A half bridge induction heating generator and a capacitor as ^¬ sembly for a half bridge induction heating generator

The present invention relates to a half bridge induction heat ^¬ ing generator according to the preamble of claim 1. Further, the present invention relates to a capacitor assembly according to the preamble of claim 11.

A half bridge induction heating generator is used in an induction heating converter. FIG 2 illustrates a half bridge induc ^¬ tion heating generator according to the prior art. Said half bridge induction heating generator comprises two transistors Ql and Q2, two diodes Dl and D2, an induction coil L and five ca ^¬ pacitors CI, C2, C3, C4 and C5. The first capacitors CI acts as a link filter for the direct current. The second and third ca ^¬ pacitors C2 and C3 are resonant capacitors. The resonant ca ^¬ pacitors C2 and C3 match the resonant frequency of the induc- tion heating generator. The fourth and fifth capacitors C4 and C5 are snubber capacitors managing the switching behaviour of the transistors Ql and Q2, respectively.

The induction heating generator includes a relative large amount of capacitors CI, C2, C3, C4 and C5. Further, the ca ^¬ pacitances of the capacitors CI, C2, C3, C4 and C5 are also relative high. The capacitors CI, C2, C3, C4 and C5 have to be placed on a printed circuit board of the converter in a careful way. The stray inductance has to be minimized. The power track should be able to carry on the large amount of switching cur ^¬ rent. A space on the printed circuit board should be provided for other components of the induction heating generator. High power terminals should be provided for the supply voltage and the induction coil L. It is an object of the present invention to provide a half bridge induction heating generator, which satisfies the above conditions by low complexity. The object of the present invention is achieved by the half bridge induction heating generator according to claim 1.

According to the present invention the four capacitors of the bridge circuit and the further capacitor are arranged inside a common housing, wherein said housing and the capacitors form a capacitor assembly, which is a single component and mounted or mountable on and electrically connected or connectable to a printed circuit board. The main idea of the present invention is that the capacitors are arranged inside the common housing and form the capacitor assembly. The capacitor assembly with the housing and the ca ^¬ pacitors reduces the components to be installed on the printed circuit board. This result in a faster production process and lower production costs. Additional components may be arranged inside the capacitor assembly. The capacitor assembly allows a better performance of the power management of the induction heating generator. The capacitor assembly saves space on the printed circuit board.

In particular, the housing is filled with a hardening liquid, so that the capacitor assembly form a robust block. This con ^¬ tributes to the stability of the housing and the capacitor as ^¬ sembly. Further, no heat sinks occur inside the capacitor as- sembly.

Preferably, the power terminal is arranged at the outside of the housing of the capacitor assembly, wherein the power terminal is connected or connectable to a corresponding wiring coun- terpart. This is particularly advantageous, if the housing is mounted on an insulated metal substrate (IMS) printed circuit board by the surface mount device (SMD) technology. Further, the housing comprises a plurality of terminals corre ^¬ sponding with the electrodes of the capacitors, wherein the electric connections of the capacitors are performed or per- formable on the printed circuit board.

For example, the space between the housing and the printed cir ^¬ cuit board is provided for further electric and/or electronic components. This constellation saves space on the printed cir- cuit board.

Additionally, further electric and/or electronic components are arranged inside the housing. Further, at least one diode is connected in parallel to each of the both semiconductor switches. Thus, the induction heating generator includes at least two diodes at all, wherein one di ^¬ ode is connected in parallel to one of the both semiconductor switches in each case.

For example, the housing is mounted or mountable on and elec ^¬ trically connected or connectable to the printed circuit board with through-hole-technology. Alternatively, the housing is mounted or mountable on and elec ^¬ trically connected or connectable to an insulated metal sub ^¬ strate (IMS) printed circuit board by the surface mount device (SMD) technology. In this case, the power terminal is prefera ^¬ bly arranged at the housing of the capacitor assembly.

Preferably, a first input terminal is connected to a control input of the one semiconductor switch, and a second input ter ^¬ minal is connected to a control input of the other semiconduc ^¬ tor switch.

For example, the semiconductor switches are bipolar transis ^¬ tors. In this case, the first input terminal and the second in- put terminal may be connected to the base electrodes of the bi ^¬ polar transistors in each case.

Alternatively, the semiconductor switches are field effect transistors, wherein the first input terminal and the second input terminal may be connected to the gate electrodes of the field effect transistors in each case.

The object of the present invention is further achieved by the capacitor assembly according to claim 11.

According to the present invention the four capacitors of the bridge circuit and the further capacitor are arranged inside a common housing, wherein said housing and the capacitors form a capacitor assembly, which is a single component and mountable on and electrically connectable to a printed circuit board.

Preferably, the housing is filled with a hardening liquid, so that the capacitor assembly form a robust block. This contrib- utes to the stability of the housing and the capacitor assem ^¬ bly. Further, no heat sinks occur inside the capacitor assembly.

For example, the housing is mountable on and electrically con- nectable to a printed circuit board with through-hole- technology .

Alternatively, the housing is mountable on and electrically connectable to an insulated metal substrate (IMS) printed cir- cuit board by the surface mount device (SMD) technology.

In this case, the power terminal is preferably arranged at the housing of the capacitor assembly.

At last, a power terminal may be arranged at the housing of the capacitor assembly, wherein the power terminal is provided for the connection to a corresponding wiring counterpart. Novel and inventive features of the present invention are set forth in the appended claims.

The present invention will be described in further detail with reference to the drawings, in which

FIG 1 illustrates a circuit diagram of a half bridge induc ^¬ tion heating generator according to a preferred embodiment of the present invention, and

FIG 2 illustrates a circuit diagram of a half bridge induc ^¬ tion heating generator according to the prior art.

