Texas Instruments 28xxx manual PWM-Chopper PC Submodule, Purpose of the PWM-Chopper Submodule

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PWM-Chopper (PC) Submodule

2.6PWM-Chopper (PC) Submodule

Figure 2-30illustrates the PWM-chopper (PC) submodule within the ePWM module.

Figure 2-30. PWM-Chopper Submodule

EPWMxSYNCI

EPWMxSYNCO

Time-Base

(TB)

Counter

Compare

(CC)

CTR = PRD

CTR = 0

CTR_Dir

CTR = CMPA

CTR = CMPB

		CTR = PRD	Event
		CTR = 0
			Trigger
Action	CTR = CMPA
			and
Qualifier
			Interrupt
(AQ)		CTR = CMPB
		CTR_Dir	(ET)

EPWMxB
Dead	PWM-	Trip
Band	chopper	Zone
(DB)	(PC)	(TZ)
EPWMxA
	CTR = 0
PIE	EPWMxTZINT

EPWMxINT

EPWMxSOCA

EPWMxSOCB

EPWMxA

EPWMxB

TZ1 to TZ6

PIE

ADC

GPIO MUX

The PWM-chopper submodule allows a high-frequency carrier signal to modulate the PWM waveform generated by the action-qualifier and dead-band submodules. This capability is important if you need pulse transformer-based gate drivers to control the power switching elements.

2.6.1 Purpose of the PWM-Chopper Submodule

The key functions of the PWM-chopper submodule are:

∙Programmable chopping (carrier) frequency

∙Programmable pulse width of first pulse

∙Programmable duty cycle of second and subsequent pulses

∙Can be fully bypassed if not required

2.6.2Controlling the PWM-Chopper Submodule

The PWM-chopper submodule operation is controlled via the registers in Table 2-15.

Table 2-15. PWM-Chopper Submodule Registers

mnemonic	Address offset	Shadowed	Description
PCCTL	0x001E	No	PWM-chopper Control Register

2.6.3 Operational Highlights for the PWM-Chopper Submodule

Figure 2-31shows the operational details of the PWM-chopper submodule. The carrier clock is derived from SYSCLKOUT. Its frequency and duty cycle are controlled via the CHPFREQ and CHPDUTY bits in the PCCTL register. The one-shot block is a feature that provides a high energy first pulse to ensure hard and fast power switch turn on, while the subsequent pulses sustain pulses, ensuring the power switch remains on. The one-shot width is programmed via the OSHTWTH bits. The PWM-chopper submodule can be fully disabled (bypassed) via the CHPEN bit.

SPRU791D–November 2004–Revised October 2007 ePWM Submodules 55

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