I T 驱动电路设计过程

3.4 IGBT Switch

Figure 3.12: H-Bridge position (a)Figure 3.13: H-Bridge position (b)

The IGBT - Switch is used to supply the voltage multiplier with a high frequency rectangular voltage.Figure 3.12 and Figure 3.13 show the principle of the four-valve switch, also called H - Bridge.By changing the switching position of Figure 3.12 to Figure 3.13 the voltage between point a and point b is alternating. It is important to ensure, that S1 and S3, as well as S2 and S4 are never closed at the same time. Else there will be a short circuiting of U 12.

U 12 must be a direct voltage. By rectifying a three phase supply smaller smoothing - capacitors are needed than by rectifying a single - phase supply.

As switching devices IGBTs offer a high power, high voltage switching capability at high frequency and low cost. Because S1 and S2 are on a high level when switched on, a floating gate driver is needed.The easiest way to fulfil these criteria is to use an IR2235, an integrated circuit from International Rectifier [IR-DS-IR2235]. It provides three floating and three low side gate drivers.

Figure 3.14 shows the Protel schematics of the left channel, Figure 3.15 of the right channel of the H -Bridge.

J_DC+ of both channels are connected together to connector +DC of Figure 3.7.

J_IGBT_low of both channels are connected to connector -DC of Figure 3.7.

Figure 3.14: H - bridge: Left channel

Figure 3.15: H - Bridge: Right channel

Figure 3.16: Top-view: H - Bridge

Figure 3.16 is a photo of the mounted H - Bridge, (a) are suppressing capacitors, (b) are the switching IGBTs and (c) are shunt resistors.

Figure 3.17 is the Protel Schematic of the power supply for the driver board. J_230V_in is connected to the main switch, J_out is connected to J_power_in in Figure 3.18.

Figure 3.17: IGBT - switch: Power supply

Figure 3.18 is the Protel Schematic of the IGBT driver board. Heard of the circuit is a IR2235 chip from International Rectifier [IR-DS-IR2235]. The signal in- and output is isolated by optocouplers. The connectors Jg1 - Jg4 are connected to the H - Bridge (Figure 3.14 and Figure 3.15).

Figure 3.18: Protel Schematic: IGBT - driver

Figure 3.19: Top-view: Driver PCB

Figure 3.19 and Figure 3.20 are photos of the mounted and tested IGBT driver PCB. All resistors and some capacitors are Surface Mounted Devices to minimise size and electromagnetic interference.

Figure 3.20: Bottom-view: Driver PCB

This page is part of a Frameset: Electrodynamic Sculpture: A Thesis by Rafael Bräg.