FIG 1 illustrates a circuit diagram of a half bridge induction heating generator according to a preferred embodiment of the present invention.

The half bridge induction heating generator comprises a first transistor Ql, a second transistor Q2, a first diode Dl, a sec- ond diode D2, an induction coil L and five capacitors CI, C2, C3, C4 and C5.

The first transistor Ql and the second transistor Q2 are connected in series. The first diode Dl is connected in parallel to the first transistor Ql . In a similar way, the second diode D2 is connected in parallel to the second transistor Q2.

The second capacitor C2 and the third capacitor C3 are connected in series and form a first capacitor series. The fourth capacitor C4 and the fifth capacitor C5 are connected in series and form a second capacitor series. The first capacitor series, the second capacitor series and the first capacitor CI are con ^¬ nected in parallel and installed inside a common housing 20. Said housing 20 is formed as a single component installed or installable on the printed board. The housing 20 and the ca ^¬ pacitors CI, C2, C3, C4 and C5 inside said housing 20 form a capacitor assembly. Further, the series of the first transistor Ql and the second transistor Q2 is connected in parallel to the first capacitor series, the second capacitor series and the first capacitor CI. This parallel arrangement is interconnected between a power terminal 10 and a ground 12. The power terminal 10 is provided for the supply of a direct current voltage.

Moreover, the connecting point of the first transistor Ql and the second transistor Q2 is connected to the connecting point of the fourth capacitor C4 and the fifth capacitor C5. Thus, the fourth capacitor C4 is connected in parallel to the first transistor Ql and the first diode Dl . In a similar way, the fifth capacitor C5 is connected in parallel to the second tran- sistor Q2 and the second diode D2.

The induction coil L is connected to the connecting point of the first transistor Ql and the second transistor Q2 on the one end. On the other end, the induction coil L is connected to the connecting point of the second capacitor C2 and the third ca ^¬ pacitor C3.

A first input terminal 14 is connected to the base electrode of the first transistor Ql . In a similar way, a second input ter- minal 16 is connected to the base electrode of the second tran ^¬ sistor Q2. The first input terminal 14 and the second input terminal 16 are provided for the supply of rectangular signals.

The first capacitor CI acts as a link filter for the direct current supplied to the power terminal 10. The second capacitor C2 and the third capacitor C3 are resonant capacitors. The resonant capacitors C2 and C3 match the resonant frequency of the induction heating generator. The fourth capacitor C4 and the fifth capacitor C5 are snubber capacitors managing the switching behaviour of the transistors Ql and Q2, respectively. The capacitor assembly, i.e. the housing 20 including the capacitors CI, C2, C3, C4 and C5, may be provided for a printed circuit board with through-hole-technology as well as for an insulated metal substrate (IMS) printed circuit board. For ex- ample, the power terminal 10 may be formed according to the standard "RAST5" in both cases. The power terminal 10 is pro ^¬ vided for the connection to a corresponding wiring counterpart.

If the capacitor assembly is provided for the printed circuit board with through-hole-technology, then the capacitor assembly comprises a number of pins penetrating through the printed circuit board. Said pins are connectable or connected by solder points on the printed circuit board. If the capacitor assembly is provided for the IMS printed cir ^¬ cuit board, then the capacitor assembly is fastened on the IMS printed circuit board by the surface mount device (SMD) tech ^¬ nology. In this case, the capacitor assembly comprises a number of solder joints formed as L-shaped pins. Said solder joints are fastened on the IMS printed circuit board by the SMD tech ^¬ nology in each case.

If the capacitor assembly is provided for the IMS printed cir ^¬ cuit board, then the power terminal 10 is preferably a part of the capacitor assembly. When the wiring counterpart of the power terminal 10 is plugged to or unplugged from the power terminal 10, then the occurrent force between the power termi ^¬ nal 10 and the IMS printed circuit board is distributed to the solder joints. Thus, the capacitor assembly allows an attach- ment of the power terminal 10 with a sufficient stability on the IMS printed circuit board.

The capacitor assembly with the housing 20 and the capacitors CI, C2, C3, C4 and C5 reduces the components to be installed on the printed circuit board. This result in a faster production process and lower production costs. Additional components may be arranged inside the capacitor assembly. The capacitor assem- bly allows a better performance of the power management of the induction heating generator. At last, the capacitor assembly saves space on the printed circuit board. FIG 2 illustrates a circuit diagram of the half bridge induc ^¬ tion heating generator according to the prior art.

The conventional half bridge induction heating generator comprises the two transistors Ql and Q2, the two diodes Dl and D2, the induction coil L and the five capacitors CI, C2, C3, C4 and C5. The first capacitor CI acts as the link filter for the di ^¬ rect current. The second and third capacitors C2 and C3 are the resonant capacitors. The resonant capacitors C2 and C3 match the resonant frequency of the induction heating generator. The fourth and fifth capacitors C4 and C5 are snubber capacitors managing the switching behaviour of the transistors Ql and Q2, respectively .

This conventional half bridge induction heating generator is equal in view of the electric connections with the half bridge induction heating generator according to the preferred embodiment of the present invention. However, the capacitors CI, C2, C3, C4 and C5 of the conventional half bridge induction heating generator are formed as separate components in each case.

Although an illustrative embodiment of the present invention has been described herein, it is to be understood that the pre ^¬ sent invention is not limited to that precise embodiment, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention. All such changes and modifi ^¬ cations are intended to be included within the scope of the in ^¬ vention as defined by the appended claims. List of reference numerals

10 power terminal

12 ground terminal

14 first input terminal

16 second input terminal

20 housing

Ql first transistor

Q2 second transistor

Dl first diode

D2 second diode

CI first capacitor

C2 second capacitor

C3 third capacitor

C4 fourth capacitor

C5 fifth capacitor

L induction coil