controlling the direction of the bidirectional power flow; furthermore, the half-bridge buck-boost converter and the resonant DC-to-DC converter can realize the instant operation without power interruption, thereby Can simplify circuit design.

The above-described embodiments are merely illustrative of the features and functions of the present invention, and are not intended to limit the scope of the technical scope of the present invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the scope of the claims described below.

Claims (9)

A half-bridge resonant bidirectional DC-to-DC converter circuit comprising: a half-bridge buck-boost converter coupled to an external DC power supply, the DC power supply providing a stable DC voltage, The half-bridge buck-boost converter includes: a first transistor having an anode coupled to the positive output of the DC power source; and a second transistor having a source terminal coupled to the negative output of the DC power source, The source terminal of the first transistor is coupled to the 汲 terminal of the second transistor; an inductor having an input coupled to a first end between the source terminal of the first transistor and the 汲 terminal of the second transistor And a first capacitor, wherein the input end is coupled to the output end of the inductor, and the output end is coupled to a second node between the source terminal of the second transistor and the negative output terminal of the DC power source And a resonant DC-to-DC converter coupled to the half-bridge buck-boost converter as a rear stage circuit of the half-bridge buck-boost converter, the resonant DC-to-DC converter including a first Secondary side (first-order sid e) a switching unit, a voltage conversion unit and a second-order side switching unit, the resonant DC-to-DC converter being adapted to respond to the half-bridge buck-boost converter in a fixed frequency mode Converting the input of the half bridge buck-boost converter into an induced current output; The first side switch unit includes a first switch, a second switch, a third switch, and a fourth switch. The first switch is coupled to the anode of the first capacitor and the output of the inductor. a third node between the terminals, the source terminal of the second switch is coupled to a fourth node between the negative pole of the first capacitor and the second node, and a source terminal of the first switch is coupled to the third node The 汲 terminal of the second switch, the third switch is coupled to the third node, the source terminal of the fourth switch is coupled to the fourth node, and the source terminal of the third switch is coupled to the fourth switch Extremely extreme. The half-bridge resonant bidirectional DC-to-DC converter circuit of claim 1, wherein the first-stage switching unit is coupled to the half-bridge buck-boost converter, and the voltage conversion unit is coupled to the first The one-side switch unit is coupled to the voltage conversion unit. The half-bridge resonant bidirectional DC-to-DC converter circuit of claim 1, wherein the voltage conversion unit comprises a first coil and a second coil, and the second coil is induced by a current flowing into the first coil. An induced voltage is generated, the number of turns of the first coil being different from the number of turns of the second coil. The half-bridge resonant bidirectional DC-to-DC converter circuit of claim 3, wherein the first end of the first coil is coupled to a source between the source terminal of the first switch and the second terminal of the second switch The fifth node, the second end of the first coil is coupled to a sixth node between the source terminal of the third switch and the drain terminal of the fourth switch. The half-bridge resonant bidirectional DC-to-DC converter circuit of claim 3, wherein the second secondary side switching unit comprises a fifth switch, a sixth switch, a second capacitor, and a third capacitor, the first The source of the fifth switch is coupled to the first end of the second coil, the second end of the sixth switch is coupled to the first end of the second coil, and the second capacitor is coupled to the second end of the second coil. The third capacitor is coupled to the second end of the second coil, and the fifth switch, the sixth switch, the second capacitor, and the third capacitor adjust and output the induced voltage. The half-bridge resonant bidirectional DC-to-DC converter circuit of claim 5, wherein the second sub-side switching unit further includes a voltage control current source coupled to the 汲 terminal of the fifth switch, the sixth switch The source terminal, the second capacitor and the third capacitor output the induced current according to the adjusted induced voltage. The half-bridge resonant bidirectional DC-to-DC converter circuit of claim 5, wherein the first end of the second coil is coupled between the source terminal of the fifth switch and the 汲 terminal of the sixth switch The seventh node, the second end of the second coil is coupled to an eighth node between the second capacitor and the third capacitor. The half-bridge resonant bidirectional DC-to-DC converter circuit of claim 1, wherein the inductor is used as an input current source of the resonant DC-to-DC converter. The half-bridge resonant bidirectional DC-to-DC converter circuit of claim 1, wherein the switching duty cycle of the half-bridge buck-boost converter is 50%.