Reduction of voltage spikes in switching half-bridge stages
A path configuration for a power switch and driver can introduce independent parasitic inductance coupled to the power switch to slow a switching speed of the switch and reduce voltage spikes on the switch during switching events. The path for low side supply of the drive to the negative DC voltage reference is separate from the path of the power switch to the reference. The resulting reduction in voltage spikes due to the slowed switching time maintains performance in an audio amplifier without modifying a switch command signal to compensate for voltage spikes. The path configuration avoids reliance on specifying higher rated components that increase application costs.
1. A circuit configuration for a power switch driver and a power switch in an IC, comprising:
a low side power supply connection for the power switch driver;
an IC pin for providing an external electrical connection to one side of the switch;
the low side power supply connection connected to the pin connection; and
separate paths for the connections between the low side power supply connection to the pin and between the one side of the switch to the pin, the separate paths including corresponding separate bond pads and bond wires, whereby the bondwires of the separate paths have parasitic inductances that impact the switching time of the power switch.
2. An audio amplifier comprising the circuit configuration according to claim 1 .
3. A switching half bridge circuit composed of two switches, one or more of the switches comprising the circuit configuration according to claim 1 .
4. The circuit configuration according to claim 1 , wherein the power switch is a MOS-gated switch.
5. A method for reducing voltage spikes on a power switch, comprising;
arranging a separate path for a connection to one side of the power switch in relation to a power supply for a switch driver; and
decreasing a switching time of the power switch based on inherent characteristics of the separate path, whereby the voltage spike magnitude is reduced.
6. The method according to claim 4 , further comprising forming a parasitic inductor in the separate path.
7. A class D audio amplifier power stage IC, comprising:
a power switch for switching power in the power stage;
a power switch driver for driving the power switch in accordance with a switching command applied to the driver and having a low side power supply connection;
separate paths for each of the low side power supply connection and one side of the power switch to an external IC pin;
the characteristics of the path to the one side of the power switch contributing to decreasing a switching speed of the power switch to reduce a magnitude of a voltage spike during switching events.
8. The IC according to claim 7 , further comprising:
another power switch for switching power in conjunction with the one power switch; and
another power switch driver for driving the another power switch in accordance with another switching command applied to the another driver, and having a another low side power supply connection.
9. The IC according to claim 8 , further comprising separate paths for each of the another low side power supply connection and one side of the another power switch to an external IC pin.